when we're talking about backfilling data in federation, call it backfilling - not pagination.
This commit is contained in:
Matthew Hodgson
parent
f729f13735
commit
59dfbaba3b
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@ -24,7 +24,7 @@ Where the bottom (the transport layer) is what talks to the internet via HTTP, a
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* duplicate pdu_id's - i.e., it makes sure we ignore them.
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* responding to requests for a given pdu_id
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* responding to requests for all metadata for a given context (i.e. room)
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* handling incoming pagination requests
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* handling incoming backfill requests
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So it has to parse incoming messages to discover which are metadata and which aren't, and has to correctly clobber existing metadata where appropriate.
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@ -155,9 +155,9 @@ To fetch all the state of a given context:
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PDUs that encode the state.
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To paginate events on a given context:
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To backfill events on a given context:
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GET .../paginate/:context/
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GET .../backfill/:context/
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Query args: v, limit
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Response: JSON encoding of a single Transaction containing multiple PDUs
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@ -1,11 +1,11 @@
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Versioning is, like, hard for paginating backwards because of the number of Home Servers involved.
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Versioning is, like, hard for backfilling backwards because of the number of Home Servers involved.
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The way we solve this is by doing versioning as an acyclic directed graph of PDUs. For pagination purposes, this is done on a per context basis.
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The way we solve this is by doing versioning as an acyclic directed graph of PDUs. For backfilling purposes, this is done on a per context basis.
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When we send a PDU we include all PDUs that have been received for that context that hasn't been subsequently listed in a later PDU. The trivial case is a simple list of PDUs, e.g. A <- B <- C. However, if two servers send out a PDU at the same to, both B and C would point at A - a later PDU would then list both B and C.
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Problems with opaque version strings:
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- How do you do clustering without mandating that a cluster can only have one transaction in flight to a given remote home server at a time.
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If you have multiple transactions sent at once, then you might drop one transaction, receive anotherwith a version that is later than the dropped transaction and which point ARGH WE LOST A TRANSACTION.
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- How do you do pagination? A version string defines a point in a stream w.r.t. a single home server, not a point in the context.
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If you have multiple transactions sent at once, then you might drop one transaction, receive another with a version that is later than the dropped transaction and which point ARGH WE LOST A TRANSACTION.
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- How do you do backfilling? A version string defines a point in a stream w.r.t. a single home server, not a point in the context.
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We only need to store the ends of the directed graph, we DO NOT need to do the whole one table of nodes and one of edges.
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@ -104,12 +104,12 @@ class InputOutput(object):
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#self.print_line("OK.")
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return
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m = re.match("^paginate (\S+)$", line)
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m = re.match("^backfill (\S+)$", line)
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if m:
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# we want to paginate a room
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# we want to backfill a room
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room_name, = m.groups()
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self.print_line("paginate %s" % room_name)
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self.server.paginate(room_name)
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self.print_line("backfill %s" % room_name)
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self.server.backfill(room_name)
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return
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self.print_line("Unrecognized command")
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@ -307,7 +307,7 @@ class HomeServer(ReplicationHandler):
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except Exception as e:
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logger.exception(e)
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def paginate(self, room_name, limit=5):
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def backfill(self, room_name, limit=5):
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room = self.joined_rooms.get(room_name)
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if not room:
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@ -315,7 +315,7 @@ class HomeServer(ReplicationHandler):
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dest = room.oldest_server
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return self.replication_layer.paginate(dest, room_name, limit)
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return self.replication_layer.backfill(dest, room_name, limit)
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def _get_room_remote_servers(self, room_name):
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return [i for i in self.joined_rooms.setdefault(room_name,).servers]
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@ -75,8 +75,8 @@ class FederationEventHandler(object):
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@log_function
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@defer.inlineCallbacks
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def backfill(self, room_id, limit):
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# TODO: Work out which destinations to ask for pagination
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# self.replication_layer.paginate(dest, room_id, limit)
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# TODO: Work out which destinations to ask for backfill
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# self.replication_layer.backfill(dest, room_id, limit)
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pass
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@log_function
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@ -114,14 +114,14 @@ class PduActions(object):
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@defer.inlineCallbacks
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@log_function
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def paginate(self, context, pdu_list, limit):
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def backfill(self, context, pdu_list, limit):
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""" For a given list of PDU id and origins return the proceeding
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`limit` `Pdu`s in the given `context`.
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Returns:
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Deferred: Results in a list of `Pdu`s.
