glusterfs-snapshot.git/xlators/cluster/afr, branch development

glusterfs: zerofill support

2013-11-11T05:25:49+00:00

Add support for a new ZEROFILL fop. Zerofill writes zeroes to a file in
the specified range. This fop will be useful when a whole file needs to
be initialized with zero (could be useful for zero filled VM disk image
provisioning or  during scrubbing of VM disk images).

Client/application can issue this FOP for zeroing out. Gluster server
will zero out required range of bytes ie server offloaded zeroing. In
the absence of this fop,  client/application has to repetitively issue
write (zero) fop to the server, which is very inefficient method because
of the overheads involved in RPC calls  and acknowledgements.

WRITESAME is a  SCSI T10 command that takes a block of data as input and
writes the same data to other blocks and this write is handled
completely within the storage and hence is known as offload . Linux ,now
has support for SCSI WRITESAME command which is exposed to the user in
the form of BLKZEROOUT ioctl.  BD Xlator can exploit BLKZEROOUT ioctl to
implement this fop. Thus zeroing out operations can be completely
offloaded to the storage device , making it highly efficient.

The fop takes two arguments offset and size. It zeroes out 'size' number
of bytes in an opened file starting from 'offset' position.

This patch adds zerofill support to the following areas:
	- libglusterfs
	- io-stats
	- performance/md-cache,open-behind
	- quota
	- cluster/afr,dht,stripe
	- rpc/xdr
	- protocol/client,server
	- io-threads
	- marker
	- storage/posix
	- libgfapi

Client applications can exloit this fop by using glfs_zerofill introduced in
libgfapi.FUSE support to this fop has not been added as there is no system call
for this fop.

Changes from previous version 3:
* Removed redundant memory failure log messages

Changes from previous version 2:
* Rebased and fixed build error

Changes from previous version 1:
* Rebased for latest master

TODO :
     * Add zerofill support to trace xlator
     * Expose zerofill capability as part of gluster volume info

Here is a performance comparison of server offloaded zeofill vs zeroing
out using repeated writes.

[root@llmvm02 remote]# time ./offloaded aakash-test log 20

real	3m34.155s
user	0m0.018s
sys	0m0.040s
[root@llmvm02 remote]# time ./manually aakash-test log 20

real	4m23.043s
user	0m2.197s
sys	0m14.457s
[root@llmvm02 remote]# time ./offloaded aakash-test log 25;

real	4m28.363s
user	0m0.021s
sys	0m0.025s
[root@llmvm02 remote]# time ./manually aakash-test log 25

real	5m34.278s
user	0m2.957s
sys	0m18.808s

The argument log is a file which we want to set for logging purpose and
the third argument is size in GB .

As we can see there is a performance improvement of around 20% with this
fop.

Change-Id: I081159f5f7edde0ddb78169fb4c21c776ec91a18
BUG: 1028673
Signed-off-by: Aakash Lal Das 
Signed-off-by: M. Mohan Kumar 
Reviewed-on: http://review.gluster.org/5327
Tested-by: Gluster Build System 
Reviewed-by: Vijay Bellur

cluster/afr: Remove 'max' from the log

2013-10-17T09:26:26+00:00

This patch avoids giving more info to the user about the
internal heuristic employed in afr, for quota sizes.

Change-Id: Ice3a164399f09b6967500ec0c17dc340e7ae9aba
BUG: 1016683
Signed-off-by: Pranith Kumar K 
Reviewed-on: http://review.gluster.org/6098
Reviewed-by: Vijay Bellur 
Tested-by: Vijay Bellur

afr: check for split-brain before proceeding with fops

2013-10-17T02:30:14+00:00

Bail out of fops if split brain has been detected during lookup

Change-Id: Id387dbb1a25eec4a121dedceadc6069bdea24b5d
BUG: 1010834
Signed-off-by: Ravishankar N 
Reviewed-on: http://review.gluster.org/5988
Tested-by: Gluster Build System 
Reviewed-by: Anand Avati

libglusterfs: Add monotonic clocking counter for timer thread

2013-10-15T07:14:57+00:00

gettimeofday() returns the current wall clock time and timezone.
Using these functions in order to measure the passage of time
(how long an operation took) therefore seems like a no-brainer.

