diff options
Diffstat (limited to 'doc/developer-guide')
21 files changed, 647 insertions, 569 deletions
diff --git a/doc/developer-guide/Language-Bindings.md b/doc/developer-guide/Language-Bindings.md index 33f2e58504c..951f5fae2f6 100644 --- a/doc/developer-guide/Language-Bindings.md +++ b/doc/developer-guide/Language-Bindings.md @@ -1,3 +1,4 @@ +# Language Bindings GlusterFS 3.4 introduced the libgfapi client API for C programs. This page lists bindings to the libgfapi C library from other languages. diff --git a/doc/developer-guide/README.md b/doc/developer-guide/README.md index 4c6346e83d4..aaf9c7476b0 100644 --- a/doc/developer-guide/README.md +++ b/doc/developer-guide/README.md @@ -18,11 +18,9 @@ code check-in. the GPL v2 and the LGPL v3 or later - [GlusterFS Coding Standards](./coding-standard.md) -Developing ----------- +- If you are not sure of where to start, and what to do, we have a small + write-up on what you can pick. [Check it out](./options-to-contribute.md) -- [Language Bindings](./Language Bindings.md) - Connect to - GlusterFS using various language bindings Adding File operations ---------------------- @@ -53,20 +51,29 @@ Daemon Management Framework Translators ----------- -- [Block Device Tanslator](./bd-xlator.md) - [Performance/write-Behind Translator](./write-behind.md) - [Translator Development](./translator-development.md) - [Storage/posix Translator](./posix.md) -- [Compression translator](./network_compression.md) + + +Brick multiplex +--------------- + +- [Brick mux resource reduction](./brickmux-thread-reduction.md) + +Fuse +---- + +- [Interrupt handling](./fuse-interrupt.md) Testing/Debugging ----------------- - [Unit Tests in GlusterFS](./unittest.md) - [Using the Gluster Test - Framework](./Using Gluster Test Framework.md) - Step by + Framework](./Using-Gluster-Test-Framework.md) - Step by step instructions for running the Gluster Test Framework -- [Coredump Analysis](./coredump-analysis.md) - Steps to analize coredumps generated by regression machines. +- [Coredump Analysis](../debugging/analyzing-regression-cores.md) - Steps to analize coredumps generated by regression machines. - [Identifying Resource Leaks](./identifying-resource-leaks.md) Release Process diff --git a/doc/developer-guide/Using-Gluster-Test-Framework.md b/doc/developer-guide/Using-Gluster-Test-Framework.md index 96fa9247e84..d2bb1c391da 100644 --- a/doc/developer-guide/Using-Gluster-Test-Framework.md +++ b/doc/developer-guide/Using-Gluster-Test-Framework.md @@ -1,3 +1,4 @@ +# USing Gluster Test Framwork Description ----------- diff --git a/doc/developer-guide/afr-locks-evolution.md b/doc/developer-guide/afr-locks-evolution.md index 7d2a136d871..2dabbcfeb13 100644 --- a/doc/developer-guide/afr-locks-evolution.md +++ b/doc/developer-guide/afr-locks-evolution.md @@ -32,10 +32,10 @@ AFR makes use of locks xlator extensively: * For Entry self-heal, it is `entrylk(NULL name, parent inode)`. Specifying NULL for the name takes full lock on the directory referred to by the inode. * For data self-heal, there is a bit of history as to how locks evolved: -###Initial version (say version 1) : +### Initial version (say version 1) : There was no concept of selfheal daemon (shd). Only client lookups triggered heals. so AFR always took `inodelk(0,0,DATA_DOMAIN)` for healing. The issue with this approach was that when heal was in progress, I/O from clients was blocked . -###version 2: +### version 2: shd was introduced. We needed to allow I/O to go through when heal was going,provided the ranges did not overlap. To that extent, the following approach was adopted: + 1.shd takes (full inodelk in DATA_DOMAIN). Thus client FOPS are blocked and cannot modify changelog-xattrs @@ -79,7 +79,7 @@ It modifies data but the FOP succeeds only on brick 2. writev returns success, a and thus goes ahead and copies stale 128Kb from brick 1 to brick2. Thus as far as application is concerned, `writev` returned success but bricks have stale data. What needs to be done is `writev` must return success only if it succeeded on atleast one source brick (brick b1 in this case). Otherwise The heal still happens in reverse direction but as far as the application is concerned, it received an error. -###Note on lock **domains** +### Note on lock **domains** We have used conceptual names in this document like DATA_DOMAIN/ METADATA_DOMAIN/ SELF_HEAL_DOMAIN. In the code, these are mapped to strings that are based on the AFR xlator name like so: DATA_DOMAIN --->"vol_name-replicate-n" diff --git a/doc/developer-guide/afr-self-heal-daemon.md b/doc/developer-guide/afr-self-heal-daemon.md index b85ddd1c856..65940d420b7 100644 --- a/doc/developer-guide/afr-self-heal-daemon.md +++ b/doc/developer-guide/afr-self-heal-daemon.md @@ -39,7 +39,7 @@ When a client (mount) performs an operation on the file, the index xlator presen and removes it in post-op phase if the operation is successful. Thus if an entry is present inside the .glusterfs/indices/xattrop/ directory when there is no I/O happening on the file, it means the file needs healing (or atleast an examination if the brick crashed after the post-op completed but just before the removal of the hardlink). -####Index heal steps: +#### Index heal steps: <pre><code> In shd process of *each node* { opendir +readdir (.glusterfs/indices/xattrop/) diff --git a/doc/developer-guide/bd-xlator.md b/doc/developer-guide/bd-xlator.md deleted file mode 100644 index 1771fb6e24b..00000000000 --- a/doc/developer-guide/bd-xlator.md +++ /dev/null @@ -1,469 +0,0 @@ -#Block device translator - -Block device translator (BD xlator) is a translator added to GlusterFS which provides block backend for GlusterFS. This replaces the existing bd_map translator in GlusterFS that provided similar but very limited functionality. GlusterFS expects the underlying brick to be formatted with a POSIX compatible file system. BD xlator changes that and allows for having bricks that are raw block devices like LVM which needn’t have any file systems on them. Hence with BD xlator, it becomes possible to build a GlusterFS volume comprising of bricks that are logical volumes (LV). - -##bd - -BD xlator maps underlying LVs to files and hence the LVs appear as files to GlusterFS clients. Though BD volume externally appears very similar to the usual Posix volume, not all operations are supported or possible for the files on a BD volume. Only those operations that make sense for a block device are supported and the exact semantics are described in subsequent sections. - -While Posix volume takes a file system directory as brick, BD volume needs a volume group (VG) as brick. In the usual use case of BD volume, a file created on BD volume will result in an LV being created in the brick VG. In addition to a VG, BD volume also needs a file system directory that should be specified at the volume creation time. This directory is necessary for supporting the notion of directories and directory hierarchy for the BD volume. Metadata about LVs (size, mapping info) is stored in this directory. - -BD xlator was mainly developed to use block devices directly as VM images when GlusterFS is used as storage for KVM virtualization. Some of the salient points of BD xlator are - -* Since BD supports file level snapshots and clones by leveraging the snapshot and clone capabilities of LVM, it can be used to fully off-load snapshot and cloning operations from QEMU to the storage (GlusterFS) itself. - -* BD understands dm-thin LVs and hence can support files that are backed by thinly provisioned LVs. This capability of BD xlator translates to having thinly provisioned raw VM images. - -* BD enables thin LVs from a thin pool to be used from multiple nodes that have visibility to GlusterFS BD volume. Thus thin pool can be used as a VM image repository allowing access/visibility to it from multiple nodes. - -* BD supports true zerofill by using BLKZEROOUT ioctl on underlying block devices. Thus BD allows SCSI WRITESAME to be used on underlying block device if the device supports it. - -Though BD xlator is primarily intended to be used with block devices, it does provide full Posix xlator compatibility for files that are created on BD volume but are not backed by or mapped to a block device. Such files which don’t have a block device mapping exist on the Posix directory that is specified during BD volume creation. BD xlator is available from GlusterFS-3.5 release. - -###Compiling BD translator - -BD xlator needs lvm2 development library. –enable-bd-xlator option can be used with `./configure` script to explicitly