malloc -> new
[oweals/gnunet.git] / src / statistics / statistics_api.c
index 3289745b15300cc09348c33b56e4604433404aea..04e85a07e95323b65d2026990c05d66c836e306b 100644 (file)
@@ -1,10 +1,10 @@
 /*
      This file is part of GNUnet.
-     (C) 2009 Christian Grothoff (and other contributing authors)
+     (C) 2009, 2010, 2011 Christian Grothoff (and other contributing authors)
 
      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
  * @author Christian Grothoff
  */
 #include "platform.h"
-#include "gnunet_client_lib.h"
-#include "gnunet_container_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"
 
 /**
  * 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).  
+ * service does not react within this timeframe).
  */
-#define SET_TRANSMIT_TIMEOUT GNUNET_TIME_relative_multiply (GNUNET_TIME_UNIT_MILLISECONDS, 250)
+#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 proc
+   */
+  void *proc_cls;
+
 };
 
 
@@ -71,7 +115,7 @@ struct GNUNET_STATISTICS_GetHandle
    * Main statistics handle.
    */
   struct GNUNET_STATISTICS_Handle *sh;
+
   /**
    * What subsystem is this action about? (can be NULL)
    */
@@ -118,7 +162,7 @@ struct GNUNET_STATISTICS_GetHandle
   int aborted;
 
   /**
-   * Is this a GET, SET or UPDATE?
+   * Is this a GET, SET, UPDATE or WATCH?
    */
   enum ActionType type;
 
@@ -135,11 +179,6 @@ struct GNUNET_STATISTICS_GetHandle
  */
 struct GNUNET_STATISTICS_Handle
 {
-  /**
-   * Our scheduler.
-   */
-  struct GNUNET_SCHEDULER_Handle *sched;
-
   /**
    * Name of our subsystem.
    */
@@ -178,80 +217,317 @@ struct GNUNET_STATISTICS_Handle
    */
   struct GNUNET_STATISTICS_GetHandle *current;
 
+  /**
+   * Array of watch entries.
+   */
+  struct GNUNET_STATISTICS_WatchEntry **watches;
+
+  /**
+   * Task doing exponential back-off trying to reconnect.
+   */
+  GNUNET_SCHEDULER_TaskIdentifier backoff_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 '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;
+
 };
 
 
+/**
+ * Obtain statistics about this process's memory consumption and
+ * report those as well (if they changed).
+ */
+static void
+update_memory_statistics (struct GNUNET_STATISTICS_Handle *h)
+{
+#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
+}
+
+
+/**
+ * Schedule the next action to be performed.
+ *
+ * @param h statistics handle to reconnect
+ */
+static void
+schedule_action (struct GNUNET_STATISTICS_Handle *h);
+
+
+/**
+ * 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
+schedule_watch_request (struct GNUNET_STATISTICS_Handle *h,
+                        struct GNUNET_STATISTICS_WatchEntry *watch)
+{
+
+  struct GNUNET_STATISTICS_GetHandle *ai;
+  size_t slen;
+  size_t nlen;
+  size_t nsize;
+
+  GNUNET_assert (NULL != h);
+  GNUNET_assert (NULL != watch);
+
+  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);
+}
+
+
+/**
+ * Free memory associated with the given action item.
+ *
+ * @param gh action item to free
+ */
+static void
+free_action_item (struct GNUNET_STATISTICS_GetHandle *gh)
+{
+  GNUNET_free_non_null (gh->subsystem);
+  GNUNET_free_non_null (gh->name);
+  GNUNET_free (gh);
+}
+
+
+/**
+ * Disconnect from the statistics service.
+ *
+ * @param h statistics handle to disconnect from
+ */
+static void
+do_disconnect (struct GNUNET_STATISTICS_Handle *h)
+{
+  struct GNUNET_STATISTICS_GetHandle *c;
+
+  if (NULL != h->th)
+  {
+    GNUNET_CLIENT_notify_transmit_ready_cancel (h->th);
+    h->th = NULL;
+  }
+  h->receiving = GNUNET_NO;
+  if (NULL != (c = h->current))
+  {
+    h->current = NULL;
+    if ( (NULL != c->cont) &&
+        (GNUNET_YES != c->aborted) )
+      c->cont (c->cls, GNUNET_SYSERR);
+    free_action_item (c);
+  }
+  if (NULL != h->client)
+  {
+    GNUNET_CLIENT_disconnect (h->client);
+    h->client = NULL;
+  }
+}
+
+
 /**
  * Try to (re)connect to the statistics service.
  *
- * @return GNUNET_YES on success, GNUNET_NO on failure.
+ * @param h statistics handle to reconnect
+ * @return #GNUNET_YES on success, #GNUNET_NO on failure.
  */
 static int
-try_connect (struct GNUNET_STATISTICS_Handle *ret)
+try_connect (struct GNUNET_STATISTICS_Handle *h)
 {
-  if (ret->client != NULL)
+  struct GNUNET_STATISTICS_GetHandle *gh;
+  struct GNUNET_STATISTICS_GetHandle *gn;
+  unsigned int i;
+
+  if (GNUNET_SCHEDULER_NO_TASK != h->backoff_task)
+    return GNUNET_NO;
+  if (NULL != h->client)
     return GNUNET_YES;
-  ret->client = GNUNET_CLIENT_connect (ret->sched, "statistics", ret->cfg);
-  if (ret->client != NULL)
+  h->client = GNUNET_CLIENT_connect ("statistics", h->cfg);
+  if (NULL != h->client)
+  {
+    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 (i = 0; i < h->watches_size; i++)
+    {
+      if (NULL != h->watches[i])
+        schedule_watch_request (h, h->watches[i]);
+    }
     return GNUNET_YES;
-#if DEBUG_STATISTICS
-  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
-              _("Failed to connect to statistics service!\n"));
-#endif
+  }
+  LOG (GNUNET_ERROR_TYPE_DEBUG,
+       "Failed to connect to statistics service!\n");
   return GNUNET_NO;
 }
 
