Boto3 Lambda - Existing custom IoT Rule as event source

Question

Hello forum,

We know and are able to set existing custom IoT Rule as a Trigger for AWS Lambda.

We are currently using boto3 to [create lambda function](https://boto3.amazonaws.com/v1/documentation/api/latest/reference/services/lambda.html#Lambda.Client.create_function).

After creating lambda function we tried to set an existing custom IoT Rule as trigger using [create_event_source_mapping()](https://boto3.amazonaws.com/v1/documentation/api/latest/reference/services/lambda.html#Lambda.Client.create_event_source_mapping).

This is resulting in below error -

`An error occurred (InvalidParameterValueException) when calling the CreateEventSourceMapping operation: Unrecognized event source, must be kinesis, dynamodb stream or sqs. Unsupported source arn : arn:aws:iot:xx-xx-1:xxxxxxxxxxxx:rule/ruleName`

Please find the code for the same below -

```
import boto3
import botocore.exceptions

function_name = sample_function
trigger_arn = arn:aws:iot:xx-xx-1:xxxxxxxxxxxx:rule/ruleName

client = boto3.client('lambda')
client.create_event_source_mapping(EventSourceArn=trigger_arn,FunctionName=function_name)
```

Is this not supported or possible using boto3?

How to fix this?

Uri · Answer

Lambda event source mapping is used only for the event sources that Lambda needs to poll such as SQS, Kinesis, Kafka, etc. IoT Rules are different. In order to trigger a Lambda function from an IoT rule you need to use the [create_topic_rule](https://boto3.amazonaws.com/v1/documentation/api/latest/reference/services/iot.html#IoT.Client.create_topic_rule) in the IoT client.

Boto3 Lambda - Existing custom IoT Rule as event source

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