Version: 9.4.7.v20170914 |

Persistent Sessions: Google Cloud DataStore
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## Persistent Sessions: Google Cloud DataStore

### Preparation

You will first need to create a project and enable the Google Cloud api: https://cloud.google.com/docs/authentication#preparation. Take note of the project id that you create in this step as you need to supply it in later steps.

#### Communicating with GCloudDataStore

##### When running Jetty outside of google infrastructure

Before running Jetty, you will need to choose one of the following methods to set up the local environment to enable remote GCloud DataStore communications.

1. Using the GCloud SDK:

   - Ensure you have the GCloud SDK installed: https://cloud.google.com/sdk/?hl=en.
   - Use the GCloud tool to set up the project you created in the preparation step: `gcloud config set project PROJECT_ID`
   - Use the GCloud tool to authenticate a google account associated with the project created in the preparation step: `gcloud auth login ACCOUNT`

2. Using environment variables

   - Define the environment variable `GCLOUD_PROJECT` with the project id you created in the preparation step.
   - Generate a JSON service account key and then define the environment variable `GOOGLE_APPLICATION_CREDENTIALS=/path/to/my/key.json`

##### When Running Jetty Inside of Google Infrastructure

The Google deployment tools will automatically configure the project and authentication information for you.

### Configuring Indexes for Session Data

Using some special, composite indexes can speed up session search operations, although it may make write operations slower. By default, indexes will not be used. In order to use them, you will need to manually upload a file that defines the indexes. This file is named `index.yaml` and you can find it in your distribution in `${jetty.base}/etc/sessions/gcloud/index.yaml`.

Follow the instructions here to upload the pre-generated `index.yaml` file.

#### Communicating with the GCloudDataStore Emulator

To enable communication using the GCloud Emulator:

- Ensure you have the GCloud SDK installed: https://cloud.google.com/sdk/?hl=en
- Follow the instructions here on how to start the GCloud datastore emulator, and how to propagate the environment variables that it creates to the terminal in which you run Jetty.

### Enabling the Google Cloud DataStore Module

When using the Jetty distribution, you will first need to enable the `session-store-gcloud` module for your Jetty base using the `--add-to-start` argument on the command line.

    $ java -jar ../start.jar --create-startd
    INFO : Base directory was modified

    $ java -jar ../start.jar --add-to-start=session-store-gcloud

    ALERT: There are enabled module(s) with licenses.
    The following 2 module(s):
     + contains software not provided by the Eclipse Foundation!
     + contains software not covered by the Eclipse Public License!
     + has not been audited for compliance with its license

     Module: gcloud
      + GCloudDatastore is an open source project hosted on Github and released under the Apache 2.0 license.
      + https://github.com/GoogleCloudPlatform/gcloud-java
      + http://www.apache.org/licenses/LICENSE-2.0.html

     Module: slf4j-api
      + SLF4J is distributed under the MIT License.
      + Copyright (c) 2004-2013 QOS.ch
      + All rights reserved.
      + Permission is hereby granted, free  of charge, to any person obtaining
      + a  copy  of this  software  and  associated  documentation files  (the
      + "Software"), to  deal in  the Software without  restriction, including
      + without limitation  the rights to  use, copy, modify,  merge, publish,
      + distribute,  sublicense, and/or sell  copies of  the Software,  and to
      + permit persons to whom the Software  is furnished to do so, subject to
      + the following conditions:
      + The  above  copyright  notice  and  this permission  notice  shall  be
      + included in all copies or substantial portions of the Software.
      + THE  SOFTWARE IS  PROVIDED  "AS  IS", WITHOUT  WARRANTY  OF ANY  KIND,
      + EXPRESS OR  IMPLIED, INCLUDING  BUT NOT LIMITED  TO THE  WARRANTIES OF
      + MERCHANTABILITY,    FITNESS    FOR    A   PARTICULAR    PURPOSE    AND
      + NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
      + LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
      + OF CONTRACT, TORT OR OTHERWISE,  ARISING FROM, OUT OF OR IN CONNECTION
      + WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

