Always read footer checksum from FileInfo #69428
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Searchable snapshots IndexInput implementations detect read operations that are executed on the last 16 bytes of files which contain the footer checksum, and then serves them from memory (FileInfo) instead of relying on cache mechanisms. But the current implementation expect an exact checksum read: ie a read operation that starts at file length - 16 bytes and expects to read exactly 16 bytes. This is not always the case as IndexInput implementations extend BufferedIndexInput which uses an internal buffer of 1024 bytes: in some case the remaining length (ie, the last portion of the file) might be less than 16 bytes long and thus a very small read is engaged using cache (or direct) read where it could instead be also served from memory.
tlrx
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:Distributed Coordination/Snapshot/Restore
elasticmachine
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Team:Distributed (Obsolete)
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Pinging @elastic/es-distributed (Team:Distributed) |
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Searchable snapshots IndexInput implementations detect
read operations that are executed on the last 16 bytes of
files which contain the footer checksum, and then serves
them from memory (FileInfo) instead of relying on cache
mechanisms.
But the current implementation expect an exact checksum
read: ie a read operation that starts at file length - 16 bytes
and expects to read exactly 16 bytes. This is not always the
case as IndexInput implementations extend
BufferedIndexInput which uses an internal buffer of 1024
bytes: in some case the remaining length (ie, the last portion
of the file) might be less than 16 bytes long and thus a very
small read is engaged using cache (or direct) read where it
could instead be also served from memory.
Backport of #69415