enable BD translator. The following snippet from the output of configure script shows that BD xlator is enabled for compilation. - - -#####GlusterFS configure summary - - … - Block Device xlator : yes - - -###Creating a BD volume - -BD supports hosting of both linear LV and thin LV within the same volume. However seperate examples are provided below. As noted above, the prerequisite for a BD volume is VG which is created from a loop device here, but it can be any other device too. - - -* Creating BD volume with linear LV backend - -* Create a loop device - - - [root@node ~]# dd if=/dev/zero of=bd-loop count=1024 bs=1M - - [root@node ~]# losetup /dev/loop0 bd-loop - - -* Prepare a brick by creating a VG - - [root@node ~]# pvcreate /dev/loop0 - - [root@node ~]# vgcreate bd-vg /dev/loop0 - - -* Create the BD volume - -* Create a POSIX directory first - - - [root@node ~]# mkdir /bd-meta - -It is recommended that this directory is created on an LV in the brick VG itself so that both data and metadata live together on the same device. - - -* Create and mount the volume - - [root@node ~]# gluster volume create bd node:/bd-meta?bd-vg force - - -The general syntax for specifying the brick is `host:/posix-dir?volume-group-name` where “?” is the separator. - - - - [root@node ~]# gluster volume start bd - [root@node ~]# gluster volume info bd - Volume Name: bd - Type: Distribute - Volume ID: cb042d2a-f435-4669-b886-55f5927a4d7f - Status: Started - Xlator 1: BD - Capability 1: offload_copy - Capability 2: offload_snapshot - Number of Bricks: 1 - Transport-type: tcp - Bricks: - Brick1: node:/bd-meta - Brick1 VG: bd-vg - - - - [root@node ~]# mount -t glusterfs node:/bd /mnt - -* Create a file that is backed by an LV - - [root@node ~]# ls /mnt - - [root@node ~]# - -Since the volume is empty now, so is the underlying VG. - - [root@node ~]# lvdisplay bd-vg - [root@node ~]# - -Creating a file that is mapped to an LV is a 2 step operation. First the file should be created on the mount point and a specific extended attribute should be set to map the file to LV. - - [root@node ~]# touch /mnt/lv - [root@node ~]# setfattr -n “user.glusterfs.bd” -v “lv” /mnt/lv - -Now an LV got created in the VG brick and the file /mnt/lv maps to this LV. Any read/write to this file ends up as read/write to the underlying LV. - - [root@node ~]# lvdisplay bd-vg - — Logical volume — - LV Path /dev/bd-vg/6ff0f25f-2776-4d19-adfb-df1a3cab8287 - LV Name 6ff0f25f-2776-4d19-adfb-df1a3cab8287 - VG Name bd-vg - LV UUID PjMPcc-RkD5-RADz-6ixG-UYsk-oclz-vL0nv6 - LV Write Access read/write - LV Creation host, time node, 2013-11-26 16:15:45 +0530 - LV Status available - open 0 - LV Size 4.00 MiB - Current LE 1 - Segments 1 - Allocation inherit - Read ahead sectors 0 - Block device 253:6 - -The file gets created with default LV size which is 1 LE which is 4MB in this case. - - [root@node ~]# ls -lh /mnt/lv - -rw-r–r–. 1 root root 4.0M Nov 26 16:15 /mnt/lv - -truncate can be used to set the required file size. - - [root@node ~]# truncate /mnt/lv -s 256M - [root@node ~]# lvdisplay bd-vg - — Logical volume — - LV Path /dev/bd-vg/6ff0f25f-2776-4d19-adfb-df1a3cab8287 - LV Name 6ff0f25f-2776-4d19-adfb-df1a3cab8287 - VG Name bd-vg - LV UUID PjMPcc-RkD5-RADz-6ixG-UYsk-oclz-vL0nv6 - LV Write Access read/write - LV Creation host, time node, 2013-11-26 16:15:45 +0530 - LV Status available - # open 0 - LV Size 256.00 MiB - Current LE 64 - Segments 1 - Allocation inherit - Read ahead sectors 0 - Block device 253:6 - - - [root@node ~]# ls -lh /mnt/lv - -rw-r–r–. 1 root root 256M Nov 26 16:15 /mnt/lv - - currently LV size has been set to 256 - -The size of the file/LV can be specified during creation/mapping time itself like this: - - setfattr -n “user.glusterfs.bd” -v “lv:256MB” /mnt/lv - -2. Creating BD volume with thin LV backend - -* Create a loop device - - - [root@node ~]# dd if=/dev/zero of=bd-loop-thin count=1024 bs=1M - - [root@node ~]# losetup /dev/loop0 bd-loop-thin - - -* Prepare a brick by creating a VG and thin pool - - - [root@node ~]# pvcreate /dev/loop0 - - [root@node ~]# vgcreate bd-vg-thin /dev/loop0 - - -* Create a thin pool - - - [root@node ~]# lvcreate –thin bd-vg-thin -L 1000M - - Rounding up size to full physical extent 4.00 MiB - Logical volume “lvol0″ created - -lvdisplay shows the thin pool - - [root@node ~]# lvdisplay bd-vg-thin - — Logical volume — - LV Name lvol0 - VG Name bd-vg-thin - LV UUID HVa3EM-IVMS-QG2g-oqU6-1UxC-RgqS-g8zhVn - LV Write Access read/write - LV Creation host, time node, 2013-11-26 16:39:06 +0530 - LV Pool transaction ID 0 - LV Pool metadata lvol0_tmeta - LV Pool data lvol0_tdata - LV Pool chunk size 64.00 KiB - LV Zero new blocks yes - LV Status available - # open 0 - LV Size 1000.00 MiB - Allocated pool data 0.00% - Allocated metadata 0.88% - Current LE 250 - Segments 1 - Allocation inherit - Read ahead sectors auto - Block device 253:9 - -* Create the BD volume - -* Create a POSIX directory first - - - [root@node ~]# mkdir /bd-meta-thin - -* Create and mount the volume - - [root@node ~]# gluster volume create bd-thin node:/bd-meta-thin?bd-vg-thin force - - [root@node ~]# gluster volume start bd-thin - - - [root@node ~]# gluster volume info bd-thin - Volume Name: bd-thin - Type: Distribute - Volume ID: 27aa7eb0-4ffa-497e-b639-7cbda0128793 - Status: Started - Xlator 1: BD - Capability 1: thin - Capability 2: offload_copy - Capability 3: offload_snapshot - Number of Bricks: 1 - Transport-type: tcp - Bricks: - Brick1: node:/bd-meta-thin - Brick1 VG: bd-vg-thin - - - [root@node ~]# mount -t glusterfs node:/bd-thin /mnt - -* Create a file that is backed by a thin LV - - - [root@node ~]# ls /mnt - - [root@node ~]# - -Creating a file that is mapped to a thin LV is a 2 step operation. First the file should be created on the mount point and a specific extended attribute should be set to map the file to a thin LV. - - [root@node ~]# touch /mnt/thin-lv - - [root@node ~]# setfattr -n “user.glusterfs.bd” -v “thin:256MB” /mnt/thin-lv - -Now /mnt/thin-lv is a thin provisioned file that is backed by a thin LV and size has been set to 256. - - [root@node ~]# lvdisplay bd-vg-thin - — Logical volume — - LV Name lvol0 - VG Name bd-vg-thin - LV UUID HVa3EM-IVMS-QG2g-oqU6-1UxC-RgqS-g8zhVn - LV Write Access read/write - LV Creation host, time node, 2013-11-26 16:39:06 +0530 - LV Pool transaction ID 1 - LV Pool metadata lvol0_tmeta - LV Pool data lvol0_tdata - LV Pool chunk size 64.00 KiB - LV Zero new blocks yes - LV Status available - # open 0 - LV Size 000.00 MiB - Allocated pool data 0.00% - Allocated metadata 0.98% - Current LE 250 - Segments 1 - Allocation inherit - Read ahead sectors auto - Block device 253:9 - - - - - — Logical volume — - LV Path dev/bd-vg-thin/081b01d1-1436-4306-9baf-41c7bf5a2c73 - LV Name 081b01d1-1436-4306-9baf-41c7bf5a2c73 - VG Name bd-vg-thin - LV UUID coxpTY-2UZl-9293-8H2X-eAZn-wSp6-csZIeB - LV Write Access read/write - LV Creation host, time node, 2013-11-26 16:43:19 +0530 - LV Pool name lvol0 - LV Status available - # open 0 - LV Size 256.00 MiB - Mapped size 0.00% - Current LE 64 - Segments 1 - Allocation inherit - Read ahead sectors auto - Block device 253:10 - - - - - -As can be seen from above, creation of a file resulted in creation of a thin LV in the brick. - - -###Improvisation on BD translator: - -First version of BD xlator ( block backend) had few limitations such as - -* Creation of directories not supported -* Supports only single brick -* Does not use extended attributes (and client gfid) like posix xlator -* Creation of special files (symbolic links, device nodes etc) not - supported - -Basic limitation of not allowing directory creation was blocking -oVirt/VDSM to consume BD xlator as part of Gluster domain since VDSM -creates multi-level directories when GlusterFS is used as storage -backend for storing VM images. - -To overcome these limitations a new BD xlator with following -improvements are implemented. - -* New hybrid BD xlator that handles both regular files and block device - files -* The volume will have both POSIX and BD bricks. Regular files are - created on POSIX bricks, block devices are created on the BD brick (VG) -* BD xlator leverages exiting POSIX xlator for most POSIX calls and - hence sits above the POSIX xlator -* Block device file is differentiated from regular file by an extended - attribute -* The xattr 'user.glusterfs.bd' (BD_XATTR) plays a role in mapping a - posix file to Logical Volume (LV). -* When a client sends a request to set BD_XATTR on a posix file, a new - LV is created and mapped to posix