track replication destination health, and perform exponential back-off when sending transactions. does *not* yet retry transactions, but drops them on the floor if waiting for a server to recover.

synapse/federation/replication.py

@@ -723,6 +723,8 @@ class _TransactionQueue(object):
         deferreds = []
 
         for destination in destinations:
+            # XXX: why don't we specify an errback for this deferred
+            # like we do for EDUs? --matthew
             deferred = defer.Deferred()
             self.pending_pdus_by_dest.setdefault(destination, []).append(
                 (pdu, deferred, order)
@@ -739,6 +741,9 @@ class _TransactionQueue(object):
     def enqueue_edu(self, edu):
         destination = edu.destination
         
+        if destination == self.server_name:
+            return
+
         deferred = defer.Deferred()
         self.pending_edus_by_dest.setdefault(destination, []).append(
             (edu, deferred)
@@ -770,10 +775,19 @@ class _TransactionQueue(object):
     @defer.inlineCallbacks
     @log_function
     def _attempt_new_transaction(self, destination):
-        if destination in self.pending_transactions:
+        
+        (retry_last_ts, retry_interval) = self.store.get_destination_retry_timings(destination)
+        if retry_last_ts + retry_interval > int(self._clock.time_msec()):
+            logger.info("TX [%s] not ready for retry yet - dropping transaction for now")
             return
         
-        #  list of (pending_pdu, deferred, order)
+        if destination in self.pending_transactions:
+            # XXX: pending_transactions can get stuck on by a never-ending request
+            # at which point pending_pdus_by_dest just keeps growing.
+            # we need application-layer timeouts of some flavour of these requests
+            return
+
+        # list of (pending_pdu, deferred, order)
         pending_pdus = self.pending_pdus_by_dest.pop(destination, [])
         pending_edus = self.pending_edus_by_dest.pop(destination, [])
         pending_failures = self.pending_failures_by_dest.pop(destination, [])
@@ -781,7 +795,8 @@ class _TransactionQueue(object):
         if not pending_pdus and not pending_edus and not pending_failures:
             return
 
-        logger.debug("TX [%s] Attempting new transaction", destination)
+        logger.debug("TX [%s] Attempting new transaction (pdus: %d, edus: %d, failures: %d)",
+            destination, len(pending_pdus), len(pending_edus), len(pending_failures))
 
         # Sort based on the order field
         pending_pdus.sort(key=lambda t: t[2])
@@ -814,7 +829,7 @@ class _TransactionQueue(object):
             yield self.transaction_actions.prepare_to_send(transaction)
 
             logger.debug("TX [%s] Persisted transaction", destination)
-            logger.debug("TX [%s] Sending transaction...", destination)
+            logger.info("TX [%s] Sending transaction [%s]", destination, transaction.transaction_id)
 
             # Actually send the transaction
 
@@ -835,6 +850,8 @@ class _TransactionQueue(object):
                 transaction, json_data_cb
             )
 
+            logger.info("TX [%s] got %d response", destination, code)
+
             logger.debug("TX [%s] Sent transaction", destination)
             logger.debug("TX [%s] Marking as delivered...", destination)
 
@@ -849,6 +866,7 @@ class _TransactionQueue(object):
                 if code == 200:
                     deferred.callback(None)
                 else:
+                    start_retrying(destination, retry_interval)
                     deferred.errback(RuntimeError("Got status %d" % code))
 
                 # Ensures we don't continue until all callbacks on that
@@ -861,11 +879,11 @@ class _TransactionQueue(object):
             logger.debug("TX [%s] Yielded to callbacks", destination)
 
         except Exception as e:
-            logger.error("TX Problem in _attempt_transaction")
-
             # We capture this here as there as nothing actually listens
             # for this finishing functions deferred.
-            logger.exception(e)
+            logger.exception("TX [%s] Problem in _attempt_transaction: %s", destination, e)
+
+            start_retrying(destination, retry_interval)
             
             for deferred in deferreds:
                 if not deferred.called:
@@ -877,3 +895,14 @@ class _TransactionQueue(object):
 
