title: Postgres BDR replication stopped - replication slot inactive
body: <p>Our Postgres BDR database system stopped replicating data between the nodes.</p>
  
  <p>When I did a check using the <code>pg_xlog_location_diff</code> I noticed that there is a growing buffer in the replication slot.</p>
  
  <pre><code>SELECT slot_name, database, active, pg_xlog_location_diff(pg_current_xlog_insert_location(), restart_lsn) AS retained_bytes
  FROM pg_replication_slots
  WHERE plugin = 'bdr';
                  slot_name                |   database   | active | retained_bytes
  -----------------------------------------+--------------+--------+----------------
   bdr_26702_6275336279642079463_1_20305__ | ourdatabase  | f      |       32253352
  </code></pre>
  
  <p>I also noticed that the slot is marked as active=false.</p>
  
  <pre><code>SELECT * FROM pg_replication_slots;
  -[ RECORD 1 ]+----------------------------------------
  slot_name    | bdr_26702_6275336279642079463_1_20305__
  plugin       | bdr
  slot_type    | logical
  datoid       | 26702
  database     | ourdatabase
  active       | f
  xmin         |
  catalog_xmin | 8041
  restart_lsn  | 0/5F0C6C8
  </code></pre>
  
  <p>I increased the Postgres logging level, but then only messages I see in the log are:</p>
  
  <pre><code>LOCATION:  LogicalIncreaseRestartDecodingForSlot, logical.c:886
  DEBUG:  00000: updated xmin: 1 restart: 0
  LOCATION:  LogicalConfirmReceivedLocation, logical.c:958
  DEBUG:  00000: failed to increase restart lsn: proposed 0/7DCE6F8, after 0/7DCE6F8, current candidate 0/7DCE6F8, current after 0/7DCE6F8, flushed up to 0/7DCE6F8
  </code></pre>
  
  <p>Please let me know if you have an idea how I can re-activate the replication slot and allow the replication to resume.</p>