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"""
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results = yield self.store.get_pagination(
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results = yield self.store.get_backfill(
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context, pdu_list, limit
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)
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@ -131,7 +131,7 @@ class PduActions(object):
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def is_new(self, pdu):
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""" When we receive a `Pdu` from a remote home server, we want to
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figure out whether it is `new`, i.e. it is not some historic PDU that
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we haven't seen simply because we haven't paginated back that far.
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we haven't seen simply because we haven't backfilled back that far.
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Returns:
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Deferred: Results in a `bool`
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@ -118,7 +118,7 @@ class ReplicationLayer(object):
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*Note:* The home server should always call `send_pdu` even if it knows
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that it does not need to be replicated to other home servers. This is
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in case e.g. someone else joins via a remote home server and then
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paginates.
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backfills.
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TODO: Figure out when we should actually resolve the deferred.
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@ -179,13 +179,13 @@ class ReplicationLayer(object):
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@defer.inlineCallbacks
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@log_function
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def paginate(self, dest, context, limit):
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def backfill(self, dest, context, limit):
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"""Requests some more historic PDUs for the given context from the
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given destination server.
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Args:
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dest (str): The remote home server to ask.
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context (str): The context to paginate back on.
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context (str): The context to backfill.
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limit (int): The maximum number of PDUs to return.
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Returns:
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@ -193,16 +193,16 @@ class ReplicationLayer(object):
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"""
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extremities = yield self.store.get_oldest_pdus_in_context(context)
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logger.debug("paginate extrem=%s", extremities)
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logger.debug("backfill extrem=%s", extremities)
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# If there are no extremeties then we've (probably) reached the start.
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if not extremities:
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return
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transaction_data = yield self.transport_layer.paginate(
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transaction_data = yield self.transport_layer.backfill(
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dest, context, extremities, limit)
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logger.debug("paginate transaction_data=%s", repr(transaction_data))
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logger.debug("backfill transaction_data=%s", repr(transaction_data))
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transaction = Transaction(**transaction_data)
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@ -281,9 +281,9 @@ class ReplicationLayer(object):
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@defer.inlineCallbacks
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@log_function
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def on_paginate_request(self, context, versions, limit):
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def on_backfill_request(self, context, versions, limit):
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pdus = yield self.pdu_actions.paginate(context, versions, limit)
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pdus = yield self.pdu_actions.backfill(context, versions, limit)
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defer.returnValue((200, self._transaction_from_pdus(pdus).get_dict()))
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@ -427,7 +427,7 @@ class ReplicationLayer(object):
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# Get missing pdus if necessary.
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is_new = yield self.pdu_actions.is_new(pdu)
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if is_new and not pdu.outlier:
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# We only paginate backwards to the min depth.
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# We only backfill backwards to the min depth.
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min_depth = yield self.store.get_min_depth_for_context(pdu.context)
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if min_depth and pdu.depth > min_depth:
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@ -112,7 +112,7 @@ class TransportLayer(object):
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return self._do_request_for_transaction(destination, subpath)
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@log_function
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def paginate(self, dest, context, pdu_tuples, limit):
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def backfill(self, dest, context, pdu_tuples, limit):
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""" Requests `limit` previous PDUs in a given context before list of
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PDUs.
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@ -126,14 +126,14 @@ class TransportLayer(object):
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Deferred: Results in a dict received from the remote homeserver.
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"""
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logger.debug(
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"paginate dest=%s, context=%s, pdu_tuples=%s, limit=%s",
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"backfill dest=%s, context=%s, pdu_tuples=%s, limit=%s",
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dest, context, repr(pdu_tuples), str(limit)
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)
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if not pdu_tuples:
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return
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subpath = "/paginate/%s/" % context
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subpath = "/backfill/%s/" % context
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args = {"v": ["%s,%s" % (i, o) for i, o in pdu_tuples]}
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args["limit"] = limit
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@ -251,8 +251,8 @@ class TransportLayer(object):
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self.server.register_path(
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"GET",
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re.compile("^" + PREFIX + "/paginate/([^/]*)/$"),
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lambda request, context: self._on_paginate_request(
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re.compile("^" + PREFIX + "/backfill/([^/]*)/$"),
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lambda request, context: self._on_backfill_request(
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context, request.args["v"],
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request.args["limit"]
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)
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@ -352,7 +352,7 @@ class TransportLayer(object):
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defer.returnValue(data)
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@log_function
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def _on_paginate_request(self, context, v_list, limits):
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def _on_backfill_request(self, context, v_list, limits):
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if not limits:
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return defer.succeed(
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(400, {"error": "Did not include limit param"})
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@ -362,7 +362,7 @@ class TransportLayer(object):
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versions = [v.split(",", 1) for v in v_list]
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return self.request_handler.on_paginate_request(
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return self.request_handler.on_backfill_request(
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context, versions, limit)
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@ -371,14 +371,14 @@ class TransportReceivedHandler(object):
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"""
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def on_incoming_transaction(self, transaction):
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""" Called on PUT /send/<transaction_id>, or on response to a request
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that we sent (e.g. a pagination request)
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that we sent (e.g. a backfill request)
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Args:
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transaction (synapse.transaction.Transaction): The transaction that
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was sent to us.
