migrate secretsharing to new service API
[oweals/gnunet.git] / src / statistics / statistics_api.c
index 5cbbfc9b614df9bba38de11b2599ba8550b50b38..ad4453b2a62a0e8515317e0d972bdd1c740aabab 100644 (file)
@@ -1,10 +1,10 @@
 /*
      This file is part of GNUnet.
-     (C) 2009 Christian Grothoff (and other contributing authors)
+     Copyright (C) 2009, 2010, 2011, 2016 GNUnet e.V.
 
      GNUnet is free software; you can redistribute it and/or modify
      it under the terms of the GNU General Public License as published
-     by the Free Software Foundation; either version 2, or (at your
+     by the Free Software Foundation; either version 3, or (at your
      option) any later version.
 
      GNUnet is distributed in the hope that it will be useful, but
@@ -14,8 +14,8 @@
 
      You should have received a copy of the GNU General Public License
      along with GNUnet; see the file COPYING.  If not, write to the
-     Free Software Foundation, Inc., 59 Temple Place - Suite 330,
-     Boston, MA 02111-1307, USA.
+     Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
+     Boston, MA 02110-1301, USA.
 */
 
 /**
  * @author Christian Grothoff
  */
 #include "platform.h"
-#include "gnunet_client_lib.h"
+#include "gnunet_util_lib.h"
+#include "gnunet_constants.h"
 #include "gnunet_protocols.h"
-#include "gnunet_server_lib.h"
 #include "gnunet_statistics_service.h"
-#include "gnunet_strings_lib.h"
 #include "statistics.h"
 
-#define SET_TRANSMIT_TIMEOUT GNUNET_TIME_relative_multiply (GNUNET_TIME_UNIT_SECONDS, 30)
+/**
+ * How long do we wait until a statistics request for setting
+ * a value times out?  (The update will be lost if the
+ * service does not react within this timeframe).
+ */
+#define SET_TRANSMIT_TIMEOUT GNUNET_TIME_relative_multiply (GNUNET_TIME_UNIT_SECONDS, 2)
 
+#define LOG(kind,...) GNUNET_log_from (kind, "statistics-api",__VA_ARGS__)
 
 /**
  * Types of actions.
  */
 enum ActionType
 {
+  /**
+   * Get a value.
+   */
   ACTION_GET,
+
+  /**
+   * Set a value.
+   */
   ACTION_SET,
-  ACTION_UPDATE
+
+  /**
+   * Update a value.
+   */
+  ACTION_UPDATE,
+
+  /**
+   * Watch a value.
+   */
+  ACTION_WATCH
+};
+
+
+/**
+ * Entry kept for each value we are watching.
+ */
+struct GNUNET_STATISTICS_WatchEntry
+{
+
+  /**
+   * What subsystem is this action about? (never NULL)
+   */
+  char *subsystem;
+
+  /**
+   * What value is this action about? (never NULL)
+   */
+  char *name;
+
+  /**
+   * Function to call
+   */
+  GNUNET_STATISTICS_Iterator proc;
+
+  /**
+   * Closure for @e proc
+   */
+  void *proc_cls;
+
 };
 
 
 /**
  * Linked list of things we still need to do.
  */
-struct ActionItem
+struct GNUNET_STATISTICS_GetHandle
 {
+
+  /**
+   * This is a doubly linked list.
+   */
+  struct GNUNET_STATISTICS_GetHandle *next;
+
   /**
-   * This is a linked list.
+   * This is a doubly linked list.
    */
-  struct ActionItem *next;
+  struct GNUNET_STATISTICS_GetHandle *prev;
+
+  /**
+   * Main statistics handle.
+   */
+  struct GNUNET_STATISTICS_Handle *sh;
 
   /**
    * What subsystem is this action about? (can be NULL)
@@ -76,7 +137,7 @@ struct ActionItem
   GNUNET_STATISTICS_Iterator proc;
 
   /**
-   * Closure for proc and cont.
+   * Closure for @e proc and @e cont.
    */
   void *cls;
 
@@ -88,7 +149,7 @@ struct ActionItem
   /**
    * Associated value.
    */
-  unsigned long long value;
+  uint64_t value;
 
   /**
    * Flag for SET/UPDATE actions.
@@ -101,7 +162,7 @@ struct ActionItem
   int aborted;
 
   /**
-   * Is this a GET, SET or UPDATE?
+   * Is this a #ACTION_GET, #ACTION_SET, #ACTION_UPDATE or #ACTION_WATCH?
    */
   enum ActionType type;
 
@@ -118,11 +179,6 @@ struct ActionItem
  */
 struct GNUNET_STATISTICS_Handle
 {
-  /**
-   * Our scheduler.
-   */
-  struct GNUNET_SCHEDULER_Handle *sched;
-
   /**
    * Name of our subsystem.
    */
@@ -131,169 +187,296 @@ struct GNUNET_STATISTICS_Handle
   /**
    * Configuration to use.
    */
-  struct GNUNET_CONFIGURATION_Handle *cfg;
+  const struct GNUNET_CONFIGURATION_Handle *cfg;
 
   /**
-   * Socket (if available).
+   * Message queue to the service.
    */
-  struct GNUNET_CLIENT_Connection *client;
+  struct GNUNET_MQ_Handle *mq;
 
   /**
    * Head of the linked list of pending actions (first action
    * to be performed).
    */
-  struct ActionItem *action_head;
+  struct GNUNET_STATISTICS_GetHandle *action_head;
 
   /**
    * Tail of the linked list of actions (for fast append).
    */
-  struct ActionItem *action_tail;
+  struct GNUNET_STATISTICS_GetHandle *action_tail;
 
   /**
    * Action we are currently busy with (action request has been
    * transmitted, we're now receiving the response from the
    * service).
    */
-  struct ActionItem *current;
+  struct GNUNET_STATISTICS_GetHandle *current;
 
   /**
-   * Should this handle be destroyed once we've processed
-   * all actions?
+   * Array of watch entries.
+   */
+  struct GNUNET_STATISTICS_WatchEntry **watches;
+
+  /**
+   * Task doing exponential back-off trying to reconnect.
+   */
+  struct GNUNET_SCHEDULER_Task *backoff_task;
+
+  /**
+   * Task for running #do_destroy().
+   */
+  struct GNUNET_SCHEDULER_Task *destroy_task;
+
+  /**
+   * Time for next connect retry.
+   */
+  struct GNUNET_TIME_Relative backoff;
+
+  /**
+   * Maximum heap size observed so far (if available).
+   */
+  uint64_t peak_heap_size;
+
+  /**
+   * Maximum resident set side observed so far (if available).
+   */
+  uint64_t peak_rss;
+
+  /**
+   * Size of the @e watches array.
+   */
+  unsigned int watches_size;
+
+  /**
+   * Should this handle auto-destruct once all actions have
+   * been processed?
    */
   int do_destroy;
 
