refactoring datastore API to use MQ API, also fixing misc. bugs in new mysql backend
[oweals/gnunet.git] / src / fs / gnunet-service-fs_push.c
index 9f515e2ee10129c874d3a1d31f8f0aac56dd6e53..71a8e81e4f0293ae5d1433121e4e847a5e2e3e8a 100644 (file)
@@ -1,6 +1,6 @@
 /*
      This file is part of GNUnet.
-     (C) 2011 Christian Grothoff (and other contributing authors)
+     Copyright (C) 2011 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
@@ -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-service-fs.h"
+#include "gnunet-service-fs_cp.h"
+#include "gnunet-service-fs_indexing.h"
 #include "gnunet-service-fs_push.h"
 
 
-/* FIXME: below are only old code fragments to use... */
+/**
+ * Maximum number of blocks we keep in memory for migration.
+ */
+#define MAX_MIGRATION_QUEUE 8
+
+/**
+ * Blocks are at most migrated to this number of peers
+ * plus one, each time they are fetched from the database.
+ */
+#define MIGRATION_LIST_SIZE 2
+
+/**
+ * How long must content remain valid for us to consider it for migration?
+ * If content will expire too soon, there is clearly no point in pushing
+ * it to other peers.  This value gives the threshold for migration.  Note
+ * that if this value is increased, the migration testcase may need to be
+ * adjusted as well (especially the CONTENT_LIFETIME in fs_test_lib.c).
+ */
+#define MIN_MIGRATION_CONTENT_LIFETIME GNUNET_TIME_relative_multiply (GNUNET_TIME_UNIT_MINUTES, 30)
+
 
 /**
  * Block that is ready for migration to other peers.  Actual data is at the end of the block.
@@ -49,15 +71,15 @@ struct MigrationReadyBlock
   /**
    * Query for the block.
    */
-  GNUNET_HashCode query;
+  struct GNUNET_HashCode query;
 
   /**
-   * When does this block expire? 
+   * When does this block expire?
    */
   struct GNUNET_TIME_Absolute expiration;
 
   /**
-   * Peers we would consider forwarding this
+   * Peers we already forwarded this
    * block to.  Zero for empty entries.
    */
   GNUNET_PEER_Id target_list[MIGRATION_LIST_SIZE];
@@ -79,6 +101,40 @@ struct MigrationReadyBlock
 };
 
 
+/**
+ * Information about a peer waiting for
+ * migratable data.
+ */
+struct MigrationReadyPeer
+{
+  /**
+   * This is a doubly-linked list.
+   */
+  struct MigrationReadyPeer *next;
+
+  /**
+   * This is a doubly-linked list.
+   */
+  struct MigrationReadyPeer *prev;
+
+  /**
+   * Handle to peer.
+   */
+  struct GSF_ConnectedPeer *peer;
+
+  /**
+   * Handle for current transmission request,
+   * or NULL for none.
+   */
+  struct GSF_PeerTransmitHandle *th;
+
+  /**
+   * Message we are trying to push right now (or NULL)
+   */
+  struct PutMessage *msg;
+};
+
+
 /**
  * Head of linked list of blocks that can be migrated.
  */
@@ -89,6 +145,16 @@ static struct MigrationReadyBlock *mig_head;
  */
 static struct MigrationReadyBlock *mig_tail;
 
+/**
+ * Head of linked list of peers.
+ */
+static struct MigrationReadyPeer *peer_head;
+
+/**
+ * Tail of linked list of peers.
+ */
+static struct MigrationReadyPeer *peer_tail;
+
 /**
  * Request to datastore for migration (or NULL).
  */
@@ -97,7 +163,7 @@ static struct GNUNET_DATASTORE_QueueEntry *mig_qe;
 /**
  * ID of task that collects blocks for migration.
  */
-static GNUNET_SCHEDULER_TaskIdentifier mig_task;
+static struct GNUNET_SCHEDULER_Task * mig_task;
 
 /**
  * What is the maximum frequency at which we are allowed to
@@ -106,14 +172,19 @@ static GNUNET_SCHEDULER_TaskIdentifier mig_task;
 static struct GNUNET_TIME_Relative min_migration_delay;
 
