Google Cloud Platform Jetty Docker Image
This repository contains the source for the Google-maintained Jetty docker image. This image can be used as the base image for running Java web applications on Google App Engine Flexible Environment and Google Container Engine. It provides the Jetty Servlet container on top of the OpenJDK image.
This image is mirrored at both
Configuring the Jetty image
Arguments passed to the
docker run command are passed to Jetty, so the
configuration of the jetty server can be seen with a command like:
docker run gcr.io/google-appengine/jetty --list-config
Alternate commands can also be passed to the
docker run command, so the
image can be explored with
docker run -it --rm launcher.gcr.io/google/jetty bash
Various environment variables (see below) can also be used to set jetty properties, enable modules and
disable modules. These variables may be set either in an
app.yaml or passed in to a docker run
docker run -it --rm -e JETTY_PROPERTIES=jetty.http.idleTimeout=10000 launcher.gcr.io/google/jetty
To update the server configuration in a derived Docker image, the
enable additional modules with
RUN commands like:
WORKDIR $JETTY_BASE RUN java -jar "$JETTY_HOME/start.jar" --add-to-startd=jmx,stats
Modules may be configured in a
Dockerfile by editing the properties in the corresponding mod files in
/var/lib/jetty/start.d/ or the module can be deactivated by removing that file.
Enabling gzip compression
The gzip handler is bundled with Jetty but not activated by default. To activate this module you have to set the environment
For example with docker:
docker run -p 8080 -e JETTY_MODULES_ENABLE=gzip gcr.io/yourproject/yourimage
Or with GAE (app.yaml):
env_variables: JETTY_MODULES_ENABLE: gzip
Jetty provides mechanisms to speed up the start time of your application by pre-scanning its content and generating configuration files.
If you are using an extended image you can active quickstart by executing
/scripts/jetty/quickstart.sh in your Dockerfile, after the application WAR is added.
FROM launcher.gcr.io/google/jetty ADD your-application.war $JETTY_BASE/webapps/root.war # generate quickstart-web.xml RUN /scripts/jetty/quickstart.sh
App Engine Flexible Environment
When using App Engine Flexible, you can use the runtime without worrying about Docker by specifying
runtime: java in your
runtime: java env: flex
The runtime image
launcher.gcr.io/google/jetty will be automatically selected if you are attempting to deploy a WAR (
If you want to use the image as a base for a custom runtime, you can specify
runtime: custom in your
app.yaml and then
write the Dockerfile like this:
FROM launcher.gcr.io/google/jetty ADD your-application.war $APP_DESTINATION_WAR
That will add the WAR in the correct location for the Docker container.
You can also use exploded-war artifacts:
ADD your-application $APP_DESTINATION_EXPLODED_WAR
Once you have this configuration, you can use the Google Cloud SDK to deploy this directory containing the 2 configuration files and the WAR using:
gcloud app deploy app.yaml
Container Engine & other Docker hosts
For other Docker hosts, you'll need to create a Dockerfile based on this image that copies your application code and installs dependencies. For example:
FROM launcher.gcr.io/google/jetty COPY your-application.war $APP_DESTINATION_WAR
If your artifact is an exploded-war, then use the
APP_DESTINATION_EXPLODED_WAR environment variable instead. You can then build the docker container using
docker build or Google Cloud Container Builder.
By default, the CMD is set to start the Jetty server. You can change this by specifying your own
Entry Point Features
This image updates the docker
CMD and adds the
script to include options and arguments to run the Jetty container, unless an executable argument is passed to the docker image.
Additional environment variables are used/set including:
|Env Var||Maven Prop||Value/Comment|
||Comma separated list of
||Comma separated list of modules to enable by appending to
||Comma separated list of modules to disable by removing from
||Arguments passed to jetty's
||JVM runtime arguments|
If a WAR file is found at
$ROOT_WAR, it is unpacked to
$ROOT_DIR if it is newer than the directory or the directory
does not exist. If there is no
/app is symbolic linked to
$ROOT_DIR is discovered or made by this script, then it is set as the working directory.