+  /**
+   * Are we currently receiving from the service?
+   */
+  int receiving;
+
 };
 
 
 /**
- * Try to (re)connect to the statistics service.
- *
- * @return GNUNET_YES on success, GNUNET_NO on failure.
+ * Obtain statistics about this process's memory consumption and
+ * report those as well (if they changed).
  */
-static int
-try_connect (struct GNUNET_STATISTICS_Handle *ret)
+static void
+update_memory_statistics (struct GNUNET_STATISTICS_Handle *h)
 {
-  if (ret->client != NULL)
-    return GNUNET_OK;
-  ret->client = GNUNET_CLIENT_connect (ret->sched, "statistics", ret->cfg);
-  if (ret->client != NULL)
-    return GNUNET_YES;
-#if DEBUG_STATISTICS
-  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
-              _("Failed to connect to statistics service!\n"));
+#if ENABLE_HEAP_STATISTICS
+  uint64_t current_heap_size = 0;
+  uint64_t current_rss = 0;
+
+  if (GNUNET_NO != h->do_destroy)
+    return;
+#if HAVE_MALLINFO
+  {
+    struct mallinfo mi;
+
+    mi = mallinfo();
+    current_heap_size = mi.uordblks + mi.fordblks;
+  }
+#endif
+#if HAVE_GETRUSAGE
+  {
+    struct rusage ru;
+
+    if (0 == getrusage (RUSAGE_SELF, &ru))
+    {
+      current_rss = 1024LL * ru.ru_maxrss;
+    }
+  }
+#endif
+  if (current_heap_size > h->peak_heap_size)
+  {
+    h->peak_heap_size = current_heap_size;
+    GNUNET_STATISTICS_set (h,
+                          "# peak heap size",
+                          current_heap_size,
+                          GNUNET_NO);
+  }
+  if (current_rss > h->peak_rss)
+  {
+    h->peak_rss = current_rss;
+    GNUNET_STATISTICS_set (h,
+                          "# peak resident set size",
+                          current_rss,
+                          GNUNET_NO);
+  }
 #endif
-  return GNUNET_NO;
 }
 
 
 /**
- * Free memory associated with the given action item.
+ * Reconnect at a later time, respecting back-off.
+ *
+ * @param h statistics handle
+ */
+static void
+reconnect_later (struct GNUNET_STATISTICS_Handle *h);
+
+
+/**
+ * Schedule the next action to be performed.
+ *
+ * @param cls statistics handle to reconnect
+ */
+static void
+schedule_action (void *cls);
+
+
+/**
+ * Transmit request to service that we want to watch
+ * the development of a particular value.
+ *
+ * @param h statistics handle
+ * @param watch watch entry of the value to watch
  */
 static void
-free_action_item (struct ActionItem *ai)
+schedule_watch_request (struct GNUNET_STATISTICS_Handle *h,
+                        struct GNUNET_STATISTICS_WatchEntry *watch)
 {
-  GNUNET_free_non_null (ai->subsystem);
-  GNUNET_free_non_null (ai->name);
-  GNUNET_free (ai);
+  struct GNUNET_STATISTICS_GetHandle *ai;
+  size_t slen;
+  size_t nlen;
+  size_t nsize;
+
+  slen = strlen (watch->subsystem) + 1;
+  nlen = strlen (watch->name) + 1;
+  nsize = sizeof (struct GNUNET_MessageHeader) + slen + nlen;
+  if (nsize >= GNUNET_SERVER_MAX_MESSAGE_SIZE)
+  {
+    GNUNET_break (0);
+    return;
+  }
+  ai = GNUNET_new (struct GNUNET_STATISTICS_GetHandle);
+  ai->sh = h;
+  ai->subsystem = GNUNET_strdup (watch->subsystem);
+  ai->name = GNUNET_strdup (watch->name);
+  ai->timeout = GNUNET_TIME_UNIT_FOREVER_ABS;
+  ai->msize = nsize;
+  ai->type = ACTION_WATCH;
+  ai->proc = watch->proc;
+  ai->cls = watch->proc_cls;
+  GNUNET_CONTAINER_DLL_insert_tail (h->action_head,
+                                    h->action_tail,
+                                   ai);
+  schedule_action (h);
 }
 
 
 /**
- * Get handle for the statistics service.
+ * Free memory associated with the given action item.
  *
- * @param subsystem name of subsystem using the service
- * @param cfg services configuration in use
- * @return handle to use
+ * @param gh action item to free
  */
-struct GNUNET_STATISTICS_Handle *
-GNUNET_STATISTICS_create (struct GNUNET_SCHEDULER_Handle *sched,
-                          const char *subsystem,
-                          struct GNUNET_CONFIGURATION_Handle *cfg)
+static void
+free_action_item (struct GNUNET_STATISTICS_GetHandle *gh)
 {
-  struct GNUNET_STATISTICS_Handle *ret;
-
-  GNUNET_assert (subsystem != NULL);
-  GNUNET_assert (sched != NULL);
-  GNUNET_assert (cfg != NULL);
-  ret = GNUNET_malloc (sizeof (struct GNUNET_STATISTICS_Handle));
-  ret->sched = sched;
-  ret->cfg = cfg;
-  ret->subsystem = GNUNET_strdup (subsystem);
-  try_connect (ret);
-  return ret;
+  GNUNET_free_non_null (gh->subsystem);
+  GNUNET_free_non_null (gh->name);
+  GNUNET_free (gh);
 }
 
 
 /**
- * Actually free the handle.
+ * Disconnect from the statistics service.
+ *
+ * @param h statistics handle to disconnect from
  */
 static void
-do_destroy (struct GNUNET_STATISTICS_Handle *h)
+do_disconnect (struct GNUNET_STATISTICS_Handle *h)
 {
-  GNUNET_assert (h->action_head == NULL);
-  GNUNET_assert (h->current == NULL);
-  if (h->client != NULL)
+  struct GNUNET_STATISTICS_GetHandle *c;
+
+  h->receiving = GNUNET_NO;
+  if (NULL != (c = h->current))
+  {
+    h->current = NULL;
+    if ( (NULL != c->cont) &&
+        (GNUNET_YES != c->aborted) )
     {
-      GNUNET_CLIENT_disconnect (h->client);
-      h->client = NULL;
+      c->cont (c->cls,
+               GNUNET_SYSERR);
+      c->cont = NULL;
     }
-  GNUNET_free (h->subsystem);
-  GNUNET_free (h);
+    free_action_item (c);
+  }
+  if (NULL != h->mq)
+  {
+    GNUNET_MQ_destroy (h->mq);
+    h->mq = NULL;
+  }
 }
 