file. So every block device will - have a representative file in POSIX brick with 'user.glusterfs.bd' - (BD_XATTR) set. -* Here after all operations on this file results in LV related - operations. - -For example, opening a file that has BD_XATTR set results in opening -the LV block device, reading results in reading the corresponding LV -block device. - -When BD xlator gets request to set BD_XATTR via setxattr call, it -creates a LV and information about this LV is placed in the xattr of the -posix file. xattr "user.glusterfs.bd" used to identify that posix file -is mapped to BD. - -Usage: -Server side: - - [root@host1 ~]# gluster volume create bdvol host1:/storage/vg1_info?vg1 host2:/storage/vg2_info?vg2 - -It creates a distributed gluster volume 'bdvol' with Volume Group vg1 -using posix brick /storage/vg1_info in host1 and Volume Group vg2 using -/storage/vg2_info in host2. - - - [root@host1 ~]# gluster volume start bdvol - -Client side: - - [root@node ~]# mount -t glusterfs host1:/bdvol /media - [root@node ~]# touch /media/posix - -It creates regular posix file 'posix' in either host1:/vg1 or host2:/vg2 brick - - [root@node ~]# mkdir /media/image - - [root@node ~]# touch /media/image/lv1 - - -It also creates regular posix file 'lv1' in either host1:/vg1 or -host2:/vg2 brick - - [root@node ~]# setfattr -n "user.glusterfs.bd" -v "lv" /media/image/lv1 - - [root@node ~]# - - -Above setxattr results in creating a new LV in corresponding brick's VG -and it sets 'user.glusterfs.bd' with value 'lv:<default-extent-size'' - - - [root@node ~]# truncate -s5G /media/image/lv1 - - -It results in resizig LV 'lv1'to 5G - -New BD xlator code is placed in `xlators/storage/bd` directory. - -Also add volume-uuid to the VG so that same VG cannot be used for other -bricks/volumes. After deleting a gluster volume, one has to manually -remove the associated tag using vgchange <vg-name> --deltag -`<trusted.glusterfs.volume-id:<volume-id>>` - - -#### Exposing volume capabilities - -With multiple storage translators (posix and bd) being supported in GlusterFS, it becomes -necessary to know the volume type so that user can issue appropriate calls that are relevant -only to the a given volume type. Hence there needs to be a way to expose the type of -the storage translator of the volume to the user. - -BD xlator is capable of providing server offloaded file copy, server/storage offloaded -zeroing of a file etc. This capabilities should be visible to the client/user, so that these -features can be exploited. - -BD xlator exports capability information through gluster volume info (and --xml) output. For eg: - -`snip of gluster volume info output for a BD based volume` - - Xlator 1: BD - Capability 1: thin - -`snip of gluster volume info --xml output for a BD based volume` - - <xlators> - <xlator> - <name>BD</name> - <capabilities> - <capability>thin</capability> - </capabilities> - </xlator> - </xlators> - -But this capability information should also exposed through some other means so that a host -which is not part of Gluster peer could also avail this capabilities. - -* Type - -BD translator supports both regular files and block device, i,e., one can create files on -GlusterFS volume backed by BD translator and this file could end up as regular posix file or -a logical volume (block device) based on the user''s choice. User can do a setxattr on the -created file to convert it to a logical volume. - -Users of BD backed volume like QEMU would like to know that it is working with BD type of volume -so that it can issue an additional setxattr call after creating a VM image on GlusterFS backend. -This is necessary to ensure that the created VM image is backed by LV instead of file. - -There are different ways to expose this information (BD type of volume) to user. -One way is to export it via a `getxattr` call. That said, When a client issues getxattr("volume_type") -on a root gfid, bd xlator will return 1 implying its BD xlator. But posix xlator will return ENODATA -and client code can interpret this as posix xlator. Also capability list can be returned via -getxattr("caps") for root gfid. - -* Capabilities - -BD xlator supports new features such as server offloaded file copy, thin provisioned VM images etc. - -There is no standard way of exploiting these features from client side (such as syscall -to exploit server offloaded copy). So these features need to be exported to the client so that -they can be used. BD xlator latest version exports these capabilities information through -gluster volume info (and --xml) output. But if a client is not part of GlusterFS peer -it can''t run volume info command to get the list of capabilities of a given GlusterFS volume. -For example, GlusterFS block driver in qemu need to get the capability list so that these features are used. - - - -Parts of this documentation were originally published here -#http://raobharata.wordpress.com/2013/11/27/glusterfs-block-device-translator/ diff --git a/doc/developer-guide/brickmux-thread-reduction.md b/doc/developer-guide/brickmux-thread-reduction.md new file mode 100644 index 00000000000..7d76e8ff579 --- /dev/null +++ b/doc/developer-guide/brickmux-thread-reduction.md @@ -0,0 +1,64 @@ +# Resource usage reduction in brick multiplexing + +Each brick is regresented with a graph of translators in a brick process. +Each translator in the graph has its own set of threads and mem pools +and other system resources allocations. Most of the times all these +resources are not put to full use. Reducing the resource consumption +of each brick is a problem in itself that needs to be addressed. The other +aspect to it is, sharing of resources across brick graph, this becomes +critical in brick multiplexing scenario. In this document we will be discussing +only about the threads. + +If a brick mux process hosts 50 bricks there are atleast 600+ threads created +in that process. Some of these are global threads that are shared by all the +brick graphs, and others are per translator threads. The global threads like +synctask threads, timer threads, sigwaiter, poller etc. are configurable and +do not needs to be reduced. The per translator threads keeps growing as the +number of bricks in the process increases. Each brick spawns atleast 10+ +threads: +- io-threads +- posix threads: + 1. Janitor + 2. Fsyncer + 3. Helper + 4. aio-thread +- changelog and bitrot threads(even when the features are not enabled) + +## io-threads + +io-threads should be made global to the process, having 16+ threads for +each brick does not make sense. But io-thread translator is loaded in +the graph, and the position of io-thread translator decides from when +the fops will be parallelised across threads. We cannot entirely move +the io-threads to libglusterfs and say the multiplexing happens from +the master translator or so. Hence, the io-thread orchestrator code +is moved to libglusterfs, which ensures there is only one set of +io-threads that is shared among the io-threads translator in each brick. +This poses performance issues due to lock-contention in the io-threds +layer. This also shall be addressed by having multiple locks instead of +one global lock for io-threads. + +## Posix threads +Most of the posix threads execute tasks in a timely manner, hence it can be +replaced with a timer whose handler register a task to synctask framework, once +the task is complete, the timer is registered again. With this we can eliminate +the need of one thread for each task. The problem with using synctasks is +the performance impact it will have due to make/swapcontext. For task that +does not involve network wait, we need not do makecontext, instead the task +function with arg can be stored and executed when a synctask thread is free. +We need to implement an api in synctask to execute atomic tasks(no network wait) +without the overhead of make/swapcontext. This will solve the performance +impact associated with using synctask framework. + +And the other challenge, is to cancel all the tasks pending from a translator. +This is important to cleanly detach brick. For this, we need to implement an +api in synctask that can cancel all the tasks from a given translator. + +For future, this will be replced to use global thread-pool(once implemented). + +## Changelog and bitrot threads + +In the initial implementation, the threads are not created if the feature is +not enabled. We need to share threads across changelog instances if we plan +to enable these features in brick mux scenario. + diff --git a/doc/developer-guide/coding-standard.md b/doc/developer-guide/coding-standard.md index 7c1beddc2d5..031c6c0da99 100644 --- a/doc/developer-guide/coding-standard.md +++ b/doc/developer-guide/coding-standard.md @@ -6,23 +6,23 @@ Before you get started Before starting with other part of coding standard, install `clang-format` On Fedora: - +``` $ dnf install clang - +``` On debian/Ubuntu: - +``` $ apt-get install clang - +``` Once you are done with all the local changes, you need to run below set of commands, before submitting the patch for review. - - $ git add $file # if any - $ git commit -a -s -m "commit message" - $ git show --pretty="format:" --name-only | grep -v "contrib/" | egrep "*\.