Apache Tomcat

This document describes how to configure your Google Kubernetes Engine deployment so that you can use Google Cloud Managed Service for Prometheus to collect metrics from Apache Tomcat. This document shows you how to do the following:

  • Set up the exporter for Tomcat to report metrics.
  • Access a predefined dashboard in Cloud Monitoring to view the metrics.
  • Configure alerting rules to monitor the metrics.

These instructions apply only if you are using managed collection with Managed Service for Prometheus. If you are using self-deployed collection, then see the source repository for the JMX exporter for installation information.

These instructions are provided as an example and are expected to work in most Kubernetes environments. If you are having trouble installing an application or exporter due to restrictive security or organizational policies, then we recommend you consult open-source documentation for support.

For information about Apache Tomcat, see Apache Tomcat.

Prerequisites

To collect metrics from Tomcat by using Managed Service for Prometheus and managed collection, your deployment must meet the following requirements:

  • Your cluster must be running Google Kubernetes Engine version 1.28.15-gke.2475000 or later.
  • You must be running Managed Service for Prometheus with managed collection enabled. For more information, see Get started with managed collection.

  • To use dashboards available in Cloud Monitoring for the Tomcat integration, you must use jmx-exporter version 0.17.0 or later.

    For more information about available dashboards, see View dashboards.

Tomcat supports JMX, which can be enabled by configuring the CATALINA_OPTS environment variable.

Install the Tomcat exporter

We recommend that you install the Tomcat exporter, jmx-exporter, as a sidecar to your Tomcat workload. For information about using sidecars, see Extended applications on Kubernetes with multi-container pods.

To install jmx-exporter as a sidecar to Tomcat, modify your Tomcat configuration as shown in the following example:

# Copyright 2023 Google LLC # # Licensed under the Apache License, Version 2.0 (the "License"); # you may not use this file except in compliance with the License. # You may obtain a copy of the License at # # https://www.apache.org/licenses/LICENSE-2.0 # # Unless required by applicable law or agreed to in writing, software # distributed under the License is distributed on an "AS IS" BASIS, # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. # See the License for the specific language governing permissions and # limitations under the License. apiVersion: v1 kind: ConfigMap metadata:  name: tomcat-exporter data:  config.yml: |  hostPort: 127.0.0.1:9010  lowercaseOutputLabelNames: true  lowercaseOutputName: true  rules:  - pattern: 'Catalina<type=GlobalRequestProcessor, name=\"(\w+-\w+)-(\d+)\"><>(\w+):'  name: tomcat_$3_total  labels:  port: "$2"  protocol: "$1"  help: Tomcat global $3  type: COUNTER  - pattern: 'Catalina<j2eeType=Servlet, WebModule=//([-a-zA-Z0-9+&@#/%?=~_|!:.,;]*[-a-zA-Z0-9+&@#/%=~_|]), name=([-a-zA-Z0-9+/$%~_-|!.]*), J2EEApplication=none, J2EEServer=none><>(requestCount|maxTime|processingTime|errorCount):'  name: tomcat_servlet_$3_total  labels:  module: "$1"  servlet: "$2"  help: Tomcat servlet $3 total  type: COUNTER  - pattern: 'Catalina<type=ThreadPool, name="(\w+-\w+)-(\d+)"><>(currentThreadCount|currentThreadsBusy|keepAliveCount|pollerThreadCount|connectionCount):'  name: tomcat_threadpool_$3  labels:  port: "$2"  protocol: "$1"  help: Tomcat threadpool $3  type: GAUGE  - pattern: 'Catalina<type=Manager, host=([-a-zA-Z0-9+&@#/%?=~_|!:.,;]*[-a-zA-Z0-9+&@#/%=~_|]), context=([-a-zA-Z0-9+/$%~_-|!.]*)><>(processingTime|sessionCounter|rejectedSessions|expiredSessions):'  name: tomcat_session_$3_total  labels:  context: "$2"  host: "$1"  help: Tomcat session $3 total  type: COUNTER --- apiVersion: apps/v1 kind: Deployment metadata:  name: tomcat spec:  selector:  matchLabels: + app.kubernetes.io/name: tomcat  template:  metadata:  labels: + app.kubernetes.io/name: tomcat  spec:  containers:  - name: tomcat  image: tomcat:9.0.46-jdk11-openjdk-buster  ports:  - containerPort: 8080  name: http  env: + - name: CATALINA_OPTS + value: "-Dcom.sun.management.jmxremote.local.only=false -Dcom.sun.management.jmxremote.authenticate=false -Dcom.sun.management.jmxremote.ssl=false -Dcom.sun.management.jmxremote.port=9010 -Dcom.sun.management.jmxremote.rmi.port=9010" + - name: exporter + image: bitnami/jmx-exporter:0.17.0 + ports: + - containerPort: 9113 + name: prometheus + command: + - java + - -jar + - jmx_prometheus_httpserver.jar + args: + - "9113" + - /opt/jmx_exporter/config.yml + volumeMounts: + - mountPath: /opt/jmx_exporter/config.yml + subPath: config.yml + name: tomcat-exporter + volumes: + - name: tomcat-exporter + configMap: + name: tomcat-exporter + items: + - key: config.yml + path: config.yml

You must add any lines preceded by the + symbol to your configuration.

