[Bugs] [Bug 1486120] New: symlinks trigger faulty geo-replication state ( rsnapshot usecase)

[bugzilla at redhat.com]

https://bugzilla.redhat.com/show_bug.cgi?id=1486120

            Bug ID: 1486120
           Summary: symlinks trigger faulty geo-replication state
                    (rsnapshot usecase)
           Product: GlusterFS
           Version: 3.12
         Component: geo-replication
          Keywords: Triaged
          Severity: high
          Assignee: bugs at gluster.org
          Reporter: khiremat at redhat.com
                CC: avishwan at redhat.com, bugs at gluster.org,
                    khiremat at redhat.com, lohmaier+rhbz at gmail.com,
                    ndevos at redhat.com
        Depends On: 1432046
            Blocks: 1431081



+++ This bug was initially created as a clone of Bug #1432046 +++

+++ This bug was initially created as a clone of Bug #1431081 +++
+++                                                           +++
+++ Use this bug to get a fix in the master branch before     +++
+++ backporting it to the maintained versions.                +++

Description of problem:
operations as done by rsnapshot easily trigger faulty geo-replication state

Version-Release number of selected component (if applicable):
3.10, but 3.8 affected the same way

How reproducible:
100%

Steps to Reproduce:
0) create volume on master and slave and setup geo-replication between them
1) mount master volume and cd to it (nfs or fuse doesn't make a difference)
2) simulate a rsnapshot run that updates a symlink like this:

mkdir /tmp/symlinkbug
ln -f -s /does/not/exist /tmp/symlinkbug/a_symlink
rsync -a /tmp/symlinkbug ./
cp -al symlinkbug symlinkbug.0
ln -f -s /does/not/exist2 /tmp/symlinkbug/a_symlink
rsync -a /tmp/symlinkbug ./
cp -al symlinkbug symlinkbug.1

(rsnapshot uses hardlinks between rotations, that's why it is using cp -al)

Actual results:
geo-replication goes to faulty state, and symlinkbug/a_symlink still points to
the old location

Expected results:
geo-replication should update the link destination, and not choke/go into
faulty state on the second cp -al

Additional info:
you can pause in between the steps, add checkpoints and verify those to have
all steps synced separately - doesn't make a difference.

--- Additional comment from Worker Ant on 2017-08-09 06:36:51 EDT ---

REVIEW: https://review.gluster.org/18011 (geo-rep: Fix syncing of hardlink of
symlink) posted (#2) for review on master by Kotresh HR (khiremat at redhat.com)

--- Additional comment from Worker Ant on 2017-08-23 23:13:56 EDT ---

COMMIT: https://review.gluster.org/18011 committed in master by Aravinda VK
(avishwan at redhat.com) 
------
commit e893962deaabab8e934813f8a0443a8f94e009f2
Author: Kotresh HR <khiremat at redhat.com>
Date:   Tue Aug 8 10:12:14 2017 -0400

    geo-rep: Fix syncing of hardlink of symlink

    Problem:
    If there is a hardlink to a symlink on master
    and if the symlink file is deleted on master,
    geo-rep fails to sync the hardlink.

    Typical Usecase:
    It's easily hit with rsnapshot use case where
    it uses hardlinks.

    Example Reproducer:
    Setup geo-replication between master and slave
    volume and in master mount point, do the following.

     1. mkdir /tmp/symlinkbug
     2. ln -f -s /does/not/exist /tmp/symlinkbug/a_symlink
     3. rsync -a /tmp/symlinkbug ./
     4. cp -al symlinkbug symlinkbug.0
     5. ln -f -s /does/not/exist2 /tmp/symlinkbug/a_symlink
     6. rsync -a /tmp/symlinkbug ./
     7. cp -al symlinkbug symlinkbug.1

    Cause:
    If the source was not present while syncing hardlink,
    it was always packing the blob as regular file.

    Fix:
    If the source was not present while syncing hardlink,
    pack the blob based on the mode.

    Change-Id: Iaa12d6f99de47b18e0650e7c4eb455f23f8390f2
    BUG: 1432046
    Signed-off-by: Kotresh HR <khiremat at redhat.com>
    Reported-by: Christian Lohmaier <lohmaier+rhbz at gmail.com>
    Reviewed-on: https://review.gluster.org/18011
    Smoke: Gluster Build System <jenkins at build.gluster.org>
    CentOS-regression: Gluster Build System <jenkins at build.gluster.org>
    Reviewed-by: Aravinda VK <avishwan at redhat.com>


Referenced Bugs:

https://bugzilla.redhat.com/show_bug.cgi?id=1431081
[Bug 1431081] symlinks trigger faulty geo-replication state (rsnapshot
usecase)
https://bugzilla.redhat.com/show_bug.cgi?id=1432046
[Bug 1432046] symlinks trigger faulty geo-replication state (rsnapshot
usecase)
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