X-Git-Url: https://git.librecmc.org/?a=blobdiff_plain;f=src%2Fstatistics%2Fgnunet-service-statistics.c;h=6c3d173c44b78b19eb0386bd4e08745ebce21e80;hb=372afebb55cc8b40d5f7115a398564e6ffd61434;hp=3ff751efec059ebd69f14b73d86d2cf307d1f47d;hpb=01d888e4e6703810a8a526f626050c7d20bfcb14;p=oweals%2Fgnunet.git

diff --git a/src/statistics/gnunet-service-statistics.c b/src/statistics/gnunet-service-statistics.c
index 3ff751efe..6c3d173c4 100644
--- a/src/statistics/gnunet-service-statistics.c
+++ b/src/statistics/gnunet-service-statistics.c
@@ -1,6 +1,6 @@
 /*
      This file is part of GNUnet.
-     (C) 2009 Christian Grothoff (and other contributing authors)
+     (C) 2009, 2010, 2012 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
@@ -22,11 +22,10 @@
  * @file statistics/gnunet-service-statistics.c
  * @brief program that tracks statistics
  * @author Christian Grothoff
- * 
- * TODO:
- * - use BIO for IO operations
  */
 #include "platform.h"
+#include "gnunet_bio_lib.h"
+#include "gnunet_container_lib.h"
 #include "gnunet_disk_lib.h"
 #include "gnunet_getopt_lib.h"
 #include "gnunet_protocols.h"
@@ -36,6 +35,73 @@
 #include "gnunet_time_lib.h"
 #include "statistics.h"
 
+/**
+ * Watch entry.
+ */
+struct WatchEntry
+{
+
+  /**
+   * Watch entries are kept in a linked list.
+   */
+  struct WatchEntry *next;
+
+  /**
+   * Watch entries are kept in a linked list.
+   */
+  struct WatchEntry *prev;
+
+  /**
+   * For which client is this watch entry?
+   */
+  struct GNUNET_SERVER_Client *client;
+
+  /**
+   * Last value we communicated to the client for this watch entry.
+   */
+  uint64_t last_value;
+
+  /**
+   * Unique watch number for this client and this watched value.
+   */
+  uint32_t wid;
+
+  /**
+   * Is last_value valid
+   * GNUNET_NO : last_value is n/a, GNUNET_YES: last_value is valid
+   */
+  int last_value_set;
+
+};
+
+
+/**
+ * Client entry.
+ */
+struct ClientEntry
+{
+  /**
+   * Clients are kept in a linked list.
+   */
+  struct ClientEntry *next;
+
+  /**
+   * Clients are kept in a linked list.
+   */
+  struct ClientEntry *prev;
+
+  /**
+   * Corresponding server handle.
+   */
+  struct GNUNET_SERVER_Client *client;
+
+  /**
+   * Maximum watch ID used by this client so far.
+   */
+  uint32_t max_wid;
+
+};
+
 /**
  * Entry in the statistics list.
  */
@@ -65,6 +131,18 @@ struct StatsEntry
    */
   struct GNUNET_STATISTICS_SetMessage *msg;
 
+  /**
+   * Watch context for changes to this
+   * value, or NULL for none.
+   */
+  struct WatchEntry *we_head;
+
+  /**
+   * Watch context for changes to this
+   * value, or NULL for none.
+   */
+  struct WatchEntry *we_tail;
+
   /**
    * Our value.
    */
@@ -80,6 +158,12 @@ struct StatsEntry
    */
   int persistent;
 
+  /**
+   * Is this value set?
+   * GNUNET_NO : value is n/a, GNUNET_YES: value is valid
+   */
+  int set;
+
 };
 
 /**
@@ -92,6 +176,54 @@ static const struct GNUNET_CONFIGURATION_Handle *cfg;
  */
 static struct StatsEntry *start;
 
