ApiGateway has 500 error when Lambda is updating

Question

I am seeing a rare race condition. Sometimes, if I update my image-based Lambda to have a new image, the ApiGateway api that is triggering the Lambda returns the following error:

```
(f654758f-d377-4222-a4c3-766325f0de32) Lambda invocation failed with status: 409. Lambda request id: 1e69c921-26ce-4c4d-81ad-183264a08c59
(f654758f-d377-4222-a4c3-766325f0de32) Execution failed due to configuration error: The operation cannot be performed at this time. The function is currently in the following state: Pending
(f654758f-d377-4222-a4c3-766325f0de32) Method completed with status: 500
```

Here is how I'm updating the Lambda which causes the race condition to occur:
```
# publish the new docker image to the function
aws lambda update-function-code --publish --function-name "$name" --image-uri "$image"
# update my alias to the new published version
aws lambda update-alias --name "$stage" --function-name "$name" --function-version "$version"
```

I must be doing something wrong, because if a Lambda image or alias can't be updated atomically, that is a deal-breaker for reliable deployments.

Accepted Answer

Lambda functions can be in one of several [states](https://docs.aws.amazon.com/lambda/latest/dg/functions-states.html). This happens during function creation and update.

I assume your API is configured to invoke a specific lambda alias. It seems you are moving your alias before the new lambda version is in the Active state. You should be update the alias only after the function gets into the Active state.

ApiGateway has 500 error when Lambda is updating

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