healthchecks: reference count status file data - #13432
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Thanks for fixing this.
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Replaced file data was retired onto a freelist and freed after a timeout, but its deadline came from a timestamp taken before a blocking inotify read. That stale deadline let transactions retain references to data that was already freed. Files exactly 16 KiB long were also reported as empty because a final zero-byte read overwrote the saved length. This holds each immutable snapshot in an atomic shared_ptr. Every transaction pins its snapshot, so data lives exactly as long as it is referenced, without a freelist or request-path mutex. This also preserves the last successful file-read length and adds AuTest coverage for concurrent replacement and the 16 KiB boundary. Fixes: apache#8735 Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
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Replaced file data was retired onto a freelist and freed after a timeout, but its deadline came from a timestamp taken before a blocking inotify read. That stale deadline let transactions retain references to data that was already freed. Files exactly 16 KiB long were also reported as empty because a final zero-byte read overwrote the saved length. This holds each immutable snapshot in an atomic shared_ptr. Every transaction pins its snapshot, so data lives exactly as long as it is referenced, without a freelist or request-path mutex. This also preserves the last successful file-read length and adds AuTest coverage for concurrent replacement and the 16 KiB boundary. Fixes: #8735 (cherry picked from commit 16bd59a)
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Cherry-picked to the 10.2.x branch as f1b771c for the 10.2.0 release. |
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Replaced file data was retired onto a freelist and freed after a
timeout, but the deadline was computed from a timestamp taken before
the blocking inotify read. That timestamp is stale by however long the
watcher waited for an event, so the deadline was routinely already in
the past and the data was freed while transactions still referenced it.
The patch addresses this issue by holding the data in a shared_ptr and
letting each transaction pin its own snapshot. The data now lives
exactly as long as it is referenced, which removes both the freelist
and the guess about how long a transaction can last.
Fixes: #8735