# EventBridge — Amazon EventBridge Buses, rules and targets, with matched events delivered in-process to eight target types, filtered by every event-pattern match type bar three. **Status:** ⚠️ Partial ## Quick start Route an event to an SQS queue: ```bash export AWS_ENDPOINT_URL=http://localhost:4566 QUEUE=$(aws sqs create-queue --queue-name orders --query QueueUrl --output text) ARN=$(aws sqs get-queue-attributes --queue-url "$QUEUE" \ --attribute-names QueueArn --query Attributes.QueueArn --output text) aws events put-rule --name orders --event-pattern '{"source":["app.orders"]}' aws events put-targets --rule orders --targets "Id=1,Arn=$ARN" aws events put-events --entries \ '[{"Source":"app.orders","DetailType":"OrderPlaced","Detail":"{\"id\":1}"}]' aws sqs receive-message --queue-url "$QUEUE" ``` Any credentials work; with none configured, run `eval "$(overcast env)"` first — see [Using AWS SDKs and CLI](/docs/sdk-cli/index.md#credentials). ## What works | Area | Behaviour | | --- | --- | | Buses and rules | Bus, rule, target and tag CRUD. `CreateEventBus` stores `Description`, `DeadLetterConfig` and `KmsKeyIdentifier`; `DescribeEventBus` answers for `default` whether or not it was created. | | Bus permissions | `PutPermission` grants a statement, individually or as a whole `Policy` document that replaces the bus's policy; `RemovePermission` revokes one by `StatementId` or clears the policy with `RemoveAllPermissions`. `DescribeEventBus` reports the result as `Policy`. Stored, not enforced — like the rest of Overcast's IAM policies, nothing consults it to authorize a cross-account `PutEvents` call. | | Event patterns | Exact values plus `prefix`, `suffix`, `exists`, `equals-ignore-case`, `numeric` and `anything-but`. | | Rule validation | `PutRule` refuses a rule with no trigger, one naming an event bus that does not exist, and one whose pattern cannot be evaluated. | | Rule deletion | `DeleteRule` refuses a rule that still has targets, so `RemoveTargets` comes first. CloudFormation detaches them for you. | | Delivery | `PutEvents` evaluates every rule on the bus and delivers matches to Lambda, SQS, SNS, Step Functions, Kinesis, Firehose, ECS `RunTask` and another event bus. | | Scheduled rules | `rate(...)` and AWS's six-field `cron(...)` fire on an in-process clock, through the same target dispatcher. | | Input shaping | `Input`, `InputPath` and `InputTransformer`, at most one per target, over the JSONPath subset AWS uses (`$`, dotted members, array indexing). | | Retries and dead-lettering | `RetryPolicy.MaximumRetryAttempts`, `MaximumEventAgeInSeconds` measured from the envelope's `time`, and a `DeadLetterConfig` SQS queue. | | Service-originated events | CloudWatch alarm transitions, S3 object created/deleted, EC2 and ECS state changes, Auto Scaling launch and terminate events, and Step Functions execution status changes publish onto the default bus. | `InputTransformer` templates may reference ``, ``, `` and ``. Recent per-target outcomes — delivered, retried, dead-lettered, dropped — are readable at `GET /_overcast/eventbridge/deliveries`, an emulator-only endpoint backed by an in-memory ring that does not survive a restart. ## Differences from AWS | Area | On AWS | Overcast | | --- | --- | --- | | Event patterns | Also has `cidr`, `wildcard` and `$or` | Those three are refused by `PutRule` | | Target types | ~20 | Eight; anything else is refused by `PutTargets` | | Retry timing | Exponential backoff over up to 24 hours | Immediate, capped at 5 retries | | Bus-to-bus forwarding | Independent delivery, no hop budget | Nested in-process call, capped at 4 hops | | Archives, replay, API destinations | Supported | Not implemented | | Service-originated events | Substantially more | Six publishers | A target ARN naming an unsupported service comes back in `PutTargets`'s `FailedEntries` with `ErrorCode: UnsupportedTargetType`, rather than being stored as a rule that provisions cleanly and never fires. ## Gotchas > [!WARNING] > **`cidr`, `wildcard` and `$or` are refused, not ignored.** `PutRule` and > `TestEventPattern` answer `InvalidEventPatternException` naming the match > type, so a rule that could never fire is never stored. Rewrite the clause, or > filter on what the target receives. `PutRule` applies the same check to a pattern's shape: a field whose value is a bare string rather than an array, and a match type EventBridge does not define, are both `InvalidEventPatternException` rather than a rule that provisions and stays quiet. > [!IMPORTANT] > **Remove a rule's targets before deleting it.** `DeleteRule` answers > `ValidationException` while any target is attached, as AWS does. `Force` does > not help — it is the managed-rule escape, and AWS ignores it for every other > rule. Deleting an `AWS::Events::Rule` through CloudFormation needs nothing > extra; the stack detaches the targets it attached. Scheduled rules reach the same targets on an in-process clock, and are as strict about their expressions as AWS is. > [!IMPORTANT] > A `cron(...)` expression takes AWS's **six** fields, and day-of-week is 1-7 > from Sunday. The five-field Unix form is refused, as it is on AWS: every five > minutes is `cron(*/5 * * * ? *)`. `L`, `LW`, `W`, `L`, `#` > and the three-letter month and day names all work. ## Operations 20 of 31 listed operations are implemented. Per-operation status, notes and AWS API links: [EventBridge operations](/docs/services/eventbridge/operations/index.md). ## Related - [Scheduler](/docs/services/scheduler/index.md) — the same target dispatcher, on a clock - [Pipes](/docs/services/pipes/index.md) — point-to-point source → target wiring - [Step Functions](/docs/services/stepfunctions/index.md) — one of the eight target types - [All service pages](/docs/services/index.md) - [Service names and state overrides](/docs/configuration/index.md#service-names) - [AWS API reference](https://docs.aws.amazon.com/eventbridge/latest/APIReference/Welcome.html)