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apache / openwhisk-package-kafka / 53a2ded161fea760ef1d62ad23ee32f3a01c63d5
commit53a2ded161fea760ef1d62ad23ee32f3a01c63d5[log] [tgz]
authorCarlos Santana <csantana23@gmail.com>Thu Feb 16 15:55:18 2017 -0500
committerJustin Berstler <bjustin@us.ibm.com>Thu Feb 16 15:55:18 2017 -0500
tree0e6145704543a5de43e692d98407b2696fbf9488
parentd950a10f2607ec4c6a13e36bc633e78c6442c1e3 [diff]
update readme with content from core repo (#139)

* update readme with content from core repo

* update section title

* update to use JSONData
1 file changed
tree: 0e6145704543a5de43e692d98407b2696fbf9488
  1. action/
  2. gradle/
  3. provider/
  4. tests/
  5. tools/
  6. .gitignore
  7. .travis.yml
  8. build.gradle
  9. CONTRIBUTING.md
  10. Dockerfile
  11. gradlew
  12. gradlew.bat
  13. installCatalog.sh
  14. installKafka.sh
  15. LICENSE.txt
  16. NOTICE
  17. README.md
  18. settings.gradle
README.md

This project is an OpenWhisk package that allows you to communicate with Kafka or IBM Message Hub instances.

Using the Messaging package

This package allows you to create triggers that react when messages are posted to either an IBM Message Hub instance, or to a generic Kafka instance. Since the parameters required for each of these situations are different, there are two separate feeds to handle them: /messaging/messageHubFeed and messaging/kafkaFeed.

Additionally, two actions are included which allow you to produce messages to either Message Hub, or generic Kafka instances. These are, /messaging/messageHubProduce and /messaging/kafkaProduce, respectively.

Creating a Trigger that Listens to an IBM MessageHub Instance

In order to create a trigger that reacts when messages are posted to a Message Hub instance, you need to use the feed named messaging/messageHubFeed. This feed supports the following parameters:

NameTypeDescription
kafka_brokers_saslJSON Array of StringsThis parameter is an array of <host>:<port> strings which comprise the brokers in your Message Hub instance
userStringYour Message Hub user name
passwordStringYour Message Hub password
topicStringThe topic you would like the trigger to listen to
kafka_admin_urlURL StringThe URL of the Message Hub admin REST interface
isJSONDataBoolean (Optional - default=false)When set to true this will cause the feed to attempt the message content as JSON before passing it along as the trigger payload.

While this list of parameters may seem daunting, they can be automatically set for you by using the package refresh CLI command:

  1. Create an instance of Message Hub service under your current organization and space that you are using for OpenWhisk.

  2. Verify that the the topic you want to listen to already exists in Message Hub or create a new topic, for example mytopic.

  3. Refresh the packages in your namespace. The refresh automatically creates a package binding for the Message Hub service instance that you created.

$ wsk package refresh

created bindings:
Bluemix_Message_Hub_Credentials-1

$ wsk package list

packages
/myBluemixOrg_myBluemixSpace/Bluemix_Message_Hub_Credentials-1 private

Your package binding now contains the credentials associated with your Message Hub instance.

  1. Now all you need to do is create a Trigger that will be fired when new messages are posted to your Message Hub topic.
$ wsk trigger create MyMessageHubTrigger -f /myBluemixOrg_myBluemixSpace/Bluemix_Message_Hub_Credentials-1/messageHubFeed -p topic mytopic

Setting up a Message Hub package outside Bluemix

If you're not using OpenWhisk in Bluemix or if you want to set up your Message Hub outside of Bluemix, you must manually create a package binding for your Message Hub service. You need the Message Hub service credentials and connection information.

  1. Create a package binding that is configured for your Message Hub service.
$ wsk package bind /whisk.system/messaging myMessageHub -p kafka_brokers_sasl "[\"kafka01-prod01.messagehub.services.us-south.bluemix.net:9093\", \"kafka02-prod01.messagehub.services.us-south.bluemix.net:9093\", \"kafka03-prod01.messagehub.services.us-south.bluemix.net:9093\"]" -p user <your Message Hub user> -p password <your Message Hub password> -p kafka_admin_url https://kafka-admin-prod01.messagehub.services.us-south.bluemix.net:443
  1. Now you can create a Trigger using your new package that will be fired when new messages are posted to your Message Hub topic.
$ wsk trigger create MyMessageHubTrigger -f myMessageHub/messageHubFeed -p topic mytopic -p isJSONData true

Creating a Trigger that Listens to a Generic Kafka Instance

In order to create a trigger that reacts when messages are posted to an unauthenticated Kafka instance, you need to use the feed named messaging/kafkaFeed. This feed supports the following parameters:

NameTypeDescription
brokersJSON Array of StringsThis parameter is an array of <host>:<port> strings which comprise the brokers in your Message Hub instance
topicStringThe topic you would like the trigger to listen to
isJSONDataBoolean (Optional - default=false)When set to true this will cause the feed to attempt the message content as JSON before passing it along as the trigger payload.

