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MessageHub Trigger Provider Architecture

Create Trigger Feed

MessageHub Trigger Create

Scenario: User wants to create a trigger trigger1 for MessageHub service instance instance1, using Credentials Credential-1 and use rule rule1 to invoke action action1 with messages from topic topic1.

  1. Developer creates a MessageHub service instance1
  2. Developer creates topic topic1 in MessageHub service instance1
  3. Developer creates Credential key Credential-1 for MessageHub instance1
  4. Developer creates trigger trigger1 on OpenWhisk, the trigger stores the annotation feed with the feedAction name from system package or binded package.(/whisk.system/messagingWeb/messageHubFeed).
  5. Developer invokes action feedAction to create trigger feed passing input parameters (lifeCycle:CREATE, trigger1, Credentials1, Options:topic1)
  6. The feedAction invokes feedWebAction forwarding input parameter.
  7. The feedWebAction inserts trigger feed doc into the DB for worker group 0 (feedWebAction protects DB credentials)
  8. DB insertion notifies workers group 0 via Cloudant/CouchDB changes API, workers listen on DB view with a filter for their group worker0 and gets the DB doc.
  9. Kafka Consumer is created on each worker in a consumer group and starts polling for messages on topic1 from instance1 using Credentials-1.
  10. Developer creates rule1 indicating that when trigger1 fires invoke action1.
  11. Event source produces messages on topic1.
  12. Both consumers will batch the messages from topic1 and fire trigger1.
    • The fire is done with an http request containing the batch of messages in the body.
    • Consumer will not poll for more messages and will not commit batch of messages until the http request gets a response from OpenWhisk trigger endpoint.
    • Consumers in the same consumer group get assigned a set of partitions, each consumer on each worker host will get a unique set of messages avoiding duplicate messages being included in trigger fires.
  13. OpenWhisk will process the trigger fire for trigger1 and finds the rule1 and invokes action1 with messages from topic topic1.

Update Trigger Feed

MessageHub Trigger Update

Scenario: User wants to update trigger trigger1 to change from topic topic1 to topic topic2.

  1. Developer creates topic topic2 in MessageHub service instance1.
  2. Developer gets the annotation feed from trigger trigger1.
  3. Developer invokes feedAction to update trigger feed passing input parameters (lifeCycle:UPDATE, trigger1, Options:topic2).
  4. The feedAction invokes feedWebAction forwarding input parameter.
  5. The feedWebAction inserts trigger feed doc into the DB for worker group 0 (feedWebAction protects DB credentials).
  6. DB insertion notifies workers group 0 via Cloudant/CouchDB changes API, workers listen on DB view with a filter for their group worker0 and gets the DB doc.
  7. Kafka Consumer is re-created on each worker in a consumer group and starts polling for messages on topic2 from instance1 using Credentials-1.
  8. Event source produces messages on topic2.
  9. Both consumers will now handle topic2 instead of topic1.
  10. OpenWhisk will process the trigger fire for trigger1, finds the rule rule1 and invokes action1 with messages from topic topic2.

Read Trigger Feed

MessageHub Trigger Read

Scenario: User wants to read the configuration and status for trigger trigger1.

  1. Developer gets the annotation feed from trigger trigger1.
  2. Developer invokes feedAction to read the trigger feed passing input parameters (lifeCycle:READ, trigger1).
  3. The feedAction invokes feedWebAction forwarding input parameter.
  4. The feedWebAction gets the trigger feed doc from the DB (feedWebAction protects DB credentials).
  5. The DB returns the trigger feed doc for trigger1.
  6. The feedWebAction returns a response to feedAction.
  7. The feedAction returns response (config, status) to Developer.

Delete Trigger Feed

MessageHub Trigger Read

Scenario: User wants to delete trigger trigger1.

  1. Developer deletes rule rule1
  2. Developer gets the annotation feed from trigger trigger1.
  3. Developer invokes feedAction to delete the trigger feed passing input parameters (lifeCycle:DELETE, trigger1).
  4. The feedAction invokes feedWebAction forwarding input parameter.
  5. The feedWebAction updates the trigger feed doc into the DB with a field delete:true(feedWebAction protects DB credentials).
  6. DB update notifies workers group 0 via Cloudant/CouchDB changes API, workers listen on DB view with a filter for their group worker0 and gets the DB doc. The Kafka consumers for trigger1/topic2 get destroyed.
  7. The feedWebAction deletes the trigger feed doc from the DB.
  8. The Developer deletes trigger trigger1