+/**
+ * Head of linked list of connected clients.
+ */
+static struct ClientEntry *client_head;
+
+/**
+ * Tail of linked list of connected clients.
+ */
+static struct ClientEntry *client_tail;
+
+/**
+ * Handle to our server.
+ */
+static struct GNUNET_SERVER_Handle *srv;
+
+/**
+ * Our notification context.
+ */
+static struct GNUNET_SERVER_NotificationContext *nc;
+
+/**
+ * Counter used to generate unique values.
+ */
+static uint32_t uidgen;
+
+/**
+ * Set to YES if we are shutting down as soon as possible.
+ */
+static int in_shutdown;
+
+
+/**
+ * Inject a message to our server with a client of 'NULL'.
+ *
+ * @param cls the 'struct GNUNET_SERVER_Handle'
+ * @param client unused
+ * @param msg message to inject
+ */
+static int
+inject_message (void *cls, void *client, const struct GNUNET_MessageHeader *msg)
+{
+  struct GNUNET_SERVER_Handle *server = cls;
+
+  GNUNET_break (GNUNET_OK == GNUNET_SERVER_inject (server, NULL, msg));
+  return GNUNET_OK;
+}
+
+
 /**
  * Load persistent values from disk.  Disk format is
  * exactly the same format that we also use for
@@ -103,121 +235,135 @@ static void
 load (struct GNUNET_SERVER_Handle *server)
 {
   char *fn;
-  struct GNUNET_DISK_FileHandle *fh;
-  struct GNUNET_DISK_MapHandle *mh;
-  struct stat sb;
+  struct GNUNET_BIO_ReadHandle *rh;
+  uint64_t fsize;
   char *buf;
-  size_t off;
-  const struct GNUNET_MessageHeader *msg;
-
-  fn = GNUNET_DISK_get_home_filename (cfg,
-                                      "statistics", "statistics.data", NULL);
-  if (fn == NULL)
+  struct GNUNET_SERVER_MessageStreamTokenizer *mst;
+  char *emsg;
+
+  if (GNUNET_OK !=
+      GNUNET_CONFIGURATION_get_value_filename (cfg,
+                                               "STATISTICS",
+                                               "DATABASE",
+                                               &fn))
+  {
+    GNUNET_log_config_missing (GNUNET_ERROR_TYPE_ERROR,
+                               "STATISTICS",
+                               "DATABASE");
     return;
-  if ((0 != stat (fn, &sb)) || (sb.st_size == 0))
-    {
-      GNUNET_free (fn);
-      return;
-    }
-  fh = GNUNET_DISK_file_open (fn, GNUNET_DISK_OPEN_READ,
-			      GNUNET_DISK_PERM_NONE);
-  if (!fh)
-    {
-      GNUNET_free (fn);
-      return;
-    }
-  buf = GNUNET_DISK_file_map (fh, &mh, GNUNET_DISK_MAP_TYPE_READ, sb.st_size);
-  if (NULL == buf)
-    {
-      GNUNET_log_strerror_file (GNUNET_ERROR_TYPE_WARNING, "mmap", fn);
-      GNUNET_break (GNUNET_OK == GNUNET_DISK_file_close (fh));
-      GNUNET_free (fn);
-      return;
-    }
+  }
+  if ( (GNUNET_OK !=
+        GNUNET_DISK_file_size (fn, &fsize, GNUNET_NO, GNUNET_YES)) ||
+       (0 == fsize) )
+  {
+    GNUNET_free (fn);
+    return;
+  }
+  buf = GNUNET_malloc (fsize);
+  rh = GNUNET_BIO_read_open (fn);
+  if (!rh)
+  {
+    GNUNET_free (buf);
+    GNUNET_free (fn);
+    return;
+  }
+  if (GNUNET_OK != GNUNET_BIO_read (rh, fn, buf, fsize))
+  {
+    GNUNET_log_strerror_file (GNUNET_ERROR_TYPE_WARNING, "read", fn);
+    GNUNET_break (GNUNET_OK == GNUNET_BIO_read_close (rh, &emsg));
+    GNUNET_free (buf);
+    GNUNET_free_non_null (emsg);
+    GNUNET_free (fn);
+    return;
+  }
   GNUNET_log (GNUNET_ERROR_TYPE_INFO,
               _("Loading %llu bytes of statistics from `%s'\n"),
-              (unsigned long long) sb.st_size, fn);
-  off = 0;
-  while (off + sizeof (struct GNUNET_MessageHeader) < sb.st_size)
-    {
-      msg = (const struct GNUNET_MessageHeader *) &buf[off];
-      if ((ntohs (msg->size) + off > sb.st_size) ||
-          (GNUNET_OK != GNUNET_SERVER_inject (server, NULL, msg)))
-        {
-          GNUNET_break (0);
-          break;
-        }
-      off += ntohs (msg->size);
-    }
-  GNUNET_break (GNUNET_OK == GNUNET_DISK_file_unmap (mh));
-  GNUNET_break (GNUNET_OK == GNUNET_DISK_file_close (fh));
+              fsize, fn);
+  mst = GNUNET_SERVER_mst_create (&inject_message, server);
+  GNUNET_break (GNUNET_OK ==
+                GNUNET_SERVER_mst_receive (mst, NULL, buf, fsize,
+                                           GNUNET_YES, GNUNET_NO));
+  GNUNET_SERVER_mst_destroy (mst);
+  GNUNET_free (buf);
+  GNUNET_break (GNUNET_OK == GNUNET_BIO_read_close (rh, &emsg));
+  GNUNET_free_non_null (emsg);
   GNUNET_free (fn);
 }
 
