This modules demonstrates Apache Sling Journal Based Distribution on Apache Kafka. By going through the instructions, you will setup a basic Kafka deployment as well as Sling instances configured with Journal based distribution.

The following commands will download Kafka and extract it locally in the kafka_2.12-2.1.0 folder.

curl  https://archive.apache.org/dist/kafka/2.1.0/kafka_2.12-2.1.0.tgz | tar xz

From the kafka_2.12-2.1.0 folder run the commands

bin/zookeeper-server-start.sh config/zookeeper.properties &
bin/kafka-server-start.sh config/server.properties &

From the kafka_2.12-2.1.0 folder, once your Kafka setup is started, create the topics with the following commands

bin/kafka-topics.sh --create --zookeeper localhost:2181 --replication-factor 1 --partitions 1 --topic aemdistribution_package
bin/kafka-topics.sh --create --zookeeper localhost:2181 --replication-factor 1 --partitions 1 --topic aemdistribution_discovery
bin/kafka-topics.sh --create --zookeeper localhost:2181 --replication-factor 1 --partitions 1 --topic aemdistribution_command
bin/kafka-topics.sh --create --zookeeper localhost:2181 --replication-factor 1 --partitions 1 --topic aemdistribution_status
bin/kafka-topics.sh --create --zookeeper localhost:2181 --replication-factor 1 --partitions 1 --topic aemdistribution_event

The project is configured to start an author instance on port 9090 and a publish publish instance on port 9091. Make sure that Apache Maven is available on your setup and if needed install Apache Maven. Clone this project on your local file system, then run the following command

mvn clean install

The slingstart-maven-plugin will take care of starting the Sling instances. Have a look at the provisioning model files to see what OSGi bundles and configurations are used.

Once you have done the setup, you should be able to play with it. The setup has created a forwardPublisher Pub agent on author and a forwardSubscriber Sub agent on publish.

You can get the list of queues managed by the Pub agents by running the command

curl -u admin:admin http://localhost:9090/libs/sling/distribution/services/agents/forwardPublisher/queues.json

The forwardSubscriber should automatically subscribe to the forwardPublisher and appear as a queue in the response as shown below

{"sling:resourceType":"sling/distribution/service/agent/queue/list","items":["bd1f9e8c-b5c8-4f68-90d4-5eb9e4911ada-forwardSubscriber"]}

You can get the status of a queue managed by the Pub agent by running the command similar to the following (for the queue bd1f9e8c-b5c8-4f68-90d4-5eb9e4911ada-forwardSubscriber)

curl -u admin:admin http://localhost:9090/libs/sling/distribution/services/agents/forwardPublisher/queues/bd1f9e8c-b5c8-4f68-90d4-5eb9e4911ada-forwardSubscriber.json

When the queue contains items, you'll get a response similar to the one below

{"capabilities":["removable","clearable"],"sling:resourceType":"sling/distribution/service/agent/queue","state":"RUNNING","items":["aemdistribution_package-0@67"],"itemsCount":"1","empty":false}

First, create some test content on author using the Apache Sling POST servlet. The command below creates a resource test under /content/test.

curl -u admin:admin -F"sling:resourceType=some/resource" -F"title=Test" http://localhost:9090/content/test

Then distribute this test content using the forwardPublisher agent

curl -v -u admin:admin http://localhost:9090/libs/sling/distribution/services/agents/forwardPublisher -d 'action=ADD' -d 'path=/content/test'

Finally check on the publish instance that the test content has been distributed.

curl -u admin:admin http://localhost:9091/content/test.json

which should repond with a 200 HTTP status and the content

{"jcr:primaryType":"sling:OrderedFolder","jcr:createdBy":"","jcr:created":"Thu Aug 22 2019 16:45:12 GMT+0200","title":"Test","sling:resourceType":"some/resource"}

ab -A admin:admin -c 100 -n 10000 -T application/x-www-form-urlencoded -p <(echo "action=ADD&path=/content/test") http://localhost:9090/libs/sling/distribution/services/agents/forwardPublisher