 /**
- * Are we allowed to push out content from this peer.
+ * Size of the doubly-linked list of migration blocks.
  */
-static int active_from_migration;
+static unsigned int mig_size;
 
 /**
- * Size of the doubly-linked list of migration blocks.
+ * Is this module enabled?
  */
-static unsigned int mig_size;
+static int enabled;
+
+/**
+ * Did we find anything in the datastore?
+ */
+static int value_found;
 
 
 /**
@@ -124,160 +195,246 @@ static unsigned int mig_size;
 static void
 delete_migration_block (struct MigrationReadyBlock *mb)
 {
-  GNUNET_CONTAINER_DLL_remove (mig_head,
-                              mig_tail,
-                              mb);
-  GNUNET_PEER_decrement_rcs (mb->target_list,
-                            MIGRATION_LIST_SIZE);
+  GNUNET_CONTAINER_DLL_remove (mig_head, mig_tail, mb);
+  GNUNET_PEER_decrement_rcs (mb->target_list, MIGRATION_LIST_SIZE);
   mig_size--;
   GNUNET_free (mb);
 }
 
 
 /**
- * Compare the distance of two peers to a key.
+ * Find content for migration to this peer.
+ */
+static void
+find_content (struct MigrationReadyPeer *mrp);
+
+
+/**
+ * Transmit the message currently scheduled for transmission.
  *
- * @param key key
- * @param p1 first peer
- * @param p2 second peer
- * @return GNUNET_YES if P1 is closer to key than P2
+ * @param cls the `struct MigrationReadyPeer`
+ * @param buf_size number of bytes available in @a buf
+ * @param buf where to copy the message, NULL on error (peer disconnect)
+ * @return number of bytes copied to @a buf, can be 0 (without indicating an error)
  */
-static int
-is_closer (const GNUNET_HashCode *key,
-          const struct GNUNET_PeerIdentity *p1,
-          const struct GNUNET_PeerIdentity *p2)
+static size_t
+transmit_message (void *cls,
+                  size_t buf_size,
+                  void *buf)
 {
-  return GNUNET_CRYPTO_hash_xorcmp (&p1->hashPubKey,
-                                   &p2->hashPubKey,
-                                   key);
+  struct MigrationReadyPeer *peer = cls;
+  struct PutMessage *msg;
+  uint16_t msize;
+
+  peer->th = NULL;
+  msg = peer->msg;
+  peer->msg = NULL;
+  if (NULL == buf)
+  {
+    GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+                "Failed to migrate content to another peer (disconnect)\n");
+    GNUNET_free (msg);
+    return 0;
+  }
+  msize = ntohs (msg->header.size);
+  GNUNET_assert (msize <= buf_size);
+  memcpy (buf, msg, msize);
+  GNUNET_free (msg);
+  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+              "Pushing %u bytes to %s\n",
+              msize,
+              GNUNET_i2s (GSF_connected_peer_get_identity2_(peer->peer)));
+  find_content (peer);
+  return msize;
 }
 
