Exemplo n.º 1
0
class TransactionStore(SQLBaseStore):
    """A collection of queries for handling PDUs.
    """
    def __init__(self, db_conn, hs):
        super(TransactionStore, self).__init__(db_conn, hs)

        self._clock.looping_call(self._start_cleanup_transactions,
                                 30 * 60 * 1000)

        self._destination_retry_cache = ExpiringCache(
            cache_name="get_destination_retry_timings",
            clock=self._clock,
            expiry_ms=5 * 60 * 1000,
        )

    def get_received_txn_response(self, transaction_id, origin):
        """For an incoming transaction from a given origin, check if we have
        already responded to it. If so, return the response code and response
        body (as a dict).

        Args:
            transaction_id (str)
            origin(str)

        Returns:
            tuple: None if we have not previously responded to
            this transaction or a 2-tuple of (int, dict)
        """

        return self.runInteraction("get_received_txn_response",
                                   self._get_received_txn_response,
                                   transaction_id, origin)

    def _get_received_txn_response(self, txn, transaction_id, origin):
        result = self._simple_select_one_txn(
            txn,
            table="received_transactions",
            keyvalues={
                "transaction_id": transaction_id,
                "origin": origin,
            },
            retcols=(
                "transaction_id",
                "origin",
                "ts",
                "response_code",
                "response_json",
                "has_been_referenced",
            ),
            allow_none=True,
        )

        if result and result["response_code"]:
            return result["response_code"], db_to_json(result["response_json"])

        else:
            return None

    def set_received_txn_response(self, transaction_id, origin, code,
                                  response_dict):
        """Persist the response we returened for an incoming transaction, and
        should return for subsequent transactions with the same transaction_id
        and origin.

        Args:
            txn
            transaction_id (str)
            origin (str)
            code (int)
            response_json (str)
        """

        return self._simple_insert(
            table="received_transactions",
            values={
                "transaction_id":
                transaction_id,
                "origin":
                origin,
                "response_code":
                code,
                "response_json":
                db_binary_type(encode_canonical_json(response_dict)),
                "ts":
                self._clock.time_msec(),
            },
            or_ignore=True,
            desc="set_received_txn_response",
        )

    def prep_send_transaction(self, transaction_id, destination,
                              origin_server_ts):
        """Persists an outgoing transaction and calculates the values for the
        previous transaction id list.

        This should be called before sending the transaction so that it has the
        correct value for the `prev_ids` key.

        Args:
            transaction_id (str)
            destination (str)
            origin_server_ts (int)

        Returns:
            list: A list of previous transaction ids.
        """
        return defer.succeed([])

    def delivered_txn(self, transaction_id, destination, code, response_dict):
        """Persists the response for an outgoing transaction.

        Args:
            transaction_id (str)
            destination (str)
            code (int)
            response_json (str)
        """
        pass

    @defer.inlineCallbacks
    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
            Otherwise a dict for the retry scheme
        """

        result = self._destination_retry_cache.get(destination, SENTINEL)
        if result is not SENTINEL:
            defer.returnValue(result)

        result = yield self.runInteraction("get_destination_retry_timings",
                                           self._get_destination_retry_timings,
                                           destination)

        # We don't hugely care about race conditions between getting and
        # invalidating the cache, since we time out fairly quickly anyway.
        self._destination_retry_cache[destination] = result
        defer.returnValue(result)

    def _get_destination_retry_timings(self, txn, destination):
        result = self._simple_select_one_txn(
            txn,
            table="destinations",
            keyvalues={
                "destination": destination,
            },
            retcols=("destination", "retry_last_ts", "retry_interval"),
            allow_none=True,
        )

        if result and result["retry_last_ts"] > 0:
            return result
        else:
            return None

    def set_destination_retry_timings(self, destination, retry_last_ts,
                                      retry_interval):
        """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
        """

        self._destination_retry_cache.pop(destination, None)
        return self.runInteraction(
            "set_destination_retry_timings",
            self._set_destination_retry_timings,
            destination,
            retry_last_ts,
            retry_interval,
        )

    def _set_destination_retry_timings(self, txn, destination, retry_last_ts,
                                       retry_interval):
        self.database_engine.lock_table(txn, "destinations")

