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Do not try to store invalid data in the stats table #8226

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Sep 2, 2020
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Do not try to store invalid data in the stats table #8226

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3329c8f
Do not try to store stats information of invalid data.
clokep Sep 1, 2020
e1cbf94
Fix newsfragment #.
clokep Sep 1, 2020
228b715
Remove some spacing in the changelog.
clokep Sep 1, 2020
8005dbb
Update comments.
clokep Sep 1, 2020
a592557
Do not adding missing fields.
clokep Sep 1, 2020
a2ab4c7
Allow None values to pass through.
clokep Sep 1, 2020
94e8a18
Fix tense in the changelog.
clokep Sep 1, 2020
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1 change: 1 addition & 0 deletions changelog.d/8226.bugfix
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@@ -0,0 +1 @@
Fixes a longstanding bug where stats updates could break when unexpected profile data was included in events.
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5 changes: 3 additions & 2 deletions synapse/storage/databases/main/stats.py
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Expand Up @@ -231,7 +231,8 @@ async def update_room_state(self, room_id: str, fields: Dict[str, Any]) -> None:
"""

# For whatever reason some of the fields may contain null bytes, which
# postgres isn't a fan of, so we replace those fields with null.
# postgres isn't a fan of, or be an unexpected type. Replace those
# fields with null.
for col in (
"join_rules",
"history_visibility",
Expand All @@ -242,7 +243,7 @@ async def update_room_state(self, room_id: str, fields: Dict[str, Any]) -> None:
"canonical_alias",
):
field = fields.get(col)
if field and "\0" in field:
if not isinstance(field, str) or "\0" in field:
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I'm not sure if it matters, but this changes the behaviour of fields that do not exist or are NULL.

Before, they would not be part of an upsert — now they will be upserted to NULL.

Is this fine? I get a funny feeling it may not be.

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Yes, I think this would violate the assumption that seems to be part of

synapse/synapse/handlers/stats.py

Line 297 in b5133dd

await self.store.update_room_state(room_id, state)
; I believe it will give you a dict only populated with the fields that have changed.

I must apologise for the lack of docstring which makes it clear, though it also looks like I inherited this function..?

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Ah, I was assuming that the dictionary would include strings or None for all fields, but you're 100% correct that this does slightly change the behavior!

In the case of invalid data, does upserting with None make sense?

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The code as-is will never "clear" a value (e.g. if topic goes from "foo" -> None it will be stale and stay at "foo" forever). I'm unsure if this is correct behavior.

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The code as-is will never "clear" a value (e.g. if topic goes from "foo" -> None it will be stale and stay at "foo" forever). I'm unsure if this is correct behavior.

I guess I didn't think too hard about unsetting topics; can you do that, or would it be empty string? (not that empty string was properly handled to begin with, by the looks)...

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I think upserting with None when you get invalid data is fine, if that corresponds with the interpretation that clients, etc are meant to have.

If you get a history_visibility entry with an invalid value, what happens? Stays the same, or resets to some 'default' value? I suppose that is ultimately what might guide us here.

(Though this isn't used for any important information other than the room directory really, so as long as it always leads to a 'safer' outcome I suppose it's fine; e.g. not revealing private rooms in the public room list even if they have sent nonsense visibility and join rule state events)...

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I pushed some changes which should stop overriding data that wasn't submitted. I also fixed the issue of being unable to submit None values into the method. I'm not 100% sure that's correct or not though.

fields[col] = None

await self.db_pool.simple_upsert(
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