 
 /**
- * Destroy a handle (free all state associated with
- * it).
+ * Process a #GNUNET_MESSAGE_TYPE_STATISTICS_VALUE message.
+ *
+ * @param cls statistics handle
+ * @param smsg message received from the service, never NULL
+ * @return #GNUNET_OK if the message was well-formed
  */
-void
-GNUNET_STATISTICS_destroy (struct GNUNET_STATISTICS_Handle *handle)
+static int
+check_statistics_value (void *cls,
+                        const struct GNUNET_STATISTICS_ReplyMessage *smsg)
 {
-  GNUNET_assert (handle->do_destroy == GNUNET_NO);
-  if ((handle->action_head != NULL) || (handle->current != NULL))
-    {
-      handle->do_destroy = GNUNET_YES;
-      return;
-    }
-  do_destroy (handle);
+  const char *service;
+  const char *name;
+  uint16_t size;
+
+  size = ntohs (smsg->header.size);
+  size -= sizeof (struct GNUNET_STATISTICS_ReplyMessage);
+  if (size !=
+      GNUNET_STRINGS_buffer_tokenize ((const char *) &smsg[1],
+                                      size,
+                                      2,
+                                      &service,
+                                      &name))
+  {
+    GNUNET_break (0);
+    return GNUNET_SYSERR;
+  }
+  return GNUNET_OK;
 }
 
 
 /**
- * Process the message.
+ * Process a #GNUNET_MESSAGE_TYPE_STATISTICS_VALUE message.
  *
- * @return GNUNET_OK if the message was well-formed
+ * @param cls statistics handle
+ * @param msg message received from the service, never NULL
+ * @return #GNUNET_OK if the message was well-formed
  */
-static int
-process_message (struct GNUNET_STATISTICS_Handle *h,
-                 const struct GNUNET_MessageHeader *msg)
+static void
+handle_statistics_value (void *cls,
+                         const struct GNUNET_STATISTICS_ReplyMessage *smsg)
 {
-  char *service;
-  char *name;
-  const struct GNUNET_STATISTICS_ReplyMessage *smsg;
+  struct GNUNET_STATISTICS_Handle *h = cls;
+  const char *service;
+  const char *name;
   uint16_t size;
 
   if (h->current->aborted)
-    return GNUNET_OK;           /* don't bother */
-  size = ntohs (msg->size);
-  if (size < sizeof (struct GNUNET_STATISTICS_ReplyMessage))
-    {
-      GNUNET_break (0);
-      return GNUNET_SYSERR;
-    }
-  smsg = (const struct GNUNET_STATISTICS_ReplyMessage *) msg;
+    return;           /* iteration aborted, don't bother */
+
+  size = ntohs (smsg->header.size);
   size -= sizeof (struct GNUNET_STATISTICS_ReplyMessage);
-  if (size != GNUNET_STRINGS_buffer_tokenize ((const char *) &smsg[1],
-                                              size, 2, &service, &name))
-    {
-      GNUNET_break (0);
-      return GNUNET_SYSERR;
-    }
-#if DEBUG_STATISTICS
-  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
-              "Received valid statistic on `%s:%s': %llu\n",
-              service, name, GNUNET_ntohll (smsg->value));
-#endif
+  GNUNET_assert (size ==
+                 GNUNET_STRINGS_buffer_tokenize ((const char *) &smsg[1],
+                                                 size,
+                                                 2,
+                                                 &service,
+                                                 &name));
+  LOG (GNUNET_ERROR_TYPE_DEBUG,
+       "Received valid statistic on `%s:%s': %llu\n",
+       service, name,
+       GNUNET_ntohll (smsg->value));
   if (GNUNET_OK !=
       h->current->proc (h->current->cls,
                         service,
@@ -301,167 +484,381 @@ process_message (struct GNUNET_STATISTICS_Handle *h,
                         GNUNET_ntohll (smsg->value),
                         0 !=
                         (ntohl (smsg->uid) & GNUNET_STATISTICS_PERSIST_BIT)))
+  {
+    LOG (GNUNET_ERROR_TYPE_DEBUG,
+         "Processing of remaining statistics aborted by client.\n");
+    h->current->aborted = GNUNET_YES;
+  }
+}
+
+
+/**
+ * We have received a watch value from the service.  Process it.
+ *
+ * @param cls statistics handle
+ * @param msg the watch value message
+ */
+static void
+handle_statistics_watch_value (void *cls,
+                               const struct GNUNET_STATISTICS_WatchValueMessage *wvm)
+{
+  struct GNUNET_STATISTICS_Handle *h = cls;
+  struct GNUNET_STATISTICS_WatchEntry *w;
+  uint32_t wid;
+
+  GNUNET_break (0 == ntohl (wvm->reserved));
+  wid = ntohl (wvm->wid);
+  if (wid >= h->watches_size)
+  {
+    do_disconnect (h);
+    reconnect_later (h);
+    return;
+  }
+  w = h->watches[wid];
+  if (NULL == w)
+    return;
+  (void) w->proc (w->proc_cls,
+                  w->subsystem,
+                  w->name,
+                  GNUNET_ntohll (wvm->value),
+                  0 != (ntohl (wvm->flags) & GNUNET_STATISTICS_PERSIST_BIT));
+}
+
+
+/**
+ * Generic error handler, called with the appropriate error code and
+ * the same closure specified at the creation of the message queue.
+ * Not every message queue implementation supports an error handler.
+ *
+ * @param cls closure with the `struct GNUNET_STATISTICS_Handle *`
+ * @param error error code
+ */
+static void
+mq_error_handler (void *cls,
+                  enum GNUNET_MQ_Error error)
+{
+  struct GNUNET_STATISTICS_Handle *h = cls;
+
+  if (GNUNET_NO != h->do_destroy)
+  {
+    h->do_destroy = GNUNET_NO;
+    if (NULL != h->destroy_task)
     {
-#if DEBUG_STATISTICS
-      GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
-                  "Processing of remaining statistics aborted by client.\n");
-#endif
-      h->current->aborted = GNUNET_YES;
+      GNUNET_SCHEDULER_cancel (h->destroy_task);
+      h->destroy_task = NULL;
     }
-  return GNUNET_OK;
+    GNUNET_STATISTICS_destroy (h,
+                               GNUNET_NO);
+    return;
+  }
+  do_disconnect (h);
+  reconnect_later (h);
 }
 
 
+/**
+ * Task used to destroy the statistics handle.
+ *
+ * @param cls the `struct GNUNET_STATISTICS_Handle`
+ */
+static void
+do_destroy (void *cls)
+{
+  struct GNUNET_STATISTICS_Handle *h = cls;
+
+  h->destroy_task = NULL;
+  h->do_destroy = GNUNET_NO;
+  LOG (GNUNET_ERROR_TYPE_DEBUG,
+       "Running final destruction\n");
+  GNUNET_STATISTICS_destroy (h,
+                             GNUNET_NO);
+}
+
 