        # We need to be careful here as the data may have changed from under us
        # due to a worker setting the timings.

        prev_row = self._simple_select_one_txn(
            txn,
            table="destinations",
            keyvalues={
                "destination": destination,
            },
            retcols=("retry_last_ts", "retry_interval"),
            allow_none=True,
        )

        if not prev_row:
            self._simple_insert_txn(txn,
                                    table="destinations",
                                    values={
                                        "destination": destination,
                                        "retry_last_ts": retry_last_ts,
                                        "retry_interval": retry_interval,
                                    })
        elif retry_interval == 0 or prev_row["retry_interval"] < retry_interval:
            self._simple_update_one_txn(
                txn,
                "destinations",
                keyvalues={
                    "destination": destination,
                },
                updatevalues={
                    "retry_last_ts": retry_last_ts,
                    "retry_interval": retry_interval,
                },
            )

    def get_destinations_needing_retry(self):
        """Get all destinations which are due a retry for sending a transaction.

        Returns:
            list: A list of dicts
        """

        return self.runInteraction("get_destinations_needing_retry",
                                   self._get_destinations_needing_retry)

    def _get_destinations_needing_retry(self, txn):
        query = ("SELECT * FROM destinations"
                 " WHERE retry_last_ts > 0 and retry_next_ts < ?")

        txn.execute(query, (self._clock.time_msec(), ))
        return self.cursor_to_dict(txn)

    def _start_cleanup_transactions(self):
        return run_as_background_process(
            "cleanup_transactions",
            self._cleanup_transactions,
        )

    def _cleanup_transactions(self):
        now = self._clock.time_msec()
        month_ago = now - 30 * 24 * 60 * 60 * 1000

        def _cleanup_transactions_txn(txn):
            txn.execute("DELETE FROM received_transactions WHERE ts < ?",
                        (month_ago, ))

        return self.runInteraction("_cleanup_transactions",
                                   _cleanup_transactions_txn)
Exemplo n.º 2
0
class TransactionStore(SQLBaseStore):
    """A collection of queries for handling PDUs.
    """
    def __init__(self, database: DatabasePool, db_conn, hs):
        super().__init__(database, db_conn, hs)

        self._clock.looping_call(self._start_cleanup_transactions,
                                 30 * 60 * 1000)

        self._destination_retry_cache = ExpiringCache(
            cache_name="get_destination_retry_timings",
            clock=self._clock,
            expiry_ms=5 * 60 * 1000,
        )

    async def get_received_txn_response(
            self, transaction_id: str,
            origin: str) -> Optional[Tuple[int, JsonDict]]:
        """For an incoming transaction from a given origin, check if we have
        already responded to it. If so, return the response code and response
        body (as a dict).

        Args:
            transaction_id
            origin

        Returns:
            None if we have not previously responded to this transaction or a
            2-tuple of (int, dict)
        """

        return await self.db_pool.runInteraction(
            "get_received_txn_response",
            self._get_received_txn_response,
            transaction_id,
            origin,
        )

    def _get_received_txn_response(self, txn, transaction_id, origin):
        result = self.db_pool.simple_select_one_txn(
            txn,
            table="received_transactions",
            keyvalues={
                "transaction_id": transaction_id,
                "origin": origin
            },
            retcols=(
                "transaction_id",
                "origin",
                "ts",
                "response_code",
                "response_json",
                "has_been_referenced",
            ),
            allow_none=True,
        )

        if result and result["response_code"]:
            return result["response_code"], db_to_json(result["response_json"])

        else:
            return None

    async def set_received_txn_response(self, transaction_id: str, origin: str,
                                        code: int,
                                        response_dict: JsonDict) -> None:
        """Persist the response we returned for an incoming transaction, and
        should return for subsequent transactions with the same transaction_id
        and origin.

        Args:
            transaction_id: The incoming transaction ID.
            origin: The origin server.
            code: The response code.
            response_dict: The response, to be encoded into JSON.
        """

        await self.db_pool.simple_insert(
            table="received_transactions",
            values={
                "transaction_id":
                transaction_id,
                "origin":
                origin,
                "response_code":
                code,
                "response_json":
                db_binary_type(encode_canonical_json(response_dict)),
                "ts":
                self._clock.time_msec(),
            },
            or_ignore=True,
            desc="set_received_txn_response",
        )

    async 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
            Otherwise a dict for the retry scheme
        """

        result = self._destination_retry_cache.get(destination, SENTINEL)
        if result is not SENTINEL:
            return result

        result = await self.db_pool.runInteraction(
            "get_destination_retry_timings",
            self._get_destination_retry_timings,
            destination,
        )