+
 /**
  * Write persistent statistics to disk.
  */
 static void
-save ()       
+save ()
 {
   struct StatsEntry *pos;
   char *fn;
-  struct GNUNET_DISK_FileHandle *fh;
+  struct GNUNET_BIO_WriteHandle *wh;
   uint16_t size;
   unsigned long long total;
 
-  fh = NULL;
-  fn = GNUNET_DISK_get_home_filename (cfg,
-                                      "statistics", "statistics.data", NULL);
-  if (fn != NULL)
-    fh = GNUNET_DISK_file_open (fn, GNUNET_DISK_OPEN_WRITE
-        | GNUNET_DISK_OPEN_CREATE | GNUNET_DISK_OPEN_TRUNCATE,
-        GNUNET_DISK_PERM_USER_READ | GNUNET_DISK_PERM_USER_WRITE);
+  if (GNUNET_OK !=
+      GNUNET_CONFIGURATION_get_value_filename (cfg,
+                                               "STATISTICS",
+                                               "DATABASE",
+                                               &fn))
+  {
+    GNUNET_log_config_missing (GNUNET_ERROR_TYPE_ERROR,
+                               "STATISTICS",
+                               "DATABASE");
+    return;
+  }
+  (void) GNUNET_DISK_directory_create_for_file (fn);
+  wh = GNUNET_BIO_write_open (fn);
   total = 0;
   while (NULL != (pos = start))
+  {
+    start = pos->next;
+    if ((pos->persistent) && (NULL != wh))
     {
-      start = pos->next;
-      if ((pos->persistent) && (NULL != fh))
-        {
-          size = htons (pos->msg->header.size);
-          if (size != GNUNET_DISK_file_write (fh, pos->msg, size))
-            {
-              GNUNET_log_strerror_file (GNUNET_ERROR_TYPE_WARNING,
-                                        "write", fn);
-              GNUNET_DISK_file_close (fh);
-	      fh = NULL;
-            }
-          else
-            total += size;
-        }
-      GNUNET_free (pos);
-    }
-  if (NULL != fh)
-    {
-      GNUNET_DISK_file_close (fh);
-      if (total == 0)
-        GNUNET_break (0 == UNLINK (fn));
+      size = htons (pos->msg->header.size);
+      if (GNUNET_OK != GNUNET_BIO_write (wh, pos->msg, size))
+      {
+        GNUNET_log_strerror_file (GNUNET_ERROR_TYPE_WARNING, "write", fn);
+        if (GNUNET_OK != GNUNET_BIO_write_close (wh))
+	  GNUNET_log_strerror_file (GNUNET_ERROR_TYPE_WARNING, "close", fn);
+        wh = NULL;
+      }
       else
-        GNUNET_log (GNUNET_ERROR_TYPE_INFO,
-                    _("Wrote %llu bytes of statistics to `%s'\n"), total, fn);
+        total += size;
     }
+    GNUNET_free (pos);
+  }
+  if (NULL != wh)
+  {
+    if (GNUNET_OK != GNUNET_BIO_write_close (wh))
+      GNUNET_log_strerror_file (GNUNET_ERROR_TYPE_WARNING, "close", fn);
+    if (total == 0)
+      GNUNET_break (0 == UNLINK (fn));
+    else
+      GNUNET_log (GNUNET_ERROR_TYPE_INFO,
+                  _("Wrote %llu bytes of statistics to `%s'\n"), total, fn);
+  }
   GNUNET_free_non_null (fn);
 }
 
