Sending Events to Amazon CloudWatch Events

This Python example shows you how to:

• Create and update a rule used to trigger an event
• Define one or more targets to respond to an event
• Send events that are matched to targets for handling

The Scenario

CloudWatch Events delivers a near real-time stream of system events that describe changes in Amazon Web Services (AWS) resources to any of various targets. Using simple rules, you can match events and route them to one or more target functions or streams.

In this example, Python code is used to send events to CloudWatch Events. The code uses the AWS SDK for Python to manage instances using these methods of the CloudWatchEvents client class:

• put_rule.
• put_targets.
• put_events.

For more information about CloudWatch Events, see Adding Events with PutEvents in the Amazon CloudWatch Events User Guide.

All the example code for the Amazon Web Services (AWS) SDK for Python is available here on GitHub.

Prerequisite Task

• Configure your AWS credentials, as described in Quickstart.

• Create a Lambda function using the hello-world blueprint to serve as the target for events. To learn how, see Step 1: Create an AWS Lambda function in the Amazon CloudWatch Events User Guide.

• Create an IAM role whose policy grants permission to CloudWatch Events and that includes events.amazonaws.com as a trusted entity. For more information about creating an IAM role, see Creating a Role to Delegate Permissions to an AWS Service in the IAM User Guide.

  Use the following role policy when creating the IAM role.

{
   "Version": "2012-10-17",
   "Statement": [
      {
         "Sid": "CloudWatchEventsFullAccess",
         "Effect": "Allow",
         "Action": "events:*",
         "Resource": "*"
      },
      {
         "Sid": "IAMPassRoleForCloudWatchEvents",
         "Effect": "Allow",
         "Action": "iam:PassRole",
         "Resource": "arn:aws:iam::*:role/AWS_Events_Invoke_Targets"
      }
   ]
}

Use the following trust relationship when creating the IAM role.

{
   "Version": "2012-10-17",
   "Statement": [
      {
         "Effect": "Allow",
         "Principal": {
            "Service": "events.amazonaws.com"
         },
         "Action": "sts:AssumeRole"
      }
   ]
}

Create a Scheduled Rule

Create or update the specified rule. Rules are enabled by default, or based on value of the state. You can disable a rule using DisableRule.

The example below shows how to:

• Create a CloudWatch Events rule using put_rule.

Example

import boto3


# Create CloudWatchEvents client
cloudwatch_events = boto3.client('events')

# Put an event rule
response = cloudwatch_events.put_rule(
    Name='DEMO_EVENT',
    RoleArn='IAM_ROLE_ARN',
    ScheduleExpression='rate(5 minutes)',
    State='ENABLED'
)
print(response['RuleArn'])

Add a Lambda Function Target

Add the specified targets to the specified rule, or update the targets if they are already associated with the rule.

The example below shows how to:

• Add a target to a rule using put_targets.

Example

import boto3

# Create CloudWatchEvents client
cloudwatch_events = boto3.client('events')

# Put target for rule
response = cloudwatch_events.put_targets(
    Rule='DEMO_EVENT',
    Targets=[
        {
            'Arn': 'LAMBDA_FUNCTION_ARN',
            'Id': 'myCloudWatchEventsTarget',
        }
    ]
)
print(response)

Send Events

Send custom events to Amazon CloudWatch Events so that they can be matched to rules.

The example below shows how to:

• Send a custom event to CloudWatch Events using put_events.

Example

import json

import boto3


# Create CloudWatchEvents client
cloudwatch_events = boto3.client('events')

# Put an event
response = cloudwatch_events.put_events(
    Entries=[
        {
            'Detail': json.dumps({'key1': 'value1', 'key2': 'value2'}),
            'DetailType': 'appRequestSubmitted',
            'Resources': [
                'RESOURCE_ARN',
            ],
            'Source': 'com.company.myapp'
        }
    ]
)
print(response['Entries'])