 /**
- * Schedule the next action to be performed.
+ * Handle a #GNUNET_MESSAGE_TYPE_STATISTICS_DISCONNECT_CONFIRM
+ * message. We receive this message at the end of the shutdown when
+ * the service confirms that all data has been written to disk.
+ *
+ * @param cls our `struct GNUNET_STATISTICS_Handle *`
+ * @param msg the message
  */
-static void schedule_action (struct GNUNET_STATISTICS_Handle *h);
+static void
+handle_disconnect_confirm (void *cls,
+                          const struct GNUNET_MessageHeader *msg)
+{
+  struct GNUNET_STATISTICS_Handle *h = cls;
+
+  if (GNUNET_SYSERR != h->do_destroy)
+  {
+    /* not in shutdown, why do we get 'TEST'? */
+    GNUNET_break (0);
+    do_disconnect (h);
+    reconnect_later (h);
+    return;
+  }
+  LOG (GNUNET_ERROR_TYPE_DEBUG,
+       "Received DISCONNNECT_CONFIRM message from statistics, can complete disconnect\n");
+  if (NULL != h->destroy_task)
+    GNUNET_SCHEDULER_cancel (h->destroy_task);
+  h->destroy_task = GNUNET_SCHEDULER_add_now (&do_destroy,
+                                              h);
+}
 
 
 /**
- * GET processing is complete, tell client about it.
+ * Handle a #GNUNET_MESSAGE_TYPE_STATISTICS_END message. We receive
+ * this message in response to a query to indicate that there are no
+ * further matching results.
+ *
+ * @param cls our `struct GNUNET_STATISTICS_Handle *`
+ * @param msg the message
  */
 static void
-finish (struct GNUNET_STATISTICS_Handle *h, int code)
+handle_statistics_end (void *cls,
+                       const struct GNUNET_MessageHeader *msg)
 {
-  struct ActionItem *pos = h->current;
+  struct GNUNET_STATISTICS_Handle *h = cls;
+  struct GNUNET_STATISTICS_GetHandle *c;
+
+  LOG (GNUNET_ERROR_TYPE_DEBUG,
+       "Received end of statistics marker\n");
+  if (NULL == (c = h->current))
+  {
+    GNUNET_break (0);
+    do_disconnect (h);
+    reconnect_later (h);
+    return;
+  }
+  h->backoff = GNUNET_TIME_UNIT_MILLISECONDS;
   h->current = NULL;
   schedule_action (h);
-  if (pos->cont != NULL)
-    pos->cont (pos->cls, code);
-  free_action_item (pos);
+  if (NULL != c->cont)
+  {
+    c->cont (c->cls,
+             GNUNET_OK);
+    c->cont = NULL;
+  }
+  free_action_item (c);
 }
 
 
 /**
- * Function called with messages from stats service.
+ * Try to (re)connect to the statistics service.
  *
- * @param cls closure
- * @param msg message received, NULL on timeout or fatal error
+ * @param h statistics handle to reconnect
+ * @return #GNUNET_YES on success, #GNUNET_NO on failure.
+ */
+static int
+try_connect (struct GNUNET_STATISTICS_Handle *h)
+{
+  struct GNUNET_MQ_MessageHandler handlers[] = {
+    GNUNET_MQ_hd_fixed_size (disconnect_confirm,
+                             GNUNET_MESSAGE_TYPE_STATISTICS_DISCONNECT_CONFIRM,
+                             struct GNUNET_MessageHeader,
+                             h),
+    GNUNET_MQ_hd_fixed_size (statistics_end,
+                             GNUNET_MESSAGE_TYPE_STATISTICS_END,
+                             struct GNUNET_MessageHeader,
+                             h),
+    GNUNET_MQ_hd_var_size (statistics_value,
+                           GNUNET_MESSAGE_TYPE_STATISTICS_VALUE,
+                           struct GNUNET_STATISTICS_ReplyMessage,
+                           h),
+    GNUNET_MQ_hd_fixed_size (statistics_watch_value,
+                             GNUNET_MESSAGE_TYPE_STATISTICS_WATCH_VALUE,
+                             struct GNUNET_STATISTICS_WatchValueMessage,
+                             h),
+    GNUNET_MQ_handler_end ()
+  };
+  struct GNUNET_STATISTICS_GetHandle *gh;
+  struct GNUNET_STATISTICS_GetHandle *gn;
+
+  if (NULL != h->backoff_task)
+    return GNUNET_NO;
+  if (NULL != h->mq)
+    return GNUNET_YES;
+  h->mq = GNUNET_CLIENT_connect (h->cfg,
+                                 "statistics",
+                                 handlers,
+                                 &mq_error_handler,
+                                 h);
+  if (NULL == h->mq)
+  {
+    LOG (GNUNET_ERROR_TYPE_DEBUG,
+         "Failed to connect to statistics service!\n");
+    return GNUNET_NO;
+  }
+  gn = h->action_head;
+  while (NULL != (gh = gn))
+  {
+    gn = gh->next;
+    if (gh->type == ACTION_WATCH)
+    {
+      GNUNET_CONTAINER_DLL_remove (h->action_head,
+                                   h->action_tail,
+                                   gh);
+      free_action_item (gh);
+    }
+  }
+  for (unsigned int i = 0; i < h->watches_size; i++)
+    if (NULL != h->watches[i])
+      schedule_watch_request (h,
+                              h->watches[i]);
+  return GNUNET_YES;
+}
+
+
+/**
+ * We've waited long enough, reconnect now.
+ *
+ * @param cls the `struct GNUNET_STATISTICS_Handle` to reconnect
  */
 static void
-receive_stats (void *cls, const struct GNUNET_MessageHeader *msg)
+reconnect_task (void *cls)
 {
   struct GNUNET_STATISTICS_Handle *h = cls;
 
-  if (msg == NULL)
-    {
-      GNUNET_CLIENT_disconnect (h->client);
-      h->client = NULL;
-#if DEBUG_STATISTICS
-      GNUNET_log (GNUNET_ERROR_TYPE_DEBUG | GNUNET_ERROR_TYPE_BULK,
-                 "Error receiving statistics from service, is the service running?\n" );
-#endif
-      finish (h, GNUNET_SYSERR);
-      return;
-    }
-  switch (ntohs (msg->type))
-    {
-    case GNUNET_MESSAGE_TYPE_STATISTICS_END:
-#if DEBUG_STATISTICS
-      GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
-                  "Received end of statistics marker\n");
-#endif
-      finish (h, GNUNET_OK);
-      return;
-    case GNUNET_MESSAGE_TYPE_STATISTICS_VALUE:
-      if (GNUNET_OK == process_message (h, msg))
-        {
-          /* finally, look for more! */
-          GNUNET_CLIENT_receive (h->client,
-                                 &receive_stats,
-                                 h,
-                                 GNUNET_TIME_absolute_get_remaining
-                                 (h->current->timeout));
-          return;
-        }
-      GNUNET_break (0);
-      break;
-    default:
-      GNUNET_break (0);
-      break;
-    }
-  GNUNET_CLIENT_disconnect (h->client);
-  h->client = NULL;
-  finish (h, GNUNET_SYSERR);
+  h->backoff_task = NULL;
+  schedule_action (h);
 }
 
