CloudWatch log subscription from Lambda doesn't show in the AWS Console UI, if created via CLI

Question

If I have a Lambda that's set up to ingest CloudWatch logs from a particular log group, I can add a trigger via the UI and it will be listed along with that Lambda under "Configuration" > "Triggers". It will also be listed if I go to the log group itself in CloudWatch and select "Subscription filters".

However, I can accomplish much the same thing via the CLI by doing the following:
```
aws logs put-subscription-filter --log-group-name [whatever-the-name-is] --filter-name [a-name-for-the-subscription] --filter-pattern "" --destination-arn "arn:aws:lambda:[region]:[id]:[the-lambda-in-question]" --distribution ByLogStream
```

If I do this it will show up as a "Subscription filter" for the log group, but not as a "Trigger" for the Lambda. It still works the same way, though.

Answer

Hi there

Here are the steps to configure an Amazon CloudWatch subscription filter to invoke an AWS Lambda Function:

1. You will need to grant CloudWatch Logs permission to invoke the Lambda Function using the "AddPermission" API:

********** CLI Command **********

aws lambda add-permission \
    --function-name "FunctionName" \
    --statement-id "AllowCWToInvokeLambdaFunction" \
    --principal "logs.amazonaws.com" \
    --action "lambda:InvokeFunction" \
    --source-arn "arn:aws:logs:region:AccountID:log-group:YourLogGroup:*" \
    --source-account "AccountID"

********** CLI Command **********

---> Replace "FunctionName" with the name of your Lambda Function.
---> Replace "AccountID" with your AWS Account ID.
---> Replace "YourLogGroup" with the name of your CloudWatch Log Group.

2. Create a Subscription Filter using the "PutSubscriptionFilter" API to send Log Events that contain a keyword. In the below example, the keyword "ERROR" is being used:

********** CLI Command **********

aws logs put-subscription-filter \
    --log-group-name YourLogGroup \
    --filter-name demo \
    --filter-pattern "ERROR" \
    --destination-arn arn:aws:lambda:region:AccountID:function:FunctionName

********** CLI Command **********

---> Replace "FunctionName" with the name of your Lambda Function.
---> Replace "AccountID" with your AWS Account ID.
---> Replace "YourLogGroup" with the name of your CloudWatch Log Group.

The CloudWatch Log Group "YourLogGroup" will invoke the Lambda Function when it receives a Log Event with the "ERROR" keyword.

References:
[1] https://docs.aws.amazon.com/AmazonCloudWatch/latest/logs/SubscriptionFilters.html#LambdaFunctionExample

CloudWatch log subscription from Lambda doesn't show in the AWS Console UI, if created via CLI

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