Troubleshoot issues with response streaming in API Gateway - Amazon API Gateway
General troubleshootingTroubleshoot cURL errorsTroubleshoot using access logging

Troubleshoot issues with response streaming in API Gateway

The following troubleshooting guidance might help resolve issues with your APIs that use response streaming.

General troubleshooting

You can use the TestInvokeMethod or the console's test tab to test your stream response. The following considerations might impact your use of test invoke for response streaming:

  • When you test your method, API Gateway buffers your streamed response payload. Once any of the following conditions have been met, API Gateway returns a one-time response containing the buffered payload:

    • The request is complete

    • 35 seconds have elapsed

    • More than 1 MB of response payload has been buffered

  • If more than 35 seconds elapse before your method returns an HTTP response status and all headers, then the response status returned in TestInvokeMethod is 0.

  • API Gateway doesn't produce any execution logs.

After you've deployed your API, you can test your stream response by using a curl command. We recommend that you use the -i option to include protocol response headers in the output. To see the response data as it arrives, use the curl option --no-buffer

Troubleshoot cURL errors

If you're testing an integration and you receive the error curl: (18) transfer closed with outstanding read data remaining, make sure the timeout of your integration is long enough. If you're using a Lambda function, you need to update the response timeout of the Lambda function. For more information, see Configure Lambda function timeout.

Troubleshoot using access logging

You can use access logs for your REST API stage to log and troubleshoot your response stream. In addition to the existing variables, you can use the following access log variables:

$context.integration.responseTransferMode

The response transfer mode of your integration. This can be either BUFFERED or STREAMED.

$context.integration.timeToAllHeaders

The time between when API Gateway establishes the integration connection to when it receives all integration response headers from the client.

$context.integration.timeToFirstContent

The time between when API Gateway establishes the integration connection to when it receives the first content bytes.

$context.integration.latency or $context.integrationLatency

The time when API Gateway establishes the integration connection to when the integration response stream is complete.

The following figure shows how these access log variables represent different components of a response stream.

Access log variables for response streaming in API Gateway

For more information about access logs, see Set up CloudWatch logging for REST APIs in API Gateway. You can also use X-Ray to monitor your response stream. For more information, see Trace user requests to REST APIs using X-Ray in API Gateway.