        # We don't hugely care about race conditions between getting and
        # invalidating the cache, since we time out fairly quickly anyway.
        self._destination_retry_cache[destination] = result
        return result

    def _get_destination_retry_timings(self, txn, destination):
        result = self.db_pool.simple_select_one_txn(
            txn,
            table="destinations",
            keyvalues={"destination": destination},
            retcols=("destination", "failure_ts", "retry_last_ts",
                     "retry_interval"),
            allow_none=True,
        )

        # check we have a row and retry_last_ts is not null or zero
        # (retry_last_ts can't be negative)
        if result and result["retry_last_ts"]:
            return result
        else:
            return None

    async def set_destination_retry_timings(
        self,
        destination: str,
        failure_ts: Optional[int],
        retry_last_ts: int,
        retry_interval: int,
    ) -> None:
        """Sets the current retry timings for a given destination.
        Both timings should be zero if retrying is no longer occuring.

        Args:
            destination
            failure_ts: when the server started failing (ms since epoch)
            retry_last_ts: time of last retry attempt in unix epoch ms
            retry_interval: how long until next retry in ms
        """

        self._destination_retry_cache.pop(destination, None)
        return await self.db_pool.runInteraction(
            "set_destination_retry_timings",
            self._set_destination_retry_timings,
            destination,
            failure_ts,
            retry_last_ts,
            retry_interval,
        )

    def _set_destination_retry_timings(self, txn, destination, failure_ts,
                                       retry_last_ts, retry_interval):

        if self.database_engine.can_native_upsert:
            # Upsert retry time interval if retry_interval is zero (i.e. we're
            # resetting it) or greater than the existing retry interval.

            sql = """
                INSERT INTO destinations (
                    destination, failure_ts, retry_last_ts, retry_interval
                )
                    VALUES (?, ?, ?, ?)
                ON CONFLICT (destination) DO UPDATE SET
                        failure_ts = EXCLUDED.failure_ts,
                        retry_last_ts = EXCLUDED.retry_last_ts,
                        retry_interval = EXCLUDED.retry_interval
                    WHERE
                        EXCLUDED.retry_interval = 0
                        OR destinations.retry_interval IS NULL
                        OR destinations.retry_interval < EXCLUDED.retry_interval
            """

            txn.execute(
                sql, (destination, failure_ts, retry_last_ts, retry_interval))

            return

        self.database_engine.lock_table(txn, "destinations")

        # We need to be careful here as the data may have changed from under us
        # due to a worker setting the timings.

        prev_row = self.db_pool.simple_select_one_txn(
            txn,
            table="destinations",
            keyvalues={"destination": destination},
            retcols=("failure_ts", "retry_last_ts", "retry_interval"),
            allow_none=True,
        )

        if not prev_row:
            self.db_pool.simple_insert_txn(
                txn,
                table="destinations",
                values={
                    "destination": destination,
                    "failure_ts": failure_ts,
                    "retry_last_ts": retry_last_ts,
                    "retry_interval": retry_interval,
                },
            )
        elif (retry_interval == 0 or prev_row["retry_interval"] is None
              or prev_row["retry_interval"] < retry_interval):
            self.db_pool.simple_update_one_txn(
                txn,
                "destinations",
                keyvalues={"destination": destination},
                updatevalues={
                    "failure_ts": failure_ts,
                    "retry_last_ts": retry_last_ts,
                    "retry_interval": retry_interval,
                },
            )

    def _start_cleanup_transactions(self):
        return run_as_background_process("cleanup_transactions",
                                         self._cleanup_transactions)

    async def _cleanup_transactions(self) -> None:
        now = self._clock.time_msec()
        month_ago = now - 30 * 24 * 60 * 60 * 1000

        def _cleanup_transactions_txn(txn):
            txn.execute("DELETE FROM received_transactions WHERE ts < ?",
                        (month_ago, ))

        await self.db_pool.runInteraction("_cleanup_transactions",
                                          _cleanup_transactions_txn)

    async def store_destination_rooms_entries(
        self,
        destinations: Iterable[str],
        room_id: str,
        stream_ordering: int,
    ) -> None:
        """
        Updates or creates `destination_rooms` entries in batch for a single event.

