Tomcat

Tomcat is is an open source implementation of the Java Servlet, JavaServer Pages, Java Expression Language and Java WebSocket technologies.

Introduction

This chart creates a tomcat application server Deployment, plus http Services for the server. The chart offers an optimization for application updates running in a servlet container-type engines like tomcat and Jboss. The chart uses the WAR, EAR, and other deployable components outside of the Servlet engine as sidecar container so application upgrades requires the sidecar container image only to be updated and not the Servlet engine as if both would run at the same image.

Prerequisites

• Kubernetes 1.10+

Provider-specific Prerequisites

Installing the Chart

To install the chart with the release name my-release:

$ helm install --name my-release stable/tomcat

This command deploys a tomcat dedicated server with sane defaults.

Tip: List all releases using helm list

Uninstalling the Chart

To uninstall/delete the my-release deployment:

$ helm delete my-release

The command removes all the Kubernetes components associated with the chart and deletes the release.

Configuration

The following table lists the configurable parameters of the tomcat chart and their default values.

Parameter	Description	Default
image.webarchive.repository	Sidecar image source repository name	ananwaresystems/webarchive
image.webarchive.tag	webarchive release tag.	1.0
image.tomcat.repository	Tomact image source repository name	tomcat
image.tomcat.tag	tomcat release tag.	7.0
image.pullPolicy	Image pull policy	IfNotPresent
image.pullSecrets	Image pull secrets	[]
deploy.directory	Webarchive deployment directory	/usr/local/tomcat/webapps
env	Environment variables	[]
extraVolumes	Extra volumes	[]
extraVolumeMounts	Extra volume mounts	[]
extraInitContainers	Extra init containers	[]
hostPort	hostPort	8009
service.name	Tomcat service name	http
service.externalPort	Kubernetes service port	80
service.internalPort	Tomcat front port	8080
service.type	Kubernetes service type	LoadBalancer
readinessProbe.path	HTTP path to check for readiness	/sample
livenessProbe.path	HTTP path to check for readiness	/sample
resources	CPU/Memory resource requests/limits	{}
nodeSelector	Node affinity	{}
tolerations	Node tolerations	{}

Refer to values.yaml for the full run-down on defaults. These are a mixture of Kubernetes and tomcat-related directives that map to environment variables.

Specify each parameter using the --set key=value[,key=value] argument to helm install. For example,

$ helm install --name my-release \
  --set Values.someval=My Server,ImageTag=1.0 \
    stable/tomcat

The above command deploys Tomcat dedicated with a server name of My Server and docker-tomcat image version 1.0.

Alternatively, a YAML file that specifies the values for the parameters can be provided while installing the chart. For example,

$ helm install --name my-release -f values.yaml stable/stable

Tip: You can use the default values.yaml

Persistence

"An emptyDir volume is first created when a Pod is assigned to a Node, and exists as long as that Pod is running on that node. When a Pod is removed from a node for any reason, the data in the emptyDir is deleted forever."

Credits

Java Web Application with Tomcat and Sidecar Container