MySQL cannot create the operating-system event object needed to interrupt the timer notifier thread, so the server aborts startup with error 40.
MySQL Error 40: EE_FAILED_TO_CREATE_TIMER_NOTIFY_THREAD_INTERRUPT_EVENT appears when the server cannot create an OS interrupt event for its timer thread, usually due to low system resources or OS-level permission limits. Free system resources, increase file-handle limits, then restart the MySQL service to resolve the issue.
Failed to create event to interrupt timer notifier thread (OS errno %d). EE_FAILED_TO_CREATE_TIMER_NOTIFY_THREAD_INTERRUPT_EVENT was added in 8.0.13.
The server raises this global error while initializing its internal event scheduler. MySQL needs an operating-system interrupt event so it can wake the timer notifier thread on demand. When the OS call fails, the server logs error 40 and stops.
The condition was introduced in MySQL 8.0.13, so only 8.x users encounter it.
Fixing the underlying OS problem lets the server complete startup.
The message appears during server startup or restart, before networking is initialised. It can also surface after a crash recovery when MySQL recreates background threads.
Because the failure happens early, no client connections are possible; the instance remains offline until the issue is resolved.
An unusable MySQL instance blocks applications and background jobs. Replication topologies can stall, and monitoring systems trigger outages.
Rapid remediation restores service continuity and protects data availability.
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Yes. A primary or replica that fails to start breaks replication until the server is restarted successfully.
No committed data is lost; the server stops before modifying tables. Regular backups remain safe.
No server-side variable disables the timer notifier. You must fix the OS resource issue.
Galaxy surfaces startup errors immediately in its connection pane and links to documentation, helping teams resolve issues faster.
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