 
 /**
- * Free memory associated with the given action item.
+ * We've waited long enough, reconnect now.
+ *
+ * @param cls the 'struct GNUNET_STATISTICS_Handle' to reconnect
+ * @param tc scheduler context (unused)
  */
 static void
-free_action_item (struct GNUNET_STATISTICS_GetHandle *ai)
+reconnect_task (void *cls, const struct GNUNET_SCHEDULER_TaskContext *tc)
 {
-  GNUNET_free_non_null (ai->subsystem);
-  GNUNET_free_non_null (ai->name);
-  GNUNET_free (ai);
+  struct GNUNET_STATISTICS_Handle *h = cls;
+
+  h->backoff_task = GNUNET_SCHEDULER_NO_TASK;
+  schedule_action (h);
 }
 
 
 /**
- * Schedule the next action to be performed.
+ * Task used by 'reconnect_later' to shutdown the handle
+ *
+ * @param cls the statistics handle
+ * @param tc scheduler context
  */
-static void schedule_action (struct GNUNET_STATISTICS_Handle *h);
+static void
+do_destroy (void *cls,
+              const struct GNUNET_SCHEDULER_TaskContext *tc)
+{
+  struct GNUNET_STATISTICS_Handle *h = cls;
+
+  GNUNET_STATISTICS_destroy (h, GNUNET_NO);
+}
 
 
 /**
- * GET processing is complete, tell client about it.
+ * Reconnect at a later time, respecting back-off.
+ *
+ * @param h statistics handle
  */
 static void
-finish (struct GNUNET_STATISTICS_Handle *h, int code)
+reconnect_later (struct GNUNET_STATISTICS_Handle *h)
 {
-  struct GNUNET_STATISTICS_GetHandle *pos = h->current;
-  h->current = NULL;
-  schedule_action (h);
-  if (pos != NULL)
-    {
-      if (pos->cont != NULL)
-       pos->cont (pos->cls, code);
-      free_action_item (pos);
-    }
+  int loss;
+  struct GNUNET_STATISTICS_GetHandle *gh;
+
+  GNUNET_assert (GNUNET_SCHEDULER_NO_TASK == 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"));
+    h->do_destroy = GNUNET_NO;
+    GNUNET_SCHEDULER_add_continuation (&do_destroy, h,
+                                      GNUNET_SCHEDULER_REASON_PREREQ_DONE);
+    return;
+  }
+  h->backoff_task =
+    GNUNET_SCHEDULER_add_delayed (h->backoff, &reconnect_task, h);
+  h->backoff = GNUNET_TIME_STD_BACKOFF (h->backoff);
 }
 
 
 /**
- * Process the message.
+ * Process a 'GNUNET_MESSAGE_TYPE_STATISTICS_VALUE' message.
  *
+ * @param h 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)
+process_statistics_value_message (struct GNUNET_STATISTICS_Handle *h,
+                                 const struct GNUNET_MessageHeader *msg)
 {
   char *service;
   char *name;
@@ -259,44 +535,91 @@ process_message (struct GNUNET_STATISTICS_Handle *h,
   uint16_t size;
 