             # Check to see if there is anything else to send.
             self._attempt_new_transaction(destination)
+
+def start_retrying(destination, retry_interval):
+    # track that this destination is having problems and we should
+    # give it a chance to recover before trying it again
+    if retry_interval:
+        retry_interval *= 2
+    else:
+        retry_interval = 2 # try again at first after 2 seconds
+    self.store.set_destination_retry_timings(destination,
+        int(self._clock.time_msec()), retry_interval)
+    

synapse/federation/transport.py

@@ -155,7 +155,7 @@ class TransportLayer(object):
     @defer.inlineCallbacks
     @log_function
     def send_transaction(self, transaction, json_data_callback=None):
-        """ Sends the given Transaction to it's destination
+        """ Sends the given Transaction to its destination
 
         Args:
             transaction (Transaction)

synapse/http/matrixfederationclient.py

@@ -89,7 +89,7 @@ class MatrixFederationHttpClient(object):
             ("", "", path_bytes, param_bytes, query_bytes, "",)
         )
 
-        logger.debug("Sending request to %s: %s %s",
+        logger.info("Sending request to %s: %s %s",
                      destination, method, url_bytes)
 
         logger.debug(
@@ -101,7 +101,10 @@ class MatrixFederationHttpClient(object):
             ]
         )
 
-        retries_left = 5
+        # was 5; for now, let's only try once at the HTTP layer and then
+        # rely on transaction-layer retries for exponential backoff and
+        # getting the message through.
+        retries_left = 0
 
         endpoint = self._getEndpoint(reactor, destination)
 
@@ -131,7 +134,8 @@ class MatrixFederationHttpClient(object):
                                 e)
                     raise SynapseError(400, "Domain specified not found.")
 
-                logger.exception("Got error in _create_request")
+                logger.exception("Sending request failed to %s: %s %s : %s",
+                    destination, method, url_bytes, e)
                 _print_ex(e)
 
                 if retries_left:
@@ -140,15 +144,15 @@ class MatrixFederationHttpClient(object):
                 else:
                     raise
 
+        logger.info("Received response %d %s for %s: %s %s",
+            response.code, response.phrase, destination, method, url_bytes)
+        
         if 200 <= response.code < 300:
             # We need to update the transactions table to say it was sent?
             pass
         else:
             # :'(
             # Update transactions table?
-            logger.error(
-                "Got response %d %s", response.code, response.phrase
-            )
             raise CodeMessageException(
                 response.code, response.phrase
             )

synapse/rest/transactions.py

@@ -19,7 +19,7 @@ import logging
 
 logger = logging.getLogger(__name__)
 
-
+# FIXME: elsewhere we use FooStore to indicate something in the storage layer...
 class HttpTransactionStore(object):
 
     def __init__(self):

synapse/storage/__init__.py

@@ -67,7 +67,7 @@ SCHEMAS = [
 
 # Remember to update this number every time an incompatible change is made to
 # database schema files, so the users will be informed on server restarts.
-SCHEMA_VERSION = 8
+SCHEMA_VERSION = 9
 
 
 class _RollbackButIsFineException(Exception):

synapse/storage/_base.py

@@ -650,7 +650,7 @@ class JoinHelper(object):
     to dump the results into.
 
     Attributes:
-        taples (list): List of `Table` classes
+        tables (list): List of `Table` classes
         EntryType (type)
     """
 

synapse/storage/schema/delta/v9.sql

@@ -0,0 +1,23 @@
+/* Copyright 2014 OpenMarket Ltd
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+-- To track destination health
+CREATE TABLE IF NOT EXISTS destinations(
+    destination TEXT PRIMARY KEY,
+    retry_last_ts INTEGER,
+    retry_interval INTEGER
+);
+
+PRAGMA user_version = 9;

synapse/storage/schema/transactions.sql

@@ -59,3 +59,9 @@ CREATE INDEX IF NOT EXISTS transaction_id_to_pdu_tx ON transaction_id_to_pdu(tra
 CREATE INDEX IF NOT EXISTS transaction_id_to_pdu_dest ON transaction_id_to_pdu(destination);
 CREATE INDEX IF NOT EXISTS transaction_id_to_pdu_index ON transaction_id_to_pdu(transaction_id, destination);
 
