Fix stream token ordering
This commit is contained in:
Mark Haines
parent
38e3241eb7
commit
895fcb377e
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@ -39,6 +39,8 @@ from ._base import SQLBaseStore
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from synapse.api.errors import SynapseError
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from synapse.util.logutils import log_function
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from collections import namedtuple
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import logging
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@ -52,58 +54,76 @@ _STREAM_TOKEN = "stream"
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_TOPOLOGICAL_TOKEN = "topological"
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def _parse_stream_token(string):
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try:
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if string[0] != 's':
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raise
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return int(string[1:])
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except:
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raise SynapseError(400, "Invalid token")
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class _StreamToken(namedtuple("_StreamToken", "topological stream")):
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"""Tokens are positions between events. The token "s1" comes after event 1.
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s0 s1
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| |
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[0] V [1] V [2]
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def _parse_topological_token(string):
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try:
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if string[0] != 't':
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raise
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parts = string[1:].split('-', 1)
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return (int(parts[0]), int(parts[1]))
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except:
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raise SynapseError(400, "Invalid token")
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Tokens can either be a point in the live event stream or a cursor going
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through historic events.
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When traversing the live event stream events are ordered by when they
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arrived at the homeserver.
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def is_stream_token(string):
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try:
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_parse_stream_token(string)
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return True
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except:
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return False
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When traversing historic events the events are ordered by their depth in
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the event graph "topological_ordering" and then by when they arrived at the
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homeserver "stream_ordering".
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Live tokens start with an "s" followed by the "stream_ordering" id of the
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event it comes after. Historic tokens start with a "t" followed by the
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"topological_ordering" id of the event it comes after, follewed by "-",
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followed by the "stream_ordering" id of the event it comes after.
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"""
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__slots__ = []
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def is_topological_token(string):
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try:
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_parse_topological_token(string)
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return True
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except:
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return False
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@classmethod
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def parse(cls, string):
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try:
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if string[0] == 's':
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return cls(None, int(string[1:]))
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if string[0] == 't':
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parts = string[1:].split('-', 1)
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return cls(int(parts[1]), int(parts[0]))
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except:
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pass
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raise SynapseError(400, "Invalid token %r" % (string,))
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@classmethod
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def parse_stream_token(cls, string):
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try:
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if string[0] == 's':
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return cls(None, int(string[1:]))
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except:
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pass
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raise SynapseError(400, "Invalid token %r" % (string,))
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def _get_token_bound(token, comparison):
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try:
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s = _parse_stream_token(token)
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return "%s %s %d" % ("stream_ordering", comparison, s)
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except:
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pass
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def __str__(self):
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if self.topological is not None:
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return "t%d-%d" % (self.topological, self.stream)
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else:
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return "s%d" % (self.stream,)
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try:
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top, stream = _parse_topological_token(token)
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return "%s %s %d AND %s %s %d" % (
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"topological_ordering", comparison, top,
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"stream_ordering", comparison, stream,
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)
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except:
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pass
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def lower_bound(self):
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if self.topological is None:
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return "(%d < %s)" % (self.stream, "stream_ordering")
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else:
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return "(%d < %s OR (%d == %s AND %d < %s))" % (
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self.topological, "topological_ordering",
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self.topological, "topological_ordering",
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self.stream, "stream_ordering",
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)
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raise SynapseError(400, "Invalid token")
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def upper_bound(self):
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if self.topological is None:
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return "(%d >= %s)" % (self.stream, "stream_ordering")
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else:
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return "(%d > %s OR (%d == %s AND %d >= %s))" % (
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self.topological, "topological_ordering",
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self.topological, "topological_ordering",
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self.stream, "stream_ordering",
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)
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class StreamStore(SQLBaseStore):
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@ -162,8 +182,8 @@ class StreamStore(SQLBaseStore):
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limit = MAX_STREAM_SIZE
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# From and to keys should be integers from ordering.
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from_id = _parse_stream_token(from_key)
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to_id = _parse_stream_token(to_key)
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from_id = _StreamToken.parse_stream_token(from_key)
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to_id = _StreamToken.parse_stream_token(to_key)
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if from_key == to_key:
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return defer.succeed(([], to_key))
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@ -181,7 +201,7 @@ class StreamStore(SQLBaseStore):
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}
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def f(txn):
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txn.execute(sql, (user_id, user_id, from_id, to_id,))
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txn.execute(sql, (user_id, user_id, from_id.stream, to_id.stream,))
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rows = self.cursor_to_dict(txn)
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@ -211,17 +231,21 @@ class StreamStore(SQLBaseStore):
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# Tokens really represent positions between elements, but we use
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# the convention of pointing to the event before the gap. Hence
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# we have a bit of asymmetry when it comes to equalities.
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from_comp = '<=' if direction == 'b' else '>'
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to_comp = '>' if direction == 'b' else '<='
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order = "DESC" if direction == 'b' else "ASC"
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args = [room_id]
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bounds = _get_token_bound(from_key, from_comp)
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if to_key:
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bounds = "%s AND %s" % (
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bounds, _get_token_bound(to_key, to_comp)
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)
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if direction == 'b':
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order = "DESC"
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bounds = _StreamToken.parse(from_key).upper_bound()
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if to_key:
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bounds = "%s AND %s" % (
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bounds, _StreamToken.parse(to_key).lower_bound()
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)
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else:
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order = "ASC"
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bounds = _StreamToken.parse(from_key).lower_bound()
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if to_key:
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bounds = "%s AND %s" % (
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bounds, _StreamToken.parse(to_key).upper_bound()
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)
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if int(limit) > 0:
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args.append(int(limit))
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@ -249,9 +273,13 @@ class StreamStore(SQLBaseStore):
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topo = rows[-1]["topological_ordering"]
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toke = rows[-1]["stream_ordering"]
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if direction == 'b':
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topo -= 1
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# Tokens are positions between events.
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# This token points *after* the last event in the chunk.
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# We need it to point to the event before it in the chunk
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# when we are going backwards so we subtract one from the
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# stream part.
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toke -= 1
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next_token = "t%s-%s" % (topo, toke)
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next_token = str(_StreamToken(topo, toke))
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else:
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# TODO (erikj): We should work out what to do here instead.
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next_token = to_key if to_key else from_key
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@ -284,13 +312,14 @@ class StreamStore(SQLBaseStore):
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rows.reverse() # As we selected with reverse ordering
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if rows:
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# XXX: Always subtract 1 since the start token always goes
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# backwards (parity with paginate_room_events). It isn't
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# obvious that this is correct; we should clarify the algorithm
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# used here.
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topo = rows[0]["topological_ordering"] - 1
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# Tokens are positions between events.
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# This token points *after* the last event in the chunk.
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# We need it to point to the event before it in the chunk
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# since we are going backwards so we subtract one from the
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# stream part.
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topo = rows[0]["topological_ordering"]
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toke = rows[0]["stream_ordering"] - 1
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start_token = "t%s-%s" % (topo, toke)
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start_token = str(_StreamToken(topo, toke))
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token = (start_token, end_token)
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else:
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