   if (h->current->aborted)
+  {
+    LOG (GNUNET_ERROR_TYPE_DEBUG, "Iteration was aborted, ignoring VALUE\n");
     return GNUNET_OK;           /* don't bother */
+  }
   size = ntohs (msg->size);
   if (size < sizeof (struct GNUNET_STATISTICS_ReplyMessage))
-    {
-      GNUNET_break (0);
-      return GNUNET_SYSERR;
-    }
+  {
+    GNUNET_break (0);
+    return GNUNET_SYSERR;
+  }
   smsg = (const struct GNUNET_STATISTICS_ReplyMessage *) msg;
   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
+  if (size !=
+      GNUNET_STRINGS_buffer_tokenize ((const char *) &smsg[1], size, 2,
+                                      &service, &name))
+  {
+    GNUNET_break (0);
+    return GNUNET_SYSERR;
+  }
+  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,
-                       name,
-                       GNUNET_ntohll (smsg->value),
-                       0 !=
-                       (ntohl (smsg->uid) & GNUNET_STATISTICS_PERSIST_BIT)))
-    {
-#if DEBUG_STATISTICS
-      GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
-                 "Processing of remaining statistics aborted by client.\n");
-#endif
-      h->current->aborted = GNUNET_YES;    
-    }
+      h->current->proc (h->current->cls, service, name,
+                        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;
+  }
+  LOG (GNUNET_ERROR_TYPE_DEBUG, "VALUE processed successfully\n");
   return GNUNET_OK;
 }
 
 
+/**
+ * We have received a watch value from the service.  Process it.
+ *
+ * @param h statistics handle
+ * @param msg the watch value message
+ * @return GNUNET_OK if the message was well-formed, GNUNET_SYSERR if not,
+ *         GNUNET_NO if this watch has been cancelled
+ */
+static int
+process_watch_value (struct GNUNET_STATISTICS_Handle *h,
+                     const struct GNUNET_MessageHeader *msg)
+{
+  const struct GNUNET_STATISTICS_WatchValueMessage *wvm;
+  struct GNUNET_STATISTICS_WatchEntry *w;
+  uint32_t wid;
+
+  if (sizeof (struct GNUNET_STATISTICS_WatchValueMessage) != ntohs (msg->size))
+  {
+    GNUNET_break (0);
+    return GNUNET_SYSERR;
+  }
+  wvm = (const struct GNUNET_STATISTICS_WatchValueMessage *) msg;
+  GNUNET_break (0 == ntohl (wvm->reserved));
+  wid = ntohl (wvm->wid);
+  if (wid >= h->watches_size)
+  {
+    GNUNET_break (0);
+    return GNUNET_SYSERR;
+  }
+  w = h->watches[wid];
+  if (NULL == w)
+    return GNUNET_NO;
+  (void) w->proc (w->proc_cls, w->subsystem, w->name,
+                  GNUNET_ntohll (wvm->value),
+                  0 != (ntohl (wvm->flags) & GNUNET_STATISTICS_PERSIST_BIT));
+  return GNUNET_OK;
+}
+
+
+static void
+destroy_task (void *cls,
+             const struct GNUNET_SCHEDULER_TaskContext *tc)
+{
+  struct GNUNET_STATISTICS_Handle *h = cls;
+
+  GNUNET_STATISTICS_destroy (h, GNUNET_NO);
+}
+
+
 /**
  * Function called with messages from stats service.
  *
@@ -307,103 +630,206 @@ static void
 receive_stats (void *cls, const struct GNUNET_MessageHeader *msg)
 {
   struct GNUNET_STATISTICS_Handle *h = cls;
-
-  if (msg == NULL)
+  struct GNUNET_STATISTICS_GetHandle *c;
+  int ret;
+
+  if (NULL == msg)
+  {
+    LOG (GNUNET_ERROR_TYPE_DEBUG | GNUNET_ERROR_TYPE_BULK,
+         "Error receiving statistics from service, is the service running?\n");
+    do_disconnect (h);
+    reconnect_later (h);
+    return;
+  }
+  switch (ntohs (msg->type))
+  {
+  case GNUNET_MESSAGE_TYPE_TEST:
+    if (GNUNET_SYSERR != h->do_destroy)
     {
-      if (NULL != h->client)
-       {
-         GNUNET_CLIENT_disconnect (h->client, GNUNET_NO);
-         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);
+      /* not in shutdown, why do we get 'TEST'? */
+      GNUNET_break (0);
+      do_disconnect (h);
+      reconnect_later (h);
       return;
     }
-  switch (ntohs (msg->type))
+    h->do_destroy = GNUNET_NO;
+    GNUNET_SCHEDULER_add_continuation (&destroy_task, h,
+                                      GNUNET_SCHEDULER_REASON_PREREQ_DONE);
+    break;
+  case GNUNET_MESSAGE_TYPE_STATISTICS_END:
+    LOG (GNUNET_ERROR_TYPE_DEBUG, "Received end of statistics marker\n");
+    if (NULL == (c = h->current))
     {
-    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;
+      do_disconnect (h);
+      reconnect_later (h);
+      return;
     }
-  if (NULL != h->client)
+    h->backoff = GNUNET_TIME_UNIT_MILLISECONDS;
+    if (h->watches_size > 0)
+    {
+      GNUNET_CLIENT_receive (h->client, &receive_stats, h,
+                             GNUNET_TIME_UNIT_FOREVER_REL);
+    }
+    else
     {
-      GNUNET_CLIENT_disconnect (h->client, GNUNET_NO);
-      h->client = NULL;
+      h->receiving = GNUNET_NO;
     }
-  finish (h, GNUNET_SYSERR);
+    h->current = NULL;
+    schedule_action (h);
+    if (NULL != c->cont)
+      c->cont (c->cls, GNUNET_OK);
+    free_action_item (c);
+    return;
+  case GNUNET_MESSAGE_TYPE_STATISTICS_VALUE:
+    if (GNUNET_OK != process_statistics_value_message (h, msg))
+    {
+      do_disconnect (h);
+      reconnect_later (h);
+      return;
+    }
+    /* finally, look for more! */
+    LOG (GNUNET_ERROR_TYPE_DEBUG,
+        "Processing VALUE done, now reading more\n");
+    GNUNET_CLIENT_receive (h->client, &receive_stats, h,
+                          GNUNET_TIME_absolute_get_remaining (h->
+                                                              current->timeout));
+    h->backoff = GNUNET_TIME_UNIT_MILLISECONDS;
+    return;
+  case GNUNET_MESSAGE_TYPE_STATISTICS_WATCH_VALUE:
+    if (GNUNET_OK !=
+       (ret = process_watch_value (h, msg)))
+    {
+      do_disconnect (h);
+      if (GNUNET_NO == ret)
+       h->backoff = GNUNET_TIME_UNIT_MILLISECONDS;
+      reconnect_later (h);
+      return;
+    }
+    h->backoff = GNUNET_TIME_UNIT_MILLISECONDS;
+    GNUNET_assert (h->watches_size > 0);
+    GNUNET_CLIENT_receive (h->client, &receive_stats, h,
+                          GNUNET_TIME_UNIT_FOREVER_REL);
+    return;
+  default:
+    GNUNET_break (0);
+    do_disconnect (h);
+    reconnect_later (h);
+    return;
+  }
 }
 
