Apache Tomcat¶

The tomcat probe monitors Apache Tomcat via Jolokia HTTP REST, reporting active HTTP sessions, request throughput, JVM heap and garbage collection, and the Tomcat thread pool state.

Quick start¶

# probes.d/10-tomcat.yaml — each file under probes.d/ is a YAML array of probes
- name: tomcat
  type: tomcat
  params:
    jolokia_url: http://localhost:8080/jolokia

Parameters¶

Parameter	Default	Description
`jolokia_url`	`http://localhost:8080/jolokia`	URL to the Jolokia agent endpoint on the Tomcat instance
`username`	—	Jolokia Basic-auth username (if required)
`password`	—	Jolokia Basic-auth password — reference a stored secret via `${secret:tomcat.password}`, `${env:VAR}` or `${file:/path}`. Inline plaintext is auto-sealed into the OS secret store on install.

Metrics¶

Metric	Unit	Description
`senhub.tomcat.up`	1	1 when Jolokia is reachable
`tomcat.sessions.active`	{session}	Active HTTP sessions per web application context, tagged with `context`
`tomcat.request.count`	{request}	Requests processed per connector, tagged with `connector`
`tomcat.request.error.count`	{error}	Request errors per connector
`tomcat.request.elapsed_time`	s	Total time spent on requests per connector
`tomcat.threads.current`	{thread}	Current thread pool size
`tomcat.threads.busy`	{thread}	Threads currently handling a request
`tomcat.threads.max`	{thread}	Maximum thread pool size
`jvm.memory.heap.used`	By	JVM heap in use
`jvm.memory.heap.max`	By	JVM maximum heap size
`jvm.gc.collections.count`	{collection}	GC collections by collector (Minor/Major), tagged with `collector`

Operational notes¶

Jolokia must be deployed in Tomcat as a WAR or Java agent. The Jolokia WAR can be deployed at /jolokia; the Java agent is added to CATALINA_OPTS.
Multiple Tomcat instances on the same host can be monitored with multiple probe entries pointing to different Jolokia URLs.