 
+/**
+ * Reconnect at a later time, respecting back-off.
+ *
+ * @param h statistics handle
+ */
+static void
+reconnect_later (struct GNUNET_STATISTICS_Handle *h)
+{
+  int loss;
+  struct GNUNET_STATISTICS_GetHandle *gh;
+
+  GNUNET_assert (NULL == h->backoff_task);
+  if (GNUNET_YES == h->do_destroy)
+  {
+    /* So we are shutting down and the service is not reachable.
+     * Chances are that it's down for good and we are not going to connect to
+     * it anymore.
+     * Give up and don't sync the rest of the data.
+     */
+    loss = GNUNET_NO;
+    for (gh = h->action_head; NULL != gh; gh = gh->next)
+      if ( (gh->make_persistent) &&
+          (ACTION_SET == gh->type) )
+       loss = GNUNET_YES;
+    if (GNUNET_YES == loss)
+      GNUNET_log (GNUNET_ERROR_TYPE_WARNING,
+                 _("Could not save some persistent statistics\n"));
+    if (NULL != h->destroy_task)
+      GNUNET_SCHEDULER_cancel (h->destroy_task);
+    h->destroy_task = GNUNET_SCHEDULER_add_now (&do_destroy,
+                                                h);
+    return;
+  }
+  h->backoff_task
+    = GNUNET_SCHEDULER_add_delayed (h->backoff,
+                                    &reconnect_task,
+                                    h);
+  h->backoff = GNUNET_TIME_STD_BACKOFF (h->backoff);
+}
+
+
+
 /**
  * Transmit a GET request (and if successful, start to receive
  * the response).
+ *
+ * @param handle statistics handle
  */
-static size_t
-transmit_get (struct GNUNET_STATISTICS_Handle *handle, size_t size, void *buf)
+static void
+transmit_get (struct GNUNET_STATISTICS_Handle *handle)
 {
+  struct GNUNET_STATISTICS_GetHandle *c;
   struct GNUNET_MessageHeader *hdr;
+  struct GNUNET_MQ_Envelope *env;
   size_t slen1;
   size_t slen2;
-  uint16_t msize;
 
-  if (buf == NULL)
-    {
-      /* timeout / error */
-#if DEBUG_STATISTICS
-      GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
-                  "Transmission of request for statistics failed!\n");
-#endif
-      finish (handle, GNUNET_SYSERR);
-      return 0;
-    }
+  GNUNET_assert (NULL != (c = handle->current));
+  slen1 = strlen (c->subsystem) + 1;
+  slen2 = strlen (c->name) + 1;
+  env = GNUNET_MQ_msg_extra (hdr,
+                             slen1 + slen2,
+                             GNUNET_MESSAGE_TYPE_STATISTICS_GET);
+  GNUNET_assert (slen1 + slen2 ==
+                 GNUNET_STRINGS_buffer_fill ((char *) &hdr[1],
+                                             slen1 + slen2,
+                                             2,
+                                             c->subsystem,
+                                             c->name));
+  GNUNET_MQ_notify_sent (env,
+                         &schedule_action,
+                         handle);
+  GNUNET_MQ_send (handle->mq,
+                  env);
+}
+
+
+/**
+ * Transmit a WATCH request (and if successful, start to receive
+ * the response).
+ *
+ * @param handle statistics handle
+ */
+static void
+transmit_watch (struct GNUNET_STATISTICS_Handle *handle)
+{
+  struct GNUNET_MessageHeader *hdr;
+  struct GNUNET_MQ_Envelope *env;
+  size_t slen1;
+  size_t slen2;
+
+  LOG (GNUNET_ERROR_TYPE_DEBUG,
+       "Transmitting watch request for `%s'\n",
+       handle->current->name);
   slen1 = strlen (handle->current->subsystem) + 1;
   slen2 = strlen (handle->current->name) + 1;
-  msize = slen1 + slen2 + sizeof (struct GNUNET_MessageHeader);
-  GNUNET_assert (msize <= size);
-  hdr = (struct GNUNET_MessageHeader *) buf;
-  hdr->size = htons (msize);
-  hdr->type = htons (GNUNET_MESSAGE_TYPE_STATISTICS_GET);
+  env = GNUNET_MQ_msg_extra (hdr,
+                             slen1 + slen2,
+                             GNUNET_MESSAGE_TYPE_STATISTICS_WATCH);
   GNUNET_assert (slen1 + slen2 ==
                  GNUNET_STRINGS_buffer_fill ((char *) &hdr[1],
                                              slen1 + slen2,
                                              2,
                                              handle->current->subsystem,
                                              handle->current->name));
-  GNUNET_CLIENT_receive (handle->client,
-                         &receive_stats,
-                         handle,
-                         GNUNET_TIME_absolute_get_remaining (handle->
-                                                             current->timeout));
-  return msize;
+  GNUNET_MQ_notify_sent (env,
+                         &schedule_action,
+                         handle);
+  GNUNET_MQ_send (handle->mq,
+                  env);
+  GNUNET_assert (NULL == handle->current->cont);
+  free_action_item (handle->current);
+  handle->current = NULL;
+  schedule_action (handle);
 }
 
 
-
 /**
  * Transmit a SET/UPDATE request.
+ *
+ * @param handle statistics handle
  */
-static size_t
-transmit_set (struct GNUNET_STATISTICS_Handle *handle, size_t size, void *buf)
+static void
+transmit_set (struct GNUNET_STATISTICS_Handle *handle)
 {
   struct GNUNET_STATISTICS_SetMessage *r;
+  struct GNUNET_MQ_Envelope *env;
   size_t slen;
   size_t nlen;
-  size_t nsize;
-
-  if (NULL == buf)
-    {
-      finish (handle, GNUNET_SYSERR);
-      return 0;
-    }
 
