Eventarc for event routing in GCP - Step-by-Step Execution

Process Flow - Eventarc for event routing

Event Source emits event

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Eventarc receives event

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Eventarc matches event to trigger

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Eventarc routes event to destination

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Destination processes event

Events are sent from a source, Eventarc receives and matches them to triggers, then routes them to the right destination for processing.

Execution Sample

GCP

gcloud eventarc triggers create my-trigger \
  --destination-run-service=my-service \
  --destination-run-region=us-central1 \
  --event-filters="type=google.cloud.storage.object.v1.finalized"

This command creates an Eventarc trigger that routes storage object finalized events to a Cloud Run service.

Process Table

Step	Action	Event Data	Trigger Match	Routing Destination	Result
1	Event Source emits event	{"type":"google.cloud.storage.object.v1.finalized","bucket":"my-bucket"}	N/A	N/A	Event sent to Eventarc
2	Eventarc receives event	{"type":"google.cloud.storage.object.v1.finalized","bucket":"my-bucket"}	Checking triggers	N/A	Event received
3	Eventarc matches event to trigger	{"type":"google.cloud.storage.object.v1.finalized"}	Trigger 'my-trigger' matches	N/A	Match found
4	Eventarc routes event	Event data passed	N/A	Cloud Run service 'my-service' in us-central1	Event routed
5	Destination processes event	Event data received	N/A	Cloud Run service 'my-service'	Event processed successfully
6	No more events	N/A	N/A	N/A	Waiting for next event

💡 No more events to process, Eventarc waits for new events.

Status Tracker

Variable	Start	After Step 1	After Step 2	After Step 3	After Step 4	After Step 5	Final
Event Data	None	{"type":"google.cloud.storage.object.v1.finalized","bucket":"my-bucket"}	{"type":"google.cloud.storage.object.v1.finalized","bucket":"my-bucket"}	{"type":"google.cloud.storage.object.v1.finalized"}	Passed to destination	Received by destination	Processed
Trigger Match	None	N/A	Checking triggers	Trigger 'my-trigger' matched	N/A	N/A	N/A
Routing Destination	None	N/A	N/A	N/A	Cloud Run service 'my-service'	Cloud Run service 'my-service'	Cloud Run service 'my-service'

Key Moments - 3 Insights

How does Eventarc know which destination to send the event to?

Eventarc uses triggers that match event attributes like type. In the execution_table row 3, the event type matches the trigger 'my-trigger', so Eventarc routes the event accordingly.

What happens if no trigger matches the event?

If no trigger matches, Eventarc does not route the event to any destination. This is implied by the matching step in execution_table row 3 where no match would mean no routing.

Can Eventarc process multiple event types with one trigger?

No, each trigger filters specific event types. To handle multiple types, you create multiple triggers. This is shown in the event-filters in the execution_sample.

Visual Quiz - 3 Questions

Look at the execution_table, at which step does Eventarc decide where to send the event?

A Step 3

B Step 2

C Step 4

D Step 5

💡 Hint

Check the 'Trigger Match' column in execution_table row 3 where the match is found.

According to variable_tracker, what is the state of 'Event Data' after step 4?

A None

B Matched trigger data

C Passed to destination

D Processed

💡 Hint

Look at the 'Event Data' row under 'After Step 4' in variable_tracker.

If the event type changed to one not matching any trigger, what would happen in the execution_table?

A Eventarc routes event to destination anyway

B No trigger match found, event not routed

C Eventarc matches a different trigger

D Eventarc processes event itself

💡 Hint

Refer to key_moments about what happens if no trigger matches.

Concept Snapshot

Eventarc routes events from sources to destinations using triggers.
Triggers filter events by attributes like type.
When an event matches a trigger, Eventarc routes it to the destination.
Destinations can be Cloud Run, Pub/Sub, or others.
Eventarc waits for events and routes them automatically.

Full Transcript

Eventarc is a service that listens for events from various sources. When an event happens, it sends the event data to Eventarc. Eventarc checks its triggers to find one that matches the event type or other filters. If a trigger matches, Eventarc routes the event to the destination specified in the trigger, such as a Cloud Run service. The destination then processes the event. If no trigger matches, the event is not routed. This process repeats for every event received.