 
 /**
  * Transmit a GET request (and if successful, start to receive
  * the response).
+ *
+ * @param handle statistics handle
+ * @param size how many bytes can we write to buf
+ * @param buf where to write requests to the service
+ * @return number of bytes written to buf
  */
 static size_t
 transmit_get (struct GNUNET_STATISTICS_Handle *handle, size_t size, void *buf)
 {
+  struct GNUNET_STATISTICS_GetHandle *c;
   struct GNUNET_MessageHeader *hdr;
   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));
+  if (NULL == buf)
+  {
+    /* timeout / error */
+    LOG (GNUNET_ERROR_TYPE_DEBUG,
+         "Transmission of request for statistics failed!\n");
+    do_disconnect (handle);
+    reconnect_later (handle);
+    return 0;
+  }
+  slen1 = strlen (c->subsystem) + 1;
+  slen2 = strlen (c->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);
+  GNUNET_assert (slen1 + slen2 ==
+                 GNUNET_STRINGS_buffer_fill ((char *) &hdr[1], slen1 + slen2, 2,
+                                             c->subsystem,
+                                             c->name));
+  if (GNUNET_YES != handle->receiving)
+  {
+    LOG (GNUNET_ERROR_TYPE_DEBUG,
+         "Transmission of GET done, now reading response\n");
+    handle->receiving = GNUNET_YES;
+    GNUNET_CLIENT_receive (handle->client, &receive_stats, handle,
+                           GNUNET_TIME_absolute_get_remaining (c->timeout));
+  }
+  return msize;
+}
+
+
+/**
+ * Transmit a WATCH request (and if successful, start to receive
+ * the response).
+ *
+ * @param handle statistics handle
+ * @param size how many bytes can we write to buf
+ * @param buf where to write requests to the service
+ * @return number of bytes written to buf
+ */
+static size_t
+transmit_watch (struct GNUNET_STATISTICS_Handle *handle, size_t size, void *buf)
+{
+  struct GNUNET_MessageHeader *hdr;
+  size_t slen1;
+  size_t slen2;
+  uint16_t msize;
+
+  if (NULL == buf)
+  {
+    /* timeout / error */
+    LOG (GNUNET_ERROR_TYPE_DEBUG,
+         "Transmission of request for statistics failed!\n");
+    do_disconnect (handle);
+    reconnect_later (handle);
+    return 0;
+  }
+  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);
+  hdr->type = htons (GNUNET_MESSAGE_TYPE_STATISTICS_WATCH);
   GNUNET_assert (slen1 + slen2 ==
-                 GNUNET_STRINGS_buffer_fill ((char *) &hdr[1],
-                                             slen1 + slen2,
-                                             2,
+                 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));
+  if (GNUNET_YES != handle->receiving)
+  {
+    handle->receiving = GNUNET_YES;
+    GNUNET_CLIENT_receive (handle->client, &receive_stats, handle,
+                           GNUNET_TIME_UNIT_FOREVER_REL);
+  }
+  GNUNET_assert (NULL == handle->current->cont);
+  free_action_item (handle->current);
+  handle->current = NULL;
   return msize;
 }
 
