I can't set Mylar up as an app in Prowlarr

pidgezero_one · Post by **pidgezero_one** » Sat Jul 19, 2025 2:40 pm

The setup I have:
Windows 10 pro
Docker containers:
- Mylar: v0.8.2, Internal port 8090, host port 8088. API enabled, API key generated, restarted Mylar after enabling those things, confirmed these are intact in config.ini. No HTTPS, no username, no password.
Not docker, just running standalone on my server:
- Prowlarr: port 9696
- SABnzbd: port 9080
- qBittorrent: Port 8177
- Sonarr: port 8989
- Radarr: port 7878

The Mylar container's networking seems to be set up totally fine, because it can successfully connect to SABnzbd using http://host.docker.internal:9080 and qBittorrent using http://host.docker.internal:8177. So I thought connecting it to Prowlarr by setting up Mylar as an app in Prowlarr would work basically the same. I have Sonarr and Radarr successfully set up on Prowlarr as apps, but it doesn't seem to understand what to do with Mylar specifically.

The app setup I'm attempting:

Name: Mylar
Sync level: Full Sync
Tags: (none)
Prowlarr Server (as seen by Mylar): http://host.docker.internal:9696
Mylar Server (as seen by Prowlarr, I'm assuming): http://localhost:8088
API Key: (I am positive the key I entered here is correct.)

Here's the error I get in Prowlarr when it tries to connect:

Code: Select all

2025-07-18 10:32:30.4|Error|MylarV1Proxy|Unable to complete application test

[v1.37.0.5076] System.Net.Http.HttpRequestException: An error occurred while sending the request.
 ---> System.IO.IOException: The response ended prematurely.
   at System.Net.Http.HttpConnection.SendAsyncCore(HttpRequestMessage request, Boolean async, CancellationToken cancellationToken)
   --- End of inner exception stack trace ---
   at System.Net.Http.HttpConnection.SendAsyncCore(HttpRequestMessage request, Boolean async, CancellationToken cancellationToken)
   at System.Net.Http.AuthenticationHelper.SendWithNtAuthAsync(HttpRequestMessage request, Uri authUri, Boolean async, ICredentials credentials, Boolean isProxyAuth, HttpConnection connection, HttpConnectionPool connectionPool, CancellationToken cancellationToken)
   at System.Net.Http.HttpConnectionPool.SendWithVersionDetectionAndRetryAsync(HttpRequestMessage request, Boolean async, Boolean doRequestAuth, CancellationToken cancellationToken)
   at System.Net.Http.AuthenticationHelper.SendWithAuthAsync(HttpRequestMessage request, Uri authUri, Boolean async, ICredentials credentials, Boolean preAuthenticate, Boolean isProxyAuth, Boolean doRequestAuth, HttpConnectionPool pool, CancellationToken cancellationToken)
   at System.Net.Http.DiagnosticsHandler.SendAsyncCore(HttpRequestMessage request, Boolean async, CancellationToken cancellationToken)
   at System.Net.Http.DecompressionHandler.SendAsync(HttpRequestMessage request, Boolean async, CancellationToken cancellationToken)
   at System.Net.Http.HttpClient.<SendAsync>g__Core|83_0(HttpRequestMessage request, HttpCompletionOption completionOption, CancellationTokenSource cts, Boolean disposeCts, CancellationTokenSource pendingRequestsCts, CancellationToken originalCancellationToken)
   at NzbDrone.Common.Http.Dispatchers.ManagedHttpDispatcher.GetResponseAsync(HttpRequest request, CookieContainer cookies) in ./Prowlarr.Common/Http/Dispatchers/ManagedHttpDispatcher.cs:line 120
   at NzbDrone.Common.Http.HttpClient.ExecuteRequestAsync(HttpRequest request, CookieContainer cookieContainer) in ./Prowlarr.Common/Http/HttpClient.cs:line 171
   at NzbDrone.Common.Http.HttpClient.ExecuteAsync(HttpRequest request) in ./Prowlarr.Common/Http/HttpClient.cs:line 70
   at NzbDrone.Common.Http.HttpClient.Execute(HttpRequest request) in ./Prowlarr.Common/Http/HttpClient.cs:line 137
   at NzbDrone.Core.Applications.Mylar.MylarV1Proxy.Execute[TResource](HttpRequest request) in ./Prowlarr.Core/Applications/Mylar/MylarV3Proxy.cs:line 190
   at NzbDrone.Core.Applications.Mylar.MylarV1Proxy.GetStatus(MylarSettings settings) in ./Prowlarr.Core/Applications/Mylar/MylarV3Proxy.cs:line 36
   at NzbDrone.Core.Applications.Mylar.MylarV1Proxy.TestConnection(MylarSettings settings) in ./Prowlarr.Core/Applications/Mylar/MylarV3Proxy.cs:line 131


2025-07-18 10:32:30.4|Warn|ProwlarrErrorPipeline|Invalid request Validation failed: 
 -- : Unable to send test message. An error occurred while sending the request.
2025-07-18 10:32:30.4|Debug|Api|[POST] /api/v1/applications?forceSave=true: 400.BadRequest (22786 ms)
2025-07-18 10:33:00.6|Debug|Prowlarr.Http.Authentication.ApiKeyAuthenticationHandler|AuthenticationScheme: API was successfully authenticated.
2025-07-18 10:33:00.6|Debug|Api|[GET] /api/v1/log/file: 200.OK (23 ms)

So it looks like it's connecting to Mylar, but something on the Mylar container's side is aborting the connection prematurely, if I'm understanding this correctly? Has anyone successfully got this to work before? Is there some setup option in Mylar I'm missing, some weirdness about running it in Docker despite otherwise working networking, or some config.ini field I need to fill in, etc, that would make this work?

I'm able to get a 200 response when I curl "http://localhost:8088/api?apiKey=(the same API key I'm using in this setup)&cmd=getVersion" from Powershell, which I think is what Prowlarr is trying to do also, but only the latter fails, it seems.

Alternatively, I'd be happy to set up indexers in Mylar independently without using Prowlarr and not have to deal with this headache, but I can't figure out where I'm supposed to do that in the Mylar UI.