 
 /**
  * Transmit the given stats value.
+ *
+ * @param client receiver of the value
+ * @param e value to transmit
  */
 static void
-transmit (struct GNUNET_SERVER_TransmitContext *tc,
-          const struct StatsEntry *e)
+transmit (struct GNUNET_SERVER_Client *client, const struct StatsEntry *e)
 {
   struct GNUNET_STATISTICS_ReplyMessage *m;
   size_t size;
 
   size =
-    sizeof (struct GNUNET_STATISTICS_ReplyMessage) + strlen (e->service) + 1 +
-    strlen (e->name) + 1;
+      sizeof (struct GNUNET_STATISTICS_ReplyMessage) + strlen (e->service) + 1 +
+      strlen (e->name) + 1;
   GNUNET_assert (size < GNUNET_SERVER_MAX_MESSAGE_SIZE);
   m = GNUNET_malloc (size);
   m->header.type = htons (GNUNET_MESSAGE_TYPE_STATISTICS_VALUE);
@@ -227,28 +373,63 @@ transmit (struct GNUNET_SERVER_TransmitContext *tc,
     m->uid |= htonl (GNUNET_STATISTICS_PERSIST_BIT);
   m->value = GNUNET_htonll (e->value);
   size -= sizeof (struct GNUNET_STATISTICS_ReplyMessage);
-  GNUNET_assert (size == GNUNET_STRINGS_buffer_fill ((char *) &m[1],
-                                                     size,
-                                                     2, e->service, e->name));
-#if DEBUG_STATISTICS
+  GNUNET_assert (size ==
+                 GNUNET_STRINGS_buffer_fill ((char *) &m[1], size, 2,
+                                             e->service, e->name));
   GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
-              "Transmitting value for `%s:%s': %llu\n",
-              e->service, e->name, e->value);
-#endif
-  GNUNET_SERVER_transmit_context_append_message (tc, &m->header);
+              "Transmitting value for `%s:%s' (%d): %llu\n", e->service,
+              e->name, e->persistent, e->value);
+  GNUNET_SERVER_notification_context_unicast (nc, client, &m->header,
+                                              GNUNET_NO);
   GNUNET_free (m);
 }
 
 
 /**
  * Does this entry match the request?
+ *
+ * @param e an entry
+ * @param service name of service to match
+ * @param name value to match
+ * @return 1 if they match, 0 if not
  */
 static int
 matches (const struct StatsEntry *e, const char *service, const char *name)
 {
-  return ((0 == strlen (service)) ||
-          (0 == strcmp (service, e->service)))
-    && ((0 == strlen (name)) || (0 == strcmp (name, e->name)));
+  return ((0 == strlen (service)) || (0 == strcmp (service, e->service))) &&
+      ((0 == strlen (name)) || (0 == strcmp (name, e->name)));
+}
+
+
+/**
+ * Find a client entry for the given client handle, or create one.
+ *
+ * @param client handle to match
+ * @return corresponding client entry struct
+ */
+static struct ClientEntry *
+make_client_entry (struct GNUNET_SERVER_Client *client)
+{
+  struct ClientEntry *ce;
+
+  GNUNET_assert (client != NULL);
+  ce = client_head;
+  while (ce != NULL)
+  {
+    if (ce->client == client)
+      return ce;
+    ce = ce->next;
+  }
+  if (NULL == nc)
+  {
+    GNUNET_SERVER_receive_done (client, GNUNET_SYSERR);
+    return NULL;
+  }
+  ce = GNUNET_new (struct ClientEntry);
+  ce->client = client;
+  GNUNET_CONTAINER_DLL_insert (client_head, client_tail, ce);
+  GNUNET_SERVER_notification_context_add (nc, client);
+  return ce;
 }
 
 
@@ -262,40 +443,73 @@ matches (const struct StatsEntry *e, const char *service, const char *name)
  *         GNUNET_SYSERR to close it (signal serious error)
  */
 static void
-handle_get (void *cls,
-            struct GNUNET_SERVER_Client *client,
+handle_get (void *cls, struct GNUNET_SERVER_Client *client,
             const struct GNUNET_MessageHeader *message)
 {
+  struct GNUNET_MessageHeader end;
   char *service;
   char *name;
   struct StatsEntry *pos;
-  struct GNUNET_SERVER_TransmitContext *tc;
   size_t size;
 