[ch]$" | xargs clang-format -i - $ git diff # see if there are any changes - $ git commit -a --amend # get the format changes done - $ ./submit-for-review.sh - +``` +$ git add $file # if any +$ git commit -a -s -m "commit message" +$ git show --pretty="format:" --name-only | grep -v "contrib/" | egrep "*\.[ch]$" | xargs clang-format -i +$ git diff # see if there are any changes +$ git commit -a --amend # get the format changes done +$ ./submit-for-review.sh +``` Structure definitions should have a comment per member @@ -366,6 +366,37 @@ strcpy (entry_path, real_path); strncpy (entry_path, real_path, entry_path_len); ``` +Do not use memset prior to sprintf/snprintf/vsnprintf etc... +------------------------------------------------------------ +snprintf(and other similar string functions) terminates the buffer with a +'\0'(null character). Hence, there is no need to do a memset before using +snprintf. (Of course you need to account one extra byte for the null character +in your allocation). + +Note: Similarly if you are doing pre-memory allocation for the buffer, use +GF_MALLOC instead of GF_CALLOC, since the later is bit costlier. + +*Bad:* + +``` +char buffer[x]; +memset (buffer, 0, x); +bytes_read = snprintf (buffer, sizeof buffer, "bad standard"); +``` + +*Good:* +``` +char buffer[x]; +bytes_read = snprintf (buffer, sizeof (buffer), "good standard"); +``` + +And it is always to good initialize the char array if the string is static. + +E.g. +``` +char buffer[] = "good standard"; +``` + No dead or commented code ------------------------- @@ -589,8 +620,8 @@ If a value isn't supposed/expected to change, there's no cost to adding a ### Avoid global variables (including 'static' auto variables) Almost all state in Gluster is contextual and should be contained in the -appropriate structure reflecting its scope (e.g. call\_frame\_t, call\_stack\_t, -xlator\_t, glusterfs\_ctx\_t). With dynamic loading and graph switches in play, +appropriate structure reflecting its scope (e.g. `call\_frame\_t`, `call\_stack\_t`, +`xlator\_t`, `glusterfs\_ctx\_t`). With dynamic loading and graph switches in play, each global requires careful consideration of when it should be initialized or reinitialized, when it might _accidentally_ be reinitialized, when its value might become stale, and so on. A few global variables are needed to serve as diff --git a/doc/developer-guide/commit-guidelines.md b/doc/developer-guide/commit-guidelines.md index 9b191dac178..38bbe525cbd 100644 --- a/doc/developer-guide/commit-guidelines.md +++ b/doc/developer-guide/commit-guidelines.md @@ -118,7 +118,7 @@ The 'bug' line can reference a bug in a few ways. Gerrit creates a link to the b **Updates: bz#1193929** -- use 'Updates: bz#NNNN' if the commit is only a partial fix and more work is needed. **Updates: #175** -- use 'Updates: #NNNN' if the commit is only a partial fix and more work is needed for the feature completion. -We encourage the use of Co-Authored-By: name <name@example.com> in commit messages to indicate people who worked on a particular patch. It's a convention for recognizing multiple authors, and our projects would encourage the stats tools to observe it when collecting statistics. +We encourage the use of `Co-Authored-By: name <name@example.com>` in commit messages to indicate people who worked on a particular patch. It's a convention for recognizing multiple authors, and our projects would encourage the stats tools to observe it when collecting statistics. ### Summary of Git commit message structure diff --git a/doc/developer-guide/datastructure-inode.md b/doc/developer-guide/datastructure-inode.md index a340ab9ca8e..45d7a941e5f 100644 --- a/doc/developer-guide/datastructure-inode.md +++ b/doc/developer-guide/datastructure-inode.md @@ -1,6 +1,6 @@ -#Inode and dentry management in GlusterFS: +# Inode and dentry management in GlusterFS: -##Background +## Background Filesystems internally refer to files and directories via inodes. Inodes are unique identifiers of the entities stored in a filesystem. Whenever an application has to operate on a file/directory (read/modify), the filesystem @@ -41,11 +41,10 @@ struct _inode_table { }; ``` -#Life-cycle +# Life-cycle ``` - inode_table_new (size_t lru_limit, xlator_t *xl) - +``` This is a function which allocates a new inode table. Usually the top xlators in the graph such as protocol/server (for bricks), fuse and nfs (for fuse and nfs mounts) and libgfapi do inode managements. Hence they are the ones which will @@ -59,11 +58,8 @@ new inode table. Thus an allocated inode table is destroyed only when the filesystem daemon is killed or unmounted. -``` - -#what it contains. -``` +# what it contains. Inode table in glusterfs mainly contains a hash table for maintaining inodes. In general a file/directory is considered to be existing if there is a corresponding inode present in the inode table. If a inode for a file/directory @@ -76,21 +72,21 @@ size of the hash table (as of now it is hard coded to 14057. The hash value of a inode is calculated using its gfid). Apart from the hash table, inode table also maintains 3 important list of inodes -1) Active list: +1. Active list: Active list contains all the active inodes (i.e inodes which are currently part of some fop). -2) Lru list: +2. Lru list: Least recently used inodes list. A limit can be set for the size of the lru list. For bricks it is 16384 and for clients it is infinity. -3) Purge list: +3. Purge list: List of all the inodes which have to be purged (i.e inodes which have to be deleted from the inode table due to unlink/rmdir/forget). And at last it also contains the mem-pool for allocating inodes, dentries so that frequent malloc/calloc and free of the data structures can be avoided. -``` -#Data structure (inode) + +# Data structure (inode) ``` struct _inode { inode_table_t *table; /* the table this inode belongs to */ @@ -108,7 +104,7 @@ struct _inode { struct _inode_ctx *_ctx; /* place holder for keeping the information about the inode by different xlators */ }; - +``` As said above, inodes are internal way of identifying the files/directories. A inode uniquely represents a file/directory. A new inode is created whenever a create/mkdir/symlink/mknod operations are performed. Apart from that a new inode @@ -128,9 +124,9 @@ inodes are those inodes whose refcount is greater than zero. Whenever some operation comes on a file/directory, and the resolver tries to find the inode for it, it increments the refcount of the inode before returning the inode. The refcount of an inode can be incremented by calling the below function - +``` inode_ref (inode_t *inode) - +``` Any xlator which wants to operate on a inode as part of some fop (or wants the inode in the callback), should hold a ref on the inode. Once the fop is completed before sending the reply of the fop to the above @@ -139,18 +135,18 @@ zero, it is removed from the active inodes list and put into LRU list maintained by the inode table. Thus in short if some fop is happening on a file/directory, the corresponding inode will be in the active list or it will be in the LRU list. -``` -#Life Cycle + +# Life Cycle A new inode is created whenever a new file/directory/symlink is created OR a successful lookup of an existing entry is done. The xlators which does inode management (as of now protocol/server, fuse, nfs, gfapi) will perform inode_link operation upon successful lookup or successful creation of a new entry. - +``` inode_link (inode_t *inode, inode_t *parent, const char *name, struct iatt *buf); - +``` inode_link actually adds the inode to the inode table (to be precise it adds the inode to the hash table maintained by the inode table. The hash value is calculated based on the gfid). Copies the gfid to the inode (the gfid is @@ -160,7 +156,7 @@ A inode is removed from the inode table and eventually destroyed when unlink or rmdir operation is performed on a