 
 /**
- * Consider migrating content to a given peer.
+ * Send the given block to the given peer.
  *
- * @param cls 'struct MigrationReadyBlock*' to select
- *            targets for (or NULL for none)
- * @param key ID of the peer 
- * @param value 'struct ConnectedPeer' of the peer
- * @return GNUNET_YES (always continue iteration)
+ * @param peer target peer
+ * @param block the block
+ * @return #GNUNET_YES if the block was deleted (!)
  */
 static int
-consider_migration (void *cls,
-                   const GNUNET_HashCode *key,
-                   void *value)
+transmit_content (struct MigrationReadyPeer *peer,
+                  struct MigrationReadyBlock *block)
 {
-  struct MigrationReadyBlock *mb = cls;
-  struct ConnectedPeer *cp = value;
-  struct MigrationReadyBlock *pos;
-  struct GNUNET_PeerIdentity cppid;
-  struct GNUNET_PeerIdentity otherpid;
-  struct GNUNET_PeerIdentity worstpid;
   size_t msize;
+  struct PutMessage *msg;
   unsigned int i;
-  unsigned int repl;
-  
-  /* consider 'cp' as a migration target for mb */
-  if (GNUNET_TIME_absolute_get_remaining (cp->migration_blocked).rel_value > 0)
-    return GNUNET_YES; /* peer has requested no migration! */
-  if (mb != NULL)
+  struct GSF_PeerPerformanceData *ppd;
+  int ret;
+
+  ppd = GSF_get_peer_performance_data_ (peer->peer);
+  GNUNET_assert (NULL == peer->th);
+  msize = sizeof (struct PutMessage) + block->size;
+  msg = GNUNET_malloc (msize);
+  msg->header.type = htons (GNUNET_MESSAGE_TYPE_FS_PUT);
+  msg->header.size = htons (msize);
+  msg->type = htonl (block->type);
+  msg->expiration = GNUNET_TIME_absolute_hton (block->expiration);
+  memcpy (&msg[1], &block[1], block->size);
+  peer->msg = msg;
+  for (i = 0; i < MIGRATION_LIST_SIZE; i++)
+  {
+    if (block->target_list[i] == 0)
     {
-      GNUNET_PEER_resolve (cp->pid,
-                          &cppid);
-      repl = MIGRATION_LIST_SIZE;
-      for (i=0;i<MIGRATION_LIST_SIZE;i++)
-       {
-         if (mb->target_list[i] == 0)
-           {
-             mb->target_list[i] = cp->pid;
-             GNUNET_PEER_change_rc (mb->target_list[i], 1);
-             repl = MIGRATION_LIST_SIZE;
-             break;
-           }
-         GNUNET_PEER_resolve (mb->target_list[i],
-                              &otherpid);
-         if ( (repl == MIGRATION_LIST_SIZE) &&
-              is_closer (&mb->query,
-                         &cppid,
-                         &otherpid)) 
-           {
-             repl = i;
-             worstpid = otherpid;
-           }
-         else if ( (repl != MIGRATION_LIST_SIZE) &&
-                   (is_closer (&mb->query,
-                               &worstpid,
-                               &otherpid) ) )
-           {
-             repl = i;
-             worstpid = otherpid;
-           }       
-       }
-      if (repl != MIGRATION_LIST_SIZE) 
-       {
-         GNUNET_PEER_change_rc (mb->target_list[repl], -1);
-         mb->target_list[repl] = cp->pid;
-         GNUNET_PEER_change_rc (mb->target_list[repl], 1);
-       }
+      block->target_list[i] = ppd->pid;
+      GNUNET_PEER_change_rc (block->target_list[i], 1);
+      break;
     }
+  }
+  if (MIGRATION_LIST_SIZE == i)
+  {
+    delete_migration_block (block);
+    ret = GNUNET_YES;
+  }
+  else
+  {
+    ret = GNUNET_NO;
+  }
+  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+              "Asking for transmission of %u bytes to %s for migration\n",
+              (unsigned int) msize,
+              GNUNET_i2s (GSF_connected_peer_get_identity2_(peer->peer)));
+  peer->th = GSF_peer_transmit_ (peer->peer,
+                                 GNUNET_NO, 0 /* priority */ ,
+                                 GNUNET_TIME_UNIT_FOREVER_REL,
+                                 msize,
+                                 &transmit_message, peer);
+  return ret;
+}
+
+
+/**
+ * Count the number of peers this block has
+ * already been forwarded to.
+ *
+ * @param block the block
+ * @return number of times block was forwarded
+ */
+static unsigned int
+count_targets (struct MigrationReadyBlock *block)
+{
+  unsigned int i;
+
+  for (i = 0; i < MIGRATION_LIST_SIZE; i++)
+    if (block->target_list[i] == 0)
+      return i;
+  return i;
+}
+
+
+/**
+ * Check if sending this block to this peer would
+ * be a good idea.
+ *
+ * @param peer target peer
+ * @param block the block
+ * @return score (>= 0: feasible, negative: infeasible)
+ */
+static long
+score_content (struct MigrationReadyPeer *peer,
+               struct MigrationReadyBlock *block)
+{
+  unsigned int i;
+  struct GSF_PeerPerformanceData *ppd;
+  struct GNUNET_PeerIdentity id;
+  struct GNUNET_HashCode hc;
+  uint32_t dist;
+
+  ppd = GSF_get_peer_performance_data_ (peer->peer);
+  for (i = 0; i < MIGRATION_LIST_SIZE; i++)
+    if (block->target_list[i] == ppd->pid)
+      return -1;
+  GNUNET_assert (0 != ppd->pid);
+  GNUNET_PEER_resolve (ppd->pid, &id);
+  GNUNET_CRYPTO_hash (&id, sizeof (struct GNUNET_PeerIdentity), &hc);
+  dist = GNUNET_CRYPTO_hash_distance_u32 (&block->query, &hc);
+  /* closer distance, higher score: */
+  return UINT32_MAX - dist;
+}
+
+
+/**
+ * If the migration task is not currently running, consider
+ * (re)scheduling it with the appropriate delay.
+ */
+static void
+consider_gathering (void);
 
