The component interacts with Google Pub-Sub API. The API is an asynchronous messaging service that decouples services that produce events from services that process events.
Pub/Sub offers durable message storage and real-time message delivery with high availability and consistent performance at scale. Pub/Sub servers run in all Google Cloud regions around the world.
- Topic: A named resource to which messages are sent by publishers.
- Subscription: A named resource representing the stream of messages from a single, specific topic, to be delivered to the subscribing application. For more details about subscriptions and message delivery semantics, see the Subscriber Guide.
- Message: The combination of data and (optional) attributes that a publisher sends to a topic and is eventually delivered to subscribers.
- Message attribute: A key-value pair that a publisher can define for a message. For example, key
iana.org/language_tagand valueencould be added to messages to mark them as readable by an English-speaking subscriber.
PubSub component authentication works with
Google IAM Service Accounts
and two-legged OAuth, in order to authenticate your component you would
need to create a new Service Account on Service Accounts Page
of your project and download the JSON file with the private key.
You would need client_email and private_key values
on component authentication page (see here
for more information).
The Subscribe trigger receives a message from a Topic, emits it, and sends an acknowledgment to Pub/Sub.
Select topic to subscribe- (dropdown, required): Select one of the available topics from the list
None.
- data - (object or string, required): Data of the message, the component will try to parse it as JSON object, if fails - result will be plain text
- attributes - (object, optional): Attributes for this message - a list of
"key": valuepairs - id - (string, required): ID of this message, assigned by the server when the message is published
- publishTime - (string, required): The time at which the message was published to Google Pub-Sub server
- received - (string, required): The time at which the message was read by the component
- If you use ordinary flow (
real-timenot enabled) after flow starts you will need to run it once (make execution) to create a subscription in Google Pub-Sub
Subscribe
The Subscribe trigger receives a message from a Topic, emits it, and sends an acknowledgment to Pub/Sub.
Topic Name- (required field) fully-qualified topic resource name string, e.g.projects/<project_id>/topics/<topic_name>
The Publish action retrieves message body from a previous step and sends a message to a Topic while remaining unaware of any existing subscriptions.
Topic Name- (required field) fully-qualified topic resource name string, e.g.projects/<project_id>/topics/<topic_name>
Please take a special care of the indepmotency of your processing flow, here is the extract from PubSub Subscriber Guide
For the most part Pub/Sub delivers each message once, and in the order in which it was published. However, once-only and in-order delivery are not guaranteed: it may happen that a message is delivered more than once, and out of order. Therefore, your subscriber should be idempotent when processing messages, and, if necessary, able to handle messages received out of order. If ordering is important, we recommend that the publisher of the topic to which you subscribe include some kind of sequence information in the message; see this page for a full discussion on message ordering. Messages that are not acknowledged, are retried indefinitely for up to seven days.
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