Where are the logs and memory dumps of Azure Function crashes? - azure

Question

Sometimes my azure function fails and I have no record of what happened. Function just stops executing.
I think there is major error like StackOverflow, but since there is no record of it I can't be sure.
I created a simple azure function to emulate simple stack overflow:
public static async Task<IActionResult> Run(
[HttpTrigger(AuthorizationLevel.Function, "get", "post", Route = null)] HttpRequest req,
ILogger log, ExecutionContext executionContext)
{
RunStackOverflow();
}
private static void RunStackOverflow()
{
RunStackOverflow();
}
When I call this using http trigger, I get 502 error in browser, but there is nothing in logs about this failure. Screenshot: https://www.screencast.com/t/ymWoBey4KX
StackOverflow is just one of the exceptions that can't be caught and can result in function crash. Locally when I run the function in emulator I see stack overflow error in cmd window where function starts. Screenshot: https://www.screencast.com/t/f85U2KmdEBBt
In Azure portal I checked:
function invocations (screenshot: https://www.screencast.com/t/ufB1Zfthz)
function logs (screenshot: https://www.screencast.com/t/A2ix6yuSuJkE)
app insights (screenshot: https://www.screencast.com/t/NyRFLDK23p)
But there is no log entry of this crash anywhere.
I contacted Azure support, but they are not very helpful so far.
Update on Apr 12
Using KUDU I can create memory dump using command like this
c:\devtools\sysinternals\procdump -e -ma -w 12268
This shows me all stack traces for all threads and this is what I need, but only when first chance exception occurs.
The command to trigger memory dump when there is such exception is:
c:\devtools\sysinternals\procdump -accepteula -e -g -ma 8844
but when I run it and then trigger StackOverflow exception here is what is written out to command line:
[11:37:36] Exception: E0434352.CLR
[11:37:36] Exception: C00000FD.STACK_OVERFLOW <--- Stack overflow
[11:37:37] The process has exited.
[11:37:37] Dump count not reached.
Unfortunately there is no memory dump created, so I can't see a stack trace that caused stack overflow.
I also tried:
c:\devtools\sysinternals\procdump -accepteula -e -g -ma -t 13244
-t option triggers memory dump when process exits.
This one actually records a memory dump when Function crashes. Unfortunately this dump doesn't include stack trace for StackOverflow. It seems to get dumped after the thread already crashed.
Update on Apr 21
There are multiple ways to host Azure functions described here:
https://learn.microsoft.com/en-us/azure/azure-functions/functions-scale
The most common and default way is Consumption plan. After a bunch of trial-and-errors I found that Diagnostics Tools (https://www.screencast.com/t/DyT6Jpuqm2uo) which can be used to detect and analyze crashes are not available with Consumption plan. On the other hand they are available with App Service (Basic and plus) and other plans. Azure support told me that currently there are no plans to add it to Consumption plan.
So for now I made a new Azure Function hosted using App Service Plan and I was able to use Diagnostic tools to record crash dumps. After fixing the issues I plan to go back to Consumption plan, so it is a bit of a hack, but it does work for now.

Answer 1

Currently, this level of logs are not supported very well.
You can use Diagnose and solve problems option from azure portal by following this link, but note that some features(like Application Crashes) in this option are still in development.
Steps:
1.In azure portal -> your function app -> click Diagnose and solve problems -> then click the Function App Down or Reporting Errors link. Here is the screenshot:
2.Wait for a while before the report completes generating -> then check the items starts with red exclamation mark(by using your code, the error details are in the Web App Restarted item. But it just shows a common message like app crashes, not stackoverflow):