Cloud SDK App Engine Apache Maven Plugin

Apache Maven is a software project management and comprehension tool. It is capable of building WAR files for deployment into App Engine. The App Engine team provides both a plugin and Maven Archetypes for the purpose of speeding up development.

Requirements

To use Maven with Managed VMs, you need to do the following:

0. Download and install Maven if you don't have it installed.

1. Install the Google Cloud SDK on your machine. The new Maven plugin goals will not download it automatically on build. Make sure you install an up-to-date version (Beta or later) that has the App Engine Managed VM components installed.

2. Install the Cloud SDK app-engine-java component:

    gcloud components update app-engine-java
   

3. You must use Java 7. If you don't have Java 7, Download and install it. For App Engine Managed VMs images, it is possible to use Java 8 with some customization.

4. Set your JAVA_HOME environment variable. If you are a bash user, the following considerations apply:

   • For a typical Linux installation, add a line similar to the following to your .bashrc file:

       export JAVA_HOME=/usr/local/tools/java/jdk1.7.0_45.jdk
     

   • If you use Mac OS X and the default Terminal app, your shell session doesn't load .bashrc by default. So you may need to add a line similar to the following to your .bash_profile:

        [ -r ~/.bashrc ] && source ~/.bashrc
     

   • If you use Mac OS X but don't use the default terminal app, for example, you use a terminal management app such as tmux, you may need to add a line similar to the following line to your .bashrc file:

        export JAVA_HOME=$(/usr/libexec/java_home -v1.7)
     

5. If you want to start with a Java Managed VM sample code and tutorial, you can use the GitHub project: https://github.com/GoogleCloudPlatform/appengine-java-vm-guestbook-extras

6. The Maven plugin relies on configuration done by the cloud SDK. For example, the project name you want to use for a deployment step can be defined with:

   gcloud config set project

Adding the Cloud SDK App Engine Maven plugin to an existing Maven project

To add the Cloud SDK Google App Engine Maven plugin to an existing Maven project, add the following into the plugins section in the project pom.xml file:

<plugin>
   <groupId>com.google.appengine</groupId>
   <artifactId>gcloud-maven-plugin</artifactId>
   <version>2.0.9.86.v20151111</version>

Compile and build your project using Maven

To build an Java App Engine Web Application using Maven with its pom.xml file:

1. Change directory to the main directory for your project, for example, guestbook/

2. Invoke Maven as follows:

    mvn clean install
   

3. Wait for the project to build. When the project successfully finishes you will see a message similar to this one:

    BUILD SUCCESS
     Total time: 10.724s
     Finished at: Mon Jul 14 14:50:06 PST 2014
     Final Memory: 24M/213M
   

4. Optionally, run and test the application locally using the Cloud SDK development server, as described in the next section.

Run and test your app with the Cloud SDK development server

During the development phase, you can run and test your app at any time in the development server by invoking the Cloud SDK App Engine Maven plugin.

To run your app in the development server:

1. Build your app if you haven't already done so:

    mvn clean install
   

2. Run your app by changing directory to the top level of your project (for example, to myapp) and invoking Maven as follows:

    $ mvn gcloud:run
   

3. Wait for the the server to start and use your browser to visit http://localhost:8080/ to access your app.

4. Shut down the app and the development server by pressing Control+C in the Windows/Linux terminal window where you started it, or CMD+C on the Mac.

App Engine Maven plugin goals for the Cloud SDK

The App Engine Maven plugin goals have been extended to work with a local Cloud SDK installation that enable Managed VMs development and deployment. These goals are listed in the following sections.

Development server goals

These are the Cloud SDK App Engine development server goals:

Goal	Description
gcloud:run	Runs the Beta Cloud SDK App Engine development server for Managed VMs applications as well as non Managed VMs application.
gcloud:run_start	Performs an asynchronous start for the devserver and then returns to the command line. When this goal runs, the behavior is the same as the run goal except that Maven continues processing goals and exits after the server is up and running.
gcloud:run_stop	Stops the development server. Available only if you started the development server with gcloud:run_start.

Available parameters for all gcloud:* goals:

Parameter	Description
gcloud_directory	The location of the Cloud SDK to use from Maven. (Default is ~/google-cloud-sdk)
gcloud_project	The Cloud project you want to work with. (Default is the one set up in the Cloud SDK)

Available parameters, corresponding to gcloud app run command line flags:

Parameter	Description
admin_host	The host and port on which to start the admin server (in the format host:port)
allow_skipped_files	Make files specified in the app.yaml "skip_files" or "static" clauses readable by the application.
api_host	The host and port on which to start the API server for the dev server (in the format host:port).
appidentity_email_address	Email address associated with a service account that has a downloadable key. May be None for no local application identity.
appidentity_private_key_path	Path to private key file associated with service account (.pem format). Must be set if appidentity_email_address is set.
auth_domain	Name of the authorization domain to use
blobstore_path	Path to directory used to store blob contents (defaults to a subdirectory of storage_path if not set)
clear_datastore	Clear the datastore on startup
datastore_consistency_policy	The policy to apply when deciding whether a datastore write should appear in global queries (default is "time")
datastore_path	Path to a file used to store datastore contents (defaults to a file in storage_path if not set)
default_gcs_bucket_name	Default Google Cloud Storage bucket name
enable_sendmail	Use the "sendmail" tool to transmit e-mail sent using the Mail API (ignored if smtp_host is set)
host	The host and port on which to start the local web server (in the format host:port)
jvm_flag	Additional arguments to pass to the java command when launching an instance of the app. May be specified more than once. Example: <jvm_flag><param>-Xmx1024m</param> <param>-Xms256m</param></jvm_flag>.
log_level	The minimum verbosity of logs from your app that will be displayed in the terminal. (debug, info, warning, critical, error) Defaults to current verbosity setting.
logs_path	Path to a file used to store request logs (defaults to a file in storage_path if not set)
max_module_instances	The maximum number of runtime instances that can be started for a particular module - the value can be an integer, in which case all modules are limited to that number of instances, or a comma-separated list of module:max_instances, e.g. default:5,backend:3
php_executable_path	The full path to the PHP executable to use to run your PHP module.
python_startup_script	The script to run at the startup of new Python runtime instances (useful for tools such as debuggers)
require_indexes	Generate an error on datastore queries that require a composite index not found in index.yaml
show_mail_body	Logs the contents of e-mails sent using the Mail API
smtp_allow_tls	Allow TLS to be used when the SMTP server announces TLS support (ignored if --smtp-host is not set)
smtp_host	The host and port of an SMTP server to use to transmit e-mail sent using the Mail API, in the format host:port
smtp_password	Password to use when connecting to the SMTP server specified with smtp_host
smtp_user	Username to use when connecting to the SMTP server specified with smtp_host
storage_path	The default location for storing application data. Can be overridden for specific kinds of data using datastore_path, blobstore-path, and/or logs_path
use_mtime_file_watcher	Use mtime polling for detecting source code changes - useful if modifying code from a remote machine using a distributed file system
custom_entrypoint	Specify an entrypoint for custom runtime modules. This is required when such modules are present. Include "{port}" in the string (without quotes) to pass the port number in as an argument. For instance: --custom_entrypoint="gunicorn -b localhost:{port} mymodule:application"

The following example shows how to use some of these settings:

  <plugin>
    <groupId>com.google.appengine</groupId>
    <artifactId>gcloud-maven-plugin</artifactId>
    <version>>2.0.9.86.v20151111</version>
    <configuration>
      <gcloud_directory>/usr/foo/private/google-cloud-sdk</gcloud_directory>
      <verbosity>debug</verbosity>
      <version>specific_version</version>
      <promote>true</promote>
      <log_level>info</log_level>
      <max_module_instances>2</max_module_instances>
    </configuration>
  </plugin>

Application deployment goal

You can deploy an App Engine Application via the goal gcloud:deploy.

    $ mvn gcloud:deploy

Available parameters, corresponding to gcloud app deploy command line flags:

Parameter	Description
compile-encoding	Set the encoding to be used when compiling Java source files (default "UTF-8")
delete_jsps	Delete the JSP source files after compilation
disable_jar_jsps	Do not jar the classes generated from JSPs
enable_jar_classes	Jar the WEB-INF/classes content
enable_jar_splitting	Split large jar files (> 32M) into smaller fragments
env_vars	Environment variable overrides for your app.
force	Force deploying, overriding any previous in-progress deployments to this version.
jar_splitting_excludes	When enable-jar-splitting is specified and jar_splitting_excludes specifies a comma-separated list of suffixes, a file in a jar whose name ends with one of the suffixes will not be included in the split jar fragments
no_symlinks	Do not use symbolic links when making the temporary (staging) directory used in uploading Java apps
retain_upload_dir	Do not delete temporary (staging) directory used in uploading Java apps
server	The App Engine server to connect to. You will not typically need to change this value.
promote	Set the deployed version to be the default serving version.
version	The version of the app that will be created or replaced by this deployment.
docker_build	Perform a hosted (remote) or local Docker build. To perform a local build, you must have your local docker environment configured correctly.

Application management goals

The application and project management goals are listed in the following table:

Goal	Description
gcloud:module_cancel_deployment	Cancel (rollback) the current deployment. Useful when the deployment has been interrupted for some reason.
gcloud:module_delete	Delete the module defined by the maven project.
gcloud:module_set_default	Set as default the module.
gcloud:module_set_managed_by	Configure the specified backend.
gcloud:module_start	Start the module defined by the maven project.
gcloud:module_stop	Stop the module defined by the maven project.

Available parameters corresponding to gcloud app modules command line flags:

Parameter	Description
server	The App Engine server to connect to. You will not typically need to change this value.
version	The version of the app that will be created or replaced by this deployment.

Configuration elements override via the command line interface

Instead of editing the pom.xml with the desired configuration, all the configuration parameters can be defined in the mvn command line, following the simple pattern -Dgcloud.PARAM_NAME=PARAM_VALUE. For example:

  # To start the development server with debug flag:
  $ mvn gcloud:run -Dgcloud.verbosity=debug
  # To start the development server listening to 0.0.0.0 so it can be accessed outside of localhost:
  $ mvn gcloud:run -Dgcloud.host=0.0.0.0:8081
  # To specify a non default Cloud SDK installation directory:
  $ mvn gcloud:run -Dgcloud.gcloud_directory=YOUR_OWN_SPECIFIC_INSTALLATION_PATH
  # To specify the project ID and version at deployment time:
  $ mvn gcloud:deploy -Dgcloud.gcloud_project=myproject  -Dgcloud.version=myversion

Note: The configuration parameters cannot be overriden, due to this Maven bug.

Enterprise Archive (EAR) support

You can use the Cloud SDK Maven plugin on App Engine projects of type war and ear.