+-- To track destination health
+CREATE TABLE IF NOT EXISTS destinations(
+    destination TEXT PRIMARY KEY,
+    retry_last_ts INTEGER,
+    retry_interval INTEGER
+);

synapse/storage/transactions.py

@@ -114,7 +114,7 @@ class TransactionStore(SQLBaseStore):
     def _prep_send_transaction(self, txn, transaction_id, destination,
                                origin_server_ts):
 
-        # First we find out what the prev_txs should be.
+        # First we find out what the prev_txns should be.
         # Since we know that we are only sending one transaction at a time,
         # we can simply take the last one.
         query = "%s ORDER BY id DESC LIMIT 1" % (
@@ -205,6 +205,71 @@ class TransactionStore(SQLBaseStore):
 
         return ReceivedTransactionsTable.decode_results(txn.fetchall())
 
+    def get_destination_retry_timings(self, destination):
+        """Gets the current retry timings (if any) for a given destination.
+        
+        Args:
+            destination (str)
+        
+        Returns:
+            None if not retrying
+            tuple: (retry_last_ts, retry_interval)
+                retry_ts: time of last retry attempt in unix epoch ms
+                retry_interval: how long until next retry in ms
+        """
+        return self.runInteraction(
+            "get_destination_retry_timings",
+            self._get_destination_retry_timings, destination)
+            
+    def _get_destination_retry_timings(cls, txn, destination):
+        query = DestinationsTable.select_statement("destination = ?")
+        txn.execute(query, (destination,))
+        result = DestinationsTable.decode_single_result(txn.fetchone())
+        if result and result[0] > 0:
+            return result
+        else:
+            return None
+        
+    def set_destination_retry_timings(self, destination):
+        """Sets the current retry timings for a given destination.
+        Both timings should be zero if retrying is no longer occuring.
+        
+        Args:
+            destination (str)
+            retry_last_ts (int) - time of last retry attempt in unix epoch ms
+            retry_interval (int) - how long until next retry in ms
+        """
+        return self.runInteraction(
+            "set_destination_retry_timings",
+            self._set_destination_retry_timings, destination, retry_last_ts, retry_interval)
+            
+    def _set_destination_retry_timings(cls, txn, destination, retry_last_ts, retry_interval):
+
+        query = (
+            "INSERT OR REPLACE INTO %s "
+            "(retry_last_ts, retry_interval) "
+            "VALUES (?, ?) "
+            "WHERE destination = ?"
+        ) % DestinationsTable.table_name
+
+        txn.execute(query, (retry_last_ts, retry_interval, destination))
+
+    def get_destinations_needing_retry(self):
+        """Get all destinations which are due a retry for sending a transaction.
+                    
+        Returns:
+            list: A list of `DestinationsTable.EntryType`
+        """
+        return self.runInteraction(
+            "get_destinations_needing_retry",
+            self._get_destinations_needing_retry
+        )
+        
+    def _get_destinations_needing_retry(cls, txn):
+        where = "retry_last_ts > 0 and retry_next_ts < now()"
+        query = DestinationsTable.select_statement(where)
+        txn.execute(query)
+        return DestinationsTable.decode_results(txn.fetchall())    
 
 class ReceivedTransactionsTable(Table):
     table_name = "received_transactions"
@@ -247,3 +312,14 @@ class TransactionsToPduTable(Table):
     ]
 
     EntryType = namedtuple("TransactionsToPduEntry", fields)
+    
+class DestinationsTable(Table):
+    table_name = "destinations"
+    
+    fields = [
+        "destination",
+        "retry_last_ts",
+        "retry_interval",
+    ]
+
+    EntryType = namedtuple("DestinationsEntry", fields)