    Proceed (y/N)? y
    INFO  : webapp          transitively enabled, ini template available with --add-to-start=webapp
    INFO  : jul-impl        transitively enabled
    INFO  : server          transitively enabled, ini template available with --add-to-start=server
    INFO  : sessions        transitively enabled, ini template available with --add-to-start=sessions
    INFO  : servlet         transitively enabled
    INFO  : gcloud          transitively enabled, ini template available with --add-to-start=gcloud
    INFO  : annotations     transitively enabled
    INFO  : plus            transitively enabled
    INFO  : slf4j-api       transitively enabled
    INFO  : security        transitively enabled
    INFO  : gcloud-datastore transitively enabled
    INFO  : jcl-slf4j       transitively enabled
    INFO  : session-store-gcloud initialized in ${jetty.base}/start.d/session-store-gcloud.ini
    INFO  : jndi            transitively enabled
    MKDIR : ${jetty.base}/etc
    COPY  : ${jetty.home}/modules/jul-impl/etc/java-util-logging.properties to ${jetty.base}/etc/java-util-logging.properties
    MKDIR : ${jetty.base}/lib/slf4j
    DOWNLD: http://central.maven.org/maven2/org/slf4j/slf4j-api/1.7.21/slf4j-api-1.7.21.jar to ${jetty.base}/lib/slf4j/slf4j-api-1.7.21.jar
    MKDIR : ${jetty.base}/lib/gcloud
    COPY  : /Users/chris/.m2/repository/aopalliance/aopalliance/1.0/aopalliance-1.0.jar to ${jetty.base}/lib/gcloud/aopalliance-1.0.jar
    COPY  : /Users/chris/.m2/repository/com/fasterxml/jackson/core/jackson-core/2.1.3/jackson-core-2.1.3.jar to ${jetty.base}/lib/gcloud/jackson-core-2.1.3.jar
    COPY  : /Users/chris/.m2/repository/com/google/api-client/google-api-client-appengine/1.21.0/google-api-client-appengine-1.21.0.jar to ${jetty.base}/lib/gcloud/google-api-client-appengine-1.21.0.jar
    COPY  : /Users/chris/.m2/repository/com/google/api-client/google-api-client/1.20.0/google-api-client-1.20.0.jar to ${jetty.base}/lib/gcloud/google-api-client-1.20.0.jar
    COPY  : /Users/chris/.m2/repository/com/google/api-client/google-api-client-servlet/1.21.0/google-api-client-servlet-1.21.0.jar to ${jetty.base}/lib/gcloud/google-api-client-servlet-1.21.0.jar
    DOWNLD: http://central.maven.org/maven2/com/google/api/gax/0.0.21/gax-0.0.21.jar to ${jetty.base}/lib/gcloud/gax-0.0.21.jar
    COPY  : /Users/chris/.m2/repository/com/google/api/grpc/grpc-google-common-protos/0.1.0/grpc-google-common-protos-0.1.0.jar to ${jetty.base}/lib/gcloud/grpc-google-common-protos-0.1.0.jar
    COPY  : /Users/chris/.m2/repository/com/google/api/grpc/grpc-google-iam-v1/0.1.0/grpc-google-iam-v1-0.1.0.jar to ${jetty.base}/lib/gcloud/grpc-google-iam-v1-0.1.0.jar
    COPY  : /Users/chris/.m2/repository/com/google/auth/google-auth-library-credentials/0.3.1/google-auth-library-credentials-0.3.1.jar to ${jetty.base}/lib/gcloud/google-auth-library-credentials-0.3.1.jar