        Args:
            destinations: list of destinations
            room_id: the room_id of the event
            stream_ordering: the stream_ordering of the event
        """

        return await self.db_pool.runInteraction(
            "store_destination_rooms_entries",
            self._store_destination_rooms_entries_txn,
            destinations,
            room_id,
            stream_ordering,
        )

    def _store_destination_rooms_entries_txn(
        self,
        txn: LoggingTransaction,
        destinations: Iterable[str],
        room_id: str,
        stream_ordering: int,
    ) -> None:

        # ensure we have a `destinations` row for this destination, as there is
        # a foreign key constraint.
        if isinstance(self.database_engine, PostgresEngine):
            q = """
                INSERT INTO destinations (destination)
                    VALUES (?)
                    ON CONFLICT DO NOTHING;
            """
        elif isinstance(self.database_engine, Sqlite3Engine):
            q = """
                INSERT OR IGNORE INTO destinations (destination)
                    VALUES (?);
            """
        else:
            raise RuntimeError("Unknown database engine")

        txn.execute_batch(q, ((destination, ) for destination in destinations))

        rows = [(destination, room_id) for destination in destinations]

        self.db_pool.simple_upsert_many_txn(
            txn,
            "destination_rooms",
            ["destination", "room_id"],
            rows,
            ["stream_ordering"],
            [(stream_ordering, )] * len(rows),
        )

    async def get_destination_last_successful_stream_ordering(
            self, destination: str) -> Optional[int]:
        """
        Gets the stream ordering of the PDU most-recently successfully sent
        to the specified destination, or None if this information has not been
        tracked yet.

        Args:
            destination: the destination to query
        """
        return await self.db_pool.simple_select_one_onecol(
            "destinations",
            {"destination": destination},
            "last_successful_stream_ordering",
            allow_none=True,
            desc="get_last_successful_stream_ordering",
        )

    async def set_destination_last_successful_stream_ordering(
            self, destination: str,
            last_successful_stream_ordering: int) -> None:
        """
        Marks that we have successfully sent the PDUs up to and including the
        one specified.

        Args:
            destination: the destination we have successfully sent to
            last_successful_stream_ordering: the stream_ordering of the most
                recent successfully-sent PDU
        """
        return await self.db_pool.simple_upsert(
            "destinations",
            keyvalues={"destination": destination},
            values={
                "last_successful_stream_ordering":
                last_successful_stream_ordering
            },
            desc="set_last_successful_stream_ordering",
        )

    async def get_catch_up_room_event_ids(
        self,
        destination: str,
        last_successful_stream_ordering: int,
    ) -> List[str]:
        """
        Returns at most 50 event IDs and their corresponding stream_orderings
        that correspond to the oldest events that have not yet been sent to
        the destination.

        Args:
            destination: the destination in question
            last_successful_stream_ordering: the stream_ordering of the
                most-recently successfully-transmitted event to the destination

        Returns:
            list of event_ids
        """
        return await self.db_pool.runInteraction(
            "get_catch_up_room_event_ids",
            self._get_catch_up_room_event_ids_txn,
            destination,
            last_successful_stream_ordering,
        )

    @staticmethod
    def _get_catch_up_room_event_ids_txn(
        txn: LoggingTransaction,
        destination: str,
        last_successful_stream_ordering: int,
    ) -> List[str]:
        q = """
                SELECT event_id FROM destination_rooms
                 JOIN events USING (stream_ordering)
                WHERE destination = ?
                  AND stream_ordering > ?
                ORDER BY stream_ordering
                LIMIT 50
            """
        txn.execute(
            q,
            (destination, last_successful_stream_ordering),
        )
        event_ids = [row[0] for row in txn]
        return event_ids

    async def get_catch_up_outstanding_destinations(
            self, after_destination: Optional[str]) -> List[str]:
        """
        Gets at most 25 destinations which have outstanding PDUs to be caught up,
        and are not being backed off from
        Args:
            after_destination:
                If provided, all destinations must be lexicographically greater
                than this one.