+  if ( (NULL != client) &&
+       (NULL == make_client_entry (client)) )
+    return; /* new client during shutdown */
   size = ntohs (message->size) - sizeof (struct GNUNET_MessageHeader);
-  if (size != GNUNET_STRINGS_buffer_tokenize ((const char *) &message[1],
-                                              size, 2, &service, &name))
-    {
-      GNUNET_break (0);
-      GNUNET_SERVER_receive_done (client, GNUNET_SYSERR);
-      return;
-    }
-#if DEBUG_STATISTICS
+  if (size !=
+      GNUNET_STRINGS_buffer_tokenize ((const char *) &message[1], size, 2,
+                                      &service, &name))
+  {
+    GNUNET_break (0);
+    GNUNET_SERVER_receive_done (client, GNUNET_SYSERR);
+    return;
+  }
   GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
               "Received request for statistics on `%s:%s'\n",
               strlen (service) ? service : "*", strlen (name) ? name : "*");
-#endif
-  tc = GNUNET_SERVER_transmit_context_create (client);
-  pos = start;
-  while (pos != NULL)
+  for (pos = start; NULL != pos; pos = pos->next)
+    if (matches (pos, service, name))
+      transmit (client, pos);
+  end.size = htons (sizeof (struct GNUNET_MessageHeader));
+  end.type = htons (GNUNET_MESSAGE_TYPE_STATISTICS_END);
+  GNUNET_SERVER_notification_context_unicast (nc, client, &end, GNUNET_NO);
+  GNUNET_SERVER_receive_done (client, GNUNET_OK);
+}
+
+
+/**
+ * Notify all clients listening about a change to a value.
+ *
+ * @param se value that changed
+ */
+static void
+notify_change (struct StatsEntry *se)
+{
+  struct GNUNET_STATISTICS_WatchValueMessage wvm;
+  struct WatchEntry *pos;
+
+  for (pos = se->we_head; NULL != pos; pos = pos->next)
+  {
+    if (GNUNET_YES == pos->last_value_set)
+    {
+      if (pos->last_value == se->value)
+        continue;
+    }
+    else
     {
-      if (matches (pos, service, name))
-        transmit (tc, pos);
-      pos = pos->next;
+      pos->last_value_set = GNUNET_YES;
     }
-  GNUNET_SERVER_transmit_context_append_data (tc, NULL, 0,
-					      GNUNET_MESSAGE_TYPE_STATISTICS_END);
-  GNUNET_SERVER_transmit_context_run (tc, GNUNET_TIME_UNIT_FOREVER_REL);
+    wvm.header.type = htons (GNUNET_MESSAGE_TYPE_STATISTICS_WATCH_VALUE);
+    wvm.header.size =
+      htons (sizeof (struct GNUNET_STATISTICS_WatchValueMessage));
+    wvm.flags = htonl (se->persistent ? GNUNET_STATISTICS_PERSIST_BIT : 0);
+    wvm.wid = htonl (pos->wid);
+    wvm.reserved = htonl (0);
+    wvm.value = GNUNET_htonll (se->value);
+    GNUNET_SERVER_notification_context_unicast (nc, pos->client, &wvm.header,
+						GNUNET_NO);
+    pos->last_value = se->value;
+  }
 }
 
 
@@ -307,15 +521,9 @@ handle_get (void *cls,
  * @param message the actual message
  */
 static void
-handle_set (void *cls,
-            struct GNUNET_SERVER_Client *client,
+handle_set (void *cls, struct GNUNET_SERVER_Client *client,
             const struct GNUNET_MessageHeader *message)
 {
-  /**
-   * Counter used to generate unique values.
-   */
-  static uint32_t uidgen;
-
   char *service;
   char *name;
   uint16_t msize;
@@ -326,82 +534,100 @@ handle_set (void *cls,
   uint32_t flags;
   uint64_t value;
   int64_t delta;
+  int changed;
+  int initial_set;
 
+  if ( (NULL != client) &&
+       (NULL == make_client_entry (client)) )
+    return; /* new client during shutdown */
   msize = ntohs (message->size);
   if (msize < sizeof (struct GNUNET_STATISTICS_SetMessage))
-    {
-      GNUNET_break (0);
-      GNUNET_SERVER_receive_done (client, GNUNET_SYSERR);
-      return;
-    }
+  {
+    GNUNET_break (0);
+    GNUNET_SERVER_receive_done (client, GNUNET_SYSERR);
+    return;
+  }
   size = msize - sizeof (struct GNUNET_STATISTICS_SetMessage);
   msg = (const struct GNUNET_STATISTICS_SetMessage *) message;
 
