glusterfs.git/geo-replication/syncdaemon/resource.py, branch v7.1

geo-rep: performance improvement while syncing renames with existing gfid

2019-09-25T04:46:37+00:00

Problem:
The bug[1] addresses issue of data inconsistency when handling RENAME with
existing destination. This fix requires some performance tuning considering
this issue occurs in heavy rename workload.

Solution:
If distribution count for master volume is one do not verify op's on
master and go ahead with rename.

The performance improvement with this patch can only be observed if
master volume has distribution count one.

[1]. https://bugzilla.redhat.com/show_bug.cgi?id=1694820

Backport of:

 > Patch: https://review.gluster.org/23459/
 > BUG: 1753857
 > Change-Id: I8e9bcd575e7e35f40f9f78b7961c92dee642f47b
 > Signed-off-by: Sunny Kumar 
(cherry picked from commit 30d3608c43be119f75da7798d88b94601dedcb29)


Change-Id: I8e9bcd575e7e35f40f9f78b7961c92dee642f47b
Signed-off-by: Sunny Kumar 
fixes: bz#1755212

geo-rep: Fix sync hang with tarssh

2019-05-13T11:06:41+00:00

Problem:
Geo-rep sync hangs when tarssh is used as sync
engine at heavy workload.

Analysis and Root cause:
It's found out that the tar process was hung.
When debugged further, it's found out that stderr
buffer of tar process on master was full i.e., 64k.
When the buffer was copied to a file from /proc/pid/fd/2,
the hang is resolved.

This can happen when files picked by tar process
to sync doesn't exist on master anymore. If this count
increases around 1k, the stderr buffer is filled up.

Fix:
The tar process is executed using Popen with stderr as PIPE.
The final execution is something like below.

tar | ssh  root@slave tar --overwrite -xf - -C 

It was waiting on ssh process first using communicate() and then tar.
Note that communicate() reads stdout and stderr. So when stderr of tar
process is filled up, there is no one to read until untar via ssh is
completed. This can't happen and leads to deadlock.
Hence we should be waiting on both process parallely, so that stderr is
read on both processes.

Change-Id: I609c7cc5c07e210c504771115b4d551a2e891adf
fixes: bz#1707728
Signed-off-by: Kotresh HR

geo-rep: Fix sync-method config

2019-05-09T05:18:05+00:00

Problem:
When 'use_tarssh' is set to true, it exits with successful
message but the default 'rsync' was used as sync-engine.
The new config 'sync-method' is not allowed to set from cli.

Analysis and Fix:
The 'use_tarssh' config is deprecated with new
config framework and 'sync-method' is the new
config to choose sync-method i.e. tarssh or rsync.
This patch fixes the 'sync-method' config. The allowed
values are tarssh and rsync.

Change-Id: I0edb0319cad0455b29e49f2f08a64ce324735e84
fixes: bz#1707686
Signed-off-by: Kotresh HR

geo-rep: Fix rename with existing destination with same gfid

2019-04-26T07:15:00+00:00

Problem:
   Geo-rep fails to sync the rename properly if destination exists.
It results in source to be remained on slave causing more number of
files on slave. Also heavy rename workload like logrotate caused
lot of ESTALE errors

Cause:
   Geo-rep fails to sync rename if destination exists if creation
of source file also falls into single batch of changelogs being
processed. This is because, after fixing problematic gfids verifying
from master, while re-processing original entries, CREATE also was
re-processed causing more files on slave and rename to be failed.

Solution:
   Entries need to be removed from retrial list after fixing
problematic gfids on slave so that it's not re-created again on slave.
   Also treat ESTALE as EEXIST so that the error is properly handled
verifying the op on master volume.

Change-Id: I50cf289e06b997adddff0552bf2466d9201dd1f9
fixes: bz#1694820
Signed-off-by: Kotresh HR 
Signed-off-by: Sunny Kumar

geo-rep: Fix syncing multiple rename of symlink

2019-03-29T07:23:41+00:00

Problem:
Geo-rep fails to sync rename of symlink if it's
renamed multiple times if creation and rename
happened successively

Worker crash at slave:
Traceback (most recent call last):
  File "/usr/libexec/glusterfs/python/syncdaemon/repce.py",  in worker
    res = getattr(self.obj, rmeth)(*in_data[2:])
  File "/usr/libexec/glusterfs/python/syncdaemon/resource.py", in entry_ops
    [ESTALE, EINVAL, EBUSY])
  File "/usr/libexec/glusterfs/python/syncdaemon/syncdutils.py", in errno_wrap
    return call(*arg)
  File "/usr/libexec/glusterfs/python/syncdaemon/libcxattr.py", in lsetxattr
    cls.raise_oserr()
  File "/usr/libexec/glusterfs/python/syncdaemon/libcxattr.py", in raise_oserr
    raise OSError(errn, os.strerror(errn))
OSError: [Errno 12] Cannot allocate memory

Geo-rep Behaviour:
1. SYMLINK doesn't record target path in changelog.
   So while syncing SYMLINK, readlink is done on
   master to get target path.

2. Geo-rep will create destination if source is not
   present while syncing RENAME. Hence while syncing
   RENAME of SYMLINK, target path is collected from
   destination.