        Returns:
            list of up to 25 destinations with outstanding catch-up.
                These are the lexicographically first destinations which are
                lexicographically greater than after_destination (if provided).
        """
        time = self.hs.get_clock().time_msec()

        return await self.db_pool.runInteraction(
            "get_catch_up_outstanding_destinations",
            self._get_catch_up_outstanding_destinations_txn,
            time,
            after_destination,
        )

    @staticmethod
    def _get_catch_up_outstanding_destinations_txn(
            txn: LoggingTransaction, now_time_ms: int,
            after_destination: Optional[str]) -> List[str]:
        q = """
            SELECT destination FROM destinations
                WHERE destination IN (
                    SELECT destination FROM destination_rooms
                        WHERE destination_rooms.stream_ordering >
                            destinations.last_successful_stream_ordering
                )
                AND destination > ?
                AND (
                    retry_last_ts IS NULL OR
                    retry_last_ts + retry_interval < ?
                )
                ORDER BY destination
                LIMIT 25
        """
        txn.execute(
            q,
            (
                # everything is lexicographically greater than "" so this gives
                # us the first batch of up to 25.
                after_destination or "",
                now_time_ms,
            ),
        )

        destinations = [row[0] for row in txn]
        return destinations
Exemplo n.º 3
0
class TransactionStore(SQLBaseStore):
    """A collection of queries for handling PDUs.
    """

    def __init__(self, database: Database, db_conn, hs):
        super(TransactionStore, self).__init__(database, db_conn, hs)

        self._clock.looping_call(self._start_cleanup_transactions, 30 * 60 * 1000)

        self._destination_retry_cache = ExpiringCache(
            cache_name="get_destination_retry_timings",
            clock=self._clock,
            expiry_ms=5 * 60 * 1000,
        )

    def get_received_txn_response(self, transaction_id, origin):
        """For an incoming transaction from a given origin, check if we have
        already responded to it. If so, return the response code and response
        body (as a dict).

        Args:
            transaction_id (str)
            origin(str)

        Returns:
            tuple: None if we have not previously responded to
            this transaction or a 2-tuple of (int, dict)
        """

        return self.db.runInteraction(
            "get_received_txn_response",
            self._get_received_txn_response,
            transaction_id,
            origin,
        )

    def _get_received_txn_response(self, txn, transaction_id, origin):
        result = self.db.simple_select_one_txn(
            txn,
            table="received_transactions",
            keyvalues={"transaction_id": transaction_id, "origin": origin},
            retcols=(
                "transaction_id",
                "origin",
                "ts",
                "response_code",
                "response_json",
                "has_been_referenced",
            ),
            allow_none=True,
        )

        if result and result["response_code"]:
            return result["response_code"], db_to_json(result["response_json"])

        else:
            return None

    def set_received_txn_response(self, transaction_id, origin, code, response_dict):
        """Persist the response we returened for an incoming transaction, and
        should return for subsequent transactions with the same transaction_id
        and origin.

        Args:
            txn
            transaction_id (str)
            origin (str)
            code (int)
            response_json (str)
        """

        return self.db.simple_insert(
            table="received_transactions",
            values={
                "transaction_id": transaction_id,
                "origin": origin,
                "response_code": code,
                "response_json": db_binary_type(encode_canonical_json(response_dict)),
                "ts": self._clock.time_msec(),
            },
            or_ignore=True,
            desc="set_received_txn_response",
        )

    @defer.inlineCallbacks
    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
            Otherwise a dict for the retry scheme
        """

        result = self._destination_retry_cache.get(destination, SENTINEL)
        if result is not SENTINEL:
            return result

        result = yield self.db.runInteraction(
            "get_destination_retry_timings",
            self._get_destination_retry_timings,
            destination,
        )

        # We don't hugely care about race conditions between getting and
        # invalidating the cache, since we time out fairly quickly anyway.
        self._destination_retry_cache[destination] = result
        return result

    def _get_destination_retry_timings(self, txn, destination):
        result = self.db.simple_select_one_txn(
            txn,
            table="destinations",
            keyvalues={"destination": destination},
            retcols=("destination", "failure_ts", "retry_last_ts", "retry_interval"),
            allow_none=True,
        )

        if result and result["retry_last_ts"] > 0:
            return result
        else:
            return None

    def set_destination_retry_timings(
        self, destination, failure_ts, retry_last_ts, retry_interval
    ):
        """Sets the current retry timings for a given destination.
        Both timings should be zero if retrying is no longer occuring.