-  if (size != GNUNET_STRINGS_buffer_tokenize ((const char *) &msg[1],
-                                              size, 2, &service, &name))
-    {
-      GNUNET_break (0);
-      GNUNET_SERVER_receive_done (client, GNUNET_SYSERR);
-      return;
-    }
-#if DEBUG_STATISTICS
-  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
-              "Received request to update statistic on `%s:%s'\n",
-              service, name);
-#endif
+  if (size !=
+      GNUNET_STRINGS_buffer_tokenize ((const char *) &msg[1], size, 2, &service,
+                                      &name))
+  {
+    GNUNET_break (0);
+    GNUNET_SERVER_receive_done (client, GNUNET_SYSERR);
+    return;
+  }
   flags = ntohl (msg->flags);
   value = GNUNET_ntohll (msg->value);
+  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+              "Received request to update statistic on `%s:%s' (%u) to/by %llu\n",
+              service, name, (unsigned int) flags, (unsigned long long) value);
   pos = start;
   prev = NULL;
   while (pos != NULL)
+  {
+    if (matches (pos, service, name))
     {
-      if (matches (pos, service, name))
+      initial_set = 0;
+      if ((flags & GNUNET_STATISTICS_SETFLAG_RELATIVE) == 0)
+      {
+        changed = (pos->value != value);
+        pos->value = value;
+      }
+      else
+      {
+        delta = (int64_t) value;
+        if ((delta < 0) && (pos->value < -delta))
         {
-          if ((flags & GNUNET_STATISTICS_SETFLAG_RELATIVE) == 0)
-            {
-              pos->value = value;
-            }
-          else
-            {
-              delta = (int64_t) value;
-              if ((delta < 0) && (pos->value < -delta))
-                {
-                  pos->value = 0;
-                }
-              else
-                {
-                  GNUNET_break ((delta <= 0) ||
-                                (pos->value + delta > pos->value));
-                  pos->value += delta;
-                }
-            }
-          pos->msg->value = GNUNET_htonll (pos->value);
-          pos->msg->flags = msg->flags;
-          pos->persistent =
-            (0 != (flags & GNUNET_STATISTICS_SETFLAG_PERSISTENT));
-          if (prev != NULL)
-            {
-              /* move to front for faster setting next time! */
-              prev->next = pos->next;
-              pos->next = start;
-              start = pos;
-            }
-#if DEBUG_STATISTICS
-          GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
-                      "Statistic `%s:%s' updated to value %llu.\n",
-                      service, name, pos->value);
-#endif
-          GNUNET_SERVER_receive_done (client, GNUNET_OK);
-          return;
+          changed = (pos->value != 0);
+          pos->value = 0;
+        }
+        else
+        {
+          changed = (delta != 0);
+          GNUNET_break ((delta <= 0) || (pos->value + delta > pos->value));
+          pos->value += delta;
         }
-      prev = pos;
-      pos = pos->next;
+      }
+      if (GNUNET_NO == pos->set)
+      {
+        pos->set = GNUNET_YES;
+        initial_set = 1;
+      }
+      pos->msg->value = GNUNET_htonll (pos->value);
+      pos->msg->flags = msg->flags;
+      pos->persistent = (0 != (flags & GNUNET_STATISTICS_SETFLAG_PERSISTENT));
+      if (prev != NULL)
+      {
+        /* move to front for faster setting next time! */
+        prev->next = pos->next;
+        pos->next = start;
+        start = pos;
+      }
+      GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+                  "Statistic `%s:%s' updated to value %llu.\n", service, name,
+                  pos->value);
+      if ((changed) || (1 == initial_set))
+        notify_change (pos);
+      GNUNET_SERVER_receive_done (client, GNUNET_OK);
+      return;
     }
+    prev = pos;
+    pos = pos->next;
+  }
   pos = GNUNET_malloc (sizeof (struct StatsEntry) + msize);
   pos->next = start;
   if (((flags & GNUNET_STATISTICS_SETFLAG_RELATIVE) == 0) ||
       (0 < (int64_t) GNUNET_ntohll (msg->value)))
+  {
     pos->value = GNUNET_ntohll (msg->value);
+    pos->set = GNUNET_YES;
+  }
+  else
+  {
+    pos->set = GNUNET_NO;
+  }
   pos->uid = uidgen++;
   pos->persistent = (0 != (flags & GNUNET_STATISTICS_SETFLAG_PERSISTENT));
   pos->msg = (void *) &pos[1];
@@ -410,15 +636,127 @@ handle_set (void *cls,
   pos->name = &pos->service[strlen (pos->service) + 1];
 
   start = pos;
-#if DEBUG_STATISTICS
   GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
-              "New statistic on `%s:%s' with value %llu created.\n",
-              service, name, pos->value);
-#endif
+              "New statistic on `%s:%s' with value %llu created.\n", service,
+              name, pos->value);
   GNUNET_SERVER_receive_done (client, GNUNET_OK);
 }
 