file/directory, or the the lru limit of the inode table has been exceeded. -#Data structure (dentry) +# Data structure (dentry) ``` struct _dentry { @@ -170,22 +166,22 @@ struct _dentry { char *name; /* name of the directory entry */ inode_t *parent; /* directory of the entry */ }; - +``` A dentry is the presence of an entry for a file/directory within its parent directory. A dentry usually points to the inode to which it belongs to. In glusterfs a dentry contains the following fields. -1) a hook using which it can add itself to the list of +1. a hook using which it can add itself to the list of the dentries maintained by the inode to which it points to. -2) A hash table pointer. -3) Pointer to the inode to which it belongs to. -4) Name of the dentry -5) Pointer to the inode of the parent directory in which the dentry is present +2. A hash table pointer. +3. Pointer to the inode to which it belongs to. +4. Name of the dentry +5. Pointer to the inode of the parent directory in which the dentry is present A new dentry is created when a new file/directory/symlink is created or a hard link to an existing file is created. - +``` __dentry_create (inode_t *inode, inode_t *parent, const char *name); - +``` A dentry holds a refcount on the parent directory so that the parent inode is never removed from the active inode's list and put to the lru list (If the lru limit of the lru list is exceeded, there is @@ -212,15 +208,14 @@ deleted due to file removal or lru limit being exceeded the inode is retired purge list maintained by the inode table), the nlookup count is set to 0 via inode_forget api. The inode table, then prunes all the inodes from the purge list by destroying the inode contexts maintained by each xlator. - +``` unlinking of the dentry is done via inode_unlink; void inode_unlink (inode_t *inode, inode_t *parent, const char *name); - +``` If the inode has multiple hard links, then the unlink operation performed by the application results just in the removal of the dentry with the name provided by the application. For the inode to be removed, all the dentries of the inode should be unlinked. -``` diff --git a/doc/developer-guide/datastructure-iobuf.md b/doc/developer-guide/datastructure-iobuf.md index 5f521f1485f..03604e3672c 100644 --- a/doc/developer-guide/datastructure-iobuf.md +++ b/doc/developer-guide/datastructure-iobuf.md @@ -1,6 +1,6 @@ -#Iobuf-pool -##Datastructures -###iobuf +# Iobuf-pool +## Datastructures +### iobuf Short for IO Buffer. It is one allocatable unit for the consumers of the IOBUF API, each unit hosts @page_size(defined in arena structure) bytes of memory. As initial step of processing a fop, the IO buffer passed onto GlusterFS by the @@ -28,7 +28,7 @@ struct iobuf { }; ``` -###iobref +### iobref There may be need of multiple iobufs for a single fop, like in vectored read/write. Hence multiple iobufs(default 16) are encapsulated under one iobref. ``` @@ -40,7 +40,7 @@ struct iobref { int used; /* number of iobufs added to this iobref */ }; ``` -###iobuf_arenas +### iobuf_arenas One region of memory MMAPed from the operating system. Each region MMAPs @arena_size bytes of memory, and hosts @arena_size / @page_size IOBUFs. The same sized iobufs are grouped into one arena, for sanity of access. @@ -77,7 +77,7 @@ struct iobuf_arena { }; ``` -###iobuf_pool +### iobuf_pool Pool of Iobufs. As there may be many Io buffers required by the filesystem, a pool of iobufs are preallocated and kept, if these preallocated ones are exhausted only then the standard malloc/free is called, thus improving the @@ -139,8 +139,8 @@ arenas in the purge list are destroyed only if there is atleast one arena in (e.g: If there is an arena (page_size=128KB, count=32) in purge list, this arena is destroyed(munmap) only if there is an arena in 'arenas' list with page_size=128KB). -##APIs -###iobuf_get +## APIs +### iobuf_get ``` struct iobuf *iobuf_get (struct iobuf_pool *iobuf_pool); @@ -149,7 +149,7 @@ Creates a new iobuf of the default page size(128KB hard coded as of yet). Also takes a reference(increments ref count), hence no need of doing it explicitly after getting iobuf. -###iobuf_get2 +### iobuf_get2 ``` struct iobuf * iobuf_get2 (struct iobuf_pool *iobuf_pool, size_t page_size); @@ -179,7 +179,7 @@ if (requested iobuf size > Max iobuf size in the pool(1MB as of yet)) Also takes a reference(increments ref count), hence no need of doing it explicitly after getting iobuf. -###iobuf_ref +### iobuf_ref ``` struct iobuf *iobuf_ref (struct iobuf *iobuf); @@ -188,7 +188,7 @@ struct iobuf *iobuf_ref (struct iobuf *iobuf); xlator/function/, its a good practice to take a reference so that iobuf is not deleted by the allocator. -###iobuf_unref +### iobuf_unref ``` void iobuf_unref (struct iobuf *iobuf); ``` @@ -203,33 +203,33 @@ Unreference the iobuf, if the ref count is zero iobuf is considered free. Every iobuf_ref should have a corresponding iobuf_unref, and also every iobuf_get/2 should have a correspondning iobuf_unref. -###iobref_new +### iobref_new ``` struct iobref *iobref_new (); ``` Creates a new iobref structure and returns its pointer. -###iobref_ref +### iobref_ref ``` struct iobref *iobref_ref (struct iobref *iobref); ``` Take a reference on the iobref. -###iobref_unref +### iobref_unref ``` void iobref_unref (struct iobref *iobref); ``` Decrements the reference count of the iobref. If the ref count is 0, then unref all the iobufs(iobuf_unref) in the iobref, and destroy the iobref. -###iobref_add +### iobref_add ``` int iobref_add (struct iobref *iobref, struct iobuf *iobuf); ``` Adds the given iobuf into the iobref, it takes a ref on the iobuf before adding it, hence explicit iobuf_ref is not required if adding to the iobref. -###iobref_merge +### iobref_merge ``` int iobref_merge (struct iobref *to, struct iobref *from); ``` @@ -239,13 +239,13 @@ on all the iobufs added to the 'to' iobref. Hence iobref_unref should be performed both on 'from' and 'to' iobrefs (performing iobref_unref only on 'to' will not free the iobufs and may result in leak). -###iobref_clear +### iobref_clear ``` void iobref_clear (struct iobref *iobref); ``` Unreference all the iobufs in the iobref, and also unref the iobref. -##Iobuf Leaks +## Iobuf Leaks If all iobuf_refs/iobuf_new do not have correspondning iobuf_unref, then the iobufs are not freed and recurring execution of such code path may lead to huge memory leaks. The easiest way to identify if a memory leak is caused by iobufs diff --git a/doc/developer-guide/datastructure-mem-pool.md b/doc/developer-guide/datastructure-mem-pool.md index c71aa2a8ddd..225567cbf9f 100644 --- a/doc/developer-guide/datastructure-mem-pool.md +++ b/doc/developer-guide/datastructure-mem-pool.md @@ -1,5 +1,5 @@ -#Mem-pool -##Background +# Mem-pool +## Background There was a time when every fop in glusterfs used to incur cost of allocations/de-allocations for every stack wind/unwind between xlators because stack/frame/*_localt_t in every wind/unwind was allocated and de-allocated. Because of all these system calls in the fop path there was lot of latency and the worst part is that most of the times the number of frames/stacks active at any time wouldn't cross a threshold. So it was decided that this threshold number of frames/stacks would be allocated in the beginning of the process only once. Get one of them from the pool of stacks/frames whenever `STACK_WIND` is performed and put it back into the pool in `STACK_UNWIND`/`STACK_DESTROY` without incurring any extra system calls. The data structures are allocated only when threshold number of such items are in active use i.e. pool is in complete use.% increase in the performance once this was added to all the common data structures (inode/fd/dict etc) in xlators throughout the stack was tremendous. ## Data structure @@ -27,7 +27,7 @@ will be served from here until all the elements in the pool are in use i.e. cold }; ``` -##Life-cycle +## Life-cycle ``` mem_pool_new (data_type, unsigned long count) @@ -120,5 +120,5 @@ mem_pool_destroy (struct mem_pool *pool) Deletes this pool from the `global_list` maintained by `glusterfs-ctx` and frees all the memory allocated in `mem_pool_new`. -###How to pick pool-size +### How to pick pool-size This varies from work-load to work-load. Create the mem-pool with some random size and run the work-load. Take the statedump after the work-load is complete. In the statedump if `max_alloc` is always less than `cold_count` may be reduce the size of the pool closer to `max_alloc`. On the otherhand if there are lots of `pool-misses` then increase the `pool_size` by `max_stdalloc` to achieve better 'hit-rate' of the pool. diff --git a/doc/developer-guide/dirops-transactions-in-dht.md b/doc/developer-guide/dirops-transactions-in-dht.md index 83f63be3f45..909a97001aa 100644 --- a/doc/developer-guide/dirops-transactions-in-dht.md +++ b/doc/developer-guide/dirops-transactions-in-dht.md @@ -1,3 +1,4 @@ +# dirops transactions in dht Need for transactions during operations on directories arise from two basic design elements of DHT: @@ -269,4 +270,4 @@ And the examples are: * Both _dst_ and _dst/dst_ have same gfid - _gfid-src_. As observed earlier, symptom might be directory listing being incomplete - mkdir (dst) vs renamedir ("src", "dst") - rmdir (src) vs renamedir ("src", "dst") - - rmdir (dst) vs renamedir ("src", "dst")
