REST API In Node Deployed as Azure App Service 500 Internal Server Errors

Question

I have looked at the request trace for several requests that resulted in the same outcome. What will happen is I'll get a HttpModule="iisnode", Notification="EXECUTE_REQUEST_HANDLER", HttpStatus=500, HttpReason="Internal Server Error", HttpSubstatus=1013, ErrorCode="The pipe has been ended. (0x6d)"

This is a production API. Fewer than 1% of requests get this result but it's not the requests themselves - I can reissue the same request and it'll work.

I log telemetry for every API request - basics on the way in, things like http status and execution time as the response is on its way out.

None of the requests that get this error are in telemetry which makes me think something is happening somewhere between IIS and iisnode.

If anyone has resolved this or has solid thoughts on how to pin down what the root issue is I'd appreciate it.

Answer 1

Well for me, what's described here covered the bulk of the issue: github.com/Azure/iisnode/issues/57 Setting keepAliveTimeout to 0 on the express server reduced the 500s significantly.

Once the majority of the "noise" was eliminated it was much easier to correlate the remaining 500s that would occur to things I could see in my logs. For example, I'm using a 3rd party node package to resize images and a couple of the "images" that were loaded into the system weren't images. Instead of gracefully throwing an exception, the package seems to exit out of the running node process. True story. So on Azure, it would get restarted, but while that was happening requests would get a 500 internal server error.