To apply configuration changes from a local file, run the following command: 

 kubectl apply -n NAMESPACE_NAME -f FILE_NAME

You can also use Terraform to manage your configurations.

Define a PodMonitoring resource

For target discovery, the Managed Service for Prometheus Operator requires a PodMonitoring resource that corresponds to the JMX exporter in the same namespace.

You can use the following PodMonitoring configuration:

# Copyright 2023 Google LLC # # Licensed under the Apache License, Version 2.0 (the "License"); # you may not use this file except in compliance with the License. # You may obtain a copy of the License at # # https://www.apache.org/licenses/LICENSE-2.0 # # Unless required by applicable law or agreed to in writing, software # distributed under the License is distributed on an "AS IS" BASIS, # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. # See the License for the specific language governing permissions and # limitations under the License. apiVersion: monitoring.googleapis.com/v1 kind: PodMonitoring metadata:  name: tomcat  labels:  app.kubernetes.io/name: tomcat  app.kubernetes.io/part-of: google-cloud-managed-prometheus spec:  endpoints:  - port: prometheus  scheme: http  interval: 30s  path: /metrics  selector:  matchLabels:  app.kubernetes.io/name: tomcat

Ensure that the label selectors and the port match the selectors and port used in Install the Tomcat exporter.

To apply configuration changes from a local file, run the following command: 

 kubectl apply -n NAMESPACE_NAME -f FILE_NAME

You can also use Terraform to manage your configurations.

Define rules and alerts

You can use the following Rules configuration to define alerts on your Tomcat metrics:

# Copyright 2023 Google LLC # # Licensed under the Apache License, Version 2.0 (the "License"); # you may not use this file except in compliance with the License. # You may obtain a copy of the License at # # https://www.apache.org/licenses/LICENSE-2.0 # # Unless required by applicable law or agreed to in writing, software # distributed under the License is distributed on an "AS IS" BASIS, # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. # See the License for the specific language governing permissions and # limitations under the License. apiVersion: monitoring.googleapis.com/v1 kind: Rules metadata:  name: tomcat-rules  labels:  app.kubernetes.io/component: rules  app.kubernetes.io/name: tomcat-rules  app.kubernetes.io/part-of: google-cloud-managed-prometheus spec:  groups:  - name: tomcat  interval: 30s  rules:  - alert: TomcatHighRequestRate  annotations:  description: |-  Tomcat high request rate  VALUE = {{ $value }}  LABELS: {{ $labels }}  summary: Tomcat high request rate (instance {{ $labels.instance }})  expr: rate(tomcat_requestcount_total[5m]) >= 100  for: 5m  labels:  severity: warning  - alert: TomcatLowRequestRate  annotations:  description: |-  Tomcat low request rate  VALUE = {{ $value }}  LABELS: {{ $labels }}  summary: Tomcat low request rate (instance {{ $labels.instance }})  expr: rate(tomcat_requestcount_total[5m]) <= 10  for: 5m  labels:  severity: warning  - alert: TomcatHighErrorRate  annotations:  description: |-  Tomcat high error rate  VALUE = {{ $value }}  LABELS: {{ $labels }}  summary: Tomcat high error rate (instance {{ $labels.instance }})  expr: rate(tomcat_errorcount_total[5m]) > 100  for: 5m  labels:  severity: warning

To apply configuration changes from a local file, run the following command: 

 kubectl apply -n NAMESPACE_NAME -f FILE_NAME

You can also use Terraform to manage your configurations.

For more information about applying rules to your cluster, see Managed rule evaluation and alerting.

You can adjust the alert thresholds to suit your application.

Verify the configuration

You can use Metrics Explorer to verify that you correctly configured the JMX exporter. It might take one or two minutes for Cloud Monitoring to ingest your metrics.

To verify the metrics are ingested, do the following:

  1. In the Google Cloud console, go to the  Metrics explorer page:

    Go to Metrics explorer

    If you use the search bar to find this page, then select the result whose subheading is Monitoring.

  2. In the toolbar of the query-builder pane, select the button whose name is either  MQL or  PromQL.
  3. Verify that PromQL is selected in the Language toggle. The language toggle is in the same toolbar that lets you format your query.
  4. Enter and run the following query:
    up{job="tomcat", cluster="CLUSTER_NAME", namespace="NAMESPACE_NAME"}

View dashboards

The Cloud Monitoring integration includes the Tomcat Prometheus Overview dashboard. Dashboards are automatically installed when you configure the integration. You can also view static previews of dashboards without installing the integration.

To view an installed dashboard, do the following:

  1. In the Google Cloud console, go to the  Dashboards page:

    Go to Dashboards

    If you use the search bar to find this page, then select the result whose subheading is Monitoring.

  2. Select the Dashboard List tab.
  3. Choose the Integrations category.
  4. Click the name of the dashboard, for example, Tomcat Prometheus Overview.

To view a static preview of the dashboard, do the following:

  1. In the Google Cloud console, go to the  Integrations page:

    Go to Integrations

    If you use the search bar to find this page, then select the result whose subheading is Monitoring.

  2. Click the Kubernetes Engine deployment-platform filter.
  3. Locate the Apache Tomcat integration and click View Details.
  4. Select the Dashboards tab.

Troubleshooting

For information about troubleshooting metric ingestion problems, see Problems with collection from exporters in Troubleshooting ingestion-side problems.