document the REPLICATE command a bit better (#6305)

since I found myself wonder how it works
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Richard van der Hoff 2019-11-04 12:40:18 +00:00 committed by GitHub
parent f496d25877
commit cc6243b4c0
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5 changed files with 110 additions and 10 deletions

1
changelog.d/6305.misc Normal file
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@ -0,0 +1 @@
Add some documentation about worker replication.

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@ -199,7 +199,20 @@ client (C):
#### REPLICATE (C)
Asks the server to replicate a given stream
Asks the server to replicate a given stream. The syntax is:
```
REPLICATE <stream_name> <token>
```
Where `<token>` may be either:
* a numeric stream_id to stream updates since (exclusive)
* `NOW` to stream all subsequent updates.
The `<stream_name>` is the name of a replication stream to subscribe
to (see [here](../synapse/replication/tcp/streams/_base.py) for a list
of streams). It can also be `ALL` to subscribe to all known streams,
in which case the `<token>` must be set to `NOW`.
#### USER_SYNC (C)

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@ -14,6 +14,7 @@
# limitations under the License.
import logging
from typing import Dict
import six
@ -44,7 +45,14 @@ class BaseSlavedStore(SQLBaseStore):
self.hs = hs
def stream_positions(self):
def stream_positions(self) -> Dict[str, int]:
"""
Get the current positions of all the streams this store wants to subscribe to
Returns:
map from stream name to the most recent update we have for
that stream (ie, the point we want to start replicating from)
"""
pos = {}
if self._cache_id_gen:
pos["caches"] = self._cache_id_gen.get_current_token()

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@ -16,10 +16,17 @@
"""
import logging
from typing import Dict
from twisted.internet import defer
from twisted.internet.protocol import ReconnectingClientFactory
from synapse.replication.slave.storage._base import BaseSlavedStore
from synapse.replication.tcp.protocol import (
AbstractReplicationClientHandler,
ClientReplicationStreamProtocol,
)
from .commands import (
FederationAckCommand,
InvalidateCacheCommand,
@ -27,7 +34,6 @@ from .commands import (
UserIpCommand,
UserSyncCommand,
)
from .protocol import ClientReplicationStreamProtocol
logger = logging.getLogger(__name__)
@ -42,7 +48,7 @@ class ReplicationClientFactory(ReconnectingClientFactory):
maxDelay = 30 # Try at least once every N seconds
def __init__(self, hs, client_name, handler):
def __init__(self, hs, client_name, handler: AbstractReplicationClientHandler):
self.client_name = client_name
self.handler = handler
self.server_name = hs.config.server_name
@ -68,13 +74,13 @@ class ReplicationClientFactory(ReconnectingClientFactory):
ReconnectingClientFactory.clientConnectionFailed(self, connector, reason)
class ReplicationClientHandler(object):
class ReplicationClientHandler(AbstractReplicationClientHandler):
"""A base handler that can be passed to the ReplicationClientFactory.
By default proxies incoming replication data to the SlaveStore.
"""
def __init__(self, store):
def __init__(self, store: BaseSlavedStore):
self.store = store
# The current connection. None if we are currently (re)connecting
@ -138,11 +144,13 @@ class ReplicationClientHandler(object):
if d:
d.callback(data)
def get_streams_to_replicate(self):
def get_streams_to_replicate(self) -> Dict[str, int]:
"""Called when a new connection has been established and we need to
subscribe to streams.
Returns a dictionary of stream name to token.
Returns:
map from stream name to the most recent update we have for
that stream (ie, the point we want to start replicating from)
"""
args = self.store.stream_positions()
user_account_data = args.pop("user_account_data", None)

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@ -48,7 +48,7 @@ indicate which side is sending, these are *not* included on the wire::
> ERROR server stopping
* connection closed by server *
"""
import abc
import fcntl
import logging
import struct
@ -65,6 +65,7 @@ from twisted.python.failure import Failure
from synapse.logging.context import make_deferred_yieldable, run_in_background
from synapse.metrics import LaterGauge
from synapse.metrics.background_process_metrics import run_as_background_process
from synapse.util import Clock
from synapse.util.stringutils import random_string
from .commands import (
@ -558,11 +559,80 @@ class ServerReplicationStreamProtocol(BaseReplicationStreamProtocol):
self.streamer.lost_connection(self)
class AbstractReplicationClientHandler(metaclass=abc.ABCMeta):
"""
The interface for the handler that should be passed to
ClientReplicationStreamProtocol
"""
@abc.abstractmethod
def on_rdata(self, stream_name, token, rows):
"""Called to handle a batch of replication data with a given stream token.
Args:
stream_name (str): name of the replication stream for this batch of rows
token (int): stream token for this batch of rows
rows (list): a list of Stream.ROW_TYPE objects as returned by
Stream.parse_row.
Returns:
Deferred|None
"""
raise NotImplementedError()
@abc.abstractmethod
def on_position(self, stream_name, token):
"""Called when we get new position data."""
raise NotImplementedError()
@abc.abstractmethod
def on_sync(self, data):
"""Called when get a new SYNC command."""
raise NotImplementedError()
@abc.abstractmethod
def get_streams_to_replicate(self):
"""Called when a new connection has been established and we need to
subscribe to streams.
Returns:
map from stream name to the most recent update we have for
that stream (ie, the point we want to start replicating from)
"""
raise NotImplementedError()
@abc.abstractmethod
def get_currently_syncing_users(self):
"""Get the list of currently syncing users (if any). This is called
when a connection has been established and we need to send the
currently syncing users."""
raise NotImplementedError()
@abc.abstractmethod
def update_connection(self, connection):
"""Called when a connection has been established (or lost with None).
"""
raise NotImplementedError()
@abc.abstractmethod
def finished_connecting(self):
"""Called when we have successfully subscribed and caught up to all
streams we're interested in.
"""
raise NotImplementedError()
class ClientReplicationStreamProtocol(BaseReplicationStreamProtocol):
VALID_INBOUND_COMMANDS = VALID_SERVER_COMMANDS
VALID_OUTBOUND_COMMANDS = VALID_CLIENT_COMMANDS
def __init__(self, client_name, server_name, clock, handler):
def __init__(
self,
client_name: str,
server_name: str,
clock: Clock,
handler: AbstractReplicationClientHandler,
):
BaseReplicationStreamProtocol.__init__(self, clock)
self.client_name = client_name