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https://issues.apache.org/jira/browse/SOLR-18406?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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ASF GitHub Bot updated SOLR-18406:
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Labels: pull-request-available (was: )
> Replication filecontent returns HTTP 500 when the commit reservation expires
> ----------------------------------------------------------------------------
>
> Key: SOLR-18406
> URL: https://issues.apache.org/jira/browse/SOLR-18406
> Project: Solr
> Issue Type: Bug
> Components: replication (java)
> Affects Versions: 8.11.4, 9.10.1
> Reporter: ZhenyuLi
> Priority: Major
> Labels: pull-request-available
> Time Spent: 10m
> Remaining Estimate: 0h
>
> A follower can receive HTTP 500 while downloading an index if the leader
> deletes the requested index generation after filelist completes but before a
> subsequent filecontent request begins.
> Follower index replication consists of separate HTTP requests:
> indexversion
> -> filelist(generation=G)
> -> filecontent(file=X, generation=G)
> -> filecontent(file=Y, generation=G)
> -> ...
> The leader must retain commit G across these requests.
> While a filecontent request is active, the commit is protected with
> saveCommitPoint()/releaseCommitPoint(). Between requests, however, it is only
> protected by a timed reservation. The default commitReserveDuration is 10
> seconds.
> If the follower takes longer than that interval before requesting the next
> file, the reservation expires. A later hard commit on the leader invokes the
> index deletion policy and may delete G. The next filecontent request then
> calls
> saveCommitPoint(G), which throws IllegalStateException.
> This exception is currently exposed as HTTP 500.
> The same stale-generation condition is already handled explicitly by the
> filelist path. filelist catches IllegalStateException from
> getAndSaveCommitPoint(G) and reports:invalid index generation
> The filecontent path does not provide equivalent handling.
> A simplified graph to illustrate:
> Follower fetch thread Test/leader thread
> indexversion -> G
> filelist(G)
> \
> reservation for G expires
> pending update
> hard commit -> G+1
> deletion policy deletes G
> filecontent(G)
> -> saveCommitPoint(G)
> -> IllegalStateException
> -> HTTP 500
> Reproduction
> ============
> The issue does not require a large index. One committed document is
> sufficient.
> 1. Create and hard-commit one document on the leader, producing generation G.
> 2. Submit another update or delete without committing it.
> 3. Start an explicit fetchindex request on the follower.
> 4. Allow the follower to complete indexversion and filelist(G).
> 5. Pause before the first filecontent(G) request.
> 6. Wait until the reservation for G has expired.
> 7. Hard-commit the pending leader update, producing a newer generation and
> allowing the deletion policy to delete G.
> 8. Resume the follower so that it requests filecontent(G).
> The hard commit must occur after the reservation expires. Expiration alone
> does not delete the commit; the subsequent leader commit is what invokes the
> deletion policy.
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