-  /* consider scheduling transmission to cp for content migration */
-  if (cp->cth != NULL)        
-    return GNUNET_YES; 
-  msize = 0;
+
+/**
+ * Find content for migration to this peer.
+ *
+ * @param mrp peer to find content for
+ */
+static void
+find_content (struct MigrationReadyPeer *mrp)
+{
+  struct MigrationReadyBlock *pos;
+  long score;
+  long best_score;
+  struct MigrationReadyBlock *best;
+
+  GNUNET_assert (NULL == mrp->th);
+  best = NULL;
+  best_score = -1;
   pos = mig_head;
-  while (pos != NULL)
+  while (NULL != pos)
+  {
+    score = score_content (mrp, pos);
+    if (score > best_score)
     {
-      for (i=0;i<MIGRATION_LIST_SIZE;i++)
-       {
-         if (cp->pid == pos->target_list[i])
-           {
-             if (msize == 0)
-               msize = pos->size;
-             else
-               msize = GNUNET_MIN (msize,
-                                   pos->size);
-             break;
-           }
-       }
-      pos = pos->next;
+      best_score = score;
+      best = pos;
     }
-  if (msize == 0)
-    return GNUNET_YES; /* no content available */
-#if DEBUG_FS
-  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
-             "Trying to migrate at least %u bytes to peer `%s'\n",
-             msize,
-             GNUNET_h2s (key));
-#endif
-  if (cp->delayed_transmission_request_task != GNUNET_SCHEDULER_NO_TASK)
+    pos = pos->next;
+  }
+  if (NULL == best)
+  {
+    if (mig_size < MAX_MIGRATION_QUEUE)
     {
-      GNUNET_SCHEDULER_cancel (cp->delayed_transmission_request_task);
-      cp->delayed_transmission_request_task = GNUNET_SCHEDULER_NO_TASK;
+      GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+                  "No content found for pushing, waiting for queue to fill\n");
+      return;                   /* will fill up eventually... */
     }
-  cp->cth 
-    = GNUNET_CORE_notify_transmit_ready (core,
-                                        0, GNUNET_TIME_UNIT_FOREVER_REL,
-                                        (const struct GNUNET_PeerIdentity*) key,
-                                        msize + sizeof (struct PutMessage),
-                                        &transmit_to_peer,
-                                        cp);
-  return GNUNET_YES;
+    GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+                "No suitable content found, purging content from full queue\n");
+    /* failed to find migration target AND
+     * queue is full, purge most-forwarded
+     * block from queue to make room for more */
+    pos = mig_head;
+    while (NULL != pos)
+    {
+      score = count_targets (pos);
+      if (score >= best_score)
+      {
+        best_score = score;
+        best = pos;
+      }
+      pos = pos->next;
+    }
+    GNUNET_assert (NULL != best);
+    delete_migration_block (best);
+    consider_gathering ();
+    return;
+  }
+  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+              "Preparing to push best content to peer\n");
+  transmit_content (mrp, best);
 }
 
 
 /**
  * Task that is run periodically to obtain blocks for content
  * migration
- * 
+ *
  * @param cls unused
- * @param tc scheduler context (also unused)
  */
 static void
-gather_migration_blocks (void *cls,
-                        const struct GNUNET_SCHEDULER_TaskContext *tc);
-
-
+gather_migration_blocks (void *cls);
 
 
 /**
@@ -285,30 +442,36 @@ gather_migration_blocks (void *cls,
  * (re)scheduling it with the appropriate delay.
  */
 static void
-consider_migration_gathering ()
+consider_gathering ()
 {
   struct GNUNET_TIME_Relative delay;
 
