EventBus

caution

This is the SST v1.x Constructs doc. SST v2 is now released. If you are using v2, see the v2 Constructs doc. If you are looking to upgrade to v2, check out the upgrade steps.

The EventBus construct is a higher level CDK construct that makes it easy to create an EventBridge Event Bus. You can create a bus that has a list of rules and targets. And you can publish messages to it from any part of your serverless app.

You can have two types of targets; Function targets (with a Lambda function) or Queue targets (with an SQS queue). See the examples for more details.

Examples

Using the minimal config

import { EventBus } from "@serverless-stack/resources";

new EventBus(stack, "Bus", {
  rules: {
    myRule: {
      pattern: { source: ["myevent"] },
      targets: {
        myTarget1: "src/function1.handler",
        myTarget2: "src/function2.handler"
      },
    },
  },
});

Note that, myRule here is simply a key to identify the rule.

Configuring rules

Lazily adding rules

Add rules after the EventBus has been created.

const bus = new EventBus(stack, "Bus", {
  rules: {
    myRule: {
      pattern: { source: ["myevent"] },
      targets: {
        myTarget1: "src/target1.main",
        myTarget2: "src/target2.main",
      },
    },
  },
});

bus.addRules(this, {
  myRule2: {
    pattern: { source: ["myevent"] },
    targets: {
      myTarget3: "src/target3.main",
      myTarget4: "src/target4.main",
    },
  },
});

Configuring the Rule

Configure the internally created CDK Rule instance.

new EventBus(stack, "Bus", {
  rules: {
    myRule: {
      ruleName: "MyRule",
      pattern: { source: ["myevent"] },
      targets: {
        myTarget1: "src/target1.main",
        myTarget2: "src/target2.main",
      },
    },
  },
});

Configuring Function targets

Adding targets

You can directly pass in the path to the Function.

new EventBus(stack, "Bus", {
  rules: {
    myRule: {
      pattern: { source: ["myevent"] },
      targets: {
        myTarget1: "src/target1.main",
      },
    },
  },
});

Specifying function props for all targets

You can extend the minimal config, to set some function props and have them apply to all the rules.

new EventBus(stack, "Bus", {
  defaults: {
    function: {
      timeout: 20,
      environment: { tableName: table.tableName },
      permissions: [table],
    },
  },
  rules: {
    myRule: {
      pattern: { source: ["myevent"] },
      targets: {
        myTarget1: "src/target1.main",
        myTarget2: "src/target2.main",
      },
    },
  },
});

Configuring an individual target

Configure each Lambda function separately.

new EventBus(stack, "Bus", {
  rules: {
    myRule: {
      pattern: { source: ["myevent"] },
      targets: {
        myTarget1: {
          function: {
            srcPath: "src/",
            handler: "target1.main",
            environment: { tableName: table.tableName },
            permissions: [table],
          },
        },
      },
    },
  },
});

Note that, you can set the defaultFunctionProps while using the function per target. The function will just override the defaultFunctionProps. Except for the environment, the layers, and the permissions properties, that will be merged.

new EventBus(stack, "Bus", {
  defaults: {
    function: {
      timeout: 20,
      environment: { tableName: table.tableName },
      permissions: [table],
    },
  },
  rules: {
    myRule: {
      pattern: { source: ["myevent"] },
      targets: {
        myTarget1: {
          function: {
            handler: "src/target1.main",
            timeout: 10,
            environment: { bucketName: bucket.bucketName },
            permissions: [bucket],
          },
        },
        myTarget2: "src/target2.main",
      },
    },
  },
});

So in the above example, the target1 function doesn't use the timeout that is set in the defaultFunctionProps. It'll instead use the one that is defined in the function definition (10 seconds). And the function will have both the tableName and the bucketName environment variables set; as well as permissions to both the table and the bucket.

Configuring the target

Configure the internally created CDK Target.

import { RuleTargetInput } from 'aws-cdk-lib/aws-events';

new EventBus(stack, "Bus", {
  rules: {
    myRule: {
      pattern: { source: ["myevent"] },
      targets: {
        myTarget1: {
          function: "src/target1.main",
          cdk: {
            target: {
              retryAttempts: 20,
              message: RuleTargetInput.fromEventPath('$.detail'),
            },
          },
        },
      },
    },
  },
});

In the example above, the function is invoked with the contents of the detail property on the event, instead of the envelope - i.e. the original payload put onto the EventBus.

