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Handle bad JSON data being returned from the federation API. #9070

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Jan 12, 2021
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Handle bad JSON data being returned from the federation API. #9070

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722d0be
Do not raise errors if non-JSON data is returned.
clokep Jan 11, 2021
e741711
NEwsfragment.
clokep Jan 11, 2021
9007641
Fix tests.
clokep Jan 11, 2021
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1 change: 1 addition & 0 deletions changelog.d/9070.bugfix
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Original file line number Diff line number Diff line change
@@ -0,0 +1 @@
Fix `JSONDecodeError` spamming the logs when sending transactions to remote servers.
10 changes: 10 additions & 0 deletions synapse/http/matrixfederationclient.py
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Expand Up @@ -174,6 +174,16 @@ async def _handle_json_response(
d = timeout_deferred(d, timeout=timeout_sec, reactor=reactor)

body = await make_deferred_yieldable(d)
except ValueError as e:
# The JSON content was invalid.
Comment on lines +177 to +178
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should we not catch JSONDecodeError here?

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Arg, I forget half the time there's a specific error for this. Thank you!

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Ah, so we need to catch ValueError since we manually throw that when doing JSON validation:

synapse/synapse/util/__init__.py

Lines 30 to 32 in b6ca69e

def _reject_invalid_json(val):
"""Do not allow Infinity, -Infinity, or NaN values in JSON."""
raise ValueError("Invalid JSON value: '%s'" % val)

I had looked at raising a JSONDecodeError there, but you don't really have the necessary information, since we don't have the position of what is being parsed.

A couple of options:

  • Leave this as a ValueError
  • Change the error raised by _reject_invalid_json to a custom exception InvalidJsonError (which inherits from ValueError) and catch both here.
  • Raise JSONDecodeError in _reject_invalid_json by giving a dummy position.

What do you think?

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I think I don't feel very strongly. May as well leave it as-is.

logger.warning(
"{%s} [%s] Failed to parse JSON response - %s %s",
request.txn_id,
request.destination,
request.method,
request.uri.decode("ascii"),
)
raise RequestSendFailed(e, can_retry=False) from e
except defer.TimeoutError as e:
logger.warning(
"{%s} [%s] Timed out reading response - %s %s",
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2 changes: 1 addition & 1 deletion tests/http/test_fedclient.py
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Expand Up @@ -560,4 +560,4 @@ def test_json_error(self, return_value):
self.pump()

f = self.failureResultOf(test_d)
self.assertIsInstance(f.value, ValueError)
self.assertIsInstance(f.value, RequestSendFailed)