        Args:
            destination (str)
            failure_ts (int|None) - when the server started failing (ms since epoch)
            retry_last_ts (int) - time of last retry attempt in unix epoch ms
            retry_interval (int) - how long until next retry in ms
        """

        self._destination_retry_cache.pop(destination, None)
        return self.db.runInteraction(
            "set_destination_retry_timings",
            self._set_destination_retry_timings,
            destination,
            failure_ts,
            retry_last_ts,
            retry_interval,
        )

    def _set_destination_retry_timings(
        self, txn, destination, failure_ts, retry_last_ts, retry_interval
    ):

        if self.database_engine.can_native_upsert:
            # Upsert retry time interval if retry_interval is zero (i.e. we're
            # resetting it) or greater than the existing retry interval.

            sql = """
                INSERT INTO destinations (
                    destination, failure_ts, retry_last_ts, retry_interval
                )
                    VALUES (?, ?, ?, ?)
                ON CONFLICT (destination) DO UPDATE SET
                        failure_ts = EXCLUDED.failure_ts,
                        retry_last_ts = EXCLUDED.retry_last_ts,
                        retry_interval = EXCLUDED.retry_interval
                    WHERE
                        EXCLUDED.retry_interval = 0
                        OR destinations.retry_interval < EXCLUDED.retry_interval
            """

            txn.execute(sql, (destination, failure_ts, retry_last_ts, retry_interval))

            return

        self.database_engine.lock_table(txn, "destinations")

        # We need to be careful here as the data may have changed from under us
        # due to a worker setting the timings.

        prev_row = self.db.simple_select_one_txn(
            txn,
            table="destinations",
            keyvalues={"destination": destination},
            retcols=("failure_ts", "retry_last_ts", "retry_interval"),
            allow_none=True,
        )

        if not prev_row:
            self.db.simple_insert_txn(
                txn,
                table="destinations",
                values={
                    "destination": destination,
                    "failure_ts": failure_ts,
                    "retry_last_ts": retry_last_ts,
                    "retry_interval": retry_interval,
                },
            )
        elif retry_interval == 0 or prev_row["retry_interval"] < retry_interval:
            self.db.simple_update_one_txn(
                txn,
                "destinations",
                keyvalues={"destination": destination},
                updatevalues={
                    "failure_ts": failure_ts,
                    "retry_last_ts": retry_last_ts,
                    "retry_interval": retry_interval,
                },
            )

    def _start_cleanup_transactions(self):
        return run_as_background_process(
            "cleanup_transactions", self._cleanup_transactions
        )

    def _cleanup_transactions(self):
        now = self._clock.time_msec()
        month_ago = now - 30 * 24 * 60 * 60 * 1000

        def _cleanup_transactions_txn(txn):
            txn.execute("DELETE FROM received_transactions WHERE ts < ?", (month_ago,))

        return self.db.runInteraction(
            "_cleanup_transactions", _cleanup_transactions_txn
        )
Exemplo n.º 4
0
class TransactionStore(SQLBaseStore):
    """A collection of queries for handling PDUs.
    """

    def __init__(self, db_conn, hs):
        super(TransactionStore, self).__init__(db_conn, hs)

        self._clock.looping_call(self._start_cleanup_transactions, 30 * 60 * 1000)

        self._destination_retry_cache = ExpiringCache(
            cache_name="get_destination_retry_timings",
            clock=self._clock,
            expiry_ms=5 * 60 * 1000,
        )

    def get_received_txn_response(self, transaction_id, origin):
        """For an incoming transaction from a given origin, check if we have
        already responded to it. If so, return the response code and response
        body (as a dict).

        Args:
            transaction_id (str)
            origin(str)

        Returns:
            tuple: None if we have not previously responded to
            this transaction or a 2-tuple of (int, dict)
        """

        return self.runInteraction(
            "get_received_txn_response",
            self._get_received_txn_response,
            transaction_id,
            origin,
        )

    def _get_received_txn_response(self, txn, transaction_id, origin):
        result = self._simple_select_one_txn(
            txn,
            table="received_transactions",
            keyvalues={"transaction_id": transaction_id, "origin": origin},
            retcols=(
                "transaction_id",
                "origin",
                "ts",
                "response_code",
                "response_json",
                "has_been_referenced",
            ),
            allow_none=True,
        )

        if result and result["response_code"]:
            return result["response_code"], db_to_json(result["response_json"])

        else:
            return None

    def set_received_txn_response(self, transaction_id, origin, code, response_dict):
        """Persist the response we returened for an incoming transaction, and
        should return for subsequent transactions with the same transaction_id
        and origin.