-  if (dsh == NULL)
+  if (NULL == GSF_dsh)
+    return;
+  if (NULL != mig_qe)
     return;
-  if (mig_qe != NULL)
+  if (NULL != mig_task)
     return;
-  if (mig_task != GNUNET_SCHEDULER_NO_TASK)
+  if (mig_size >= MAX_MIGRATION_QUEUE)
     return;
-  delay = GNUNET_TIME_relative_multiply (GNUNET_TIME_UNIT_SECONDS,
-                                        mig_size);
-  delay = GNUNET_TIME_relative_divide (delay,
-                                      MAX_MIGRATION_QUEUE);
-  delay = GNUNET_TIME_relative_max (delay,
-                                   min_migration_delay);
-  mig_task = GNUNET_SCHEDULER_add_delayed (delay,
-                                          &gather_migration_blocks,
-                                          NULL);
+  delay = GNUNET_TIME_relative_multiply (GNUNET_TIME_UNIT_SECONDS, mig_size);
+  delay = GNUNET_TIME_relative_divide (delay, MAX_MIGRATION_QUEUE);
+  delay = GNUNET_TIME_relative_max (delay, min_migration_delay);
+  if (GNUNET_NO == value_found)
+  {
+    /* wait at least 5s if the datastore is empty */
+    delay = GNUNET_TIME_relative_max (delay,
+                                      GNUNET_TIME_relative_multiply (GNUNET_TIME_UNIT_SECONDS,
+                                                                     5));
+  }
+  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+              "Scheduling gathering task (queue size: %u)\n",
+              mig_size);
+  mig_task =
+      GNUNET_SCHEDULER_add_delayed (delay, &gather_migration_blocks, NULL);
 }
 
 
-
-
 /**
  * Process content offered for migration.
  *
@@ -325,50 +488,54 @@ consider_migration_gathering ()
  */
 static void
 process_migration_content (void *cls,
-                          const GNUNET_HashCode * key,
-                          size_t size,
-                          const void *data,
-                          enum GNUNET_BLOCK_Type type,
-                          uint32_t priority,
-                          uint32_t anonymity,
-                          struct GNUNET_TIME_Absolute
-                          expiration, uint64_t uid)
+                           const struct GNUNET_HashCode *key,
+                           size_t size,
+                           const void *data,
+                           enum GNUNET_BLOCK_Type type,
+                           uint32_t priority,
+                           uint32_t anonymity,
+                           struct GNUNET_TIME_Absolute expiration,
+                           uint64_t uid)
 {
   struct MigrationReadyBlock *mb;
-  
-  if (key == NULL)
-    {
-      mig_qe = NULL;
-      if (mig_size < MAX_MIGRATION_QUEUE)  
-       consider_migration_gathering ();
-      return;
-    }
-  if (GNUNET_TIME_absolute_get_remaining (expiration).rel_value < 
-      MIN_MIGRATION_CONTENT_LIFETIME.rel_value)
-    {
-      /* content will expire soon, don't bother */
-      GNUNET_DATASTORE_get_next (dsh, GNUNET_YES);
-      return;
-    }
+  struct MigrationReadyPeer *pos;
+
+  mig_qe = NULL;
+  if (NULL == key)
+  {
+    GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+                "No content found for migration...\n");
+    consider_gathering ();
+    return;
+  }
+  value_found = GNUNET_YES;
+  if (GNUNET_TIME_absolute_get_remaining (expiration).rel_value_us <
+      MIN_MIGRATION_CONTENT_LIFETIME.rel_value_us)
+  {
+    /* content will expire soon, don't bother */
+    consider_gathering ();
+    return;
+  }
   if (type == GNUNET_BLOCK_TYPE_FS_ONDEMAND)
-    {
-      if (GNUNET_OK !=
-         GNUNET_FS_handle_on_demand_block (key, size, data,
-                                           type, priority, anonymity,
-                                           expiration, uid, 
-                                           &process_migration_content,
-                                           NULL))
-       {
-         GNUNET_DATASTORE_get_next (dsh, GNUNET_YES);
-       }
-      return;
-    }
-#if DEBUG_FS
+  {
+    if (GNUNET_OK !=
+        GNUNET_FS_handle_on_demand_block (key,
+                                          size,
+                                          data,
+                                          type,
+                                          priority,
+                                          anonymity,
+                                          expiration,
+                                          uid,
+                                          &process_migration_content, NULL))
+      consider_gathering ();
+    return;
+  }
   GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
-             "Retrieved block `%s' of type %u for migration\n",
-             GNUNET_h2s (key),
-             type);
-#endif
+              "Retrieved block `%s' of type %u for migration (queue size: %u/%u)\n",
+              GNUNET_h2s (key),
+              type, mig_size + 1,
+              MAX_MIGRATION_QUEUE);
   mb = GNUNET_malloc (sizeof (struct MigrationReadyBlock) + size);
   mb->query = *key;
   mb->expiration = expiration;
@@ -376,100 +543,163 @@ process_migration_content (void *cls,
   mb->type = type;
   memcpy (&mb[1], data, size);
   GNUNET_CONTAINER_DLL_insert_after (mig_head,
-                                    mig_tail,
-                                    mig_tail,
-                                    mb);
+                                     mig_tail,
+                                     mig_tail,
+                                     mb);
   mig_size++;
-  GNUNET_CONTAINER_multihashmap_iterate (connected_peers,
-                                        &consider_migration,
-                                        mb);
-  GNUNET_DATASTORE_get_next (dsh, GNUNET_YES);
+  for (pos = peer_head; NULL != pos; pos = pos->next)
+  {
+    if (NULL == pos->th)
+    {
+      GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+                  "Preparing to push best content to peer %s\n",
+                  GNUNET_i2s (GSF_connected_peer_get_identity2_(pos->peer)));
+      if (GNUNET_YES == transmit_content (pos, mb))
+        break;                  /* 'mb' was freed! */
+    }
+  }
+  consider_gathering ();
 }
 
