mbwaheed commented on a change in pull request #1055: SOLR-13932 Review
directory locking and Blob interactions
URL: https://github.com/apache/lucene-solr/pull/1055#discussion_r356421777
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File path:
solr/core/src/java/org/apache/solr/store/blob/metadata/CorePushPull.java
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@@ -268,7 +264,7 @@ public void pullUpdateFromBlob(long requestQueuedTimeMs,
boolean waitForSearcher
}
Review comment:
Can't seem to comment on the unchanged lines, therefore, commenting here:
https://github.com/apache/lucene-solr/pull/1055/files?utf8=%E2%9C%93&diff=unified&w=1#diff-d86585f4b79b136f1575702bd7c61e38R226
is not correct, it talks about incorrect understanding of directory locking.
Pull is now an exclusive operation(i.e.no other pull or active indexing
should be happening during this time). If local directory contents have changed
we fail the pull. Therefore:
1. After closing index writer we should obtain an exclusive lock on
directory, similar to
https://github.com/apache/lucene-solr/blob/1133bf98a5fd075173efecfb75a51493fceb62b3/solr/core/src/java/org/apache/solr/update/SolrIndexSplitter.java#L161
2. We should close index writer and acquire write lock in the beginning of
method so that the chances of directory changes(most likely background merges?)
are even less. I am assuming Directory.obtainLock(IndexWriter.WRITE_LOCK_NAME)
would prevent background merges from changing index directory. @yonik can you
please chime in on that understanding?
3. The only purpose of temp directory, I see, is to prevent a partial
download of index(transient network error) from corrupting the index directory.
Otherwise we could have just downloaded directly into index directory. Comments
on temp directory usage need to be updated to reflect that.
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