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| author |  Joey Hess <joeyh@joeyh.name> | 2016-05-27 10:39:55 -0400 |
|---|---|---|
| committer | Joey Hess <joeyh@joeyh.name> | 2016-05-27 10:39:55 -0400 |
| commit | 65c1616243d02d7cbd72aa0ba8e14d7685b102bc (patch) | |
| tree | 1d64641326bc877788836c4ac15ce8545c5c9510 /doc/bugs | |
| parent | b0a4229ae1e15d53e4c0ef7982c6b332fec22334 (diff) | |
analysis
Diffstat (limited to 'doc/bugs')
| -rw-r--r-- | doc/bugs/Whereis_reports_same_UUID_multiple_times/comment_2_148e8a83da7f9208ab7e0619b70b7093._comment | 43 |
1 files changed, 43 insertions, 0 deletions
diff --git a/doc/bugs/Whereis_reports_same_UUID_multiple_times/comment_2_148e8a83da7f9208ab7e0619b70b7093._comment b/doc/bugs/Whereis_reports_same_UUID_multiple_times/comment_2_148e8a83da7f9208ab7e0619b70b7093._comment new file mode 100644 index 000000000..2c9b91791 --- /dev/null +++ b/doc/bugs/Whereis_reports_same_UUID_multiple_times/comment_2_148e8a83da7f9208ab7e0619b70b7093._comment @@ -0,0 +1,43 @@ +[[!comment format=mdwn + username="joey" + subject="""comment 2""" + date="2016-05-27T14:26:18Z" + content=""" +Received a clone of this repository (in git-annex-test-repos/annex.bundle +here), and was able to reproduce the bug. + +Looking at one duplicate UUID for one file, I see: + + 1444995510.830128s 1 0866153a-19e5-4382-aeb6-30e8210706cc + 1444995510.830128s 1 0866153a-19e5-4382-aeb6-30e8210706cc + 1444995510.830128s 1 0866153a-19e5-4382-aeb6-30e8210706cc + 1444995510.830128s 1 0866153a-19e5-4382-aeb6-30e8210706cc + 1444995510.830128s 1 0866153a-19e5-4382-aeb6-30e8210706cc + +The notable thing here is not that there are multiple lines for a UUID, but +that they somehow have the *exact* same timestamp down to the +microsecond. + +I'm a) unsure how this could happen and b) afraid that the log file +compaction fails in this case, with catastrophic results. + +Regarding how this could happen, git blame shows a single commit +adding duplicate lines with the same timestamp. Commit message was +"update". The commit touched a wide swath of the repository, including even +non-location-log files like trust.log, which also got duplicate lines with +the same timestamp. + +Some of the lines were entirely new, but some existing lines also +got duplicated. + +There were some duplicate lines before this commit, so it was not an +isolated incident. + +Clearly, log compaction needs to collapse down lines that are identical except +for timestamp. The location log code also needs to throw out all but one +current item for a given uuid, since other code treats each returned location +as a copy, expecting there to not be any duplicate UUIDs. With these changes, +whatever caused these duplicate lines to occur in the first place at least +won't result in weird output or data loss. I have not verified yet if data +loss can actually occur in this case. +"""]] |