   slen = strlen (handle->current->subsystem) + 1;
   nlen = strlen (handle->current->name) + 1;
-  nsize = sizeof (struct GNUNET_STATISTICS_SetMessage) + slen + nlen;
-  if (size < nsize)
-    {
-      GNUNET_break (0);
-      finish (handle, GNUNET_SYSERR);
-      return 0;
-    }
-  r = buf;
-  r->header.size = htons (nsize);
-  r->header.type = htons (GNUNET_MESSAGE_TYPE_STATISTICS_SET);
+  env = GNUNET_MQ_msg_extra (r,
+                             slen + nlen,
+                             GNUNET_MESSAGE_TYPE_STATISTICS_SET);
   r->flags = 0;
   r->value = GNUNET_htonll (handle->current->value);
   if (handle->current->make_persistent)
@@ -474,95 +871,195 @@ transmit_set (struct GNUNET_STATISTICS_Handle *handle, size_t size, void *buf)
                                              2,
                                              handle->current->subsystem,
                                              handle->current->name));
-  finish (handle, GNUNET_OK);
-  return nsize;
+  GNUNET_assert (NULL == handle->current->cont);
+  free_action_item (handle->current);
+  handle->current = NULL;
+  update_memory_statistics (handle);
+  GNUNET_MQ_notify_sent (env,
+                         &schedule_action,
+                         handle);
+  GNUNET_MQ_send (handle->mq,
+                  env);
+}
+
+
+/**
+ * Get handle for the statistics service.
+ *
+ * @param subsystem name of subsystem using the service
+ * @param cfg services configuration in use
+ * @return handle to use
+ */
+struct GNUNET_STATISTICS_Handle *
+GNUNET_STATISTICS_create (const char *subsystem,
+                          const struct GNUNET_CONFIGURATION_Handle *cfg)
+{
+  struct GNUNET_STATISTICS_Handle *h;
+
+  if (GNUNET_YES ==
+      GNUNET_CONFIGURATION_get_value_yesno (cfg,
+                                            "statistics",
+                                            "DISABLE"))
+    return NULL;
+  h = GNUNET_new (struct GNUNET_STATISTICS_Handle);
+  h->cfg = cfg;
+  h->subsystem = GNUNET_strdup (subsystem);
+  h->backoff = GNUNET_TIME_UNIT_MILLISECONDS;
+  return h;
 }
 
 
-static size_t
-transmit_action (void *cls, size_t size, void *buf)
+/**
+ * Destroy a handle (free all state associated with
+ * it).
+ *
+ * @param h statistics handle to destroy
+ * @param sync_first set to #GNUNET_YES if pending SET requests should
+ *        be completed
+ */
+void
+GNUNET_STATISTICS_destroy (struct GNUNET_STATISTICS_Handle *h,
+                           int sync_first)
 {
-  struct GNUNET_STATISTICS_Handle *handle = cls;
-  size_t ret;
+  struct GNUNET_STATISTICS_GetHandle *pos;
+  struct GNUNET_STATISTICS_GetHandle *next;
 
-  switch (handle->current->type)
+  if (NULL == h)
+    return;
+  GNUNET_assert (GNUNET_NO == h->do_destroy); /* Don't call twice. */
+  if ( (sync_first) &&
+       (NULL != h->mq) &&
+       (0 != GNUNET_MQ_get_length (h->mq)) )
+  {
+    if ( (NULL != h->current) &&
+         (ACTION_GET == h->current->type) )
+      h->current->aborted = GNUNET_YES;
+    next = h->action_head;
+    while (NULL != (pos = next))
     {
-    case ACTION_GET:
-      ret = transmit_get (handle, size, buf);
-      break;
-    case ACTION_SET:
-    case ACTION_UPDATE:
-      ret = transmit_set (handle, size, buf);
-      break;
-    default:
-      ret = 0;
-      GNUNET_break (0);
-      break; 
+      next = pos->next;
+      if ( (ACTION_GET == pos->type) ||
+           (ACTION_WATCH == pos->type) )
+      {
+       GNUNET_CONTAINER_DLL_remove (h->action_head,
+                                    h->action_tail,
+                                    pos);
+        free_action_item (pos);
+      }
     }
-  return ret;
+    h->do_destroy = GNUNET_YES;
+    schedule_action (h);
+    GNUNET_assert (NULL == h->destroy_task);
+    h->destroy_task
+      = GNUNET_SCHEDULER_add_delayed (GNUNET_TIME_relative_multiply (h->backoff,
+                                                                     5),
+                                      &do_destroy,
+                                      h);
+    GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+                "Deferring destruction\n");
+    return; /* do not finish destruction just yet */
+  }
+  /* do clean up all */
+  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+              "Cleaning all up\n");
+  while (NULL != (pos = h->action_head))
+  {
+    GNUNET_CONTAINER_DLL_remove (h->action_head,
+                                h->action_tail,
+                                pos);
+    free_action_item (pos);
+  }
+  do_disconnect (h);
+  if (NULL != h->backoff_task)
+  {
+    GNUNET_SCHEDULER_cancel (h->backoff_task);
+    h->backoff_task = NULL;
+  }
+  if (NULL != h->destroy_task)
+  {
+    GNUNET_break (0);
+    GNUNET_SCHEDULER_cancel (h->destroy_task);
+    h->destroy_task = NULL;
+  }
+  for (unsigned int i = 0; i < h->watches_size; i++)
+  {
+    if (NULL == h->watches[i])
+      continue;
+    GNUNET_free (h->watches[i]->subsystem);
+    GNUNET_free (h->watches[i]->name);
+    GNUNET_free (h->watches[i]);
+  }
+  GNUNET_array_grow (h->watches,
+                     h->watches_size,
+                     0);
+  GNUNET_free (h->subsystem);
+  GNUNET_free (h);
 }
 
 
 /**
  * Schedule the next action to be performed.
+ *
+ * @param cls statistics handle
  */
 static void
-schedule_action (struct GNUNET_STATISTICS_Handle *h)
+schedule_action (void *cls)
 {
-  struct GNUNET_TIME_Relative timeout;
+  struct GNUNET_STATISTICS_Handle *h = cls;
 
-  if (h->current != NULL)
+  if (NULL != h->backoff_task)
     return;                     /* action already pending */
   if (GNUNET_YES != try_connect (h))
-    {
-      finish (h, GNUNET_SYSERR);
-      return;
-    }
-
+  {
+    reconnect_later (h);
+    return;
+  }
+  if (0 < GNUNET_MQ_get_length (h->mq))
+    return; /* Wait for queue to be reduced more */    
   /* schedule next action */
-  h->current = h->action_head;
-  if (NULL == h->current)
+  while (NULL == h->current)
+  {
+    h->current = h->action_head;
+    if (NULL == h->current)
     {
-      /* no pending network action, check destroy! */
-      if (h->do_destroy != GNUNET_YES)
-        return;
-      do_destroy (h);
-      return;
-    }
-  h->action_head = h->action_head->next;
-  if (NULL == h->action_head)
-    h->action_tail = NULL;
-  h->current->next = NULL;
-
-  timeout = GNUNET_TIME_absolute_get_remaining (h->current->timeout);
-  if (NULL ==
-      GNUNET_CLIENT_notify_transmit_ready (h->client,
-                                           h->current->msize,
-                                           timeout, &transmit_action, h))
-    {
-#if DEBUG_STATISTICS
-      GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
-                  "Failed to transmit request to statistics service.\n");
-#endif
-      finish (h, GNUNET_SYSERR);
-    }
-}
-
+      struct GNUNET_MessageHeader *hdr;
+      struct GNUNET_MQ_Envelope *env;
 
