src/plugin.[ch]: Implement `plugin_dispatch_values_async'.

This function differs from `plugin_dispatch_values' in that it will add
the value_list_t to a queue rather than calling the write functions
right away. This as at least two advantages:

  - The _async function will often return faster, since no file
    operation is done.

  - The ``read thread'' and the ``write thread'' are not the same
    thread. This makes it much easier for plugins that provide both,
    `read' and `write' callbacks.

diff --git a/src/plugin.c b/src/plugin.c
index 9f42f2e..6fd74e2 100644 (file)
--- a/src/plugin.c
+++ b/src/plugin.c
@@ -50,6 +50,14 @@ struct read_func_s
 };
 typedef struct read_func_s read_func_t;
 
+struct dispatch_queue_s;
+typedef struct dispatch_queue_s dispatch_queue_t;
+struct dispatch_queue_s
+{
+       value_list_t *vl;
+       dispatch_queue_t *next;
+};
+
 /*
  * Private variables
  */
@@ -68,11 +76,19 @@ static c_avl_tree_t *data_sets;
 
 static char *plugindir = NULL;
 
-static int             read_loop = 1;
+static int             read_loop = 0;
 static pthread_mutex_t read_lock = PTHREAD_MUTEX_INITIALIZER;
 static pthread_cond_t  read_cond = PTHREAD_COND_INITIALIZER;
 static pthread_t      *read_threads = NULL;
-static int             read_threads_num = 0;
+static size_t          read_threads_num = 0;
+
+static int               dispatch_loop = 0;
+static pthread_mutex_t   dispatch_lock = PTHREAD_MUTEX_INITIALIZER;
+static pthread_cond_t    dispatch_cond = PTHREAD_COND_INITIALIZER;
+static pthread_t        *dispatch_threads = NULL;
+static size_t            dispatch_threads_num = 0;
+static dispatch_queue_t *dispatch_head;
+static dispatch_queue_t *dispatch_tail;
 
 /*
  * Static functions
@@ -244,60 +260,138 @@ static void *plugin_read_thread (void __attribute__((unused)) *args)
        return ((void *) 0);
 } /* void *plugin_read_thread */
 
-static void start_threads (int num)
+static void *plugin_dispatch_thread (void *arg)
 {
-       int i;
+       pthread_mutex_lock (&dispatch_lock);
 
-       if (read_threads != NULL)
-               return;
+       while ((dispatch_loop != 0) || (dispatch_head != NULL))
+       {
+               dispatch_queue_t *qi;
+
+               if (dispatch_head == NULL)
+                       pthread_cond_wait (&dispatch_cond, &dispatch_lock);
+
+               if (dispatch_head == NULL)
+                       continue;
+
+               qi = dispatch_head;
+
+               if (dispatch_head == dispatch_tail)
+               {
+                       dispatch_head = NULL;
+                       dispatch_tail = NULL;
+               }
+               else
+               {
+                       dispatch_head = qi->next;
+               }
+
+               pthread_mutex_unlock (&dispatch_lock);
 
-       read_threads = (pthread_t *) calloc (num, sizeof (pthread_t));
-       if (read_threads == NULL)
+               plugin_dispatch_values (qi->vl);
+               sfree (qi->vl->values);
+               sfree (qi->vl);
+               sfree (qi);
+
+               pthread_mutex_lock (&dispatch_lock);
+       } /* while */
+
+       pthread_mutex_unlock (&dispatch_lock);
+
+       return ((void *) 0);
+} /* void *plugin_dispatch_thread */
+
+static int plugin_start_threads (size_t num,
+               pthread_t **tlist, size_t *tlist_num,
+               void *(*thread_main) (void *))
+{
+       size_t i;
+       pthread_t *new_tlist;
+       size_t new_tlist_num;
+
+       if (*tlist != NULL)
+               return (-1);
+
+       new_tlist = (pthread_t *) calloc (num, sizeof (*new_tlist));
+       if (new_tlist == NULL)
        {
-               ERROR ("plugin: start_threads: calloc failed.");
-               return;
+               ERROR ("plugin: plugin_start_threads: calloc failed.");
+               return (-1);
        }
 
-       read_threads_num = 0;
+       new_tlist_num = 0;
        for (i = 0; i < num; i++)
        {
-               if (pthread_create (read_threads + read_threads_num, NULL,
-                                       plugin_read_thread, NULL) == 0)
-               {
-                       read_threads_num++;
-               }
-               else
+               int status;
+
+               status = pthread_create (new_tlist + new_tlist_num,
+                               /* attr = */ NULL, thread_main,
+                               /* arg = */ (void *) 0);
+               if (status != 0)
                {
-                       ERROR ("plugin: start_threads: pthread_create failed.");
-                       return;
+                       ERROR ("plugin: plugin_start_threads: "
+                                       "pthread_create failed.");
+                       continue;
                }
+
+               new_tlist_num++;
        } /* for (i) */
-} /* void start_threads */
 
-static void stop_threads (void)
+       if (new_tlist_num < 1)
+       {
+               ERROR ("plugin: plugin_start_threads: "
+                               "Creating threads failed.");
+               sfree (new_tlist);
+               return (-1);
+       }
+
+       *tlist     = new_tlist;
+       *tlist_num = new_tlist_num;
+
+       return (0);
+} /* int plugin_start_threads */
+
+static int plugin_stop_threads (int *loop,
+               pthread_mutex_t *lock, pthread_cond_t *cond,
+               pthread_t **ret_tlist, size_t *ret_tlist_len)
 {
-       int i;
+       pthread_t *tlist;
+       size_t tlist_len;
+       size_t i;
 
