mirror of
https://github.com/itflow-org/itflow
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a844d7b428
script and per install. Replaces the mail queue's own lock file, which was not atomic and could be deleted out from under a long run. Bounds the SMTP conversation so an unresponsive server cannot hold the lock. Recovers rows left at Sending by a run that died, which nothing previously picked up.
39 lines
2.0 KiB
PHP
39 lines
2.0 KiB
PHP
<?php
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/*
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* ITFlow - Single-run guard for cron entry points
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*
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* Required by each cron script immediately after its CLI check and before config.php,
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* with the caller setting $cron_lock_script = __FILE__ first.
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*
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* Cron work is not safe to run twice at once: autopay charges cards, the mail queue
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* sends client email, the parser creates tickets. If a run is still going when the next
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* one fires, those actions can happen twice. The lock name is derived from the calling
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* script's full path, so it is unique per script and per install - separate ITFlow
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* instances on one host never block each other, and neither do two different cron
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* scripts belonging to the same install.
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*
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* flock is used rather than a lock file whose presence is checked, because checking for
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* a file and then creating it is not atomic - two runs starting together can both find
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* it absent. flock is also released by the kernel however the process exits, so a killed
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* run leaves nothing stale behind and no age heuristic is needed to clean up after it.
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*
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* Contention is not logged: mail_queue and the email parser run every minute, so hitting
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* a run that is still going is expected, not a fault worth reporting. A lock file that
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* cannot be opened at all is a real misconfiguration and does report loudly.
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*
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* The handle is deliberately left open: the lock is held for the life of the process.
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*/
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$cron_lock_file = sys_get_temp_dir() . '/itflow_cron_' . md5($cron_lock_script) . '.lock';
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$cron_lock_handle = fopen($cron_lock_file, 'c');
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if ($cron_lock_handle === false) {
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die("Cannot open the cron lock file at $cron_lock_file - check permissions and open_basedir.\n");
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}
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if (!flock($cron_lock_handle, LOCK_EX | LOCK_NB)) {
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// Exit silently. On a per-minute schedule, finding a previous run still going is
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// normal operation rather than an error, and anything written to stdout here would
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// be mailed to the crontab owner every single minute for the length of that run.
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exit(0);
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}
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