Cause:
If symlink is created and renamed multiple times, creation of
symlink is ignored, as it's no longer present on master at
that path. While symlink is renamed multiple times at master,
when syncing first RENAME of SYMLINK, both source and destination
is not present, hence target path is not known.  In this case,
while creating destination directly at slave,  regular file
attributes were encoded into blob instead of symlink,
causing failure in gfid-access translator while decoding
blob.

Solution:
While syncing of RENAME of SYMLINK, when target is not known
and when src and destination is not present on the master,
don't create destination. Ignore the rename. It's ok to ignore.
If it's unliked, it's fine.  If it's renamed to something else,
it will be synced then.

Change-Id: Ibdfa495513b7c05b5370ab0b89c69a6802338d87
fixes: bz#1693648
Signed-off-by: Kotresh HR

geo-rep : fix rename sync on hybrid crawl

2019-01-17T10:13:52+00:00

Problem: When geo-rep is configured as hybrid crawl
         directory renames are not synced to the slave.

Solution: Rename sync of directory was failing due to incorrect
          destination path calculation.
          During check for existence on slave we miscalculated
          realpath. .

Change-Id: I23f1ea60e86a917598fe869d5d24f8da654d8a0a
fixes: bz#1665826
Signed-off-by: Sunny Kumar

geo-rep: Fix syncing of files with non-ascii filenames

2018-12-04T09:15:44+00:00

Problem:
Creation of files/directories with non-ascii names fails
to sync to the slave. It crashes with below traceback on
slave.
...
File "/usr/lib/x86_64-linux-gnu/glusterfs/python/syncdaemon/repce.py", line 118, in worker
res = getattr(self.obj, rmeth)(*in_data[2:])
File "/usr/lib/x86_64-linux-gnu/glusterfs/python/syncdaemon/resource.py", line 709, in entry_ops
[ESTALE, EINVAL, EBUSY])
File "/usr/lib/x86_64-linux-gnu/glusterfs/python/syncdaemon/syncdutils.py", line 546, in errno_wrap
return call(*arg)
File "/usr/lib/x86_64-linux-gnu/glusterfs/python/syncdaemon/libcxattr.py", line 83, in lsetxattr
cls.raise_oserr()
File "/usr/lib/x86_64-linux-gnu/glusterfs/python/syncdaemon/libcxattr.py", line 38, in raise_oserr
raise OSError(errn, os.strerror(errn))
OSError: [Errno 12] Cannot allocate memory

Cause:
The length calculation arguments passed to blob creation was done before encoding. Hence
was failing in gfid-access layer.

Fix:
It appears that the calculating lenght properly fixes this issue. But it will cause
issues in other places in 'python2' and not in 'python3'. So encoding and decoding
each required string to make geo-rep compatible with both 'python2' and 'python3'
is a nightmare and is not fool proof. Hence kept 'python2' code as is with out
encode/decode and applied encode/decode only to 'python3'

Added non-ascii filename tests to regression

fixes: bz#1650893
Change-Id: I35cfaf848e07b1a0b5cb93c01b98b472f08271a6
Signed-off-by: Kotresh HR

geo-rep: Fix traceback with symlink metadata sync

2018-11-06T02:22:35+00:00

While syncing metadata, 'os.chmod', 'os.chown',
'os.utime' should be used without de-reference.
But python supports only 'os.chown' without
de-reference. That's mostly because Linux
doesn't support 'chmod' on symlink file itself
but it does support 'chown'.

So while syncing metadata ops, if it's symlink
we should only sync 'chown' and not do 'chmod'
and 'utime'. It will lead to tracebacks with
errors like EROFS, EPERM, ACCESS, ENOENT.
All the three errors (EPERM, ACCESS, ENOENT)
were handled except EROFS. But the way it was
handled was not fool proof. The operation is
tried and failure was handled based on the errors.
All the errors with symlink file for 'chown',
'utime' had to be passed to safe errors list of
'errno_wrap'. This patch handles it better by
avoiding 'chmod' and 'utime' if it's symlink
file.

fixes: bz#1646104
Change-Id: Ic354206455cdc7ab2a87d741d81f4efe1f19d77d
Signed-off-by: Kotresh HR

geo-rep: Fix issue in gfid-conflict-resolution

2018-10-26T09:25:46+00:00

Problem:
During gfid-conflict-resolution, geo-rep crashes
with 'ValueError: list.remove(x): x not in list'

Cause and Analysis:
During gfid-conflict-resolution, the entry blob is
passed back to master along with additional
information to verify it's integrity. If everything
looks fine, the entry creation is ignored and is
deleted from the original list.  But it is crashing
during removal of entry from the list saying entry
not in list. The reason is that the stat information
in the entry blob was modified and sent back to
master if present.

Fix:
Send back the correct stat information for
gfid-conflict-resolution.

fixes: bz#1642865
Change-Id: I47a6aa60b2a495465aa9314eebcb4085f0b1c4fd
Signed-off-by: Kotresh HR

georep: python2 to python3 compat - syscalls

2018-10-08T16:36:04+00:00

1. ctypes/syscalls
    A) arguments is expected to be encoded
    B) Raw conversion of return value from bytearray into string
2. struct pack/unpack - Raw converstion of string to bytearray
3. basestring -> str

Updates: #411
Change-Id: I80f939adcdec0ed0022c87c0b76d057ad5559e5a
Signed-off-by: Kotresh HR