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Clean up some logging #6515

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Dec 11, 2019
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Clean up some logging #6515

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1 change: 1 addition & 0 deletions changelog.d/6515.misc
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Original file line number Diff line number Diff line change
@@ -0,0 +1 @@
Clean up some logging when handling incoming events over federation.
37 changes: 19 additions & 18 deletions synapse/handlers/federation.py
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Expand Up @@ -182,7 +182,7 @@ def on_receive_pdu(self, origin, pdu, sent_to_us_directly=False):
room_id = pdu.room_id
event_id = pdu.event_id

logger.info("[%s %s] handling received PDU: %s", room_id, event_id, pdu)
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Why remove the prefixing? I find it quite useful to track how we're processing an event?

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because it's in the logcontext anyway.

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Oh, so it is. I had forgotten the log context isn't the generic request one. Carry on.

logger.info("handling received PDU: %s", pdu)

# We reprocess pdus when we have seen them only as outliers
existing = yield self.store.get_event(
Expand Down Expand Up @@ -278,9 +278,15 @@ def on_receive_pdu(self, origin, pdu, sent_to_us_directly=False):
len(missing_prevs),
)

yield self._get_missing_events_for_pdu(
origin, pdu, prevs, min_depth
)
try:
yield self._get_missing_events_for_pdu(
origin, pdu, prevs, min_depth
)
except Exception as e:
raise Exception(
"Error fetching missing prev_events for %s: %s"
% (event_id, e)
)
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I'd be tempted to not include e and rely on the exception chaining (raise Exception(..) from e).

(I assume we've checked that get_missing_events_for_pdu doesn't raise any expected exceptions.)

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I'd be tempted to not include e and rely on the exception chaining (raise Exception(..) from e).

I tried that. It made for remarkably unreadable errors, not least because the exception chain is epic.

Exception chaining happens by default when you raise an exception from an except block, afaik

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(I assume we've checked that get_missing_events_for_pdu doesn't raise any expected exceptions.)

well: first, I've looked at the places on_receive_pdu is called (ie, the places that might care that we turn one sort of exception into a generic Exception). There are two such places: _handle_queued_pdus, in which all exceptions are treated equally, and get_missing_events_for_pdu (again), which does treat FederationError with code=403 specially.

Then going down through get_missing_events_for_pdu, the only things which might raise a FederationError are federation_client.get_missing_events (which I'm 99% sure doesn't), and on_receive_pdu which, as discussed, filters out such exceptions. So I'm reasonably confident it's not possible for get_missing_events_for_pdu to raise a FederationError with code=403, and therefore this change shouldn't make any difference.


# Update the set of things we've seen after trying to
# fetch the missing stuff
Expand All @@ -292,14 +298,6 @@ def on_receive_pdu(self, origin, pdu, sent_to_us_directly=False):
room_id,
event_id,
)
elif missing_prevs:
logger.info(
"[%s %s] Not recursively fetching %d missing prev_events: %s",
room_id,
event_id,
len(missing_prevs),
shortstr(missing_prevs),
)

if prevs - seen:
# We've still not been able to get all of the prev_events for this event.
Expand Down Expand Up @@ -344,6 +342,12 @@ def on_receive_pdu(self, origin, pdu, sent_to_us_directly=False):
affected=pdu.event_id,
)

logger.info(
"Event %s is missing prev_events: calculating state for a "
"backwards extremity",
event_id,
)

# Calculate the state after each of the previous events, and
# resolve them to find the correct state at the current event.
auth_chains = set()
Expand All @@ -364,10 +368,7 @@ def on_receive_pdu(self, origin, pdu, sent_to_us_directly=False):
# know about
for p in prevs - seen:
logger.info(
"[%s %s] Requesting state at missing prev_event %s",
room_id,
event_id,
p,
"Requesting state at missing prev_event %s", event_id,
)

room_version = yield self.store.get_room_version(room_id)
Expand Down Expand Up @@ -611,8 +612,8 @@ def _get_state_for_room(self, destination, room_id, event_id):
failed_to_fetch = desired_events - event_map.keys()
if failed_to_fetch:
logger.warning(
"Failed to fetch missing state/auth events for %s: %s",
room_id,
"Failed to fetch missing state/auth events for %s %s",
event_id,
failed_to_fetch,
)

Expand Down