Example:

$ wsk trigger create MyKafkaTrigger -f /whisk.system/messaging/kafkaFeed -p brokers "[\"mykafkahost:9092\", \"mykafkahost:9093\"]" -p topic mytopic -p isJSONData true

Listening for messages

After creating a trigger, the system will monitor the specified topic in your messaging service. When new messages are posted, the trigger will be fired.

The payload of that trigger will contain a messages field which is an array of messages that have been posted since the last time your trigger fired. Each message object in the array will contain the following fields:

  • topic
  • partition
  • offset
  • key
  • value

In Kafka terms, these fields should be self-evident. However, the value requires special consideration. If the isJSONData parameter was set false (or not set at all) when the trigger was created, the value field will be the raw value of the posted message. However, if isJSONData was set to true when the trigger was created, the system will attempt to parse this value as a JSON object, on a best-effort basis. If parsing is successful, then the value in the trigger payload will be the resulting JSON object.

For example, if a message of {"title": "Some string", "amount": 5, "isAwesome": true} is posted with isJSONData set to true, the trigger payload might look something like this:

{
  "messages": [
      {
        "partition": 0,
        "key": null,
        "offset": 421760,
        "topic": "mytopic",
        "value": {
            "amount": 5,
            "isAwesome": true,
            "title": "Some string"
        }
      }
  ]
}

However, if the same message content is posted with isJSONData set to false, the trigger payload would look like this:

{
  "messages": [
    {
      "partition": 0,
      "key": null,
      "offset": 421761,
      "topic": "mytopic",
      "value": "{\"title\": \"Some string\", \"amount\": 5, \"isAwesome\": true}"
    }
  ]
}

Messages are Batched

You will notice that the trigger payload contains an array of messages. This means that if you are producing messages to your messaging system very quickly, the feed will attempt to batch up the posted messages into a single firing of your trigger. This allows the messages to be posted to your trigger more rapidly and efficiently.

Please keep in mind when coding actions that are fired by your trigger, that the number of messages in the payload is technically unbounded, but will always be greater than 0.

Producing Messages to Message Hub

If you would like to use an OpenWhisk action to conveniently produce a message to Message Hub, you can use the /messaging/messageHubProduce action. This action takes the following parameters:

NameTypeDescription
kafka_brokers_saslJSON Array of StringsThis parameter is an array of <host>:<port> strings which comprise the brokers in your Message Hub instance
userStringYour Message Hub user name
passwordStringYour Message Hub password
topicStringThe topic you would like the trigger to listen to
valueStringThe value for the message you would like to produce
keyString (Optional)The key for the message you would like to produce

While the first three parameters can be automatically bound by using wsk package refresh, here is an example of invoking the action with all required parameters:

wsk action invoke /messaging/messageHubProduce -p kafka_brokers_sasl "[\"kafka01-prod01.messagehub.services.us-south.bluemix.net:9093\", \"kafka02-prod01.messagehub.services.us-south.bluemix.net:9093\", \"kafka03-prod01.messagehub.services.us-south.bluemix.net:9093\"]" -p topic mytopic -p user <your Message Hub user> -p password <your Message Hub password> -p value "This is the content of my message"

Producing Messages to a Generic Kafka Instance

If you would like to use an OpenWhisk action to conveniently produce a message to a generic Kafka instance, you can use the /messaging/kafkaProduce action. This action takes the following parameters:

NameTypeDescription
brokersJSON Array of StringsThis parameter is an array of <host>:<port> strings which comprise the brokers in your Kafka cluster
topicStringThe topic you would like the trigger to listen to
valueStringThe value for the message you would like to produce
keyString (Optional)The key for the message you would like to produce

Here is an example of invoking the action with all required parameters:

wsk action invoke /messaging/kafkaProduce -p brokers "[\"mykafkahost:9092\", \"mykafkahost:9093\"]" -p topic mytopic -p value "This is the content of my message"

Testing

An OpenWhisk deployment is required in order for the automated test suite to be executed. To run tests locally, run $ ./gradlew tests:test -Dhost=<container_address> -Dport=<docker_port> from the project‘s root directory. Where <docker_address> is the IP address of the service’s docker container, and <docker_port> is the port the docker container is listening on. In addition, OPENWHISK_HOME must be set to the root of the local OpenWhisk directory. Ex: export OPENWHISK_HOME=<openwhisk_directory>.

References