Attaching permissions for all targets

Allow all the targets in the entire EventBus to access S3.

const bus = new EventBus(stack, "Bus", {
  rules: {
    myRule: {
      pattern: { source: ["myevent"] },
      targets: {
        myTarget1: "src/target1.main",
        myTarget2: "src/target2.main",
      },
    },
  },
});

bus.attachPermissions(["s3"]);

Attaching permissions for a specific target

Allow one of the targets to access S3.

const bus = new EventBus(stack, "Bus", {
  rules: {
    myRule: {
      pattern: { source: ["myevent"] },
      targets: {
        myTarget1: "src/target1.main",
        myTarget2: "src/target2.main",
      },
    },
  },
});

bus.attachPermissionsToTarget("myRule", 0, ["s3"]);

Here we are referring to the rule using the rule key, myRule.

Configuring Queue targets

Specifying the Queue directly

You can directly pass in a Queue.

const myQueue = new Queue(this, "MyQueue");

new EventBus(stack, "Bus", {
  rules: {
    myRule: {
      pattern: { source: ["myevent"] },
      targets: {
        myTarget1: myQueue
      },
    },
  },
});

Configuring the target

Configure the internally created CDK Target.

new EventBus(stack, "Bus", {
  rules: {
    myRule: {
      pattern: { source: ["myevent"] },
      targets: {
        myTarget1: {
          queue: myQueue,
          cdk: {
            target: {
              messageGroupId: "group1",
            },
          },
        },
      },
    },
  },
});

Receiving AWS events

When an AWS service in your account emits an event, it goes to your account’s default event bus.

import * as events from "aws-cdk-lib/aws-events";

new EventBus(stack, "Bus", {
  cdk: {
    eventBus: events.EventBus.fromEventBusName(
      this, "ImportedBus", "default"
    ),
  },
  rules: {
    myRule: {
      pattern: { source: ["aws.codebuild"] },
      targets: {
        myTarget1: "src/target1.main",
        myTarget2: "src/target2.main",
      },
    },
  },
});

Advanced examples

Configuring the EventBus

Configure the internally created CDK EventBus instance.

new EventBus(stack, "Bus", {
  cdk: {
    eventBus: {
      eventBusName: "MyEventBus",
    },
  },
  rules: {
    myRule: {
      pattern: { source: ["myevent"] },
      targets: {
        myTarget1: "src/target1.main",
        myTarget2: "src/target2.main",
      },
    },
  },
});

Importing an existing EventBus

Override the internally created CDK EventBus instance.

import * as events from "aws-cdk-lib/aws-events";

new EventBus(stack, "Bus", {
  cdk: {
    eventBus: events.EventBus.fromEventBusName(
      this, "ImportedBus", eventBusName
    ),
  },
  rules: {
    myRule: {
      pattern: { source: ["myevent"] },
      targets: {
        myTarget1: "src/target1.main",
        myTarget2: "src/target2.main",
      },
    },
  },
});

Using existing Lambda functions as targets

import * as lambda from "aws-cdk-lib/aws-lambda";

new EventBus(stack, "Bus", {
  rules: {
    myRule: {
      pattern: { source: ["myevent"] },
      targets: {
        myTarget: {
          cdk: {
            function: lambda.Function.fromFunctionName(stack, "ITarget", "my-function"),
          },
        },
      },
    },
  },
});

You can create the EventBus construct in one stack, and add rules in other stacks. To do this, return the EventBus from the stack function

stacks/MainStack.ts
import { EventBus, App, StackContext } from "@serverless-stack/resources";

export function MainStack({ stack }: StackContext) {
  const bus = new EventBus(stack, "Bus", {
    rules: {
      myRule: {
        pattern: { source: ["myevent"] },
        targets: {
          myTarget1: "src/target1.main",
          myTarget2: "src/target2.main",
        },
      },
    },
  });

  return {
    bus
  }
}

Then import the auth construct into another stack with use and call addRules. Note that the AWS resources for the added routes will be created in AnotherStack.

