Fix undefined array key in DeduplicationHandler with concurrent access #2020
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When multiple requests write to the deduplication store file simultaneously, partially written lines can be read by concurrent processes. This causes 'Undefined array key' errors when trying to destructure incomplete lines. Changes: - Skip incomplete/invalid lines in isDuplicate() instead of crashing - Add LOCK_EX flag to file_put_contents() for atomic writes Fixes Seldaek#1950
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Problem
When multiple requests write to the deduplication store file simultaneously, partially written lines can be read by concurrent processes. This causes
Undefined array key 1andUndefined array key 2errors on thelist($timestamp, $level, $message) = explode(':', $store[$i], 3)line inisDuplicate().Solution
isDuplicate()— if a line doesn't have all 3 expected parts afterexplode(), it's skipped instead of causing an error. Worst case: a duplicate notification is sent (acceptable trade-off).LOCK_EXflag tofile_put_contents()when appending to the deduplication store, reducing the chance of partially written lines.Related
Fixes #1950
As suggested by @Seldaek in #1950 (comment)