 
-
 /**
  * Transmit a SET/UPDATE request.
+ *
+ * @param handle statistics handle
+ * @param size how many bytes can we write to buf
+ * @param buf where to write requests to the service
+ * @return number of bytes written to buf
  */
 static size_t
 transmit_set (struct GNUNET_STATISTICS_Handle *handle, size_t size, void *buf)
@@ -414,20 +840,21 @@ transmit_set (struct GNUNET_STATISTICS_Handle *handle, size_t size, void *buf)
   size_t nsize;
 
   if (NULL == buf)
-    {
-      finish (handle, GNUNET_SYSERR);
-      return 0;
-    }
-
+  {
+    do_disconnect (handle);
+    reconnect_later (handle);
+    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;
-    }
+  {
+    GNUNET_break (0);
+    do_disconnect (handle);
+    reconnect_later (handle);
+    return 0;
+  }
   r = buf;
   r->header.size = htons (nsize);
   r->header.type = htons (GNUNET_MESSAGE_TYPE_STATISTICS_SET);
@@ -438,37 +865,51 @@ transmit_set (struct GNUNET_STATISTICS_Handle *handle, size_t size, void *buf)
   if (handle->current->type == ACTION_UPDATE)
     r->flags |= htonl (GNUNET_STATISTICS_SETFLAG_RELATIVE);
   GNUNET_assert (slen + nlen ==
-                 GNUNET_STRINGS_buffer_fill ((char *) &r[1],
-                                             slen + nlen,
-                                             2,
+                 GNUNET_STRINGS_buffer_fill ((char *) &r[1], slen + nlen, 2,
                                              handle->current->subsystem,
                                              handle->current->name));
-  finish (handle, GNUNET_OK);
+  GNUNET_assert (NULL == handle->current->cont);
+  free_action_item (handle->current);
+  handle->current = NULL;
+  update_memory_statistics (handle);
   return nsize;
 }
 
 
+/**
+ * Function called when we are ready to transmit a request to the service.
+ *
+ * @param cls the 'struct GNUNET_STATISTICS_Handle'
+ * @param size how many bytes can we write to buf
+ * @param buf where to write requests to the service
+ * @return number of bytes written to buf
+ */
 static size_t
 transmit_action (void *cls, size_t size, void *buf)
 {
-  struct GNUNET_STATISTICS_Handle *handle = cls;
+  struct GNUNET_STATISTICS_Handle *h = cls;
   size_t ret;
 
-  handle->th = NULL;
-  switch (handle->current->type)
+  h->th = NULL;
+  ret = 0;
+  if (NULL != h->current)
+    switch (h->current->type)
     {
     case ACTION_GET:
-      ret = transmit_get (handle, size, buf);
+      ret = transmit_get (h, size, buf);
       break;
     case ACTION_SET:
     case ACTION_UPDATE:
-      ret = transmit_set (handle, size, buf);
+      ret = transmit_set (h, size, buf);
+      break;
+    case ACTION_WATCH:
+      ret = transmit_watch (h, size, buf);
       break;
     default:
-      ret = 0;
-      GNUNET_break (0);
-      break; 
+      GNUNET_assert (0);
+      break;
     }
+  schedule_action (h);
   return ret;
 }
 
@@ -476,26 +917,25 @@ transmit_action (void *cls, size_t size, void *buf)
 /**
  * Get handle for the statistics service.
  *
- * @param sched scheduler to use
  * @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 (struct GNUNET_SCHEDULER_Handle *sched,
-                          const char *subsystem,
+GNUNET_STATISTICS_create (const char *subsystem,
                           const struct GNUNET_CONFIGURATION_Handle *cfg)
 {
   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;
+  if (GNUNET_YES ==
+      GNUNET_CONFIGURATION_get_value_yesno (cfg, "statistics", "DISABLE"))
+    return NULL;
+  GNUNET_assert (NULL != subsystem);
+  GNUNET_assert (NULL != cfg);
+  ret = GNUNET_new (struct GNUNET_STATISTICS_Handle);
   ret->cfg = cfg;
   ret->subsystem = GNUNET_strdup (subsystem);
-  try_connect (ret);
+  ret->backoff = GNUNET_TIME_UNIT_MILLISECONDS;
   return ret;
 }
 