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Returns:
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twisted.internet.defer.Deferred: A deferred that get's fired when
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twisted.internet.defer.Deferred: A deferred that gets fired when
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the transaction has finished being processed.
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The result should be a tuple in the form of
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@ -438,14 +438,14 @@ class TransportRequestHandler(object):
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def on_context_state_request(self, context):
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""" Called on GET /state/<context>/
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Get's hit when someone wants all the *current* state for a given
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Gets hit when someone wants all the *current* state for a given
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contexts.
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Args:
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context (str): The name of the context that we're interested in.
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Returns:
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twisted.internet.defer.Deferred: A deferred that get's fired when
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twisted.internet.defer.Deferred: A deferred that gets fired when
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the transaction has finished being processed.
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The result should be a tuple in the form of
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@ -457,20 +457,20 @@ class TransportRequestHandler(object):
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"""
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pass
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def on_paginate_request(self, context, versions, limit):
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""" Called on GET /paginate/<context>/?v=...&limit=...
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def on_backfill_request(self, context, versions, limit):
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""" Called on GET /backfill/<context>/?v=...&limit=...
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Get's hit when we want to paginate backwards on a given context from
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Gets hit when we want to backfill backwards on a given context from
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the given point.
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Args:
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context (str): The context to paginate on
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versions (list): A list of 2-tuple's representing where to paginate
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context (str): The context to backfill
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versions (list): A list of 2-tuples representing where to backfill
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from, in the form `(pdu_id, origin)`
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limit (int): How many pdus to return.
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Returns:
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Deferred: Resultsin a tuple in the form of
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Deferred: Results in a tuple in the form of
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`(response_code, respond_body)`, where `response_body` is a python
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dict that will get serialized to JSON.
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@ -168,7 +168,7 @@ class PduStore(SQLBaseStore):
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return self._get_pdu_tuples(txn, txn.fetchall())
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def get_pagination(self, context, pdu_list, limit):
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def get_backfill(self, context, pdu_list, limit):
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"""Get a list of Pdus for a given topic that occured before (and
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including) the pdus in pdu_list. Return a list of max size `limit`.
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@ -182,12 +182,12 @@ class PduStore(SQLBaseStore):
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list: A list of PduTuples
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"""
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return self._db_pool.runInteraction(
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self._get_paginate, context, pdu_list, limit
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self._get_backfill, context, pdu_list, limit
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)
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def _get_paginate(self, txn, context, pdu_list, limit):
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def _get_backfill(self, txn, context, pdu_list, limit):
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logger.debug(
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"paginate: %s, %s, %s",
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"backfill: %s, %s, %s",
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context, repr(pdu_list), limit
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)
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@ -213,7 +213,7 @@ class PduStore(SQLBaseStore):
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new_front = []
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for pdu_id, origin in front:
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logger.debug(
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"_paginate_interaction: i=%s, o=%s",
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"_backfill_interaction: i=%s, o=%s",
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pdu_id, origin
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)
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@ -224,7 +224,7 @@ class PduStore(SQLBaseStore):
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for row in txn.fetchall():
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logger.debug(
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"_paginate_interaction: got i=%s, o=%s",
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"_backfill_interaction: got i=%s, o=%s",
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*row
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)
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new_front.append(row)
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@ -262,7 +262,7 @@ class PduStore(SQLBaseStore):
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def update_min_depth_for_context(self, context, depth):
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"""Update the minimum `depth` of the given context, which is the line
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where we stop paginating backwards on.
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on which we stop backfilling backwards.
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Args:
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context (str)
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@ -320,9 +320,9 @@ class PduStore(SQLBaseStore):
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return [(row[0], row[1], row[2]) for row in results]
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def get_oldest_pdus_in_context(self, context):
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"""Get a list of Pdus that we paginated beyond yet (and haven't seen).
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This list is used when we want to paginate backwards and is the list we
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send to the remote server.
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"""Get a list of Pdus that we haven't backfilled beyond yet (and haven't
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seen). This list is used when we want to backfill backwards and is the
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list we send to the remote server.
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Args:
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txn
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