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Limit the number of events that can be created on a given room concurrently #1620
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| max_count(int): The maximum number of concurrent access | ||
| """ | ||
| self.max_count = max_count | ||
| self.key_to_defer = {} |
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# key_to_defer is a map from the key to a 2 element list where
# the first element is the number of things executing
# the second element is a list of deferreds for the things blocked from executing.
| def queue(self, key): | ||
| entry = self.key_to_defer.setdefault(key, [0, []]) | ||
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| if entry[0] >= self.max_count: |
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# If the number of things executing is greater than the maximum
# then add a deferred to the list of blocked items
# When one of the things currently executing finishes it will callback
# this item so that it can continue executing.
| def _ctx_manager(): | ||
| try: | ||
| yield | ||
| finally: |
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# We've finished executing so check if there are any things blocked waiting to execute and start one of them
| try: | ||
| entry[1].pop(0).callback(None) | ||
| except IndexError: | ||
| if entry[0] == 0: |
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# If nothing else is executing for this key then remove it from the map
| if builder.type == EventTypes.Member: | ||
| membership = builder.content.get("membership", None) | ||
| target = UserID.from_string(builder.state_key) | ||
| with (yield self.limiter.queue(builder.room_id)): |
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# Restrict the number of events that can happen concurrently in a room.
# Otherwise synapse may try to add many event simultaneously, forking the room state and making state resolution more expensive
# See (link to github issue) for more information.
| @@ -50,6 +50,8 @@ def __init__(self, hs): | |||
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| self.pagination_lock = ReadWriteLock() | |||
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| self.limiter = Limiter(max_count=5) | |||
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Comment on the choice of 5 here.
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It'd be totes awesome to have some metrics on the total number of blocked and executing things for each limiter. |
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LGTM apart from the missing comments |
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