 
-
 /**
  * Task that is run periodically to obtain blocks for content
  * migration
- * 
+ *
  * @param cls unused
- * @param tc scheduler context (also unused)
  */
 static void
-gather_migration_blocks (void *cls,
-                        const struct GNUNET_SCHEDULER_TaskContext *tc)
+gather_migration_blocks (void *cls)
 {
-  mig_task = GNUNET_SCHEDULER_NO_TASK;
-  if (dsh != NULL)
-    {
-      mig_qe = GNUNET_DATASTORE_get_random (dsh, 0, UINT_MAX,
-                                           GNUNET_TIME_UNIT_FOREVER_REL,
-                                           &process_migration_content, NULL);
-      GNUNET_assert (mig_qe != NULL);
-    }
+  mig_task = NULL;
+  if (mig_size >= MAX_MIGRATION_QUEUE)
+    return;
+  if (NULL == GSF_dsh)
+    return;
+  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+              "Asking datastore for content for replication (queue size: %u)\n",
+              mig_size);
+  value_found = GNUNET_NO;
+  mig_qe =
+    GNUNET_DATASTORE_get_for_replication (GSF_dsh, 0, UINT_MAX,
+                                          &process_migration_content, NULL);
+  if (NULL == mig_qe)
+    consider_gathering ();
+}
+
+
+/**
+ * A peer connected to us.  Start pushing content
+ * to this peer.
+ *
+ * @param peer handle for the peer that connected
+ */
+void
+GSF_push_start_ (struct GSF_ConnectedPeer *peer)
+{
+  struct MigrationReadyPeer *mrp;
+
+  if (GNUNET_YES != enabled)
+    return;
+  for (mrp = peer_head; NULL != mrp; mrp = mrp->next)
+    if (mrp->peer == peer)
+      break;
+  if (NULL != mrp)
+  {
+    /* same peer added twice, must not happen */
+    GNUNET_break (0);
+    return;
+  }
+
+  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+              "Adding peer %s to list for pushing\n",
+              GNUNET_i2s (GSF_connected_peer_get_identity2_(peer)));
+
+  mrp = GNUNET_new (struct MigrationReadyPeer);
+  mrp->peer = peer;
+  find_content (mrp);
+  GNUNET_CONTAINER_DLL_insert (peer_head,
+                               peer_tail,
+                               mrp);
 }
 
