[Top][All Lists]

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

[libmicrohttpd] Odd Stop Behavior

From: Kenneth Mastro
Subject: [libmicrohttpd] Odd Stop Behavior
Date: Fri, 6 Jun 2014 14:50:19 -0400

I'm seeing an odd behavior when I shut down the daemon (MHD_stop_daemon).  The shutdown hangs for about 115 seconds, then it finally terminates cleanly.

I'm using the 'thread per connection' mode, which may be relevant.  After digging into microhttpd's code, I found that it was hanging on a thread join during 'close_all_connections'.

I began doing some heavy debugging, and determined that I don't have any lingering connections that I never finished with.  I even went so far as to print out the thread PIDs in both microhttpd and my code to make sure I saw the requests that were being handled by the hanging thread.  Nothing fancy - just some css and/or image files being served up (about 25 requests or so).  Through this debugging, I'm nearly certain that I'm ending the connection/request callback every time (I also did a global increment/decrement of requests, and it gets back to 0 every time - Ergo, I'm not holding onto the thread.).

Some other useful info:
* When I set the maximum number of connections/threads to 1 (instead of 20) when I start the daemon, it does not hang when I stop the daemon - it just ends immediately, as expected.

* After I start shutting down, if I make ANOTHER request from the browser (e.g.., refresh the page), the daemon stops immediately and cleanly.

* After I load the page the first time (and it makes a bunch of requests to the server, causing 1 or more threads to be used), if I wait a while (e.g., a minute) and then stop the server, it shortens the time it takes the thread to terminate.  I.e., if I wait 65 seconds, it only takes 70 seconds for the server to stop instead of 115.  If I wait longer than 115 seconds, it will end immediately, as expected.

* If I make NO requests (i.e., I just start, then stop a few seconds later), it terminates cleanly.  The 115 second delay only occurs after I've made a request to the server from the browser and then try to stop it.

* I'm using a fairly recent version: 0.9.35

I came across some vaguely related issues regarding stopping the daemon:
I saw some old archived messages about a problem that existed in microhttpd, but that was several years ago, but it sounds like it was a full-on deadlock:

Also saw this, which may be similar to what I'm dealing with (only it sounds like this was solaris specific, and I'm on Linux):

Also, this issue feels similar as well:

It seems like there's been some trouble in this area in the past, so I figured it was worth asking about.

So - any idea if I'm doing something wrong?  I'm at a bit of a loss since my code doesn't have any control over the internal threads.  I'm happy to try anything in my application and/or modify microhttpd to test, but I'm not sure where to focus my efforts.

Thanks much,

reply via email to

[Prev in Thread] Current Thread [Next in Thread]