\ No newline at end of file + - rmdir (dst) vs renamedir ("src", "dst") diff --git a/doc/developer-guide/fuse-interrupt.md b/doc/developer-guide/fuse-interrupt.md new file mode 100644 index 00000000000..ec991b81ec5 --- /dev/null +++ b/doc/developer-guide/fuse-interrupt.md @@ -0,0 +1,211 @@ +# Fuse interrupt handling + +## Conventions followed + +- *FUSE* refers to the "wire protocol" between kernel and userspace and + related specifications. +- *fuse* refers to the kernel subsystem and also to the GlusterFs translator. + +## FUSE interrupt handling spec + +The [Linux kernel FUSE documentation](https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/Documentation/filesystems/fuse.txt?h=v4.18#n148) +desrcibes how interrupt handling happens in fuse. + +## Interrupt handling in the fuse translator + +### Declarations + +This document describes the internal API in the fuse translator with which +interrupt can be handled. + +The API being internal (to be used only in fuse-bridge.c; the functions are +not exported to a header file). + +``` +enum fuse_interrupt_state { + /* ... */ + INTERRUPT_SQUELCHED, + INTERRUPT_HANDLED, + /* ... */ +}; +typedef enum fuse_interrupt_state fuse_interrupt_state_t; +struct fuse_interrupt_record; +typedef struct fuse_interrupt_record fuse_interrupt_record_t; +typedef void (*fuse_interrupt_handler_t)(xlator_t *this, + fuse_interrupt_record_t *); +struct fuse_interrupt_record { + fuse_in_header_t fuse_in_header; + void *data; + /* + ... + */ +}; + +fuse_interrupt_record_t * +fuse_interrupt_record_new(fuse_in_header_t *finh, + fuse_interrupt_handler_t handler); + +void +fuse_interrupt_record_insert(xlator_t *this, fuse_interrupt_record_t *fir); + +gf_boolean_t +fuse_interrupt_finish_fop(call_frame_t *frame, xlator_t *this, + gf_boolean_t sync, void **datap); + +void +fuse_interrupt_finish_interrupt(xlator_t *this, fuse_interrupt_record_t *fir, + fuse_interrupt_state_t intstat, + gf_boolean_t sync, void **datap); +``` + +The code demonstrates the usage of the API through `fuse_flush()`. (It's a +dummy implementation only for demonstration purposes.) Flush is chosen +because a `FLUSH` interrupt is easy to trigger (see +*tests/features/interrupt.t*). Interrupt handling for flush is switched on +by `--fuse-flush-handle-interrupt` (a hidden glusterfs command line flag). +The implementation of flush interrupt is contained in the +`fuse_flush_interrupt_handler()` function and blocks guarded by the + +``` +if (priv->flush_handle_interrupt) { ... +``` + +conditional (where `priv` is a `*fuse_private_t`). + +### Overview + +"Regular" fuse fops and interrupt handlers interact via a list containing +interrupt records. + +If a fop wishes to have its interrupts handled, it needs to set up an +interrupt record and insert it into the list; also when it's to finish +(ie. in its "cbk" stage) it needs to delete the record from the list. + +If no interrupt happens, basically that's all to it - a list insertion +and deletion. + +However, if an interrupt comes for the fop, the interrupt FUSE request +will carry the data identifying an ongoing fop (that is, its `unique`), +and based on that, the interrupt record will be looked up in the list, and +the specific interrupt handler (a member of the interrupt record) will be +called. + +Usually the fop needs to share some data with the interrupt handler to +enable it to perform its task (also shared via the interrupt record). +The interrupt API offers two approaches to manage shared data: +- _Async or reference-counting strategy_: from the point on when the interrupt + record is inserted to the list, it's owned jointly by the regular fop and + the prospective interrupt handler. Both of them need to check before they + return if the other is still holding a reference; if not, then they are + responsible for reclaiming the shared data. +- _Sync or borrow strategy_: the interrupt handler is considered a borrower + of the shared data. The interrupt handler should not reclaim the shared + data. The fop will wait for the interrupt handler to finish (ie., the borrow + to be returned), then it has to reclaim the shared data. + +The user of the interrupt API need to call the following functions to +instrument this control flow: +- `fuse_interrupt_record_insert()` in the fop to insert the interrupt record to + the list; +- `fuse_interrupt_finish_fop()`in the fop (cbk) and +- `fuse_interrupt_finish_interrupt()`in the interrupt handler + +to perform needed synchronization at the end their tenure. The data management +strategies are implemented by the `fuse_interrupt_finish_*()` functions (which +have an argument to specify which strategy to use); these routines take care +of freeing the interrupt record itself, while the reclamation of the shared data +is left to the API user. + +### Usage + +A given FUSE fop can be enabled to handle interrupts via the following +steps: + +- Define a handler function (of type `fuse_interrupt_handler_t`). + It should implement the interrupt handling logic and in the end + call (directly or as async callback) `fuse_interrupt_finish_interrupt()`. + The `intstat` argument to `fuse_interrupt_finish_interrupt` should be + either `INTERRUPT_SQUELCHED` or `INTERRUPT_HANDLED`. + - `INTERRUPT_SQUELCHED` means that the interrupt could not be delivered + and the fop is going on uninterrupted. + - `INTERRUPT_HANDLED` means that the interrupt was actually handled. In + this case the fop will be answered from interrupt context with errno + `EINTR` (that is, the fop should not send a response to the kernel). + + (the enum `fuse_interrupt_state` includes further members, which are reserved + for internal use). + + We return to the `sync` and `datap` arguments later. +- In the `fuse_<FOP>` function create an interrupt record using + `fuse_interrupt_record_new()`, passing the incoming `fuse_in_header` and + the above handler function to it. + - Arbitrary further data can be referred to via the `data` member of the + interrupt record that is to be passed on from fop context to + interrupt context. +- When it's set up, pass the interrupt record to + `fuse_interrupt_record_insert()`. +- In `fuse_<FOP>_cbk` call `fuse_interrupt_finish_fop()`. + - `fuse_interrupt_finish_fop()` returns a Boolean according to whether the + interrupt was handled. If it was, then the FUSE request is already + answered and the stack gets destroyed in `fuse_interrupt_finish_fop` so + `fuse_<FOP>_cbk()` can just return (zero). Otherwise follow the standard + cbk logic (answer the FUSE request and destroy the stack -- these are + typically accomplished by `fuse_err_cbk()`). +- The last two argument of `fuse_interrupt_finish_fop()` and + `fuse_interrupt_finish_interrupt()` are `gf_boolean_t sync` and + `void **datap`. + - `sync` represents the strategy for freeing the interrupt record. The + interrupt handler and the fop handler are in race to get at the interrupt + record first (interrupt handler for purposes of doing the interrupt + handling, fop handler for purposes of deactivating the interrupt record + upon completion of the fop handling). + - If `sync` is true, then the fop handler will wait for the interrupt + handler to finish and it takes care of freeing. + - If `sync` is false, the loser of the above race will perform freeing. + + Freeing is done within the respective interrupt finish routines, except + for the `data` field of the interrupt record; with respect to that, see + the discussion of the `datap` parameter below. The strategy has to be + consensual, that is, `fuse_interrupt_finish_fop()` and + `fuse_interrupt_finish_interrupt()` must pass the same value for `sync`. + If dismantling the resources associated with the interrupt record is + simple, `sync = _gf_false` is the suggested choice; `sync = _gf_true` can + be useful in