@@ -509,150 +949,175 @@ GNUNET_STATISTICS_create (struct GNUNET_SCHEDULER_Handle *sched,
  *        be completed
  */
 void
-GNUNET_STATISTICS_destroy (struct GNUNET_STATISTICS_Handle *h,
-                          int sync_first)
+GNUNET_STATISTICS_destroy (struct GNUNET_STATISTICS_Handle *h, int sync_first)
 {
   struct GNUNET_STATISTICS_GetHandle *pos;
   struct GNUNET_STATISTICS_GetHandle *next;
-  struct GNUNET_STATISTICS_GetHandle *prev;
   struct GNUNET_TIME_Relative timeout;
+  int i;
 
+  if (NULL == h)
+    return;
+  GNUNET_assert (GNUNET_NO == h->do_destroy); // Don't call twice.
+  if (GNUNET_SCHEDULER_NO_TASK != h->backoff_task)
+  {
+    GNUNET_SCHEDULER_cancel (h->backoff_task);
+    h->backoff_task = GNUNET_SCHEDULER_NO_TASK;
+  }
   if (sync_first)
+  {
+    if (NULL != h->current)
     {
-      if (h->current != NULL)
-       {
-         if (h->current->type == ACTION_GET)
-           {
-             GNUNET_CLIENT_notify_transmit_ready_cancel (h->th);
-             h->th = NULL;
-             free_action_item (h->current);
-             h->current = NULL;
-           }
-       }
-      pos = h->action_head;
-      prev = NULL;
-      while (pos != NULL)
-       {
-         next = pos->next;
-         if (pos->type == ACTION_GET)
-           {
-             if (prev == NULL)
-               h->action_head = next;
-             else
-               prev->next = next;
-             free_action_item (pos);
-           }
-         else
-           {
-             prev = pos;
-           }
-         pos = next;
-       }
-      h->action_tail = prev;
-      if (h->current == NULL)
-       {
-         h->current = h->action_head;
-         if (h->action_head != NULL)
-           {
-             h->action_head = h->action_head->next;
-             if (h->action_head == NULL)
-               h->action_tail = NULL;
-           }
-       }
-      h->do_destroy = GNUNET_YES;
-      if ( (h->current != NULL) &&
-          (h->th == NULL) )
-       {                                       
-         timeout = GNUNET_TIME_absolute_get_remaining (h->current->timeout);
-         h->th = GNUNET_CLIENT_notify_transmit_ready (h->client,
-                                                      h->current->msize,
-                                                      timeout,
-                                                      GNUNET_YES,
-                                                      &transmit_action, h);
-         GNUNET_assert (NULL != h->th);
-       }
-      if (h->th != NULL)
-       return;
+      if (ACTION_GET == h->current->type)
+      {
+        GNUNET_CLIENT_notify_transmit_ready_cancel (h->th);
+        h->th = NULL;
+        free_action_item (h->current);
+        h->current = NULL;
+      }
     }
-  if (NULL != h->th)
+    next = h->action_head;
+    while (NULL != (pos = next))
     {
-      GNUNET_CLIENT_notify_transmit_ready_cancel (h->th);
-      h->th = NULL;
-    }
-  if (h->current != NULL)
-    free_action_item (h->current);
-  while (NULL != (pos = h->action_head))
-    {
-      h->action_head = pos->next;
-      free_action_item (pos);
+      next = pos->next;
+      if (ACTION_GET == pos->type)
+      {
+       GNUNET_CONTAINER_DLL_remove (h->action_head,
+                                    h->action_tail,
+                                    pos);
+        free_action_item (pos);
+      }
     }
-  if (h->client != NULL)
+    if ( (NULL == h->current) &&
+        (NULL != (h->current = h->action_head)) )
+      GNUNET_CONTAINER_DLL_remove (h->action_head,
+                                  h->action_tail,
+                                  h->current);
+    h->do_destroy = GNUNET_YES;
+    if ((NULL != h->current) && (NULL == h->th) &&
+       (NULL != h->client))
     {
-      GNUNET_CLIENT_disconnect (h->client, GNUNET_YES);
-      h->client = NULL;
+      timeout = GNUNET_TIME_absolute_get_remaining (h->current->timeout);
+      h->th =
+       GNUNET_CLIENT_notify_transmit_ready (h->client, h->current->msize,
+                                            timeout, GNUNET_YES,
+                                            &transmit_action, h);
+      GNUNET_assert (NULL != h->th);
     }
+    if (NULL != h->th)
+      return; /* do not finish destruction just yet */
+  }
+  while (NULL != (pos = h->action_head))
+  {
+    GNUNET_CONTAINER_DLL_remove (h->action_head,
+                                h->action_tail,
+                                pos);
+    free_action_item (pos);
+  }
+  do_disconnect (h);
+  for (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);
 }
 