See Extending the image below for some examples of adding an application as a WAR file or directory.
The command line executed is effectively (where $@ are the args passed into the docker entry point):
java $JAVA_OPTS \ -Djetty.base=$JETTY_BASE \ -jar $JETTY_HOME/start.jar \ "$@"
This image is configured to use Java Util Logging(JUL) to capture all logging from the container and its dependencies. Applications that also use the JUL API will inherit the same logging configuration.
By default JUL is configured to use a ConsoleHandler to send logs to the
stderr of the container process. When run on as a GCP deployment, all output to
stderr is captured and is available via the Stackdriver logging console, however more detailed and integrated logs are available if the Stackdriver logging mechanism is used directly (see below).
To alter logging configuration a new
logging.properties file must be provided to the image that among other things can: alter log levels generated by Loggers; alter log levels accepted by handlers; add/remove/configure log handlers.
logging.properties via the web application
A new logging configuration file can be provided as part of the application (typically at
and the Java System Property
java.util.logging.config.file updated to reference it.
When running in a GCP environment, the system property can be set in
env_variables: JETTY_ARGS: -Djava.util.logging.config.file=WEB-INF/logging.properties
If the image is run directly, then a
-e argument to the
docker run command can be used to set the system property:
docker run \ -e JETTY_ARGS=-Djava.util.logging.config.file=WEB-INF/logging.properties \ ...
logging.properties via a custom image
If this image is being used as the base of a custom image, then the following
Dockerfile commands can be used to add either replace the existing logging configuration file or to add a new
The default logging configuration file is located at
/var/lib/jetty/etc/java-util-logging.properties, which can be replaced in a custom image is built. The default configuration can be replaced with a
FROM gcr.io/google-appengine/jetty ADD logging.properties /var/lib/jetty/etc/java-util-logging.properties ...
Alternately an entirely new location for the file can be provided and the environment amended in a
FROM gcr.io/google-appengine/jetty ADD logging.properties /etc/logging.properties ENV JETTY_ARGS -Djava.util.logging.config.file=/etc/logging.properties ...
logging.properties via docker run
logging.properties file may be added to an existing images using the
docker run command if the deployment environment allows for the run arguments to be modified. The
-v option can be used to bind a new
logging.properties file to the running instance and the
-e option can be used to set the system property to point to it:
docker run -it --rm \ -v /mylocaldir/logging.properties:/etc/logging.properties \ -e JETTY_ARGS="-Djava.util.logging.config.file=/etc/logging.properties" \ ...
Enhanced Stackdriver Logging (BETA)
When running on the Google Cloud Platform Flex environment, the Java Util Logging can be configured to send logs to Google Stackdriver Logging by providing a
logging.properties file that configures a LoggingHandler as follows:
handlers=com.google.cloud.logging.LoggingHandler # Optional configuration .level=INFO com.google.cloud.logging.LoggingHandler.level=FINE com.google.cloud.logging.LoggingHandler.log=gae_app.log com.google.cloud.logging.LoggingHandler.formatter=java.util.logging.SimpleFormatter java.util.logging.SimpleFormatter.format=%3$s: %5$s%6$s
When deployed on the GCP Flex environment, an image so configured will automatically be configured with:
- a LabelLoggingEnhancer instance, that will add labels from the monitored resource to each log entry.
- a TraceLoggingEnhancer instance that will add any trace-id set to each log entry.
gcpmodule will be enabled that configures jetty so that the setCurrentTraceId method is called for any thread handling a request.
When deployed in other environments, logging enhancers can be manually configured by setting a comma separated list of class names as the
When using Stackdriver logging, it is recommended that
sun.net logging level is kept at INFO level, as both these packages are used by Stackdriver internals and can result in verbose and/or initialisation problems.