    COPY  : /Users/chris/.m2/repository/com/google/auth/google-auth-library-oauth2-http/0.3.1/google-auth-library-oauth2-http-0.3.1.jar to ${jetty.base}/lib/gcloud/google-auth-library-oauth2-http-0.3.1.jar
    DOWNLD: http://central.maven.org/maven2/com/google/auto/value/auto-value/1.2/auto-value-1.2.jar to ${jetty.base}/lib/gcloud/auto-value-1.2.jar
    DOWNLD: http://central.maven.org/maven2/com/google/cloud/datastore/datastore-v1-proto-client/1.3.0/datastore-v1-proto-client-1.3.0.jar to ${jetty.base}/lib/gcloud/datastore-v1-proto-client-1.3.0.jar
    DOWNLD: http://central.maven.org/maven2/com/google/cloud/datastore/datastore-v1-protos/1.3.0/datastore-v1-protos-1.3.0.jar to ${jetty.base}/lib/gcloud/datastore-v1-protos-1.3.0.jar
    DOWNLD: http://central.maven.org/maven2/com/google/cloud/google-cloud-core/0.5.1/google-cloud-core-0.5.1.jar to ${jetty.base}/lib/gcloud/google-cloud-core-0.5.0.jar
    DOWNLD: http://central.maven.org/maven2/com/google/cloud/google-cloud-datastore/0.5.1/google-cloud-datastore-0.5.1.jar to ${jetty.base}/lib/gcloud/google-cloud-datastore-0.5.1.jar
    COPY  : /Users/chris/.m2/repository/com/google/code/findbugs/jsr305/1.3.9/jsr305-1.3.9.jar to ${jetty.base}/lib/gcloud/jsr305-1.3.9.jar
    COPY  : /Users/chris/.m2/repository/com/google/code/gson/gson/2.3/gson-2.3.jar to ${jetty.base}/lib/gcloud/gson-2.3.jar
    COPY  : /Users/chris/.m2/repository/com/google/guava/guava/19.0/guava-19.0.jar to ${jetty.base}/lib/gcloud/guava-19.0.jar
    COPY  : /Users/chris/.m2/repository/com/google/http-client/google-http-client-appengine/1.21.0/google-http-client-appengine-1.21.0.jar to ${jetty.base}/lib/gcloud/google-http-client-appengine-1.21.0.jar
    COPY  : /Users/chris/.m2/repository/com/google/http-client/google-http-client-jackson2/1.19.0/google-http-client-jackson2-1.19.0.jar to ${jetty.base}/lib/gcloud/google-http-client-jackson2-1.19.0.jar
    COPY  : /Users/chris/.m2/repository/com/google/http-client/google-http-client-jackson/1.21.0/google-http-client-jackson-1.21.0.jar to ${jetty.base}/lib/gcloud/google-http-client-jackson-1.21.0.jar
    COPY  : /Users/chris/.m2/repository/com/google/http-client/google-http-client/1.21.0/google-http-client-1.21.0.jar to ${jetty.base}/lib/gcloud/google-http-client-1.21.0.jar
    COPY  : /Users/chris/.m2/repository/com/google/http-client/google-http-client-jdo/1.21.0/google-http-client-jdo-1.21.0.jar to ${jetty.base}/lib/gcloud/google-http-client-jdo-1.21.0.jar
    COPY  : /Users/chris/.m2/repository/com/google/http-client/google-http-client-protobuf/1.20.0/google-http-client-protobuf-1.20.0.jar to ${jetty.base}/lib/gcloud/google-http-client-protobuf-1.20.0.jar
    COPY  : /Users/chris/.m2/repository/com/google/inject/guice/4.0/guice-4.0.jar to ${jetty.base}/lib/gcloud/guice-4.0.jar
    COPY  : /Users/chris/.m2/repository/com/google/oauth-client/google-oauth-client-appengine/1.21.0/google-oauth-client-appengine-1.21.0.jar to ${jetty.base}/lib/gcloud/google-oauth-client-appengine-1.21.0.jar
