/graphql returning 502 Bad Gateway

[jnimander]

I've been testing DAB locally and everything has been running smoothly. Then suddenly, while DAB was running and I was demoing it to a colleague, the /graphql endpoint started to return 502 Bad Gateway. I thought I had messed up something in the config file, so I created a fresh project as per https://learn.microsoft.com/en-us/azure/data-api-builder/quickstart/postgresql, except that I'm running Postgres locally on the host, not in Docker. Both REST and GraphQL endpoints work if I call them from Postman, Swagger works just fine but the Banana Cake Pop /graphql endpoint returns 502. I'm using DAB version 1.6.77, Windows 10.

This is what I can see on the terminal.

info: Microsoft.AspNetCore.Hosting.Diagnostics[1]
      Request starting HTTP/1.1 GET http://localhost:5000/graphql/ - - -
dbug: Azure.DataApiBuilder.Core.AuthenticationHelpers.ClientRoleHeaderAuthenticationMiddleware[0]
      d13335fd-dddd-4ff5-8fe0-8050dba4c1fc AuthN state: Anonymous. Role: Anonymous. Scheme: StaticWebAppsAuthentication   
info: Microsoft.AspNetCore.Routing.EndpointMiddleware[0]
      Executing endpoint 'Hot Chocolate GraphQL Pipeline'
info: Microsoft.AspNetCore.Routing.EndpointMiddleware[1]
      Executed endpoint 'Hot Chocolate GraphQL Pipeline'
info: Microsoft.AspNetCore.Hosting.Diagnostics[2]
      Request finished HTTP/1.1 GET http://localhost:5000 - 502 0 - 39260.4764ms

Any ideas?

EDIT 1
Not sure if this offers any clues but I noticed this on the application event log.

Category: Microsoft.AspNetCore.HttpsPolicy.HttpsRedirectionMiddleware
EventId: 3
SpanId: 41955771966ace68
TraceId: 3caade5689ecc5762c30b539d1616308
ParentId: 0000000000000000
ConnectionId: 0HNGTPJ4KKCPI
RequestId: 0HNGTPJ4KKCPI:00000001
RequestPath: /swagger/index.html

Failed to determine the https port for redirect.

I know this refers to Swagger but I'm wondering if this is an issue with ASP.NET Core HTTPS redirection.

EDIT 2
Tried starting DAB with dab start --no-https-redirect. That didn't help.

[aaronburtle]

Hi @jnimander thanks for letting us know about this problem you are having, I will do some investigation and get back to you about this.

[jnimander]

Thanks Aaron. A couple of observations. I tried calling the http://localhost:5000/graphql endpoint from Postman and receive HTTP 200. I also forked DAB so that I can take a look at the source code but the laptop where I have the issue doesn't have Visual Studio. I tried using VS Code to troubleshoot the issue, but I don't like VS Code. (Also, I'm not that familiar with ASP.NET Core.) The security policies in the organization that owns the laptop are very strict. Since the observed behavior of the service seems to depend on the client calling it, I'm inclined to think the browser configuration has something to do with it. In order to figure that out, this morning I configured Chrome to log network traffic, and would you believe, Banana Cake Pop started working. I'm no longer able to duplicate the issue.

[souvikghosh04]

Hi @jnimander, could you please confirm if you still face the issue?

If you have set up DAB in a container, please check the config file inside the DAB container and ensure it contains the correct connection string for your locally running PostgreSQL database. The container logs can provide additional insight into what is happening during the /graphql requests.

it may help to compare the request headers sent by Chrome and those sent by Postman (since Postman works), or Insomnia client.

[jnimander]

I'm running DAB on the host, not in a container. Same thing with my Postgres database. And the problem isn't the database connection. I was trying to look at the headers as you suggested but that didn't reveal anything. Like I said, I'm no longer facing the issue. It fixed itself but I would still like to know what caused it.

Any suggestions on what I should do, if the issue reappears? I was able to reproduce it in the debugger, but couldn't find the controller for the Banana Cake Pop endpoint.

[souvikghosh04]

This seems like an intermittent issue and could be related to the setup and configuration at that time. general troubleshooting steps can start from logs. additionally, ensure database is accessible.

About the controller/endpoint- Bana Cake Pop (now called Nitro) is a middleware and doesn't have an accessible controller. Graphql playground which is part of that is accessible only in browser- /graphql when in development mode.

[jnimander]

The issue reappears when I turn on corporate VPN. I think it sets up some kind of a virtual network adapter. Also, a lot of URLs become inaccessible. The interesting thing is, it doesn't fail immediately after I've turned on VPN. This morning it took 30-40 minutes. And all actual service endpoints and Swagger continue to work. Nitro (Banana Cake Pop) is the only endpoint affected. What I'd like to know is what is the DAB process trying to call that results in 502. Is it an external service call originating from Nitro, or ASP.NET Core, DAB? I'll see if I can track this down with TCPView when I can find the time.

Thanks for you help.