[SOLR-13872] Backup can fail to read index files w/NoSuchFileException during merges (SOLR-11616 regression)

• Type: Bug
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Fix Version/s: 8.4, 9.0
• Assignee: Chris M. Hostetter
• Reporter: Chris M. Hostetter
• Created: 25/Oct/19 00:56
• Updated: 21/Jan/20 17:00
• Resolved: 13/Nov/19 16:58

Description

SOLR-11616 purports to fix a bug in Solr's backup functionality that causes 'NoSuchFileException' errors when attempting to backup an index while it is undergoing indexing (and segment merging)

Although SOLR-11616 is marked with "Fix Version: 7.2" it's pretty easy to demonstrate that this bug still exists on master, branch_8x, and even in 7.2 - so it seems less like the current problem is a "regression" and more that the original fix didn't work.

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The crux of the problem seems to be concurrency bugs in if/how a commit is "reserved" before attempting to copy the files in that commit to the backup location.

A possible work around discussed in more depth in the comments below is to update solrconfig.xml to explicitly configure the SolrDeletionPolicy with either the maxCommitsToKeep or maxCommitAge options to ensure the commits are kept around long enough for the backup to be created.

Issue Links

• is related to: SOLR-11616 Backup failing on a constantly changing index with NoSuchFileException
• is related to: SOLR-13909 Everything about CheckBackupStatus is broken
• relates to: LUCENE-9040 Questionable/Underspecified behavior of DirectoryReader.getIndexCommit() on NRT Readers
• relates to: SOLR-13908 Possible bugs when using HdfsDirectoryFactory w/ softCommit=true + openSearcher=true