how to get return response from AWS Lambda function

Question

I have a simple lambda function that returns a dict response and another lambda function invokes that function and prints the response.

lambda function A

def handler(event,context):
    params = event['list']
    return {"params" : params + ["abc"]}

lambda function B invoking A

a=[1,2,3]
x = {"list" : a}
invoke_response = lambda_client.invoke(FunctionName="monitor-workspaces-status",
                                       InvocationType='Event',
                                       Payload=json.dumps(x))
print (invoke_response)

invoke_response

{u'Payload': <botocore.response.StreamingBody object at 0x7f47c58a1e90>, 'ResponseMetadata': {'HTTPStatusCode': 202, 'RequestId': '9a6a6820-0841-11e6-ba22-ad11a929daea'}, u'StatusCode': 202}

Why is the response status 202? Also, how can I get the response data from invoke_response? I could not find a clear documentation of how to do it.

garnaat · Accepted Answer · 2016-04-22 12:55:03Z

100

A 202 response means Accepted. It is a successful response but is telling you that the action you have requested has been initiated but has not yet completed. The reason you are getting a 202 is because you invoked the Lambda function asynchronously. Your InvocationType parameter is set to Event. If you want to make a synchronous call, change this to RequestResponse.

Once you do that, you can get the returned data like this:

data = invoke_response['Payload'].read()

answered Apr 22, 2016 at 12:55

garnaat

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7 Comments

Alexey Lysenko Over a year ago

made my day! Thanks a lot. Haven't found this anywhere in docs

Bruno Bronosky Over a year ago

.read() returns type bytes so if you were expecting a string, JSON, etc., you have to .decode() them. e.g. response['Payload'].read().decode()

Bruno Bronosky Over a year ago

And since json.dumps(obj) returns a quoted string, (if you used that for the return value of your lambda_handler) you are going to get a string if you do json.loads(response['Payload'].read().decode())' and would have to wrap another json.loads()` around that. So, don't explicitly convert to JSON in your lambda function.

2ank3th Over a year ago

Is there a way to get a callback after completion for invocation type Event?

jackxujh Over a year ago

@2ank3th I had the same issue, and I looked up in the AWS documentation. It says, for Event type invocations, there is no response body: open aws documentation

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Akshansh Shrivastava · Accepted Answer · 2019-05-28 12:14:47Z

2

try: data = invoke_response['Payload'].read() read() because it is a StreamingBody object

<botocore.response.StreamingBody object at 0x110b91c50>

It is in the boto3 docs. You can find more details about this here: https://boto3.amazonaws.com/v1/documentation/api/latest/guide/resources.html#actions

edited May 28, 2019 at 12:14

answered May 28, 2019 at 12:13

Akshansh Shrivastava

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