 
+/**
+ * Function called to transmit TEST message to service to
+ * confirm that the service has received all of our 'SET'
+ * messages (during statistics disconnect/shutdown).
+ *
+ * @param cls the 'struct GNUNET_STATISTICS_Handle'
+ * @param size how many bytes can we write to buf
+ * @param buf where to write requests to the service
+ * @return number of bytes written to buf
+ */
+static size_t
+transmit_test_on_shutdown (void *cls,
+                          size_t size,
+                          void *buf)
+{
+  struct GNUNET_STATISTICS_Handle *h = cls;
+  struct GNUNET_MessageHeader hdr;
+
+  h->th = NULL;
+  if (NULL == buf)
+  {
+    GNUNET_log (GNUNET_ERROR_TYPE_WARNING,
+               _("Failed to receive acknowledgement from statistics service, some statistics might have been lost!\n"));
+    h->do_destroy = GNUNET_NO;
+    GNUNET_SCHEDULER_add_continuation (&destroy_task, h,
+                                      GNUNET_SCHEDULER_REASON_PREREQ_DONE);
+    return 0;
+  }
+  hdr.type = htons (GNUNET_MESSAGE_TYPE_TEST);
+  hdr.size = htons (sizeof (struct GNUNET_MessageHeader));
+  memcpy (buf, &hdr, sizeof (hdr));
+  if (GNUNET_YES != h->receiving)
+  {
+    h->receiving = GNUNET_YES;
+    GNUNET_CLIENT_receive (h->client, &receive_stats, h,
+                           GNUNET_TIME_UNIT_FOREVER_REL);
+  }
+  return sizeof (struct GNUNET_MessageHeader);
+}
+
 
 /**
  * Schedule the next action to be performed.
+ *
+ * @param h statistics handle
  */
 static void
 schedule_action (struct GNUNET_STATISTICS_Handle *h)
 {
   struct GNUNET_TIME_Relative timeout;
 
-  if (h->current != NULL)
+  if ( (NULL != h->th) ||
+       (GNUNET_SCHEDULER_NO_TASK != h->backoff_task) )
     return;                     /* action already pending */
   if (GNUNET_YES != try_connect (h))
-    {
-      finish (h, GNUNET_SYSERR);
-      return;
-    }
-
+  {
+    reconnect_later (h);
+    return;
+  }
+  if (NULL != h->current)
+    return; /* action already pending */
   /* schedule next action */
   h->current = h->action_head;
   if (NULL == h->current)
+  {
+    if (GNUNET_YES == h->do_destroy)
     {
-      if (h->do_destroy)
-       {
-         h->do_destroy = GNUNET_NO;
-         GNUNET_STATISTICS_destroy (h, GNUNET_YES);
-       }
-      return;
+      h->do_destroy = GNUNET_SYSERR; /* in 'TEST' mode */
+      h->th = GNUNET_CLIENT_notify_transmit_ready (h->client,
+                                                  sizeof (struct GNUNET_MessageHeader),
+                                                  SET_TRANSMIT_TIMEOUT,
+                                                  GNUNET_NO,
+                                                  &transmit_test_on_shutdown, h);
     }
-  GNUNET_CONTAINER_DLL_remove (h->action_head,
-                              h->action_tail,
-                              h->current);
+    return;
+  }
+  GNUNET_CONTAINER_DLL_remove (h->action_head, h->action_tail, h->current);
   timeout = GNUNET_TIME_absolute_get_remaining (h->current->timeout);
   if (NULL ==
-      (h->th = GNUNET_CLIENT_notify_transmit_ready (h->client,
-                                                   h->current->msize,
-                                                   timeout,
-                                                   GNUNET_YES,
-                                                   &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);
-    }
-}
-
-
-static void
-insert_ai (struct GNUNET_STATISTICS_Handle *h, struct GNUNET_STATISTICS_GetHandle *ai)
-{
-  GNUNET_CONTAINER_DLL_insert_after (h->action_head,
-                                    h->action_tail,
-                                    h->action_tail,
-                                    ai);                                    
-  if (h->action_head == ai)
-    schedule_action (h);
+      (h->th =
+       GNUNET_CLIENT_notify_transmit_ready (h->client, h->current->msize,
+                                            timeout, GNUNET_YES,
+                                            &transmit_action, h)))
+  {
+    LOG (GNUNET_ERROR_TYPE_DEBUG,
+         "Failed to transmit request to statistics service.\n");
+    do_disconnect (h);
+    reconnect_later (h);
+  }
 }
 
