+++ This bug was initially created as a clone of Bug #1467718 +++ Description of problem: When running iozone, bonnie, smallfiles workload on master, the entry failed to sync to slave with ENOENT on slave (Parent directory does not exist on slave) The errors is like below. [2017-06-16 14:54:26.1849] E [master(/gluster/brick1/brick):785:log_failures] _GMaster: ENTRY FAILED: ({'uid': 0, 'gfid': '4d16fd49-591d-4088-8f87-e75c081ca2f9', 'gid': 0, 'mode': 33152, 'entry': '.gfid/abe8c2f6-210b-4ac3-8c05-a84d44c3b5b1/dovecot.index', 'op': 'MKNOD'}, 2) Version-Release number of selected component (if applicable): mainline How reproducible: Saw only once Steps to Reproduce: 1. Setup geo-rep and run iozone, bonnie, smallfile workload on master Actual results: Entry failure error with ENOENT Expected results: Entry failures should not happen Additional info: --- Additional comment from Kotresh HR on 2017-07-04 15:39:32 EDT --- Analysis: It was seen that the RMDIR followed by MKDIR is recorded in changelog on a particular subvolume with same gfid and pargfid/bname but not on all subvolumes as below. E 61c67a2e-07f2-45a9-95cf-d8f16a5e9c36 RMDIR \ 9cc51be8-91c3-4ef4-8ae3-17596fcfed40%2Ffedora2 E 61c67a2e-07f2-45a9-95cf-d8f16a5e9c36 MKDIR 16877 0 0 \ 9cc51be8-91c3-4ef4-8ae3-17596fcfed40%2Ffedora2 While processing this changelog, geo-rep thinks RMDIR is successful and does recursive rmdir on slave. But in the master the directory still exists. Further entry creation under this directory which hashed to that particular subvol failed with ENOENT. --- Additional comment from Worker Ant on 2017-07-04 15:43:30 EDT --- REVIEW: https://review.gluster.org/17695 (geo-rep: Fix entry failure because parent dir doesn't exist) posted (#1) for review on master by Kotresh HR (khiremat) --- Additional comment from Kotresh HR on 2017-07-04 15:45:16 EDT --- Cause: RMDIR-MKDIR pair gets recorded so in changelog when the directory removal is successful on cached subvolume and failed in one of hashed subvol for some reason (may be down). In this case, the directory is re-created on cached subvol which gets recorded as MKDIR again in changelog. Solution: So while processing RMDIR geo-replication should stat on master with gfid and should not delete it if it's present. --- Additional comment from Worker Ant on 2017-07-05 11:44:27 EDT --- COMMIT: https://review.gluster.org/17695 committed in master by Aravinda VK (avishwan) ------ commit b25bf64f3a3520a96ad557daa4903c0ceba96d72 Author: Kotresh HR <khiremat> Date: Tue Jul 4 08:46:06 2017 -0400 geo-rep: Fix entry failure because parent dir doesn't exist In a distributed volume on master, it can so happen that the RMDIR followed by MKDIR is recorded in changelog on a particular subvolume with same gfid and pargfid/bname but not on all subvolumes as below. E 61c67a2e-07f2-45a9-95cf-d8f16a5e9c36 RMDIR \ 9cc51be8-91c3-4ef4-8ae3-17596fcfed40%2Ffedora2 E 61c67a2e-07f2-45a9-95cf-d8f16a5e9c36 MKDIR 16877 0 0 \ 9cc51be8-91c3-4ef4-8ae3-17596fcfed40%2Ffedora2 While processing this changelog, geo-rep thinks RMDIR is successful and does recursive rmdir on slave. But in the master the directory still exists. This could lead to data discrepancy between master and slave. Cause: RMDIR-MKDIR pair gets recorded so in changelog when the directory removal is successful on cached subvolume and failed in one of hashed subvol for some reason (may be down). In this case, the directory is re-created on cached subvol which gets recorded as MKDIR again in changelog. Solution: So while processing RMDIR geo-replication should stat on master with gfid and should not delete it if it's present. Change-Id: If5da1d6462eb4d9ebe2e88b3a70cc454411a133e BUG: 1467718 Signed-off-by: Kotresh HR <khiremat> Reviewed-on: https://review.gluster.org/17695 Smoke: Gluster Build System <jenkins.org> CentOS-regression: Gluster Build System <jenkins.org> Reviewed-by: Aravinda VK <avishwan>
Its a very corner case and a race between how 2 changelogs are processed during rmdir and mkdir. Following is one of the case: 1. Two Subvolume having dir d1. d1 having files f1,f2 in first subvolume and f3,f4 in second subvolume. 2. rmdir of d1 is issued and mkdir with same name (d1) is issued. New files created with name f5,f6,f7,f8. If rmdir failed on one subvolume (A) for any reason, recursive rmdir is retried. At the same time some of the new files are hashed to different subvolume (B). Once the rmdir is reprocessed at A, it would delete the newly created files at B and will have only the files created after changelog processed mkdir on A.
Proposing as blocker because it can cause a data loss (Or, data miss match) at slave in the specific scenario mentioned at comment 5.
upstream patch : https://review.gluster.org/#/c/17695/
Downstream Patch: https://code.engineering.redhat.com/gerrit/#/c/111301/
There were multiple consequences for this bug: 1. ENTRY Errors in the logs 2. Data loss at the slave (Either the whole directory was missing or few files from it) Was able to reproduce this issue on 3.2.0 (3.8.4-18) build using the following steps: 1. touch dir1 => This is to find which subvolume the file hashes too 2. rm dir1 3. mkdir dir1 and create some files inside it (touch {1..99}) 4. Let it sync to slave 5. Stop the geo-replication 6. Attach gdb to mount pid and breakpoint at dht_rmdir_lock_cbk 7. continue 8. rm -rf dir1/ 9. Kill the complete Hashed subvolume (captured from step 1) 10. continue 11. Start volume with force (bring back bricks) 12. ls /mnt/dir1 13. Wait for dht heal 14. Write some more files into dir/ {touch file{1..99}} 15. Start the geo-replication On 3.2.0_async builds, tried the above use case twice and following were results: 1. In first instance some of the files were missing from slave 2. In second instance directory dir1 was missing from slave and Entry failures were reported Tried the same case with build: glusterfs-geo-replication-3.8.4-37.el7rhgs.x86_64 In both the iterations, the files were properly synced to slave without any Entry errors in the logs. Moving this bug to verified state
Since the problem described in this bug report should be resolved in a recent advisory, it has been closed with a resolution of ERRATA. For information on the advisory, and where to find the updated files, follow the link below. If the solution does not work for you, open a new bug report. https://access.redhat.com/errata/RHBA-2017:2774