Exception caught in global error handler, exception message: Object reference not set to an instance of an object.

[klaudiusz-czapla]

Expected Behavior

I'm expecting to get error details coming from ocelot.json file validation in case of invalid configuration being provided.

Actual Behavior

I had scenario where Errors collection coming from validation process (ocelot.json) is discarded and then I'm getting NullReferenceException instead which is hiding the real problem.

Exception caught in global error handler, exception message: Object reference not set to an instance of an object., exception stack:    
at Ocelot.Errors.Middleware.ExceptionHandlerMiddleware.TrySetGlobalRequestId(HttpContext httpContext, IInternalConfiguration configuration)\n   
at Ocelot.Errors.Middleware.ExceptionHandlerMiddleware.Invoke(HttpContext httpContext) 

Steps to Reproduce the Problem

You have to create ocelot.json file where one of the routes contains something like this:

"DownstreamPathTemplate": "{everything}"

During debugging Ocelot I got at some point Errors collection with message: "Downstream Path Template {everything} doesnt start with forward slash"
It was in method Ocelot.Middleware.OcelotMiddlewareExtensions.CreateConfiguration'IApplicationBuilder -> fileConfig.OnChange callback

Ocelot.dll!Ocelot.Configuration.Repository.InMemoryInternalConfigurationRepository.AddOrReplace(Ocelot.Configuration.IInternalConfiguration internalConfiguration) Line 27	C#
>	Ocelot.dll!Ocelot.Middleware.OcelotMiddlewareExtensions.CreateConfiguration.AnonymousMethod__0(Ocelot.Configuration.File.FileConfiguration config) Line 98	C#
 	Microsoft.Extensions.Options.dll!Microsoft.Extensions.Options.OptionsMonitorExtensions.OnChange.AnonymousMethod__0(System.__Canon o, string _)	Unknown

nevertheless somehow this mesage was never logged anywhere, it was discarded and finally I got NullReferenceException instead

{Ocelot.Responses.ErrorResponse<Ocelot.Configuration.IInternalConfiguration>}
-> Data -> null in my case
-> Errors -> Downstream Path Template {everything} doesnt start with forward slash
-> IsError -> true

In line

internalConfigRepo.AddOrReplace(newInternalConfig.Data);

error should be checked before accessing .Data property

Specifications

• Version: 17.0.0, 17.0.1
• Platform: Windows/Linux
• Subsystem: -

[ntruongvux]

Maybe, you configured duplication the endpoint about downstream/upstream url

[raman-m]

Klaudiusz, Klaudiusz, Klaudiusz... 😄

Hi Klaudiusz!
It is absolutely normal that if you use invalid ocelot.json file then Ocelot generates exceptions. 😸
I would recommend you to check and validate your ocelot.json file before any deployments!

---

You have to create ocelot.json file where one of the routes contains sth like this:
"DownstreamPathTemplate": "{everything}"

This is wrong template! You must add slash sign before {everything}
According to the Routing feature docs, valid template is: /{everything}

---

During debugging Ocelot I got at some point Errors collection with message: "Downstream Path Template {everything} doesnt start with forward slash"

Bingo! 🤣

---

Have a great summer, Klaudiusz! 🌞

[raman-m]

Specifications

• Version: 17.0.0, 17.0.1
• Platform: Windows/Linux
• Subsystem: -

Please, upgrade your solution to v19 (.NET 7 release)

[klaudiusz-czapla]

@raman-m Error message which I've posted was extracted by myself during debugging. In the runtime it was hidden from the user. Btw NullReferenceException should never be thrown by the application. It should be handled somehow. As I said - original error message was hidden. Without debugging Ocelot code I would never be able to get to know what was wrong and misconfigured :)

[raman-m]

Aha, I see. Sorry!
I've reopened the bug.
What's your fix?
Are you going to create a PR?

