Apache Tomac Web Server and LOG4J Framework

I am new to Web Service and LAMP Stack.Currently I am working on a Web Application.It is a PHP Based Application that uses Apache Tomcat Web Server 8.0.26 ,MySQL Database ad Linux operating system(LAMP Stack).It has Web Services in Spring. Following are the issues I am facing with the Application:-

1) Responses are slow over a period of few weeks from a web service hosted on tomcat.

Temporary Solution:-The problem is solved when we restart the Web Server.

2) What are the tools we can use to monitor tomcat / performance ?

Regards

Kaustubh