[zeromq-dev] czmq zloop proper shut down of zactors

[Michal Vyskocil]

Hi Joe,

there is a big mistake in the check_interrupt logic, because you call
zstr_recv *twice*. One time in main actor, the second time in the function.
See the changes I did to make your example working

--- t.c.orig    2018-03-09 10:04:31.685006467 +0100
+++ t.c    2018-03-09 10:13:55.594123894 +0100
@@ -2,14 +2,12 @@
 #include <iostream>
 #include <string.h>

-int check_interrupt(zsock_t *pipe) {
+int check_interrupt(const char *msg) {
     int interrupt = 0;
-    char *msg = zstr_recv(pipe);

-    if (zsys_interrupted || (msg && !strcmp(msg, "$TERM")))
+    if (zsys_interrupted || (msg && streq(msg, "$TERM")))
         interrupt = -1;

-    free(msg);
     return interrupt;
 }

@@ -28,9 +26,9 @@
     while(1) {
         char *str = zstr_recv(pipe);
         std::cout << "timer_thread received: " << str << std::endl;
-        free(str);
-        if (check_interrupt(pipe))
+        if (check_interrupt(str))
             break;
+        free(str);
         // request list from socket_thread
         zstr_send(args, "list request");
         // recv list and do stuff
@@ -57,9 +55,9 @@
     while(1) {
         char *str = zstr_recv(pipe);
         std::cout << "socket_thread: received: " << str << std::endl;
-        free(str);
-        if (check_interrupt(pipe))
+        if (check_interrupt(str))
             break;
+        free(str);
         // Parse the msg, either add msg to list or return list
     }
 }
@@ -97,5 +95,4 @@
     zactor_destroy(&timer_zactor);
     zsock_destroy(&a_zsock);
     zloop_destroy(&loop);
-    assert (loop == NULL);
 }

​

A few recommendations to make your future experiments easier.

   1. Always write start/stop test for your actors. The first thing I did
   was that I commented out most of your main to see if actor can be created
   and destroyed. Then it was easy to spot the mistake.
   2. Use modern C - there is no point of writing functions returning 0 and
   -1, there is bool type and -Wc++-compat helping you to avoid C++
   compilers incompatibility
   3. There is zstr_free function in czmq, use it and you won’t suffer from
   double free errors any more
   4. Learn zproject later on - see
   https://hintjens.gitbooks.io/scalable-c/content/chapter3.html - it's
   great way to generate great C and C++ projects including way to write unit
   tests, run them and more and more.

​


On Thu, Mar 8, 2018 at 6:24 PM, Georger, Joseph <
joseph.georger at stresearch.com> wrote:

> Okay, here is a simplified example that exhibits the behavior. I realize
> this may end up being simply how to properly terminate threads, but I want
> to make sure I don't miss anything in the czmq/zloop context....
>
> https://pastebin.com/MsjDH6k8
>
> Thanks,
> Joe
>
> 
>     ------------------------------
>
>     Message: 2
>     Date: Thu, 8 Mar 2018 10:38:34 +0100
>     From: Michal Vyskocil <michal.vyskocil at gmail.com>
>     To: ZeroMQ development list <zeromq-dev at lists.zeromq.org>
>     Subject: Re: [zeromq-dev] czmq zloop proper shut down of zactors
>     Message-ID:
>         <CAJp4ekvmyRQX+bNVEn9Qx1DdsvH+tKYtu-i9vZTRR1m8enStnw at mail.
> gmail.com>
>     Content-Type: text/plain; charset="utf-8"
>
>     Hi Joe,
>
>     can you post minimal reproducer somewhere? I tried to spot the
> problem, but
>     without having working example it's hard.
>
>     Bye
>     Michal
>
>
> _______________________________________________
> zeromq-dev mailing list
> zeromq-dev at lists.zeromq.org
> https://lists.zeromq.org/mailman/listinfo/zeromq-dev
>



-- 
best regards
     Michal Vyskocil
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