Trivial examples of all the Immutant features
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Latest commit 302e8aa Oct 3, 2016 @tobias tobias committed on GitHub Merge pull request #8 from The-Alchemist/patch-1
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Immutant Feature Demo

An app showing trivial examples of all the Immutant libraries. Most log something to stdout, but the demo.web examples are available at http://localhost:8080/.

You can view a running example here:

You need at least Java 8 and Leiningen 2.4.0

SSL and HTTP/2

By default, the web demo fires up only one HTTP listener on port 8080. But if you set the ssl-port option, it'll also fire up an HTTPS listener with a self-signed certificate. You can even enable HTTP 2.0 on that port by setting the http2? option. Doing so requires a version of ALPN to be available on the bootclasspath. We rely on a convenient Java agent to load one appropriate for your JVM. This agent is invoked, and the above options are set when the :http2 profile defined in project.clj is enabled, like so:

lein with-profile http2 run

You can run the app in several ways:

With lein run

The value of :main in project.clj is demo.core, which runs -main for all of the demo namespaces.

lein run

You can use the -m option to run specific namespaces, e.g.

lein run -m demo.web

And you can run an HTTP/2.0 listener on port 9999 like this:

lein with-profile http2 run -m demo.web ssl-port 9999

At a repl

You can fire up a repl and invoke each namespace directly

lein repl

Once at a prompt, try (demo.web/-main)

Or, for an HTTP/2.0 listener, try this:

`(demo.web/-main "ssl-port" 9999 "http2?" true)`

You'll note in the demo.web/-main function that the option keys are expected to be strings so that command line arguments can override them.

From a jar

Create an uberjar and run it

lein uberjar
java -jar target/demo-standalone.jar

To create an HTTP/2.0 listener from the uberjar, we'll need to do some work. Because we're no longer running the app from Leiningen, our :http2 profile does us no good, so we'll need to manually invoke the ALPN Java agent (described above). We'll also need to pass the necessary ssl-port and http2? command line options. Once you locate the agent jar in your local Maven repo, you may test HTTP/2 like so:

java -javaagent:{/path/to/jetty-alpn-agent.jar} -jar target/demo-standalone.jar ssl-port 8443 http2? true

This assumes you've activated the :http2 profile at some point. If you haven't, the agent jar won't be in your repo. To fetch it, try:

lein with-profile http2 check

In WildFly

WildFly is installed by downloading and unpacking an archive. For our purposes, we'll drop it in the project directory. For a list of available versions, see


# Install WildFly
unzip wildfly-$

# Create the war file and deploy it to WildFly
lein immutant war -o wildfly-$VERSION

# Fire up WildFly
wildfly-$VERSION/bin/ -c standalone-full.xml

Note the web examples will be deployed with a context path of /demo on WildFly so go to http://localhost:8080/demo/ to see the web examples. Alternatively, to mount the app at the root context, http://localhost:8080/, rename the war file beneath wildfly-$VERSION/standalone/deployments/ to ROOT.war.

In a WildFly cluster

We'll simulate a cluster by "installing" another WildFly instance:

cp -R wildfly-$VERSION wildfly-too
rm -rf wildfly-too/standalone/data/

Because we already deployed the war file, it gets copied over, too. And to avoid spurious errors, we remove the standalone/data directory where WildFly keeps some runtime state.

Now we'll start our first instance:

wildfly-$VERSION/bin/ -c standalone-full-ha.xml -Djboss.messaging.cluster.password=demo

Note the following:

  • We use the standalone-full-ha.xml file in which clustering is configured
  • Since both of our peers will be on the same host, we need to give each node a unique name
  • The cluster requires a password

In another shell, we fire up the second instance with similar options plus a system property to avoid port conflicts, since we're on the same host.

wildfly-too/bin/ -c standalone-full-ha.xml -Djboss.messaging.cluster.password=demo -Djboss.socket.binding.port-offset=100

You can correlate the output from both peers to the code beneath src/demo to observe HA singleton jobs, load-balanced messaging, and distributed caching. And you can observe session replication by reloading the following pages in your browser:

On Heroku

Press this button:

Deploy to Heroku

Or do it manually. Heroku requires a Procfile in the project root to bootstrap the app. With this in place, we simply create the heroku repo and push:

heroku create
git push heroku master

To see the log output:

heroku logs --tail

And to open the app in the browser:

heroku open

On OpenShift

The app includes start and stop action hooks beneath the .openshift/ directory that enable it to be deployed on OpenShift using the DIY cartridge.

We'll call our application demo:

rhc app-create demo diy --from-code

To see the log output:

cd demo
rhc tail

Once the app is up, visit http://demo-<YOUR_DOMAIN> The port, 8000, is optional for all but the WebSocket example, because OpenShift only supports WebSockets on port 8000.

In a WildFly cluster on OpenShift

We can use the WildFly cartridge to create a scaled application named wf. The pre_deploy_wildfly action hook will create our war file in a directory monitored by the app server.

rhc app-create wf wildfly --scaling --gear-size medium --from-code

Note we set the --scaling option and a medium --gear-size. It will take a few minutes for the command to complete. Once it does, monitor the log output:

cd wf
rhc tail

View the web examples at http://wf-<YOUR_DOMAIN>

Try scaling the app up to 2 gears:

rhc cartridge-scale wildfly 2

View the gears for your app to obtain their ssh URL's:

rhc app-show --gears

Login to a gear to monitor/control it:

rhc ssh
gear restart