If you have encountered an issue of 'Too many open files', you can monitor the open file counts from the following commands.

TID: [-1] [] [202X-0X-XX 10:30:03,426] WARN {org.apache.synapse.transport.passthru.PassThroughHttpSSLListener} - System may be unstable: HTTPS ListeningIOReactor encountered a checked exception : Too many open files {org.apache.synapse.transport.passthru.PassThroughHttpSSLListener} java.io.IOException: Too many open files at sun.nio.ch.ServerSocketChannelImpl.accept0(Native Method) at sun.nio.ch.ServerSocketChannelImpl.accept(ServerSocketChannelImpl.java:424 

Monitor the open file count and the details for specific processes via the below command.

lsof -a -d ^mem -d ^cwd -d ^rtd -d ^txt -d ^DEL -p > out_with_wso2_pid.txt 

Monitor the open file count and the details from all processes running in the VM via the below command.

lsof -a -d ^mem -d ^cwd -d ^rtd -d ^txt -d ^DEL > out_for_all.txt