B4J Question [B4J Server] Server not response after some time

[billzhan]

Hi,

I have a B4J server(http and websocket) running, but it stops to response after some time ( a day/week ). I've test it on Linux(VPS and laptop) and Windows 7, similar things.

When I inspect the server with tools like VisualJVM, JVM is still running and manual GC works. No memory leaks and exceptions in the logs. Requests to ws/handler/static files receive no response.

Threads dump shows that the "main" thread doesn't exist anymore.

Any hints will be appreciated.

Update : solved. See post #9

 

[Erel]

Seems to me that you are calling StartMessageLoop in one or more handlers and never call StopMessageLoop.

 

[billzhan]

The "main" thread doesn't exist in the thread dump, is this a problem?

I use something similar to this one:
https://www.b4x.com/android/forum/threads/creating-a-proxy.63292/#post-400026

Sub Class_Globals
  Private mResp As ServletResponse
  Private ispost As Boolean
End Sub 

Public Sub Initialize

End Sub

Sub Handle(req As ServletRequest, resp As ServletResponse)
   
    Dim httpmethod As String = req.Method

    mResp = resp
    Dim j As HttpJob    'okhttp
    j.Initialize("j", Me)
    If httpmethod.ToLowerCase = "post" Then
        ispost = True
        j.Post... 
    Else
        ispost = False
        j.Download(...)
    End If
       
    StartMessageLoop  
End Sub

Sub JobDone(Job As HttpJob)
    If Job.Success Then
     If ispost Then
        File.Copy2(Job.GetInputStream, mResp.OutputStream)
     Else
        mResp.Write("< json string >")
     End If  
    Else
     mResp.SendError(500, Job.ErrorMessage)
    End If
    StopMessageLoop  
End Sub

 

[Erel]

Start with fixing the message loop issue. This is probably the main issue.

Have you update the jCore library: https://www.b4x.com/android/forum/threads/updates-to-internal-libaries.48274/#content ?

 

[billzhan]

Yes, I have updated to 4.21 jCore.

I use a B4J wsclient within each websocket thread (ws relay), but there is no MessageLoop in websocket threads.

For now I am trying to check the server health periodically, the jar should be restarted when necessary.

 

[Erel]

Is the code posted from ShinyFolderHandler module?

 

[billzhan]

The code posted is the same structure as the one I used in ShinyFolderHandler module. I am trying to make a reproducible example.

I checked the log file which is written by a timer every 20sec in the main thread, it shows that the main thread was not running (when server stopped to response)

 

[Erel]

You need to find out why there are 150 threads locked in the StartMessageLoop call in ShinyFolderHandler.

 

[billzhan]

I've found that an exception was thrown a timer_tick sub (in the main thread) just before the server stop to response. It's caused by an null pointer exception when access to a key (in a threadsafe map) which is removed from other threads.

Server works properly after fixed this bug.