stacks/AnotherStack.ts
import { EventBus, StackContext } from "@serverless-stack/resources";
import { MainStack } from "./MainStack"

export function AnotherStack({ stack }: StackContext) {
  const { bus } = use(MainStack);
  bus.addRules(stack, {
    myRule2: {
      targets: {
        myTarget3: "src/target3.main",
        myTarget4: "src/target4.main",
      },
    },
  });
}

Constructor

new EventBus(scope, id, props)

Parameters

scope Construct
id string
props EventBusProps

EventBusProps

defaults.function?

Type : FunctionProps

The default function props to be applied to all the Lambda functions in the EventBus. The environment, permissions and layers properties will be merged with per route definitions if they are defined.

new EventBus(stack, "Bus", {
  defaults: {
    function: {
      timeout: 20,
    }
  },
});

rules?

Type : Record<string, EventBusRuleProps>

The rules for the eventbus

new EventBus(stack, "Bus", {
  rules: {
    myRule: {
      pattern: { source: ["myevent"] },
      targets: {
        myTarget: "src/function.handler"
      },
    },
  },
});

cdk.eventBus?

Type : IEventBus | EventBusProps

Override the internally created EventBus

new EventBus(stack, "Bus", {
  cdk: {
    eventBus: {
      eventBusName: "MyEventBus",
    },
  }
});

cdk.id?

Type : string

Allows you to override default id for this construct.

Properties

An instance of EventBus has the following properties.

eventBusArn

Type : string

The ARN of the internally created EventBus instance.

eventBusName

Type : string

The name of the internally created EventBus instance.

id

Type : string

cdk.eventBus

Type : IEventBus

The internally created CDK EventBus instance.

Methods

An instance of EventBus has the following methods.

addRules

addRules(scope, rules)

Parameters

scope Construct
rules Record<string, EventBusRuleProps>

Add rules after the EventBus has been created.

bus.addRules(stack, {
  myRule2: {
    pattern: { source: ["myevent"] },
      targets: {
        myTarget3: "src/function3.handler"
        myTarget4: "src/function4.handler"
      },
  },
});

attachPermissions

attachPermissions(permissions)

Parameters

permissions Permissions

Add permissions to all event targets in this EventBus.

bus.attachPermissions(["s3"]);

attachPermissionsToTarget

attachPermissionsToTarget(ruleKey, targetName, permissions)

Parameters

ruleKey string
targetName string
permissions Permissions

Add permissions to a specific event bus rule target

const bus = new EventBus(stack, "Bus", {
  rules: {
    myRule: {
      pattern: { source: ["myevent"] },
      targets: {
        myTarget1: "src/function1.handler"
        myTarget2: "src/function2.handler"
      },
    },
  },
});

bus.attachPermissionsToTarget("myRule", 0, ["s3"]);

bind

bind(constructs)

Parameters

constructs Array<SSTConstruct>

Binds the given list of resources to all event targets in this EventBus.

bus.bind([STRIPE_KEY, bucket]);

bindToTarget

bindToTarget(ruleKey, targetName, constructs)

Parameters

ruleKey string
targetName string
constructs Array<SSTConstruct>

Binds the given list of resources to a specific event bus rule target

const bus = new EventBus(stack, "Bus", {
  rules: {
    myRule: {
      pattern: { source: ["myevent"] },
      targets: {
        myTarget1: "src/function1.handler"
        myTarget2: "src/function2.handler"
      },
    },
  },
});

bus.bindToTarget("myRule", 0, [STRIPE_KEY, bucket]);

getRule

getRule(key)

Parameters

key string

Get a rule

bus.getRule("myRule");

EventBusRuleProps

Used to configure an EventBus rule

Fields to match on the detail field

new EventBus(stack, "Bus", {
  rules: {
    myRule: {
      pattern: { detail: { FOO: 1 }  },
    },
  },
});

pattern.detailType?