 
+/**
+ * Handle WATCH-message.
+ *
+ * @param cls closure
+ * @param client identification of the client
+ * @param message the actual message
+ */
+static void
+handle_watch (void *cls, struct GNUNET_SERVER_Client *client,
+              const struct GNUNET_MessageHeader *message)
+{
+  char *service;
+  char *name;
+  uint16_t msize;
+  uint16_t size;
+  struct StatsEntry *pos;
+  struct ClientEntry *ce;
+  struct WatchEntry *we;
+  size_t slen;
+
+  if (NULL == nc)
+  {
+    GNUNET_SERVER_receive_done (client, GNUNET_SYSERR);
+    return;
+  }
+  GNUNET_SERVER_client_mark_monitor (client);
+  ce = make_client_entry (client);
+  msize = ntohs (message->size);
+  if (msize < sizeof (struct GNUNET_MessageHeader))
+  {
+    GNUNET_break (0);
+    GNUNET_SERVER_receive_done (client, GNUNET_SYSERR);
+    return;
+  }
+  size = msize - sizeof (struct GNUNET_MessageHeader);
+  if (size !=
+      GNUNET_STRINGS_buffer_tokenize ((const char *) &message[1], size, 2,
+                                      &service, &name))
+  {
+    GNUNET_break (0);
+    GNUNET_SERVER_receive_done (client, GNUNET_SYSERR);
+    return;
+  }
+  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+              "Received request to watch statistic on `%s:%s'\n", service,
+              name);
+  pos = start;
+  while (pos != NULL)
+  {
+    if (matches (pos, service, name))
+      break;
+    pos = pos->next;
+  }
+  if (pos == NULL)
+  {
+    pos =
+        GNUNET_malloc (sizeof (struct StatsEntry) +
+                       sizeof (struct GNUNET_STATISTICS_SetMessage) + size);
+    pos->next = start;
+    pos->uid = uidgen++;
+    pos->set = GNUNET_NO;
+    pos->msg = (void *) &pos[1];
+    pos->msg->header.size =
+        htons (sizeof (struct GNUNET_STATISTICS_SetMessage) + size);
+    pos->msg->header.type = htons (GNUNET_MESSAGE_TYPE_STATISTICS_SET);
+    pos->service = (const char *) &pos->msg[1];
+    slen = strlen (service) + 1;
+    memcpy ((void *) pos->service, service, slen);
+    pos->name = &pos->service[slen];
+    memcpy ((void *) pos->name, name, strlen (name) + 1);
+    start = pos;
+    GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+                "New statistic on `%s:%s' with value %llu created.\n", service,
+                name, pos->value);
+  }
+  we = GNUNET_new (struct WatchEntry);
+  we->client = client;
+  we->last_value_set = GNUNET_NO;
+  we->wid = ce->max_wid++;
+  GNUNET_CONTAINER_DLL_insert (pos->we_head, pos->we_tail, we);
+  if (pos->value != 0)
+    notify_change (pos);
+  GNUNET_SERVER_receive_done (client, GNUNET_OK);
+}
+
+
+/**
+ * Actually perform the shutdown.
+ */
+static void
+do_shutdown ()
+{
+  struct WatchEntry *we;
+  struct StatsEntry *se;
+
+  if (NULL == nc)
+    return;
+  save ();
+  GNUNET_SERVER_notification_context_destroy (nc);
+  nc = NULL;
+  GNUNET_assert (NULL == client_head);
+  while (NULL != (se = start))
+  {
+    start = se->next;
+    while (NULL != (we = se->we_head))
+    {
+      GNUNET_CONTAINER_DLL_remove (se->we_head, se->we_tail, we);
+      GNUNET_free (we);
+    }
+    GNUNET_free (se);
+  }
+}
+
+
 /**
  * Task run during shutdown.
  *
@@ -426,10 +764,57 @@ handle_set (void *cls,
  * @param tc unused
  */
 static void
-shutdown_task (void *cls,
-	       const struct GNUNET_SCHEDULER_TaskContext *tc)
+shutdown_task (void *cls, const struct GNUNET_SCHEDULER_TaskContext *tc)
 {
-  save ();
+  in_shutdown = GNUNET_YES;
+  if (NULL != client_head)
+    return;
+  do_shutdown ();
+}
+
+
+/**
+ * A client disconnected.  Remove all of its data structure entries.
+ *
+ * @param cls closure, NULL
+ * @param client identification of the client
+ */
+static void
+handle_client_disconnect (void *cls, struct GNUNET_SERVER_Client *client)
+{
+  struct ClientEntry *ce;
+  struct WatchEntry *we;
+  struct WatchEntry *wen;
+  struct StatsEntry *se;
+
+  ce = client_head;
+  while (NULL != ce)
+  {
+    if (ce->client == client)
+    {
+      GNUNET_CONTAINER_DLL_remove (client_head, client_tail, ce);
+      GNUNET_free (ce);
+      break;
+    }
+    ce = ce->next;
+  }
+  se = start;
+  while (NULL != se)
+  {
+    wen = se->we_head;
+    while (NULL != (we = wen))
+    {
+      wen = we->next;
+      if (we->client != client)
+        continue;
+      GNUNET_CONTAINER_DLL_remove (se->we_head, se->we_tail, we);
+      GNUNET_free (we);
+    }
+    se = se->next;
+  }
+  if ( (NULL == client_head) &&
+       (GNUNET_YES == in_shutdown) )
+    do_shutdown ();
 }
 