This time suffer's from some limitations:

a. They have a low resolution: “High-performance” timing by
definition, requires clock resolutions into the microseconds
or better.

b. They can jump forwards and backwards in time: Computer
clocks all tick at slightly different rates, which causes
the time to drift. Most systems have NTP enabled which
periodically adjusts the system clock to keep them in sync
with “actual” time. The adjustment can cause the clock to
suddenly jump forward (artificially inflating your timing
numbers) or jump backwards (causing your timing calculations
to go negative or hugely positive). In such cases timer
thread could go into an infinite loop.

From 'man gettimeofday':
----------
..
..
The time returned by gettimeofday() is affected by discontinuous
jumps in the system time (e.g., if the system administrator manually
changes the system time).  If you need a monotonically increasing
clock, see clock_gettime(2).
..
..
----------

Rationale:

For calculating interval timing for Timer thread, all that’s
needed should be clock as a simple counter that increments
at a stable rate.

This is necessary to avoid the jumps which are caused by using
"wall time", this counter must be monotonic that can never
“tick” backwards, ever.

Change-Id: I701d31e71a85a73d21a6c5cd15583e7a5a645eeb
BUG: 1017993
Signed-off-by: Harshavardhana 
Reviewed-on: http://review.gluster.org/6070
Tested-by: Gluster Build System 
Reviewed-by: Anand Avati

cluster/afr: [Feature] Command implementation to get heal-count

2013-10-14T21:41:54+00:00

Currently to know the number of files to be healed, either user
has to go to backend and check the number of entries present in
indices/xattrop directory. But if a volume consists of large
number of bricks, going to each backend and counting the number
of entries is a time-taking task. Otherwise user can give
gluster volume heal vol-name info command but with this
approach if no. of entries are very hugh in the indices/
xattrop directory, it will comsume time.

So as a feature, new command is implemented.

Command 1: gluster volume heal vn statistics heal-count
This command will get the number of entries present in
every brick of a volume. The output displays only entries
count.

Command 2: gluster volume heal vn statistics heal-count
           replica 192.168.122.1:/home/user/brickname

           Here if we are concerned with just one replica.
So providing any one of the brick of a replica will get
the number of entries to be healed for that replica only.

Example:
Replicate volume with replica count 2.

Backend status:
--------------
[root@dhcp-0-17 xattrop]# ls -lia | wc -l
1918

NOTE: Out of 1918, 2 entries are  dummy
entries so actual no. of entries to be healed are
1916.

[root@dhcp-0-17 xattrop]# pwd
/home/user/2ty/.glusterfs/indices/xattrop

Command output:
--------------
Gathering count of entries to be healed on volume volume3 has been successful

Brick 192.168.122.1:/home/user/22iu
Status: Brick is Not connected
Entries count is not available

Brick 192.168.122.1:/home/user/2ty
Number of entries: 1916

Change-Id: I72452f3de50502dc898076ec74d434d9e77fd290
BUG: 1015990
Signed-off-by: Venkatesh Somyajulu 
Reviewed-on: http://review.gluster.org/6044
Tested-by: Gluster Build System 
Reviewed-by: Anand Avati

cluster/afr : Implementation of command "gluster volume heal vn statistics"

2013-10-14T21:41:44+00:00

"gluster volume heal volumename statistics" command gives the summary
of the afr crawl done based on the entries present in the xattrop
directory. Whenever afr crawls are attempted, the beginning time of
crawl, end time of crawl, no of files healed, heal-failed count and
number of files in split brain are shown along with the type of the
crawl. If crawl is already in progress then it will give the number
of files healed, heal failed count and number of files in split-brain
from the beginning of the crawl and instead of telling the end time of
the crawl, "CRAWL IN PROGRESS" message will be shown.