[raman-m]

I would love to review your PR and/or discuss your idea to fix this error message hiding problem.
And show me a line in source code which generates NullReferenceException please!

[ks1990cn]

@klaudiusz-czapla Hi,
I am unable to replicate NullReferenceException, when configuration is bad. I can see following validation code which doesn't allow to start application even.

My Route in Ocelot.json file is, here I removed first slash of downstream path.

 "Routes": [
   {
     "DownstreamHostAndPorts": [
       {
         "Host": "localhost",
         "Port": 5022
       },
       {
         "Host": "localhost",
         "Port": 5085
       }
     ],
     "ServiceName": "ConsulDemo",
     "LoadBalancerOptions": {
       "Type": "LeastConnection"
     },
     "UpstreamPathTemplate": "/hostname",
     "UpstreamHttpMethod": [ "GET" ],
     "DownstreamPathTemplate": "WeatherForecast/hostname",
     "DownstreamScheme": "http",
     "DangerousAcceptAnyServerCertificateValidator": true


   }
 ]

@raman-m Not sure what he was trying to explain last year, but on latest version I am unable to see any issue.
@klaudiusz-czapla Feel free to add any point here if I missed anything, else @raman-m we can close this. Thanks!

[raman-m]

These lines are under discussion: lines L92-L96
Correct, @klaudiusz-czapla ?

You've shown concrete line of code which fails in your user scenario.
But what's the problem to create a PR? Is it so hard for you?

Regarding NullReferenceException ... Yeap, it seems callback processes null newInternalConfig variable. The fix should be pretty simple. But the root cause is unknown because this callback calls IInternalConfigurationCreator service which has a lot of interconnected injected services in implementation (FileInternalConfigurationCreator.Create)... So, it is hard to say what's happen inside and why var newInternalConfig is null...

[raman-m]

@ks1990cn commented on Dec 1

No, he mentioned these lines: lines L92-L96 which are below starting the line 92...

[ks1990cn]

@raman-m how he got an error? I see code is safe

[raman-m]

@ks1990cn
It seems the problem is inside the async anonymous callback: fileConfig.OnChange...

---

The quote from the description:

In line

internalConfigRepo.AddOrReplace(newInternalConfig.Data);

error should be checked before accessing .Data property

[ks1990cn]

Okay, but code stops running before that at line 85.

[ks1990cn]

This piece of code never executed in case of bad configuration... @raman-m , still I want to understand how he reached there..?

[ks1990cn]

do someone added this code on latest version?

[raman-m]

@ks1990cn

do someone added this code on latest version?

Probably Yes...

---

Steps to Reproduce the Problem

You have to create ocelot.json file where one of the routes contains something like this:

"DownstreamPathTemplate": "{everything}"

Tanmay, his case is invalid... He was kidding in this issue, and request to fix quite wrong user case.
Here is my very first reply in the thread
So, he replied with short answer that he don't like situation when internal exception was swallowed by Ocelot core and he wants this message in upper contexts. But he pointed to the code which generates this exception.
We can fix this line of code...

---

Tanmay, once again...
His user scenario is about OnChange callback... Seems you've reproduced different case...
Author's concern is about NullReferenceException in the callback!
We don't have Steps to Repro!!!! Author is silent since July 3... more than 5+ months

We're discussing something quite specific...
Let give him 1 month to open a PR with the fix which is tiny...
If he will be silent we just add that junior style PR to fix line 95, that's it! 🆗?

[raman-m]

@klaudiusz-czapla

The title: Exception caught in global error handler

Exactly! Didn't you know the fact that Ocelot has global error handler which processes all exceptions?
Bingo! 💥 You know the fact now!

---

We've discussed the case. You pointed to the problematic line. The fix should be tiny...
Why not to create a PR?

You have one month till January 5, 2024 to create a PR

...otherwise you won't be an author of the fix, or we will close the issue at all.

CC: klaudiuszc@interia.pl

P.S.

And please fork Ocelot repo!