the opposite case, when dismantling those resources would + be inconvenient to implement in two places or to enact in non-fop context. + - If `datap` is `NULL`, the `data` member of the interrupt record will be + freed within the interrupt finish routine. If it points to a valid + `void *` pointer, and if caller is doing the cleanup (see `sync` above), + then that pointer will be directed to the `data` member of the interrupt + record and it's up to the caller what it's doing with it. + - If `sync` is true, interrupt handler can use `datap = NULL`, and + fop handler will have `datap` point to a valid pointer. + - If `sync` is false, and handlers pass a pointer to a pointer for + `datap`, they should check if the pointed pointer is NULL before + attempting to deal with the data. + +### FUSE answer for the interrupted fop + +The kernel acknowledges a successful interruption for a given FUSE request +if the filesystem daemon answers it with errno EINTR; upon that, the syscall +which induced the request will be abruptly terminated with an interrupt, rather +than returning a value. + +In glusterfs, this can be arranged in two ways. + +- If the interrupt handler wins the race for the interrupt record, ie. + `fuse_interrupt_finish_fop()` returns true to `fuse_<FOP>_cbk()`, then, as + said above, `fuse_<FOP>_cbk()` does not need to answer the FUSE request. + That's because then the interrupt handler will take care about answering + it (with errno EINTR). +- If `fuse_interrupt_finish_fop()` returns false to `fuse_<FOP>_cbk()`, then + this return value does not inform the fop handler whether there was an interrupt + or not. This return value occurs both when fop handler won the race for the + interrupt record against the interrupt handler, and when there was no interrupt + at all. + + However, the internal logic of the fop handler might detect from other + circumstances that an interrupt was delivered. For example, the fop handler + might be sleeping, waiting for some data to arrive, so that a premature + wakeup (with no data present) occurs if the interrupt handler intervenes. In + such cases it's the responsibility of the fop handler to reply the FUSE + request with errro EINTR. diff --git a/doc/developer-guide/identifying-resource-leaks.md b/doc/developer-guide/identifying-resource-leaks.md index 851fc4424bc..950cae79b0a 100644 --- a/doc/developer-guide/identifying-resource-leaks.md +++ b/doc/developer-guide/identifying-resource-leaks.md @@ -174,3 +174,27 @@ In this case, the resource leak can be addressed by adding a single line to the Running the same Valgrind command and comparing the output will show that the memory leak in `xlators/meta/src/meta.c:init` is not reported anymore. + +### Running DRD, the Valgrind thread error detector + +When configuring GlusterFS with: + +```shell +./configure --enable-valgrind +``` + +the default Valgrind tool (Memcheck) is enabled. But it's also possble to select +one of Memcheck or DRD by using: + +```shell +./configure --enable-valgrind=memcheck +``` + +or: + +```shell +./configure --enable-valgrind=drd +``` + +respectively. When using DRD, it's recommended to consult +https://valgrind.org/docs/manual/drd-manual.html before running. diff --git a/doc/developer-guide/network_compression.md b/doc/developer-guide/network_compression.md index 7327591ef63..1222a765276 100644 --- a/doc/developer-guide/network_compression.md +++ b/doc/developer-guide/network_compression.md @@ -1,9 +1,9 @@ -#On-Wire Compression + Decompression +# On-Wire Compression + Decompression The 'compression translator' compresses and decompresses data in-flight between client and bricks. -###Working +### Working When a writev call occurs, the client compresses the data before sending it to brick. On the brick, compressed data is decompressed. Similarly, when a readv call occurs, the brick compresses the data before sending it to client. On the @@ -19,7 +19,7 @@ During normal operation, this is the format of data sent over wire: The trailer contains the CRC32 checksum and length of original uncompressed data. This is used for validation. -###Usage +### Usage Turning on compression xlator: @@ -27,7 +27,7 @@ Turning on compression xlator: gluster volume set <vol_name> network.compression on ~~~ -###Configurable parameters (optional) +### Configurable parameters (optional) **Compression level** ~~~ @@ -35,10 +35,10 @@ gluster volume set <vol_name> network.compression.compression-level 8 ~~~ ~~~ -0 : no compression -1 : best speed -9 : best compression --1 : default compression + 0 : no compression + 1 : best speed + 9 : best compression +-1 : default compression ~~~ **Minimum file size** @@ -55,7 +55,7 @@ Other less frequently used parameters include `network.compression.mem-level` and `network.compression.window-size`. More details can about these options can be found by running `gluster volume set help` command. -###Known Issues and Limitations +### Known Issues and Limitations * Compression translator cannot work with striped volumes. * Mount point hangs when writing a file with write-behind xlator turned on. To @@ -65,7 +65,7 @@ set`performance.strict-write-ordering` to on. distribute volumes. This limitation is caused by AFR not being able to propagate xdata. This issue has been fixed in glusterfs versions > 3.5 -###TODO +### TODO Although zlib offers high compression ratio, it is very slow. We can make the translator pluggable to add support for other compression methods such as [lz4 compression](https://code.google.com/p/lz4/) diff --git a/doc/developer-guide/options-to-contribute.md b/doc/developer-guide/options-to-contribute.md new file mode 100644 index 00000000000..3f0d84e7645 --- /dev/null +++ b/doc/developer-guide/options-to-contribute.md @@ -0,0 +1,212 @@ +# A guide for contributors + +While you have gone through 'how to contribute' guides, if you are +not sure what to work on, but really want to help the project, you +have now landed on the right document :-) + +### Basic + +Instead of planning to fix **all** the below issues in one patch, +we recommend you to have a a constant, continuous flow of improvements +for the project. We recommend you to pick 1 file (or just few files) at +a time to address below issues. +Pick any `.c` (or `.h`) file, and you can send a patch which fixes **any** +of the below themes. Ideally, fix all such occurrences in the file, even +though, the reviewers would review even a single line change patch +from you. + +1. Check for variable definitions, and if there is an array definition, +which is very large at the top of the function, see if you can re-scope +the variable to relevant sections (if it helps). + +Most of the time, some of these arrays may be used for 'error' handling, +and it is possible to use them only in that scope. + +Reference: https://review.gluster.org/20846/ + + +2. Check for complete string initialization at the beginning of a function. +Ideally, there is no reason to initialize a string. Fix it across the file. + +Example: + +`char new_path_name[PATH_MAX] = {0};` to `char new_path_name[PATH_MAX];` + + +3. Change `calloc()` to `malloc()` wherever it makes sense. + +In a case of allocating a structures, where you expect certain (or most of) +variables to be 0 (or NULL), it makes sense to use calloc(). But otherwise, +there is an extra cost to `memset()` the whole object after allocating it. +While it is not a significant improvement in performance, code which gets +hit 1000s of times in a second, it would add some value. + +Reference: https://review.gluster.org/20878/ + + +4. You can consider using `snprintf()`, instead of `strncpy()` while dealing +with strings. + +strncpy() won't null terminate if the dest buffer isn't big enough; snprintf() +does. While most of the string operations in the code is on array, and larger +size than required, strncpy() does an extra copy of 0s at the end of +string till the size of the array. It makes sense to use `snprintf()`, +which doesn't suffer from that behavior. + +Also check the return value from snprintf() for buffer overflow and handle +accordingly + +Reference: https://review.gluster.org/20925/ + + +5. Now, pick a `.h` file, and see if a structure is very large, and see +if re-aligning them as per [coding-standard](./coding-standard.md) gives any size benefit, +if yes, go ahead and change it. Make sure you check all the structures +in the file for similar pattern. + +Reference: [Check this section](https://github.com/gluster/glusterfs/blob/master/doc/developer-guide/coding-standard.md#structure-members-should-be-aligned-based-on-the-padding-requirements + + +### If you are up for more :-) + +Good progress! Glad you are interested to know more. We are surely interested +in next level of contributions from you! + +#### Coverity + +Visit [Coverity Dashboard](https://scan.coverity.com/projects/gluster-glusterfs?tab=overview). + +Now, if the number of defect is not 0, you have an opportunity to contribute. + +You get all the detail on why the particular defect is mentioned there, and +most probable hint on how to fix it. Do it! + +Reference: https://review.gluster.org/21394/ + +Use the same reference Id (789278) as the patch, so we can capture it is in +single bugzilla. + +#### Clang-Scan + +Clang-Scan is a tool which scans the .c files and reports the possible issues, +similar to coverity, but a different tool. Over the years we have seen, they +both report very different set of issues, and hence there is a value in fixing it. + +GlusterFS project gets tested with clang-scan job every night, and the report is +posted in the [job details page](https://build.gluster.org/job/clang-scan/lastCompletedBuild/clangScanBuildBugs/). +As long as the number is not 0 in the report here, you have an opportunity to +contribute! Similar to coverity dashboard, click on 'Details' to find out the +reason behind that report, and send a patch. + +Reference: https://review.gluster.org/21025 + +Again, you can use reference Id (1622665) for these patches! + + +### I am good with programming, I would like to do more than above! + +#### Locked regions / Critical sections + +In the file you open, see if the lock is taken only to increment or decrement +a flag, counter etc. If yes, then recommend you to convert it to ATOMIC locks. +It is simple activity, but, if you know programing, you would know the benefit +here. + +NOTE: There may not always a possibility to do this! You may have to check +with developers first before going ahead. + +Reference: https://review.gluster.org/21221/ + + +#### ASan (address sanitizer) + +[The job](https://build.gluster.org/job/asan/) runs regression with asan builds, +and you can also run glusterfs with asan on your workload to identify the leaks. +If there are any leaks reported, feel free to check it, and send us patch. + +You can also run `valgrind` and let us know what it reports. + +Reference: https://review.gluster.org/21397 + + +#### Porting to different architecture + +This is something which we are not focusing right now, happy to collaborate! + +Reference: https://review.gluster.org/21276 + + +#### Fix 'TODO/FIXME' in codebase + +There are few cases of pending features, or pending validations, which are +pending from sometime. You can pick them in the given file, and choose to +fix it. + + +### I don't know C, but I am interested to contribute in some way! + +You are most welcome! Our community is open for your contribution! First thing +which comes to our mind is **documentation**. Next is, **testing** or validation. + +If you have some hardware, and want to run some performance comparisons with +different version, or options, and help us to tune better is also a great help. + + +#### Documentation + +1. We have some documentation in [glusterfs repo](../), go through these, and +see if you can help us to keep up-to-date. + +2. The https://docs.gluster.org is powered by https://github.com/gluster/glusterdocs +repo. You can check out the repo, and help in keeping that up-to-date. + +3. [Our website](https://gluster.org) is maintained by https://github.com/gluster/glusterweb +repo. Help us to keep this up-to-date, and add content there. + +4. Write blogs about Gluster, and your experience, and make world know little +more about Gluster, and your use-case, and how it helped to solve the problem. + + +#### Testing + +1. There is a regression test suite in glusterfs, which runs with every patch, and is +triggered by just running `./run-tests.sh` from the root of the project repo. + +You can add more test case to match your use-case, and send it as a patch, so you +can make sure all future patches in glusterfs would keep your usecase intact. + +2. [Glusto-Tests](https://github.com/gluster/glusto-tests): This is another testing +framework written for gluster, and makes use of clustered setup to test different +use-cases, and helps to validate many bugs. + + +#### Ansible + +Gluster Organization has rich set of ansible roles, which are actively maintained. +Feel free to check them out here - https://github.com/gluster/gluster-ansible + + +#### Monitoring + +We have prometheus repo, and are actively working on adding more metrics. Add what +you need @ https://github.com/gluster/gluster-prometheus + + +#### Health-Report + +This is a project, where at any given point in time, you want to run some set of +commands locally, and get an output to analyze the status, it can be added. +Contribute @ https://github.com/gluster/gluster-health-report + + +### All these C/bash/python is old-school, I want something in containers. + +We have something for you too :-) + +Please visit our https://github.com/gluster/gcs repo for checking how you can help, +and how gluster can help you in container world. + + +### Note + +For any queries, best way is to contact us through mailing-list, <mailto:gluster-devel@gluster.org> diff --git a/doc/developer-guide/syncop.md b/doc/developer-guide/syncop.md index 4e30451f30e..bcc8bd08e01 100644 --- a/doc/developer-guide/syncop.md +++ b/doc/developer-guide/syncop.md @@ -1,4 +1,4 @@ -#syncop framework +# syncop framework A coroutines-based, cooperative multi-tasking framework. ## Topics diff --git a/doc/developer-guide/thread-naming.md b/doc/developer-guide/thread-naming.md index 204cd7681b4..513140d4437 100644 --- a/doc/developer-guide/thread-naming.md +++ b/doc/developer-guide/thread-naming.md @@ -29,10 +29,10 @@ gf_thread_create_detached (pthread_t *thread, As max name length for a thread in POSIX is only 16 characters including the '\0' character, you have to be a little creative with naming. Also, it is important that all Gluster threads have common prefix. Considering these -conditions, we have "gluster" as prefix for all the threads created by these +conditions, we have "glfs_" as prefix for all the threads created by these wrapper functions. It is responsibility of the owner of thread to provide the suffix part of the name. It does not have to be a descriptive name, as it has -only 8 letters to work with. However, it should be unique enough such that it +only 10 letters to work with. However, it should be unique enough such that it can be matched with a table which describes it. If n number of threads are spwaned to perform same function, it is must that the @@ -87,6 +87,7 @@ such that it can be matched with a table below without ambiguity. - posixfsy - posix fsync - posixhc - posix heal - posixjan - posix janitor +- posixrsv - posix reserve - quiesce - quiesce dequeue - rdmaAsyn - rdma async event handler - rdmaehan - rdma completion handler @@ -99,6 +100,5 @@ such that it can be matched with a table below without ambiguity. - spoller - socket poller - sprocN - syncop worker thread - tbfclock - token bucket filter token generator thread -- tierfixl - tier fix layout - timer - timer thread - upreaper - upcall reaper diff --git a/doc/developer-guide/translator-development.md b/doc/developer-guide/translator-development.md index 3bf7e153354..f75935519f6 100644 --- a/doc/developer-guide/translator-development.md +++ b/doc/developer-guide/translator-development.md @@ -472,7 +472,7 @@ hello Now let's interrupt the process and see where we are. ``` -^C + Program received signal SIGINT, Interrupt. 0x0000003a0060b3dc in pthread_cond_wait@@GLIBC_2.3.2 () from /lib64/libpthread.so.0 @@ -680,4 +680,4 @@ Original author's site: Gluster community site: - * [Translators](http://www.gluster.org/community/documentation/index.php/Translators) + * [Translators](https://docs.gluster.org/en/latest/Quick-Start-Guide/Architecture/#translators) diff --git a/doc/developer-guide/xlator-classification.md b/doc/developer-guide/xlator-classification.md index 36d924d0934..6073df9375f 100644 --- a/doc/developer-guide/xlator-classification.md +++ b/doc/developer-guide/xlator-classification.md @@ -23,7 +23,7 @@ This document is intended for the following community participants, - Existing xlator maintainers - Packaging and gluster management stack maintainers -For a more user facing understanding it is recommended to read section [tbd](TBD) +For a more user facing understanding it is recommended to read section (TBD) in the gluster documentation. ## Categories |