-static void
-insert_ai (struct GNUNET_STATISTICS_Handle *h, struct ActionItem *ai)
-{
-  if (h->action_tail == NULL)
-    {
-      h->action_head = ai;
-      h->action_tail = ai;
-      schedule_action (h);
+      if (GNUNET_YES != h->do_destroy)
+        return; /* nothing to do */
+      /* let service know that we're done */
+      GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+                  "Notifying service that we are done\n");
+      h->do_destroy = GNUNET_SYSERR; /* in 'TEST' mode */
+      env = GNUNET_MQ_msg (hdr,
+                           GNUNET_MESSAGE_TYPE_STATISTICS_DISCONNECT);
+      GNUNET_MQ_notify_sent (env,
+                             &schedule_action,
+                             h);
+      GNUNET_MQ_send (h->mq,
+                      env);
+      return;
     }
-  else
+    GNUNET_CONTAINER_DLL_remove (h->action_head,
+                                 h->action_tail,
+                                 h->current);
+    switch (h->current->type)
     {
-      h->action_tail->next = ai;
-      h->action_tail = ai;
+    case ACTION_GET:
+      transmit_get (h);
+      break;
+    case ACTION_SET:
+    case ACTION_UPDATE:
+      transmit_set (h);
+      break;
+    case ACTION_WATCH:
+      transmit_watch (h);
+      break;
+    default:
+      GNUNET_assert (0);
+      break;
     }
+  }
 }
 
 
@@ -572,83 +1069,246 @@ insert_ai (struct GNUNET_STATISTICS_Handle *h, struct ActionItem *ai)
  * @param handle identification of the statistics service
  * @param subsystem limit to the specified subsystem, NULL for our subsystem
  * @param name name of the statistic value, NULL for all values
- * @param timeout after how long should we give up (and call
- *        cont with an error code)?
  * @param cont continuation to call when done (can be NULL)
+ *        This callback CANNOT destroy the statistics handle in the same call.
  * @param proc function to call on each value
- * @param cls closure for cont and proc
+ * @param cls closure for @a cont and @a proc
+ * @return NULL on error
  */
-void
+struct GNUNET_STATISTICS_GetHandle *
 GNUNET_STATISTICS_get (struct GNUNET_STATISTICS_Handle *handle,
                        const char *subsystem,
                        const char *name,
-                       struct GNUNET_TIME_Relative timeout,
                        GNUNET_STATISTICS_Callback cont,
-                       GNUNET_STATISTICS_Iterator proc, void *cls)
+                       GNUNET_STATISTICS_Iterator proc,
+                       void *cls)
 {
   size_t slen1;
   size_t slen2;
-  struct ActionItem *ai;
+  struct GNUNET_STATISTICS_GetHandle *ai;
 
-  GNUNET_assert (handle != NULL);
-  GNUNET_assert (proc != NULL);
-  if (GNUNET_YES != try_connect (handle))
-    {
-#if DEBUG_STATISTICS
-      GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
-                  "Failed to connect to statistics service, can not get value `%s:%s'.\n",
-                  strlen (subsystem) ? subsystem : "*",
-                  strlen (name) ? name : "*");
-#endif
-      if (cont != NULL)
-       cont (cls, GNUNET_SYSERR);
-      return;
-    }
-  if (subsystem == NULL)
+  if (NULL == handle)
+    return NULL;
+  GNUNET_assert (NULL != proc);
+  GNUNET_assert (GNUNET_NO == handle->do_destroy);
+  if (NULL == subsystem)
     subsystem = "";
-  if (name == NULL)
+  if (NULL == name)
     name = "";
-  slen1 = strlen (subsystem);
-  slen2 = strlen (name);
+  slen1 = strlen (subsystem) + 1;
+  slen2 = strlen (name) + 1;
   GNUNET_assert (slen1 + slen2 + sizeof (struct GNUNET_MessageHeader) <
                  GNUNET_SERVER_MAX_MESSAGE_SIZE);
-  ai = GNUNET_malloc (sizeof (struct ActionItem));
+  ai = GNUNET_new (struct GNUNET_STATISTICS_GetHandle);
+  ai->sh = handle;
   ai->subsystem = GNUNET_strdup (subsystem);
   ai->name = GNUNET_strdup (name);
   ai->cont = cont;
   ai->proc = proc;
   ai->cls = cls;
-  ai->timeout = GNUNET_TIME_relative_to_absolute (timeout);
   ai->type = ACTION_GET;
   ai->msize = slen1 + slen2 + sizeof (struct GNUNET_MessageHeader);
-  insert_ai (handle, ai);
+  GNUNET_CONTAINER_DLL_insert_tail (handle->action_head,
+                                   handle->action_tail,
+                                   ai);
+  schedule_action (handle);
+  return ai;
 }
 
