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	Must set	Default	Description
`jolokia_url`	In practice	`http://localhost:8080/jolokia`	URL of the Jolokia agent deployed in Tomcat. Example: `http://tomcat.example.com:8080/jolokia`
`username`	No	-	Basic-auth user; empty sends no credentials
`password`	No	-	Basic-auth password. A secret: reference it with `${secret:…}`, `${env:…}` or `${file:…}` rather than writing it in the file
`timeout`	No	`10`	Request timeout in seconds
`interval`	No	`60`	Seconds between collections
`instance_name`	No	-	Stable identity of this server instead of the one derived from the URL

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.requests.total`	{request}	Requests processed per connector, tagged with `connector`
`tomcat.errors.total`	{error}	Request errors per connector
`tomcat.processing_time`	s	Cumulative request processing time 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.

Metric reference¶

Every metric this probe can emit. Metric is the OpenTelemetry name the OTLP, Prometheus and Zabbix outputs derive theirs from. Name is what a Nagios check and the API metrics= filter match. PRTG channel is the label PRTG shows, placeholders filled from the series' tags.

Metric	Name	PRTG channel	Unit	Description
`senhub.tomcat.up`	`senhub.tomcat.up`	Tomcat Up	#	1 when Jolokia is reachable, 0 otherwise
`tomcat.sessions.active`	`tomcat.sessions.active`	Tomcat Sessions	#	Number of active HTTP sessions for the web application context
`tomcat.requests.total`	`tomcat.requests.total`	Tomcat Requests	#	Total number of HTTP requests processed by the connector
`tomcat.bytes.received`	`tomcat.bytes.received`	Tomcat Bytes Received	B	Total bytes received by the connector
`tomcat.bytes.sent`	`tomcat.bytes.sent`	Tomcat Bytes Sent	B	Total bytes sent by the connector
`tomcat.processing_time`	`tomcat.processing_time`	Tomcat Processing Time	ms	Cumulative request processing time in milliseconds
`tomcat.errors.total`	`tomcat.errors.total`	Tomcat Errors	#	Total number of HTTP errors produced by the connector
`tomcat.threads.current`	`tomcat.threads.current`	Tomcat Threads Current	#	Current number of threads in the connector thread pool
`tomcat.threads.busy`	`tomcat.threads.busy`	Tomcat Threads Busy	#	Number of threads currently processing requests
`tomcat.threads.max`	`tomcat.threads.max`	Tomcat Threads Max	#	Maximum number of threads allowed in the connector thread pool
`jvm.memory.heap.used`	`jvm.memory.heap.used`	JVM Heap Used	B	Amount of heap memory currently used by the JVM
`jvm.memory.heap.committed`	`jvm.memory.heap.committed`	JVM Heap Committed	B	Amount of heap memory committed (guaranteed available) to the JVM
`jvm.memory.heap.max`	`jvm.memory.heap.max`	JVM Heap Max	B	Maximum heap memory that can be used by the JVM
`jvm.gc.collections.count`	`jvm.gc.collections.count`	JVM GC Count	#	Number of garbage collection cycles performed by the collector
`jvm.gc.collections.elapsed`	`jvm.gc.collections.elapsed`	JVM GC Elapsed	ms	Total time spent in garbage collection by the collector
`jvm.threads.count`	`jvm.threads.count`	JVM Thread Count	#	Current number of live threads in the JVM