    COPY  : /Users/chris/.m2/repository/com/google/oauth-client/google-oauth-client/1.21.0/google-oauth-client-1.21.0.jar to ${jetty.base}/lib/gcloud/google-oauth-client-1.21.0.jar
    COPY  : /Users/chris/.m2/repository/com/google/oauth-client/google-oauth-client-servlet/1.21.0/google-oauth-client-servlet-1.21.0.jar to ${jetty.base}/lib/gcloud/google-oauth-client-servlet-1.21.0.jar
    COPY  : /Users/chris/.m2/repository/com/google/protobuf/protobuf-java/3.0.0/protobuf-java-3.0.0.jar to ${jetty.base}/lib/gcloud/protobuf-java-3.0.0.jar
    COPY  : /Users/chris/.m2/repository/com/google/protobuf/protobuf-java-util/3.0.0/protobuf-java-util-3.0.0.jar to ${jetty.base}/lib/gcloud/protobuf-java-util-3.0.0.jar
    COPY  : /Users/chris/.m2/repository/commons-codec/commons-codec/1.3/commons-codec-1.3.jar to ${jetty.base}/lib/gcloud/commons-codec-1.3.jar
    COPY  : /Users/chris/.m2/repository/io/grpc/grpc-context/1.0.1/grpc-context-1.0.1.jar to ${jetty.base}/lib/gcloud/grpc-context-1.0.1.jar
    COPY  : /Users/chris/.m2/repository/io/grpc/grpc-core/1.0.1/grpc-core-1.0.1.jar to ${jetty.base}/lib/gcloud/grpc-core-1.0.1.jar
    COPY  : /Users/chris/.m2/repository/io/grpc/grpc-protobuf/1.0.1/grpc-protobuf-1.0.1.jar to ${jetty.base}/lib/gcloud/grpc-protobuf-1.0.1.jar
    COPY  : /Users/chris/.m2/repository/io/grpc/grpc-protobuf-lite/1.0.1/grpc-protobuf-lite-1.0.1.jar to ${jetty.base}/lib/gcloud/grpc-protobuf-lite-1.0.1.jar
    COPY  : /Users/chris/.m2/repository/javax/inject/javax.inject/1/javax.inject-1.jar to ${jetty.base}/lib/gcloud/javax.inject-1.jar
    COPY  : /Users/chris/.m2/repository/javax/jdo/jdo2-api/2.3-eb/jdo2-api-2.3-eb.jar to ${jetty.base}/lib/gcloud/jdo2-api-2.3-eb.jar
    COPY  : /Users/chris/.m2/repository/javax/transaction/transaction-api/1.1/transaction-api-1.1.jar to ${jetty.base}/lib/gcloud/transaction-api-1.1.jar
    COPY  : /Users/chris/.m2/repository/joda-time/joda-time/2.9.2/joda-time-2.9.2.jar to ${jetty.base}/lib/gcloud/joda-time-2.9.2.jar
    COPY  : /Users/chris/.m2/repository/org/apache/httpcomponents/httpclient/4.0.1/httpclient-4.0.1.jar to ${jetty.base}/lib/gcloud/httpclient-4.0.1.jar
    COPY  : /Users/chris/.m2/repository/org/apache/httpcomponents/httpcore/4.0.1/httpcore-4.0.1.jar to ${jetty.base}/lib/gcloud/httpcore-4.0.1.jar
    COPY  : /Users/chris/.m2/repository/org/codehaus/jackson/jackson-core-asl/1.9.11/jackson-core-asl-1.9.11.jar to ${jetty.base}/lib/gcloud/jackson-core-asl-1.9.11.jar
    COPY  : /Users/chris/.m2/repository/org/json/json/20151123/json-20151123.jar to ${jetty.base}/lib/gcloud/json-20151123.jar
    DOWNLD: http://central.maven.org/maven2/org/slf4j/jcl-over-slf4j/1.7.21/jcl-over-slf4j-1.7.21.jar to ${jetty.base}/lib/slf4j/jcl-over-slf4j-1.7.21.jar
    COPY  : ${jetty.home}/modules/gcloud/index.yaml to ${jetty.base}/etc/index.yaml
    INFO  : Base directory was modified
    ERROR : Module jcl-slf4j requires a module providing slf4j-impl from one of [slf4j-simple-impl, slf4j-logback, slf4j-jul, slf4j-log4j2, slf4j-log4j]