 
@@ -665,14 +1130,14 @@ insert_ai (struct GNUNET_STATISTICS_Handle *h, struct GNUNET_STATISTICS_GetHandl
  * @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
  * @return NULL on error
  */
 struct GNUNET_STATISTICS_GetHandle *
 GNUNET_STATISTICS_get (struct GNUNET_STATISTICS_Handle *handle,
-                       const char *subsystem,
-                       const char *name,
+                       const char *subsystem, const char *name,
                        struct GNUNET_TIME_Relative timeout,
                        GNUNET_STATISTICS_Callback cont,
                        GNUNET_STATISTICS_Iterator proc, void *cls)
@@ -681,28 +1146,19 @@ GNUNET_STATISTICS_get (struct GNUNET_STATISTICS_Handle *handle,
   size_t slen2;
   struct GNUNET_STATISTICS_GetHandle *ai;
 
-  GNUNET_assert (handle != NULL);
-  GNUNET_assert (proc != NULL);
+  if (NULL == handle)
+    return NULL;
+  GNUNET_assert (NULL != proc);
   GNUNET_assert (GNUNET_NO == handle->do_destroy);
-  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
-      return NULL;
-    }
-  if (subsystem == NULL)
+  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 GNUNET_STATISTICS_GetHandle));
+  ai = GNUNET_new (struct GNUNET_STATISTICS_GetHandle);
   ai->sh = handle;
   ai->subsystem = GNUNET_strdup (subsystem);
   ai->name = GNUNET_strdup (name);
@@ -712,13 +1168,15 @@ GNUNET_STATISTICS_get (struct GNUNET_STATISTICS_Handle *handle,
   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' 
+ * Cancel a 'get' request.  Must be called before the 'cont'
  * function is called.
  *
  * @param gh handle of the request to cancel
@@ -726,46 +1184,177 @@ GNUNET_STATISTICS_get (struct GNUNET_STATISTICS_Handle *handle,
 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;
-    }
+  {
+    gh->aborted = GNUNET_YES;
+  }
   else
+  {
+    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 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 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;
+  unsigned int i;
+
+  if (NULL == handle)
+    return GNUNET_SYSERR;
+  for (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_CONTAINER_DLL_remove (gh->sh->action_head,
-                                  gh->sh->action_tail,
-                                  gh);
-      GNUNET_free (gh->name);
-      GNUNET_free (gh->subsystem);
-      GNUNET_free (gh);
+      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,
-                   uint64_t value, enum ActionType type)
+add_setter_action (struct GNUNET_STATISTICS_Handle *h, const char *name,
+                   int make_persistent, uint64_t value, enum ActionType type)
 {
   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;
+  GNUNET_assert (NULL != h);
+  GNUNET_assert (NULL != name);
   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 GNUNET_STATISTICS_GetHandle));
+    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);
@@ -774,7 +1363,8 @@ 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);
 }
 
@@ -790,10 +1380,9 @@ add_setter_action (struct GNUNET_STATISTICS_Handle *h,
  */
 void
 GNUNET_STATISTICS_set (struct GNUNET_STATISTICS_Handle *handle,
-                       const char *name,
-                       uint64_t value, int make_persistent)
+                       const char *name, uint64_t value, int make_persistent)
 {
-  if (handle == NULL)
+  if (NULL == handle)
     return;
   GNUNET_assert (GNUNET_NO == handle->do_destroy);
   add_setter_action (handle, name, make_persistent, value, ACTION_SET);
@@ -811,16 +1400,15 @@ GNUNET_STATISTICS_set (struct GNUNET_STATISTICS_Handle *handle,
  */
 void
 GNUNET_STATISTICS_update (struct GNUNET_STATISTICS_Handle *handle,
-                          const char *name,
-                          int64_t delta, int make_persistent)
+                          const char *name, int64_t delta, int make_persistent)
 {
-  if (handle == NULL)
+  if (NULL == handle)
     return;
-  if (delta == 0)
+  if (0 == delta)
     return;
   GNUNET_assert (GNUNET_NO == handle->do_destroy);
-  add_setter_action (handle, name, make_persistent,
-                     (uint64_t) delta, ACTION_UPDATE);
+  add_setter_action (handle, name, make_persistent, (uint64_t) delta,
+                     ACTION_UPDATE);
 }