        Args:
            txn
            transaction_id (str)
            origin (str)
            code (int)
            response_json (str)
        """

        return self._simple_insert(
            table="received_transactions",
            values={
                "transaction_id": transaction_id,
                "origin": origin,
                "response_code": code,
                "response_json": db_binary_type(encode_canonical_json(response_dict)),
                "ts": self._clock.time_msec(),
            },
            or_ignore=True,
            desc="set_received_txn_response",
        )

    def prep_send_transaction(self, transaction_id, destination, origin_server_ts):
        """Persists an outgoing transaction and calculates the values for the
        previous transaction id list.

        This should be called before sending the transaction so that it has the
        correct value for the `prev_ids` key.

        Args:
            transaction_id (str)
            destination (str)
            origin_server_ts (int)

        Returns:
            list: A list of previous transaction ids.
        """
        return defer.succeed([])

    def delivered_txn(self, transaction_id, destination, code, response_dict):
        """Persists the response for an outgoing transaction.

        Args:
            transaction_id (str)
            destination (str)
            code (int)
            response_json (str)
        """
        pass

    @defer.inlineCallbacks
    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
            Otherwise a dict for the retry scheme
        """

        result = self._destination_retry_cache.get(destination, SENTINEL)
        if result is not SENTINEL:
            defer.returnValue(result)

        result = yield self.runInteraction(
            "get_destination_retry_timings",
            self._get_destination_retry_timings,
            destination,
        )

        # We don't hugely care about race conditions between getting and
        # invalidating the cache, since we time out fairly quickly anyway.
        self._destination_retry_cache[destination] = result
        defer.returnValue(result)

    def _get_destination_retry_timings(self, txn, destination):
        result = self._simple_select_one_txn(
            txn,
            table="destinations",
            keyvalues={"destination": destination},
            retcols=("destination", "retry_last_ts", "retry_interval"),
            allow_none=True,
        )

        if result and result["retry_last_ts"] > 0:
            return result
        else:
            return None

    def set_destination_retry_timings(self, destination, retry_last_ts, retry_interval):
        """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
        """

        self._destination_retry_cache.pop(destination, None)
        return self.runInteraction(
            "set_destination_retry_timings",
            self._set_destination_retry_timings,
            destination,
            retry_last_ts,
            retry_interval,
        )

    def _set_destination_retry_timings(
        self, txn, destination, retry_last_ts, retry_interval
    ):
        self.database_engine.lock_table(txn, "destinations")

        # We need to be careful here as the data may have changed from under us
        # due to a worker setting the timings.

        prev_row = self._simple_select_one_txn(
            txn,
            table="destinations",
            keyvalues={"destination": destination},
            retcols=("retry_last_ts", "retry_interval"),
            allow_none=True,
        )

        if not prev_row:
            self._simple_insert_txn(
                txn,
                table="destinations",
                values={
                    "destination": destination,
                    "retry_last_ts": retry_last_ts,
                    "retry_interval": retry_interval,
                },
            )
        elif retry_interval == 0 or prev_row["retry_interval"] < retry_interval:
            self._simple_update_one_txn(
                txn,
                "destinations",
                keyvalues={"destination": destination},
                updatevalues={
                    "retry_last_ts": retry_last_ts,
                    "retry_interval": retry_interval,
                },
            )

    def get_destinations_needing_retry(self):
        """Get all destinations which are due a retry for sending a transaction.

        Returns:
            list: A list of dicts
        """

        return self.runInteraction(
            "get_destinations_needing_retry", self._get_destinations_needing_retry
        )

    def _get_destinations_needing_retry(self, txn):
        query = (
            "SELECT * FROM destinations"
            " WHERE retry_last_ts > 0 and retry_next_ts < ?"
        )

        txn.execute(query, (self._clock.time_msec(),))
        return self.cursor_to_dict(txn)

    def _start_cleanup_transactions(self):
        return run_as_background_process(
            "cleanup_transactions", self._cleanup_transactions
        )

    def _cleanup_transactions(self):
        now = self._clock.time_msec()
        month_ago = now - 30 * 24 * 60 * 60 * 1000

        def _cleanup_transactions_txn(txn):
            txn.execute("DELETE FROM received_transactions WHERE ts < ?", (month_ago,))

        return self.runInteraction("_cleanup_transactions", _cleanup_transactions_txn)