    ERROR : Unsatisfied module dependencies: jcl-slf4j

    Usage: java -jar $JETTY_HOME/start.jar [options] [properties] [configs]
           java -jar $JETTY_HOME/start.jar --help  # for more information

Doing this enables the GCloud Session module and any dependent session modules or files needed for it to run on the server. The example above is using a fresh `${jetty.base}` with nothing else enabled. Because the Google Cloud DataStore is not a technology provided by the Eclipse Foundation, users are prompted to assent to the licenses of the external vendor (Apache in this case).

You will notice, however, that the above output presented a warning: GCloud requires certain Java Commons Logging features to work correctly. GCloud has a dependency on Java Commons Logging, and by default Jetty will route this through SLF4J. Enabling the GCloud Sessions module will also enable the `jcl-slf4j` module, which sends JCL logging information to SLF4J. It does not, however, configure a SLF4J implementation for the users.

As such, you will also need to enable one of the SLF4J implementation modules listed. In this example, we will enable the `slf4j-simple-impl` module to provide a SLF4J implementation.

    $ java -jar ../start.jar --add-to-start=slf4j-simple-impl
    INFO  : slf4j-simple-impl initialized in ${jetty.base}/start.d/slf4j-simple-impl.ini
    INFO  : resources       transitively enabled
    DOWNLD: http://central.maven.org/maven2/org/slf4j/slf4j-simple/1.7.21/slf4j-simple-1.7.21.jar to ${jetty.base}/lib/slf4j/slf4j-simple-1.7.21.jar
    MKDIR : ${jetty.base}/resources
    COPY  : ${jetty.home}/modules/slf4j-simple-impl/resources/simplelogger.properties to ${jetty.base}/resources/simplelogger.properties
    INFO  : Base directory was modified

When the `--add-to-start` argument was added to the command line the first time, it enabled the the `session-store-gcloud` module as well as several others, such as as `server`, `sessions`, `webapp` and others which are required for GCloud session management to operate; the `slf4j-simple-impl` and its dependent modules were added when the the command was run the second time.

In addition to adding these modules to the classpath of the server it also added the respective configuration files to the `${jetty.base}start.d` directory.

> ### Note

> If you have updated versions of the jar files automatically downloaded by Jetty, you can place them in the associated `${jetty.base}/lib/` directory and use the `--skip-file-validation=<module name>` command line option to prevent errors when starting your server.

### Configuring GCloud Session Properties

Opening the `start.d/session-store-gcloud.ini` will display a list of all the configurable properties for the Google Cloud DataStore module:

    # ---------------------------------------
    # Module: session-store-gcloud
    # Enables GCloudDatastore session management.
    # ---------------------------------------
    --module=session-store-gcloud

    ## GCloudDatastore Session config
    #jetty.session.gracePeriod.seconds=3600
    #jetty.session.savePeriod.seconds=0
    #jetty.session.gcloud.maxRetries=5
    #jetty.session.gcloud.backoffMs=1000
    #jetty.session.gcloud.namespace=
    #jetty.session.gcloud.model.kind=GCloudSession
    #jetty.session.gcloud.model.id=id
    #jetty.session.gcloud.model.contextPath=contextPath
    #jetty.session.gcloud.model.vhost=vhost
    #jetty.session.gcloud.model.accessed=accessed
    #jetty.session.gcloud.model.lastAccessed=lastAccessed
    #jetty.session.gcloud.model.createTime=createTime
    #jetty.session.gcloud.model.cookieSetTime=cookieSetTime
    #jetty.session.gcloud.model.lastNode=lastNode
    #jetty.session.gcloud.model.expiry=expiry
    #jetty.session.gcloud.model.maxInactive=maxInactive
    #jetty.session.gcloud.model.attributes=attributes

jetty.session.gracePeriod.seconds
  Amount of time, in seconds, to wait for other nodes to be checked to verify an expired session is in fact expired throughout the cluster before closing it.
jetty.session.savePeriod.seconds=0

  By default whenever the last concurrent request leaves a session, that session is always persisted via the `SessionDataStore`, even if the only thing that changed on the session is its updated last access time. A non-zero value means that the `SessionDataStore` will skip persisting the session if only the access time changed, and it has been less than `savePeriod` seconds since the last time the session was written.

  > ### Note

  > Configuring `savePeriod` is useful if your persistence technology is very slow/costly for writes. In a clustered environment, there is a risk of the last access time of the session being out-of-date in the shared store for up to `savePeriod` seconds. This allows the possibility that a node may prematurely expire the session, even though it is in use by another node. Thorough consideration of the `maxIdleTime` of the session when setting the `savePeriod` is imperative - there is no point in setting a `savePeriod` that is larger than the `maxIdleTime`.

jetty.session.gcloud.maxRetries
  Maxmium number of tries to connect to GCloud DataStore to write sessions.
jetty.session.gcloud.backoffMs
  Amount of time, in milliseconds, between attempts to connect to the GCloud DataStore to write sessions.
jetty.session.gcloud.namespace
  Optional. Sets the namespace for GCloud Datastore to use. If set, partitions the visibility of session data between webapps, which is helpful for multi-tenant deployments. More information can be found here.

The other values listed are simply the names of properties that represent stored session data, and can be changed if needed.

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