Fix stream token ordering

This commit is contained in:
Mark Haines 2015-01-13 14:14:21 +00:00
parent 38e3241eb7
commit 895fcb377e

View file

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