-       if (read_threads == NULL)
-               return;
+       tlist     = *ret_tlist;
+       tlist_len = *ret_tlist_len;
 
-       pthread_mutex_lock (&read_lock);
-       read_loop = 0;
-       DEBUG ("plugin: stop_threads: Signalling `read_cond'");
-       pthread_cond_broadcast (&read_cond);
-       pthread_mutex_unlock (&read_lock);
+       if (tlist == NULL)
+               return (0);
+
+       DEBUG ("plugin_stop_threads: Stopping %zu threads.", tlist_len);
+
+       pthread_mutex_lock (lock);
+
+       *loop = 0;
+
+       pthread_cond_broadcast (cond);
+       pthread_mutex_unlock (lock);
 
-       for (i = 0; i < read_threads_num; i++)
+       for (i = 0; i < tlist_len; i++)
        {
-               if (pthread_join (read_threads[i], NULL) != 0)
+               int status;
+
+               status = pthread_join (tlist[i], NULL);
+               if (status != 0)
                {
-                       ERROR ("plugin: stop_threads: pthread_join failed.");
+                       ERROR ("plugin_stop_threads: pthread_join failed.");
                }
-               read_threads[i] = (pthread_t) 0;
        }
-       sfree (read_threads);
-       read_threads_num = 0;
-} /* void stop_threads */
+
+       sfree (tlist);
+
+       *ret_tlist = NULL;
+       *ret_tlist_len = 0;
+
+       return (0);
+} /* int plugin_stop_threads */
 
 /*
  * Public functions
@@ -640,8 +734,18 @@ void plugin_init_all (void)
                rt = global_option_get ("ReadThreads");
                num = atoi (rt);
                if (num != -1)
-                       start_threads ((num > 0) ? num : 5);
+               {
+                       read_loop = 1;
+                       plugin_start_threads ((num > 0) ? ((size_t ) num) : 5,
+                                       &read_threads, &read_threads_num,
+                                       plugin_read_thread);
+               }
        }
+
+       dispatch_loop = 1;
+       plugin_start_threads (/* num = */ 1, /* FIXME: Make this number configurable */
+                       &dispatch_threads, &dispatch_threads_num,
+                       plugin_dispatch_thread);
 } /* void plugin_init_all */
 
 void plugin_read_all (void)
@@ -812,7 +916,11 @@ void plugin_shutdown_all (void)
        int (*callback) (void);
        llentry_t *le;
 
-       stop_threads ();
+       plugin_stop_threads (&read_loop, &read_lock, &read_cond,
+                       &read_threads, &read_threads_num);
+
+       plugin_stop_threads (&dispatch_loop, &dispatch_lock, &dispatch_cond,
+                       &dispatch_threads, &dispatch_threads_num);
 
        if (list_shutdown == NULL)
                return;
@@ -937,6 +1045,76 @@ int plugin_dispatch_values (value_list_t *vl)
        return (0);
 } /* int plugin_dispatch_values */
 
+int plugin_dispatch_values_async (const value_list_t *vl)
+{
+       dispatch_queue_t *qi;
+       int i;
+
+       if (vl == NULL)
+               return (-EINVAL);
+
+       if (dispatch_threads_num < 1)
+       {
+               ERROR ("plugin_dispatch_values_async: "
+                               "No dispatch threads have been started!");
+#ifdef ENOTCONN
+               return (-ENOTCONN);
+#else
+               return (-1);
+#endif
+       }
+
+       qi = (dispatch_queue_t *) malloc (sizeof (*qi));
+       if (qi == NULL)
+       {
+               ERROR ("plugin_dispatch_values_async: malloc failed.");
+               return (-ENOMEM);
+       }
+       memset (qi, 0, sizeof (*qi));
+       qi->next = NULL;
+
+       qi->vl = (value_list_t *) malloc (sizeof (value_list_t));
+       if (qi->vl == NULL)
+       {
+               ERROR ("plugin_dispatch_values_async: malloc failed.");
+               sfree (qi);
+               return (-ENOMEM);
+       }
+       memcpy (qi->vl, vl, sizeof (value_list_t));
+       qi->vl->values = NULL;
+
+       qi->vl->values = (value_t *) calloc (qi->vl->values_len,
+                       sizeof (value_t));
+       if (qi->vl->values == NULL)
+       {
+               ERROR ("plugin_dispatch_values_async: malloc failed.");
+               sfree (qi->vl);
+               sfree (qi);
+               return (-ENOMEM);
+       }
+
+       for (i = 0; i < vl->values_len; i++)
+               qi->vl->values[i] = vl->values[i];
+
+       pthread_mutex_lock (&dispatch_lock);
+
+       if (dispatch_tail == NULL)
+       {
+               dispatch_head = qi;
+               dispatch_tail = qi;
+       }
+       else
+       {
+               dispatch_tail->next = qi;
+               dispatch_tail = qi;
+       }
+
+       pthread_cond_signal (&dispatch_cond);
+       pthread_mutex_unlock (&dispatch_lock);
+
+       return (0);
+} /* int plugin_dispatch_values_async */
+
 int plugin_dispatch_notification (const notification_t *notif)
 {
        int (*callback) (const notification_t *);

diff --git a/src/plugin.h b/src/plugin.h
index 3088e06..6c2c41e 100644 (file)
--- a/src/plugin.h
+++ b/src/plugin.h
@@ -264,6 +264,7 @@ int plugin_unregister_notification (const char *name);
  *              function.
  */
 int plugin_dispatch_values (value_list_t *vl);
+int plugin_dispatch_values_async (const value_list_t *vl);
 
 int plugin_dispatch_notification (const notification_t *notif);