 
@@ -437,28 +822,27 @@ shutdown_task (void *cls,
  * Process statistics requests.
  *
  * @param cls closure
- * @param sched scheduler to use
  * @param server the initialized server
  * @param c configuration to use
  */
 static void
-run (void *cls,
-     struct GNUNET_SCHEDULER_Handle *sched,
-     struct GNUNET_SERVER_Handle *server,
+run (void *cls, struct GNUNET_SERVER_Handle *server,
      const struct GNUNET_CONFIGURATION_Handle *c)
 {
   static const struct GNUNET_SERVER_MessageHandler handlers[] = {
     {&handle_set, NULL, GNUNET_MESSAGE_TYPE_STATISTICS_SET, 0},
     {&handle_get, NULL, GNUNET_MESSAGE_TYPE_STATISTICS_GET, 0},
+    {&handle_watch, NULL, GNUNET_MESSAGE_TYPE_STATISTICS_WATCH, 0},
     {NULL, NULL, 0, 0}
   };
   cfg = c;
+  srv = server;
   GNUNET_SERVER_add_handlers (server, handlers);
+  nc = GNUNET_SERVER_notification_context_create (server, 16);
+  GNUNET_SERVER_disconnect_notify (server, &handle_client_disconnect, NULL);
   load (server);
-  GNUNET_SCHEDULER_add_delayed (sched,
-				GNUNET_TIME_UNIT_FOREVER_REL,
-				&shutdown_task,
-				NULL);
+  GNUNET_SCHEDULER_add_delayed (GNUNET_TIME_UNIT_FOREVER_REL, &shutdown_task,
+                                NULL);
 }
 
 
@@ -473,11 +857,23 @@ int
 main (int argc, char *const *argv)
 {
   return (GNUNET_OK ==
-          GNUNET_SERVICE_run (argc,
-                              argv,
-                              "statistics",
-			      GNUNET_SERVICE_OPTION_NONE,
-			      &run, NULL)) ? 0 : 1;
+          GNUNET_SERVICE_run (argc, argv, "statistics",
+                              GNUNET_SERVICE_OPTION_SOFT_SHUTDOWN, &run, NULL)) ? 0 : 1;
 }
 
+#ifdef LINUX
+#include <malloc.h>
+
+/**
+ * MINIMIZE heap size (way below 128k) since this process doesn't need much.
+ */
+void __attribute__ ((constructor)) GNUNET_ARM_memory_init ()
+{
+  mallopt (M_TRIM_THRESHOLD, 4 * 1024);
+  mallopt (M_TOP_PAD, 1 * 1024);
+  malloc_trim (0);
+}
+#endif
+
+
 /* end of gnunet-service-statistics.c */