 
+/**
+ * A peer disconnected from us.  Stop pushing content
+ * to this peer.
+ *
+ * @param peer handle for the peer that disconnected
+ */
+void
+GSF_push_stop_ (struct GSF_ConnectedPeer *peer)
+{
+  struct MigrationReadyPeer *pos;
+
+  for (pos = peer_head; NULL != pos; pos = pos->next)
+    if (pos->peer == peer)
+      break;
+  if (NULL == pos)
+    return;
+  GNUNET_CONTAINER_DLL_remove (peer_head,
+                               peer_tail,
+                               pos);
+  if (NULL != pos->th)
+  {
+    GSF_peer_transmit_cancel_ (pos->th);
+    pos->th = NULL;
+  }
+  if (NULL != pos->msg)
+  {
+    GNUNET_free (pos->msg);
+    pos->msg = NULL;
+  }
+  GNUNET_free (pos);
+}
+
 
-size_t
-API_ (void *cls,
-      size_t size, void *buf)
+/**
+ * Setup the module.
+ */
+void
+GSF_push_init_ ()
 {
-    next = mig_head;
-      while (NULL != (mb = next))
-       {
-         next = mb->next;
-         for (i=0;i<MIGRATION_LIST_SIZE;i++)
-           {
-             if ( (cp->pid == mb->target_list[i]) &&
-                  (mb->size + sizeof (migm) <= size) )
-               {
-                 GNUNET_PEER_change_rc (mb->target_list[i], -1);
-                 mb->target_list[i] = 0;
-                 mb->used_targets++;
-                 memset (&migm, 0, sizeof (migm));
-                 migm.header.size = htons (sizeof (migm) + mb->size);
-                 migm.header.type = htons (GNUNET_MESSAGE_TYPE_FS_PUT);
-                 migm.type = htonl (mb->type);
-                 migm.expiration = GNUNET_TIME_absolute_hton (mb->expiration);
-                 memcpy (&cbuf[msize], &migm, sizeof (migm));
-                 msize += sizeof (migm);
-                 size -= sizeof (migm);
-                 memcpy (&cbuf[msize], &mb[1], mb->size);
-                 msize += mb->size;
-                 size -= mb->size;
-#if DEBUG_FS
-                 GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
-                             "Pushing migration block `%s' (%u bytes) to `%s'\n",
-                             GNUNET_h2s (&mb->query),
-                             (unsigned int) mb->size,
-                             GNUNET_i2s (&pid));
-#endif   
-                 break;
-               }
-             else
-               {
-#if DEBUG_FS
-                 GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
-                             "Migration block `%s' (%u bytes) is not on migration list for peer `%s'\n",
-                             GNUNET_h2s (&mb->query),
-                             (unsigned int) mb->size,
-                             GNUNET_i2s (&pid));
-#endif   
-               }
-           }
-         if ( (mb->used_targets >= MIGRATION_TARGET_COUNT) ||
-              (mb->used_targets >= GNUNET_CONTAINER_multihashmap_size (connected_peers)) )
-           {
-             delete_migration_block (mb);
-             consider_migration_gathering ();
-           }
-       }
-      consider_migration (NULL, 
-                         &pid.hashPubKey,
-                         cp);
+  enabled =
+      GNUNET_CONFIGURATION_get_value_yesno (GSF_cfg, "FS", "CONTENT_PUSHING");
+  if (GNUNET_YES != enabled)
+    return;
 
+  if (GNUNET_OK !=
+      GNUNET_CONFIGURATION_get_value_time (GSF_cfg, "fs", "MIN_MIGRATION_DELAY",
+                                           &min_migration_delay))
+  {
+    GNUNET_log_config_invalid (GNUNET_ERROR_TYPE_WARNING,
+                              "fs", "MIN_MIGRATION_DELAY",
+                              _("time required, content pushing disabled"));
+    return;
+  }
+  consider_gathering ();
 }
 
 
+/**
+ * Shutdown the module.
+ */
+void
+GSF_push_done_ ()
+{
+  if (NULL != mig_task)
+  {
+    GNUNET_SCHEDULER_cancel (mig_task);
+    mig_task = NULL;
+  }
+  if (NULL != mig_qe)
+  {
+    GNUNET_DATASTORE_cancel (mig_qe);
+    mig_qe = NULL;
+  }
+  while (NULL != mig_head)
+    delete_migration_block (mig_head);
+  GNUNET_assert (0 == mig_size);
+}
 
+/* end of gnunet-service-fs_push.c */