AWS EventBridge

Amazon EventBridge is a serverless event bus that connects applications using events. Route events from AWS services, custom applications, and SaaS partners.

Table of Contents Core Concepts Common Patterns CLI Reference Best Practices Troubleshooting References Core Concepts Event Bus

Channel that receives events. Types:

Default: Receives AWS service events Custom: Your application events Partner: SaaS application events Rules

Match incoming events and route to targets. Each rule can have up to 5 targets.

Event Patterns

JSON patterns that define which events match a rule.

Targets

AWS services that receive matched events (Lambda, SQS, SNS, Step Functions, etc.).

Scheduler

Schedule one-time or recurring events to invoke targets.

Common Patterns Create Custom Event Bus and Rule

AWS CLI:

Create custom event bus

aws events create-event-bus --name my-app-events

Create rule

aws events put-rule \ --name order-created-rule \ --event-bus-name my-app-events \ --event-pattern '{ "source": ["my-app.orders"], "detail-type": ["Order Created"] }'

Add Lambda target

aws events put-targets \ --rule order-created-rule \ --event-bus-name my-app-events \ --targets '[{ "Id": "process-order", "Arn": "arn:aws:lambda:us-east-1:123456789012:function:ProcessOrder" }]'

Add Lambda permission

aws lambda add-permission \ --function-name ProcessOrder \ --statement-id eventbridge-order-created \ --action lambda:InvokeFunction \ --principal events.amazonaws.com \ --source-arn arn:aws:events:us-east-1:123456789012:rule/my-app-events/order-created-rule

boto3:

import boto3

events = boto3.client('events')

Create event bus

events.create_event_bus(Name='my-app-events')

Create rule

events.put_rule( Name='order-created-rule', EventBusName='my-app-events', EventPattern=json.dumps({ 'source': ['my-app.orders'], 'detail-type': ['Order Created'] }), State='ENABLED' )

Add target

events.put_targets( Rule='order-created-rule', EventBusName='my-app-events', Targets=[{ 'Id': 'process-order', 'Arn': 'arn:aws:lambda:us-east-1:123456789012:function:ProcessOrder' }] )

Publish Custom Events import boto3 import json

events = boto3.client('events')

events.put_events( Entries=[ { 'Source': 'my-app.orders', 'DetailType': 'Order Created', 'Detail': json.dumps({ 'order_id': '12345', 'customer_id': 'cust-789', 'total': 99.99, 'items': [ {'product_id': 'prod-1', 'quantity': 2} ] }), 'EventBusName': 'my-app-events' } ] )

Scheduled Events

Run every 5 minutes

aws events put-rule \ --name every-5-minutes \ --schedule-expression "rate(5 minutes)"

Run at specific times (cron)

aws events put-rule \ --name daily-cleanup \ --schedule-expression "cron(0 2 * * ? *)"

Add target

aws events put-targets \ --rule every-5-minutes \ --targets '[{ "Id": "cleanup-function", "Arn": "arn:aws:lambda:us-east-1:123456789012:function:Cleanup" }]'

EventBridge Scheduler (One-Time and Flexible)

One-time schedule

aws scheduler create-schedule \ --name send-reminder \ --schedule-expression "at(2024-12-25T09:00:00)" \ --target '{ "Arn": "arn:aws:lambda:us-east-1:123456789012:function:SendReminder", "RoleArn": "arn:aws:iam::123456789012:role/scheduler-role", "Input": "{\"message\": \"Merry Christmas!\"}" }' \ --flexible-time-window '{"Mode": "OFF"}'

Recurring with flexible window

aws scheduler create-schedule \ --name hourly-sync \ --schedule-expression "rate(1 hour)" \ --target '{ "Arn": "arn:aws:lambda:us-east-1:123456789012:function:SyncData", "RoleArn": "arn:aws:iam::123456789012:role/scheduler-role" }' \ --flexible-time-window '{"Mode": "FLEXIBLE", "MaximumWindowInMinutes": 15}'

AWS Service Events

EC2 state changes

aws events put-rule \ --name ec2-state-change \ --event-pattern '{ "source": ["aws.ec2"], "detail-type": ["EC2 Instance State-change Notification"], "detail": { "state": ["stopped", "terminated"] } }'

S3 object created

aws events put-rule \ --name s3-upload \ --event-pattern '{ "source": ["aws.s3"], "detail-type": ["Object Created"], "detail": { "bucket": {"name": ["my-bucket"]}, "object": {"key": [{"prefix": "uploads/"}]} } }'

CLI Reference Event Buses Command Description aws events create-event-bus Create event bus aws events delete-event-bus Delete event bus aws events list-event-buses List event buses aws events describe-event-bus Get event bus details Rules Command Description aws events put-rule Create or update rule aws events delete-rule Delete rule aws events list-rules List rules aws events describe-rule Get rule details aws events enable-rule Enable rule aws events disable-rule Disable rule Targets Command Description aws events put-targets Add targets to rule aws events remove-targets Remove targets aws events list-targets-by-rule List rule targets Events Command Description aws events put-events Publish events Best Practices Event Design Use meaningful source names — company.service.component Use descriptive detail-types — Order Created, User Signed Up Include correlation IDs for tracing Keep events small (< 256 KB) Use versioning for event schemas

Good event structure

{ 'Source': 'mycompany.orders.api', 'DetailType': 'Order Created', 'Detail': json.dumps({ 'version': '1.0', 'correlation_id': 'req-abc-123', 'timestamp': '2024-01-15T10:30:00Z', 'order_id': '12345', 'data': {...} }) }

Reliability Use DLQs for failed deliveries Implement idempotency in consumers Monitor failed invocations Use archive and replay for recovery Security Use resource policies to control access Enable encryption with KMS Use IAM roles for targets Cost Optimization Use specific event patterns to reduce matches Batch events when publishing (up to 10 per call) Archive selectively — not all events Troubleshooting Rule Not Triggering

Debug:

Check rule status

aws events describe-rule --name my-rule

Check targets

aws events list-targets-by-rule --rule my-rule

Test event pattern

aws events test-event-pattern \ --event-pattern '{"source": ["my-app"]}' \ --event '{"source": "my-app", "detail-type": "Test"}'

Common causes:

Rule disabled Event pattern doesn't match Target permissions missing Lambda Not Invoked

Check Lambda permissions:

aws lambda get-policy --function-name MyFunction

Required permission:

{ "Principal": "events.amazonaws.com", "Action": "lambda:InvokeFunction", "Resource": "function-arn", "Condition": { "ArnLike": { "AWS:SourceArn": "rule-arn" } } }

Events Not Reaching Custom Bus

Check:

Publishing to correct bus name Event format is valid JSON Put events has proper permissions

Test publish

aws events put-events \ --entries '[{ "Source": "test", "DetailType": "Test Event", "Detail": "{}", "EventBusName": "my-app-events" }]'

Viewing Failed Events

Enable CloudWatch metrics

aws events put-rule \ --name my-rule \ --event-pattern '...' \ --state ENABLED

Check FailedInvocations metric

aws cloudwatch get-metric-statistics \ --namespace AWS/Events \ --metric-name FailedInvocations \ --dimensions Name=RuleName,Value=my-rule \ --start-time $(date -d '1 hour ago' -u +%Y-%m-%dT%H:%M:%SZ) \ --end-time $(date -u +%Y-%m-%dT%H:%M:%SZ) \ --period 300 \ --statistics Sum

References EventBridge User Guide EventBridge API Reference EventBridge CLI Reference boto3 EventBridge Event Pattern Reference