Distributed Session Storage
The Jetty session mechanism is highly customizable and the options presented below are only a subset of meaningful configurations. Consult the Jetty Sessions documentation for more details.
Google Cloud Session Store
This image can be configured to use Google Cloud Datastore for clustered session storage by enabling the
gcp-datastore-sessions jetty module. You can do this in your app.yaml:
env_variables: JETTY_MODULES_ENABLE: gcp-datastore-sessions
Jetty will use the default namespace in Datastore as the store for all session data, or
jetty.session.gcloud.namespace property can be used to set an alternative namespace. By default gcloud has no request affinity, so all session data will be retrieved and stored from the datastore on every request and no session data will be shared in memory.
Note that the
gcp-datastore-sessions module is an aggregate module and the same configuration can be achieved by activating it's dependent modules individually:
env_variables: JETTY_MODULES_ENABLE: session-cache-null,gcp-datastore,session-store-gcloud
Cached Google Cloud Session Store
The Google Load Balancer can support instance affinity for more efficient session usage. This can be configured in
network: session_affinity: true env_variables: JETTY_MODULES_ENABLE: session-cache-hash,gcp-datastore,session-store-gcloud
Sessions will be retrieved from the in memory session cache and multiple requests can share a session instance. The Google Data Cloud is only accessed for unknown sessions (if affinity changes) or if a session is modified.
Session cache behaviour can be further configured by following the Jetty Session Cache documentation. Note that affinity is achieved by the Google Load Balancer setting a
GCLB cookie rather than tracking the
Memcached Google Cloud Session Store (Alpha)
Sessions can be cached in memcache (without need for affinity) and backed by Google Cloud Datastore. This can be configured in
env_variables: JETTY_MODULES_ENABLE: gcp-memcache-datastore-sessions
Note that the
gcp-memcache-datastore-sessions module is an aggregate module and the same configuration can be achieved by activating it's dependent modules individually:
env_variables: JETTY_MODULES_ENABLE: session-cache-null,gcp-datastore,session-store-gcloud,gcp-xmemcached,session-store-cache
session-cache-null module may be replaced with the
session-cache-hash module to achieve 2 levels of caching (in memory and memcache) prior to accessing the Google Cloud Datastore, and network affinity may also be activated as above.
Extending the image
The image produced by this project may be automatically used/extended by the Cloud SDK and/or App Engine maven plugin. Alternately it may be explicitly extended with a custom Dockerfile.
The latest released version of this image is available at
launcher.gcr.io/google/jetty, alternately you may
build and push your own version with the shell commands:
mvn clean install docker tag jetty:latest gcr.io/your-project-name/jetty:your-label gcloud docker -- push gcr.io/your-project-name/jetty:your-label
Adding the root WAR application to an image
A standard war file may be deployed as the root context in an extended image by placing the war file
in the docker build directory and using a
FROM launcher.gcr.io/google/jetty COPY your-application.war $APP_DESTINATION_WAR
An exploded-war can also be used:
COPY your-application $APP_DESTINATION_EXPLODED_WAR
Adding the root application to an image
If the application exists as directory (i.e. an expanded war file), then directory must
be placed in the docker build directory and using a
FROM launcher.gcr.io/google/jetty COPY your-application-dir $JETTY_BASE/webapps/root
Mounting the root application at local runtime
If no root WAR or root directory is found, the
docker-entrypoint.bash script will link the
/app directory as the root application. Thus the root application can be added to the
image via a runtime mount:
docker run -v /some-path/your-application:/app launcher.gcr.io/google/jetty
The image's default start command will first run the jetty start.jar as a --dry-run to generate the JVM
start command before starting the jetty web server. If you wish to generate the start command in your Dockerfile
rather than at container start-time, you can run the
/scripts/jetty/generate-jetty-start.sh script to generate it
for you, i.e.
NOTE: Make sure that the web application and any additional custom jetty modules have been added to the container BEFORE running this script.
- See instructions on how to build and test this image.
- See CONTRIBUTING.md
- See LICENSE.md