 
+/**
+ * Cancel a 'get' request.  Must be called before the 'cont'
+ * function is called.
+ *
+ * @param gh handle of the request to cancel
+ */
+void
+GNUNET_STATISTICS_get_cancel (struct GNUNET_STATISTICS_GetHandle *gh)
+{
+  if (NULL == gh)
+    return;
+  gh->cont = NULL;
+  if (gh->sh->current == gh)
+  {
+    gh->aborted = GNUNET_YES;
+    return;
+  }
+  GNUNET_CONTAINER_DLL_remove (gh->sh->action_head,
+                               gh->sh->action_tail,
+                               gh);
+  GNUNET_free (gh->name);
+  GNUNET_free (gh->subsystem);
+  GNUNET_free (gh);
+}
+
+
+/**
+ * Watch statistics from the peer (be notified whenever they change).
+ *
+ * @param handle identification of the statistics service
+ * @param subsystem limit to the specified subsystem, never NULL
+ * @param name name of the statistic value, never NULL
+ * @param proc function to call on each value
+ * @param proc_cls closure for @a proc
+ * @return #GNUNET_OK on success, #GNUNET_SYSERR on error
+ */
+int
+GNUNET_STATISTICS_watch (struct GNUNET_STATISTICS_Handle *handle,
+                         const char *subsystem,
+                         const char *name,
+                         GNUNET_STATISTICS_Iterator proc,
+                         void *proc_cls)
+{
+  struct GNUNET_STATISTICS_WatchEntry *w;
+
+  if (NULL == handle)
+    return GNUNET_SYSERR;
+  w = GNUNET_new (struct GNUNET_STATISTICS_WatchEntry);
+  w->subsystem = GNUNET_strdup (subsystem);
+  w->name = GNUNET_strdup (name);
+  w->proc = proc;
+  w->proc_cls = proc_cls;
+  GNUNET_array_append (handle->watches,
+                       handle->watches_size,
+                       w);
+  schedule_watch_request (handle,
+                          w);
+  return GNUNET_OK;
+}
+
+
+/**
+ * Stop watching statistics from the peer.
+ *
+ * @param handle identification of the statistics service
+ * @param subsystem limit to the specified subsystem, never NULL
+ * @param name name of the statistic value, never NULL
+ * @param proc function to call on each value
+ * @param proc_cls closure for @a proc
+ * @return #GNUNET_OK on success, #GNUNET_SYSERR on error (no such watch)
+ */
+int
+GNUNET_STATISTICS_watch_cancel (struct GNUNET_STATISTICS_Handle *handle,
+                               const char *subsystem,
+                                const char *name,
+                               GNUNET_STATISTICS_Iterator proc,
+                                void *proc_cls)
+{
+  struct GNUNET_STATISTICS_WatchEntry *w;
+
+  if (NULL == handle)
+    return GNUNET_SYSERR;
+  for (unsigned int i=0;i<handle->watches_size;i++)
+  {
+    w = handle->watches[i];
+    if (NULL == w)
+      continue;
+    if ( (w->proc == proc) &&
+        (w->proc_cls == proc_cls) &&
+        (0 == strcmp (w->name,
+                      name)) &&
+        (0 == strcmp (w->subsystem,
+                      subsystem)) )
+    {
+      GNUNET_free (w->name);
+      GNUNET_free (w->subsystem);
+      GNUNET_free (w);
+      handle->watches[i] = NULL;
+      return GNUNET_OK;
+    }
+  }
+  return GNUNET_SYSERR;
+}
+
+
+/**
+ * Queue a request to change a statistic.
+ *
+ * @param h statistics handle
+ * @param name name of the value
+ * @param make_persistent  should the value be kept across restarts?
+ * @param value new value or change
+ * @param type type of the action (#ACTION_SET or #ACTION_UPDATE)
+ */
 static void
 add_setter_action (struct GNUNET_STATISTICS_Handle *h,
                    const char *name,
                    int make_persistent,
-                   unsigned long long value, enum ActionType type)
+                   uint64_t value,
+                   enum ActionType type)
 {
-  struct ActionItem *ai;
+  struct GNUNET_STATISTICS_GetHandle *ai;
   size_t slen;
   size_t nlen;
   size_t nsize;
+  int64_t delta;
 
-  GNUNET_assert (h != NULL);
-  GNUNET_assert (name != NULL);
-  if (GNUNET_YES != try_connect (h))
-    return;
   slen = strlen (h->subsystem) + 1;
   nlen = strlen (name) + 1;
   nsize = sizeof (struct GNUNET_STATISTICS_SetMessage) + slen + nlen;
   if (nsize >= GNUNET_SERVER_MAX_MESSAGE_SIZE)
+  {
+    GNUNET_break (0);
+    return;
+  }
+  for (ai = h->action_head; NULL != ai; ai = ai->next)
+  {
+    if (! ( (0 == strcmp (ai->subsystem,
+                         h->subsystem)) &&
+           (0 == strcmp (ai->name,
+                         name)) &&
+           ( (ACTION_UPDATE == ai->type) ||
+             (ACTION_SET == ai->type) ) ) )
+      continue;
+    if (ACTION_SET == ai->type)
     {
-      GNUNET_break (0);
-      return;
+      if (ACTION_UPDATE == type)
+      {
+       delta = (int64_t) value;
+       if (delta > 0)
+        {
+         /* update old set by new delta */
+         ai->value += delta;
+       }
+       else
+        {
+         /* update old set by new delta, but never go negative */
+         if (ai->value < -delta)
+           ai->value = 0;
+         else
+           ai->value += delta;
+       }
+      }
+      else
+      {
+       /* new set overrides old set */
+       ai->value = value;
+      }
     }
-  ai = GNUNET_malloc (sizeof (struct ActionItem));
+    else
+    {
+      if (ACTION_UPDATE == type)
+      {
+       /* make delta cummulative */
+       delta = (int64_t) value;
+       ai->value += delta;
+      }
+      else
+      {
+       /* drop old 'update', use new 'set' instead */
+       ai->value = value;
+       ai->type = type;
+      }
+    }
+    ai->timeout
+      = GNUNET_TIME_relative_to_absolute (SET_TRANSMIT_TIMEOUT);
+    ai->make_persistent
+      = make_persistent;
+    return;
+  }
+  /* no existing entry matches, create a fresh one */
+  ai = GNUNET_new (struct GNUNET_STATISTICS_GetHandle);
+  ai->sh = h;
   ai->subsystem = GNUNET_strdup (h->subsystem);
   ai->name = GNUNET_strdup (name);
   ai->timeout = GNUNET_TIME_relative_to_absolute (SET_TRANSMIT_TIMEOUT);
@@ -656,7 +1316,9 @@ add_setter_action (struct GNUNET_STATISTICS_Handle *h,
   ai->msize = nsize;
   ai->value = value;
   ai->type = type;
-  insert_ai (h, ai);
+  GNUNET_CONTAINER_DLL_insert_tail (h->action_head,
+                                    h->action_tail,
+                                   ai);
   schedule_action (h);
 }
 
@@ -673,9 +1335,17 @@ add_setter_action (struct GNUNET_STATISTICS_Handle *h,
 void
 GNUNET_STATISTICS_set (struct GNUNET_STATISTICS_Handle *handle,
                        const char *name,
-                       unsigned long long value, int make_persistent)
+                       uint64_t value,
+                       int make_persistent)
 {
-  add_setter_action (handle, name, make_persistent, value, ACTION_SET);
+  if (NULL == handle)
+    return;
+  GNUNET_assert (GNUNET_NO == handle->do_destroy);
+  add_setter_action (handle,
+                     name,
+                     make_persistent,
+                     value,
+                     ACTION_SET);
 }
 
 
@@ -691,10 +1361,19 @@ GNUNET_STATISTICS_set (struct GNUNET_STATISTICS_Handle *handle,
 void
 GNUNET_STATISTICS_update (struct GNUNET_STATISTICS_Handle *handle,
                           const char *name,
-                          long long delta, int make_persistent)
+                          int64_t delta,
+                          int make_persistent)
 {
-  add_setter_action (handle, name, make_persistent,
-                     (unsigned long long) delta, ACTION_UPDATE);
+  if (NULL == handle)
+    return;
+  if (0 == delta)
+    return;
+  GNUNET_assert (GNUNET_NO == handle->do_destroy);
+  add_setter_action (handle,
+                     name,
+                     make_persistent,
+                     (uint64_t) delta,
+                     ACTION_UPDATE);
 }