Thread Pool Exhaustion
criticalResource ContentionUpdated Sep 29, 2025
When active threads approach maximum threads, Tomcat cannot accept new requests, causing HTTP 503 errors and increased latency. This often manifests during traffic spikes or slow request processing.
Sources
How to detect:
Monitor when tomcat_threads_busy approaches tomcat_threads_max (≥80% utilization for warning, ≥90% for critical). Correlate with increasing tomcat_request_time and tomcat_error counts.
Recommended action:
Increase maxThreads in server.xml Connector configuration. Investigate slow requests using tomcat_max_time and tomcat_servlet_max_time to identify bottlenecks. Review thread dumps to identify blocked threads.