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https://issues.apache.org/jira/browse/SOLR-15371?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17363861#comment-17363861
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Jason Gerlowski commented on SOLR-15371:
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bq. I may have forgot to mention, but the directory does not get created for
the failing shard
This makes sense I think. The directory corresponding to "location+name" (
{{file:///mnt/solr-backups/search/search-06-14-2021}} in your case) is created
by the overseer node
[here|https://github.com/apache/lucene-solr/blob/branch_8_8/solr/core/src/java/org/apache/solr/cloud/api/collections/BackupCmd.java#L97]
- right before Solr sends any core-level requests to backup the individual
cores. So that location+name base dir should definitely exist - if the
{{createDirectory}} call failed then Solr wouldn't've made any of the per-shard
requests. And it also makes sense that the core-backups that finish
successfully are able to create sub-trees of their own backed up files within
that directory.
I can only think of two things that'd cause the behavior your seeing:
# There is some network blip with your NFS that you don't know about. Or maybe
your NFS isn't set up to guarantee absolutely up-to-date information in terms
of file existence/contents. But you said you've done your due-diligence in
checking for errors of that sort.
# If {{LocalFileSystemRepository.createDirectory}} is synchronous, then it's
impossible for code triggered after that call to report the dir missing. But
if {{LocalFileSystemRepository.createDirectory}} is asynchronous in some way
it's easier to imagine this happening. LFSR.createDirectory is implemented by
a passthrough to
[java.nio.file.Files.createDirectory|https://docs.oracle.com/en/java/javase/11/docs/api/java.base/java/nio/file/Files.html#createDirectory(java.nio.file.Path,java.nio.file.attribute.FileAttribute...)]
- which is well documented and says nothing about asynchronicity. I know the
nio library does support some asynchronous operations so maybe this is one of
those - but most of the information I'm finding online says that directory
operations are synchronous.
Something to dig into I guess.
> Backups randomly fail sometimes
> -------------------------------
>
> Key: SOLR-15371
> URL: https://issues.apache.org/jira/browse/SOLR-15371
> Project: Solr
> Issue Type: Bug
> Security Level: Public(Default Security Level. Issues are Public)
> Components: Backup/Restore
> Affects Versions: 8.5.2, 8.8.2
> Reporter: Roy Perkins
> Priority: Major
>
> Hi, we have an issue where sometimes one shard fails to backup due to what
> might be a race condition in creating the folder/starting the backup. When
> this happens, we have to restart the first server in a shard to get the
> backup to succeed again. The cluster backs up to a shared NFS mount. 4/5
> times the backup goes fine without issues (there is even another collection
> that the backup will run for later in the morning that will succeed fine even
> though it's all the same servers) Below is the error I get.
> {code:java}
> "Response":"Failed to backup core=slprod_shard4_replica_n6 because
> org.apache.solr.common.SolrException: Directory to contain snapshots doesn't
> exist: file:///mnt/solr_backups/slprod/slprod-04-25-2021. Note that
> Backup/Restore of a SolrCloud collection requires a shared file system
> mounted at the same path on all nodes!"},
> {code}
> And below is the line I use to backup with (obviously with bash variables set
> earlier in the script)
> {code:java}
> curl -s
> "http://localhost:8983/solr/admin/collections?action=BACKUP&name=${COLLECTION}-${DATE}&collection=${COLLECTION}&location=${BACKUP_PATH}&async=1000";
> {code}
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