Type : Array<string>

A list of detailTypes to filter on

new EventBus(stack, "Bus", {
  rules: {
    myRule: {
      pattern: { detailType: ["foo"]  },
    },
  },
});

pattern.source?

Type : Array<string>

A list of sources to filter on

new EventBus(stack, "Bus", {
  rules: {
    myRule: {
      pattern: { source: ["myevent"] },
    },
  },
});

targets?

Type : Record<string, string | Function | Queue | EventBusFunctionTargetProps | EventBusQueueTargetProps>

Configure targets for this rule. Can be a function or queue

new EventBus(stack, "Bus", {
  rules: {
    myRule: {
      targets: {
        myTarget1: "src/function.handler",
        myTarget2: new EventBus(stack, "MyQueue"),
      }
    },
  },
});

cdk.rule?

Type : Omit<RuleProps, "eventBus" | "targets">

Configure the internally created CDK Rule instance.

new EventBus(stack, "Bus", {
  rules: {
    myRule: {
      cdk: {
        rule: {
          ruleName: "my-rule",
          enabled: false,
        },
      },
      targets: {
        myTarget1: "test/lambda.handler",
      },
    },
  },
});

EventBusQueueTargetProps

queue

Type : Queue

The queue to trigger

new EventBus(stack, "Bus", {
  rules: {
    myRule: {
      targets: {
        myTarget: {
          type: "queue",
          queue: new EventBus(stack, "Queue")
        }
      }
    },
  },
});

type

Type : "queue"

String literal to signify that the target is a queue

cdk.target?

Type : SqsQueueProps

EventBusFunctionTargetProps

Used to configure an EventBus function target

function?

Type : string | Function | FunctionProps

The function to trigger

new EventBus(stack, "Bus", {
  rules: {
    myRule: {
      targets: {
        myTarget: { function: "src/function.handler" },
      }
    },
  },
});

type?

Type : "function"

String literal to signify that the target is a function

cdk.function?

Type : IFunction

cdk.target?

Type : LambdaFunctionProps

caution

Examples​

Using the minimal config​

Configuring rules​

Lazily adding rules​

Configuring the Rule​

Configuring Function targets​

Adding targets​

Specifying function props for all targets​

Configuring an individual target​

Configuring the target​

Attaching permissions for all targets​

Attaching permissions for a specific target​

Configuring Queue targets​

Specifying the Queue directly​

Configuring the target​

Receiving AWS events​

Advanced examples​

Configuring the EventBus​

Importing an existing EventBus​

Using existing Lambda functions as targets​

Sharing an EventBus across stacks​

Constructor​

EventBusProps​

defaults.function?​

rules?​

cdk.eventBus?​

cdk.id?​

Properties​

eventBusArn​

eventBusName​

id​

cdk.eventBus​

Methods​

addRules​

attachPermissions​

attachPermissionsToTarget​

bind​

bindToTarget​

getRule​

EventBusRuleProps​

pattern.detailType?​

pattern.source?​

targets?​

cdk.rule?​

EventBusQueueTargetProps​

queue​

type​

cdk.target?​

EventBusFunctionTargetProps​

function?​

type?​

cdk.function?​

cdk.target?​

Examples

Using the minimal config

Configuring rules

Lazily adding rules

Configuring the Rule

Configuring Function targets

Adding targets

Specifying function props for all targets

Configuring an individual target

Configuring the target

Attaching permissions for all targets

Attaching permissions for a specific target

Configuring Queue targets

Specifying the Queue directly

Configuring the target

Receiving AWS events

Advanced examples

Configuring the EventBus

Importing an existing EventBus

Using existing Lambda functions as targets

Sharing an EventBus across stacks

Constructor

EventBusProps

defaults.function?

rules?

cdk.eventBus?

cdk.id?

Properties

eventBusArn

eventBusName

id

cdk.eventBus

Methods

addRules

attachPermissions

attachPermissionsToTarget

bind

bindToTarget

getRule

EventBusRuleProps

pattern.detailType?

pattern.source?

targets?

cdk.rule?

EventBusQueueTargetProps

queue

type

cdk.target?

EventBusFunctionTargetProps

function?

type?

cdk.function?

cdk.target?