timers: helpers for forking separate timer procs

Helper functions for forking simple separate timer processes:

 fork_dummy_timer(...) - forks a process that will just sleep()
    for the required interval and then will call the provided
    timer function, all that in a loop.
    Care must be taken to use it only when fork_process() is
    allowed (e.g.: module  child_init function, when
    rank==PROC_MAIN; see doc/modules_init.txt for more details)
    It can be used to replace kamailio register_timer_process()
    (but note that it's not a "drop-in" replacement).

 fork_local_timer_process() - forks a process, initializes a
    local_timer for it, and returns the local_timer handler both
    to the parent and to the child process, so both of them can
    add/del timers (if appropriate locking is used).
    Example usage:
      struct local_timer* lt_h;

      pid=fork_local_timer_process(...., &lt_h);
      if (pid==0){
          timer_init(&my_timer1, my_timer_f1, 0, 0);
          ...
          local_timer_add(&lt_h, &my_timer, S_TO_TICKS(10), get_ticks_raw());
          ...
          while(1) { sleep(1); local_timer_run(lt, get_ticks_raw()); }
      }
      (note that instead of sleep()-ing the process can do some useful work,
       like polling some fds a.s.o.)

timer_proc.c

@@ -0,0 +1,116 @@
+/* 
+ * $Id$
+ * 
+ * Copyright (C) 2009 iptelorg GmbH
+ *
+ * Permission to use, copy, modify, and distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+ * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+ * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+ * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ */
+/*
+ * timer_proc.c  - separate process timers
+ * (unrelated to the main fast and slow timers)
+ */
+/*
+ * History:
+ * --------
+ *  2009-03-10  initial version (andrei)
+*/
+
+#include "timer_proc.h"
+#include "pt.h"
+#include "mem/shm_mem.h"
+
+#include <unistd.h>
+
+
+/** forks a separate simple sleep() periodic timer.
+  * Forks a very basic periodic timer process, that just sleep()s for 
+  * the specified interval and then calls the timer function.
+  * The new "dummy timer" process execution start immediately, the sleep()
+  * is called first (so the first call to the timer function will happen
+  * <interval> seconds after the call to fork_dummy_timer)
+  * @param child_id - @see fork_process()
+  * @param desc     - @see fork_process()
+  * @param make_sock - @see fork_process()
+  * @param f         - timer function/callback
+  * @param param     - parameter passed to the timer function
+  * @param interval  - interval in seconds.
+  * @return - pid of the new process on success, -1 on error
+  *           (doesn't return anything in the child process)
+  */
+int fork_dummy_timer(int child_id, char* desc, int make_sock,
+						timer_function* f, void* param, int interval)
+{
+	int pid;
+	
+	pid=fork_process(child_id, desc, make_sock);
+	if (pid<0) return -1;
+	if (pid==0){
+		/* child */
+		for(;;){
+			sleep(interval);
+			f(get_ticks(), param); /* ticks in s for compatibility with old
+									  timers */
+		}
+	}
+	/* parent */
+	return pid;
+}
+
+
+
+/** forks a timer process based on the local timer.
+ *  Forks a separate timer process running a local_timer.h type of timer
+ *  A pointer to the local_timer handle (allocated in shared memory) is
+ *  returned in lt_h. It can be used to add/delete more timers at runtime
+ *  (via local_timer_add()/local_timer_del() a.s.o).
+ *  If timers are added from separate processes, some form of locking must be
+ *  used (all the calls to local_timer* must be enclosed by locks if it
+ *  cannot be guaranteed that they cannot execute in the same time)
+ *  The timer "engine" must be run manually from the child process. For
+ *  example a very simple local timer process that just runs a single 
+ *  periodic timer can be started in the following way:
+ *      struct local_timer* lt_h;
+ *
+ *      pid=fork_local_timer_process(...., &lt_h);
+ *      if (pid==0){
+ *          timer_init(&my_timer, my_timer_f, 0, 0);
+ *          local_timer_add(&lt_h, &my_timer, S_TO_TICKS(10), get_ticks_raw());
+ *          while(1) { sleep(1); local_timer_run(lt, get_ticks_raw()); }
+ *      }
+ *
+ * @param child_id - @see fork_process()
+ * @param desc     - @see fork_process()
+ * @param make_sock - @see fork_process()
+ * @param lt_h      - local_timer handler
+ * @return - pid to the parent, 0 to the child, -1 if error.
+ */
+int fork_local_timer_process(int child_id, char* desc, int make_sock,
+						struct local_timer** lt_h)
+{
+	int pid;
+	struct local_timer* lt;
+	
+	lt=shm_malloc(sizeof(*lt));
+	if (lt==0) goto error;
+	if (init_local_timer(lt, get_ticks_raw())<0) goto error;
+	pid=fork_process(child_id, desc, make_sock);
+	if (pid<0) goto error;
+	*lt_h=lt;
+	return pid;
+error:
+	if (lt) shm_free(lt);
+	return -1;
+}
+
+
+/* vi: set ts=4 sw=4 tw=79:ai:cindent: */

timer_proc.h

@@ -0,0 +1,43 @@
+/* 
+ * $Id$
+ * 
+ * Copyright (C) 2009 iptelorg GmbH
+ *
+ * Permission to use, copy, modify, and distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+ * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+ * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+ * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ */
+/*
+ * timer_proc.h - separate process timers
+ * (unrelated to the main fast and slow timers)
+ */
+/*
+ * History:
+ * --------
+ *  2009-03-10  initial version (andrei)
+*/
+
+#ifndef __timer_proc_h
+#define __timer_proc_h
+
+#include "local_timer.h"
+
+/* forks a separate simple sleep() periodic timer */
+int fork_dummy_timer(int child_id, char* desc, int make_sock,
+						timer_function* f, void* param, int interval);
+
+/* forks a timer process based on the local timer */
+int fork_local_timer_process(int child_id, char* desc, int make_sock,
+						struct local_timer** lt_h);
+
+#endif /*__timer_proc_h*/
+
+/* vi: set ts=4 sw=4 tw=79:ai:cindent: */