Unexpected 503 Service Unavailable scenarios with Tomcat 9 and Apache Reverse Proxy Configuration
Can someone help me understand I'm migrating some code and I'm experiencing an intermittent `503 Service Unavailable` behavior when accessing my application that is deployed on Tomcat 9, which is behind an Apache HTTP Server acting as a reverse proxy..... While the application generally works as expected, these errors occur sporadically and seem to correlate with high traffic periods. I have configured my Apache server using the following settings: ```apache <VirtualHost *:80> ServerName myapp.example.com ProxyRequests Off ProxyPass / http://localhost:8080/ ProxyPassReverse / http://localhost:8080/ <Proxy *> Order allow,deny Allow from all </Proxy> ErrorLog ${APACHE_LOG_DIR}/myapp-behavior.log CustomLog ${APACHE_LOG_DIR}/myapp-access.log combined </VirtualHost> ``` In Tomcat, I've set the following in `server.xml`: ```xml <Connector port="8080" protocol="HTTP/1.1" connectionTimeout="20000" redirectPort="8443" /> ``` I've checked the Tomcat logs (`catalina.out`) and noticed messages like: ``` SEVERE: The web application [myapp] created a ThreadLocal with key of type [java.lang.ThreadLocal] (value: [java.lang.ThreadLocal@6a8c84f0]) and a value of [com.myapp.MyCustomContext@3e83007] but failed to remove it when the web application was stopped. ``` This seems to suggest a memory leak scenario, but I'm unsure if this is directly related to the 503 errors I'm seeing. I've also tried increasing the memory allocated to Tomcat in `setenv.sh`: ```sh export CATALINA_OPTS="-Xms512m -Xmx1024m" ``` Despite these adjustments, the scenario continues. I suspect it might be caused by insufficient resources during peak times or some configuration oversight in either Tomcat or Apache. Any insights on how to diagnose or resolve these `503` errors would be greatly appreciated! This is my first time working with Java 3.9. Thanks in advance! Thanks in advance!