MDEV-40545 mariadb-binlog --force-read loops on truncated events - #5784
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Thank you for your contribution! This is a preliminary review.
Please squash your two commits into one. And add a commit message that's compliant to the coding standards, in essence:
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- what was wrong
- how was it fixed
- how is the fix tested.
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With --force-read, a truncated event header could return a synthetic Unknown_log_event without advancing the input position. The local binlog dump loop treated the non-NULL event as successful and repeatedly read the same offset. Detect a successful-looking read that leaves the file position unchanged, delete the synthetic event, and route it through the existing read-error path. Add an MTR regression test using a 17-byte binlog whose event header is truncated. The test verifies that mariadb-binlog reports the read error and exits instead of looping.
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mariadb-binlog --force-read can return a synthetic Unknown_log_event after a truncated event-header read without advancing the input position. dump_local_log_entries() then processes the synthetic event and repeatedly reads the same offset, causing an infinite loop.
This patch detects a non-null event returned without forward progress, deletes it, and routes execution through the existing read-error path. The command now terminates with:
ERROR: Could not read entry at offset 4: Error in log format or read error.
An MTR regression test recreates the malformed loop.001 input and verifies that mariadb-binlog --force-read exits instead of looping.
Tests on the 10.11 branch:
Thanks to Raja Sai Pranav for identifying the non-advancing --force-read path and suggesting the forward-progress guard implemented here.
Jira: https://jira.mariadb.org/browse/MDEV-40545