Output format:
command: "gluster volume heal volume-name statistics"
Output:
Gathering afr crawl statistics crawl statistics on volume volume-name
has been successful
------------------------------------------------

Crawl statistics for brick no 0
Hostname of brick 192.168.122.248

Starting time of crawl: Wed Jul 10 15:52:38 2013

Ending time of crawl: Wed Jul 10 15:52:38 2013

Type of crawl: INDEX
No. of entries healed: 0
No. of entries in split-brain: 0
No. of heal failed entries: 0

Starting time of crawl: Wed Jul 10 15:52:38 2013

Ending time of crawl: Wed Jul 10 15:52:38 2013

Type of crawl: INDEX
No. of entries healed: 0
No. of entries in split-brain: 0
No. of heal failed entries: 0

------------------------------------------------

Crawl statistics for brick no 1
Hostname of brick 192.168.122.1

Starting time of crawl: Wed Jul 10 15:52:42 2013

Ending time of crawl: Wed Jul 10 15:52:42 2013

Type of crawl: INDEX
No. of entries healed: 0
No. of entries in split-brain: 0
No. of heal failed entries: 0

Starting time of crawl: Wed Jul 10 15:52:42 2013

Ending time of crawl: Wed Jul 10 15:52:42 2013

Type of crawl: INDEX
No. of entries healed: 0
No. of entries in split-brain: 0
No. of heal failed entries: 0

--------------------------------------------------

Change-Id: I10bf9d10b005741db9973fb1352e0dd59ed99aa9
BUG: 949400
Signed-off-by: Venkatesh Somyajulu 
Reviewed-on: http://review.gluster.org/4790
Tested-by: Gluster Build System 
Reviewed-by: Anand Avati

cluster/afr: Handle quota size xattr separately in lookup

2013-10-10T17:38:53+00:00

Quota size xattrs are not maintained by afr. There is a
possibility that they differ even when both the directory
changelog xattrs suggest everything is fine. So if there is at
least one 'source' check among the sources which has the maximum
quota size. Otherwise check among all the available ones for
maximum quota size. This way if there is a source and stale copies
it always votes for the 'source'.

Change-Id: Ia222379cbafa7043dd03f533c105860f2c7b8b0d
BUG: 1016683
Signed-off-by: Pranith Kumar K 
Reviewed-on: http://review.gluster.org/6052
Tested-by: Gluster Build System 
Reviewed-by: Varun Shastry 
Reviewed-by: Anand Avati

cluster/afr: Change Self-heal domain separator to ':'

2013-10-04T04:28:15+00:00

'-' can be present in a volume. This may lead to domain
collisions in future.

Tests:
Checked in gdb that domain comes with ':' separator:

Breakpoint 1, pl_common_inodelk (frame=0x7fdabcce51a4,
this=0x8bde20, volume=0x8b50d0 "r2-replicate-0:self-heal",
inode=0x7fdab822f0e8, cmd=6, flock=0x7fdabc76eee4,
loc=0x7fdabc76ede4, fd=0x0, xdata=0x7fdabc6e0ab0) at inodelk.c:597

Change-Id: I4456ae35ac8bf21e6361c34e9ad437f744a2e84b
BUG: 993981
Signed-off-by: Pranith Kumar K 
Reviewed-on: http://review.gluster.org/6025
Tested-by: Gluster Build System 
Reviewed-by: Anand Avati

Logging : Improved the log message on unlock failure in afr_unlock_inodelk_cbk.

2013-09-30T19:54:17+00:00

"unlock failed on 1 unlock" seems meaningless in the log message. Improved it.

Change-Id: If67d3f9d4aa5310d0b6728a6c89fa58a5cc93d12
BUG: 1012947
Signed-off-by: Anuradha 
Reviewed-on: http://review.gluster.org/6012
Reviewed-by: Pranith Kumar Karampuri 
Tested-by: Gluster Build System

cluster/afr: Have common inode-write-fop cbk

2013-09-18T21:01:52+00:00

Change-Id: Ia7b324b86d6a7051d187106d7a060155e77defc5
BUG: 910217
Signed-off-by: Pranith Kumar K 
Reviewed-on: http://review.gluster.org/5238
Reviewed-by: Ravishankar N 
Tested-by: Gluster Build System 
Reviewed-by: Anand Avati