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Tomcat Container

The Tomcat Container allows servlet 2 and 3 web applications to be run. These applications are run as the root web application in a Tomcat container.

Detection Criterion Existence of a WEB-INF/ folder in the application directory and Java Main not detected
Tags tomcat-instance=⟨version⟩, tomcat-lifecycle-support=⟨version⟩, tomcat-logging-support=⟨version⟩, tomcat-redis-store=⟨version⟩ (optional), tomcat-external_configuration=⟨version⟩ (optional)
Tags are printed to standard output by the buildpack detect script

If the application uses Spring, Spring profiles can be specified by setting the SPRING_PROFILES_ACTIVE environment variable. This is automatically detected and used by Spring. The Spring Auto-reconfiguration Framework will specify the cloud profile in addition to any others.

Configuration

For general information on configuring the buildpack, including how to specify configuration values through environment variables, refer to Configuration and Extension.

The container can be configured by modifying the config/tomcat.yml file in the buildpack fork. The container uses the Repository utility support and so it supports the version syntax defined there.

Name Description
access_logging_support.repository_root The URL of the Tomcat Access Logging Support repository index (details).
access_logging_support.version The version of Tomcat Access Logging Support to use. Candidate versions can be found in this listing.
access_logging_support.access_logging Set to enabled to turn on the access logging support. Default is disabled.
geode_store.repository_root The URL of the Geode Store repository index (details).
geode_store.version The version of Geode Store to use. Candidate versions can be found in this listing.
lifecycle_support.repository_root The URL of the Tomcat Lifecycle Support repository index (details).
lifecycle_support.version The version of Tomcat Lifecycle Support to use. Candidate versions can be found in this listing.
logging_support.repository_root The URL of the Tomcat Logging Support repository index (details).
logging_support.version The version of Tomcat Logging Support to use. Candidate versions can be found in this listing.
redis_store.connection_pool_size The Redis connection pool size. Note that this is per-instance, not per-application.
redis_store.database The Redis database to connect to.
redis_store.repository_root The URL of the Redis Store repository index (details).
redis_store.timeout The Redis connection timeout (in milliseconds).
redis_store.version The version of Redis Store to use. Candidate versions can be found in this listing.
tomcat.context_path The context path to expose the application at.
tomcat.repository_root The URL of the Tomcat repository index (details).
tomcat.version The version of Tomcat to use. Candidate versions can be found in this listing.
tomcat.external_configuration_enabled Set to true to be able to supply an external Tomcat configuration. Default is false.
external_configuration.version The version of the External Tomcat Configuration to use. Candidate versions can be found in the the repository that you have created to house the External Tomcat Configuration. Note: It is required the external configuration to allow symlinks.
external_configuration.repository_root The URL of the External Tomcat Configuration repository index (details).

Common configurations

The version of Tomcat can be configured by setting an environment variable.

$ cf set-env my-application JBP_CONFIG_TOMCAT '{tomcat: { version: 7.0.+ }}'

The context path that an application is deployed at can be configured by setting an environment variable.

$ cf set-env my-application JBP_CONFIG_TOMCAT '{tomcat: { context_path: /first-segment/second-segment }}'

Additional Resources

The container can also be configured by overlaying a set of resources on the default distribution. To do this follow one of the options below.

Buildpack Fork

Add files to the resources/tomcat directory in the buildpack fork. For example, to override the default logging.properties add your custom file to resources/tomcat/conf/logging.properties.

External Tomcat Configuration

Supply a repository with an external Tomcat configuration.

Example in a manifest.yml

env:
  JBP_CONFIG_TOMCAT: '{ tomcat: { external_configuration_enabled: true }, external_configuration: { repository_root: "http://repository..." } }'

The artifacts that the repository provides must be in TAR format and must follow the Tomcat archive structure:

tomcat
|- conf
   |- context.xml
   |- server.xml
   |- web.xml
   |...

Notes:

  • It is required the external configuration to allow symlinks. For more information check Tomcat 7 configuration or Tomcat 8 configuration.
  • JasperListener is removed in Tomcat 8 so you should not add it to the server.xml.

Session Replication

By default, the Tomcat instance is configured to store all Sessions and their data in memory. Under certain circumstances it my be appropriate to persist the Sessions and their data to a repository. When this is the case (small amounts of data that should survive the failure of any individual instance), the buildpack can automatically configure Tomcat to do so by binding an appropriate service.

Redis

To enable Redis-based session replication, simply bind a Redis service containing a name, label, or tag that has session-replication as a substring.

Tanzu GemFire for VMs

To enable session state caching on Tanzu GemFire for VMs, bind to a Tanzu GemFire service instance whose name either ends in -session-replication or is tagged with session-replication.

Service instances can be created with a tag:

$ cf create-service p-cloudcache my-service-instance -t session-replication

or existing service instances can be given a tag:

$ cf update-service new-service-instance -t session-replication

Managing Entropy

Entropy from /dev/random is used heavily to create session ids, and on startup for initializing SecureRandom, which can then cause instances to fail to start in time (see the Tomcat wiki). Also, the entropy is shared so it's possible for a single app to starve the DEA of entropy and cause apps in other containers that make use of entropy to be blocked. If this is an issue then configuring /dev/urandom as an alternative source of entropy may help. It is unlikely, but possible, that this may cause some security issues which should be taken in to account.

Example in a manifest.yml

env:
  JAVA_OPTS: -Djava.security.egd=file:///dev/urandom

Supporting Functionality

Additional supporting functionality can be found in the java-buildpack-support Git repository.