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Refactor request sending to have better excpetions (#4358)

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* Correctly retry and back off if we get a HTTPerror response

* Refactor request sending to have better excpetions

MatrixFederationHttpClient blindly reraised exceptions to the caller
without differentiating "expected" failures (e.g. connection timeouts
etc) versus more severe problems (e.g. programming errors).

This commit adds a RequestSendFailed exception that is raised when
"expected" failures happen, allowing the TransactionQueue to log them as
warnings while allowing us to log other exceptions as actual exceptions.
This commit is contained in:
Erik Johnston 2019-01-08 11:04:28 +00:00 • committed by Richard van der Hoff
parent 1dcb086f33
commit b970cb0e96
6 changed files with 119 additions and 44 deletions
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105
synapse/http/matrixfederationclient.py
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@ -19,7 +19,7 @@ import random
import sys
from io import BytesIO
from six import PY3, string_types
from six import PY3, raise_from, string_types
from six.moves import urllib
import attr
@ -41,6 +41,7 @@ from synapse.api.errors import (
Codes,
FederationDeniedError,
HttpResponseException,
RequestSendFailed,
SynapseError,
)
from synapse.http.endpoint import matrix_federation_endpoint
@ -231,7 +232,7 @@ class MatrixFederationHttpClient(object):
Deferred: resolves with the http response object on success.
Fails with ``HttpResponseException``: if we get an HTTP response
code >= 300.
code >= 300 (except 429).
Fails with ``NotRetryingDestination`` if we are not yet ready
to retry this server.
@ -239,8 +240,8 @@ class MatrixFederationHttpClient(object):
Fails with ``FederationDeniedError`` if this destination
is not on our federation whitelist
(May also fail with plenty of other Exceptions for things like DNS
failures, connection failures, SSL failures.)
Fails with ``RequestSendFailed`` if there were problems connecting to
the remote, due to e.g. DNS failures, connection timeouts etc.
"""
if timeout:
_sec_timeout = timeout / 1000
@ -335,23 +336,74 @@ class MatrixFederationHttpClient(object):
reactor=self.hs.get_reactor(),
)
with Measure(self.clock, "outbound_request"):
response = yield make_deferred_yieldable(
request_deferred,
try:
with Measure(self.clock, "outbound_request"):
response = yield make_deferred_yieldable(
request_deferred,
)
except DNSLookupError as e:
raise_from(RequestSendFailed(e, can_retry=retry_on_dns_fail), e)
except Exception as e:
raise_from(RequestSendFailed(e, can_retry=True), e)
logger.info(
"{%s} [%s] Got response headers: %d %s",
request.txn_id,
request.destination,
response.code,
response.phrase.decode('ascii', errors='replace'),
)
if 200 <= response.code < 300:
pass
else:
# :'(
# Update transactions table?
d = treq.content(response)
d = timeout_deferred(
d,
timeout=_sec_timeout,
reactor=self.hs.get_reactor(),
)
try:
body = yield make_deferred_yieldable(d)
except Exception as e:
# Eh, we're already going to raise an exception so lets
# ignore if this fails.
logger.warn(
"{%s} [%s] Failed to get error response: %s %s: %s",
request.txn_id,
request.destination,
request.method,
url_str,
_flatten_response_never_received(e),
)
body = None
e = HttpResponseException(
response.code, response.phrase, body
)
# Retry if the error is a 429 (Too Many Requests),
# otherwise just raise a standard HttpResponseException
if response.code == 429:
raise_from(RequestSendFailed(e, can_retry=True), e)
else:
raise e
break
except Exception as e:
except RequestSendFailed as e:
logger.warn(
"{%s} [%s] Request failed: %s %s: %s",
request.txn_id,
request.destination,
request.method,
url_str,
_flatten_response_never_received(e),
_flatten_response_never_received(e.inner_exception),
)
if not retry_on_dns_fail and isinstance(e, DNSLookupError):
if not e.can_retry:
raise
if retries_left and not timeout:
@ -376,29 +428,16 @@ class MatrixFederationHttpClient(object):
else:
raise
logger.info(
"{%s} [%s] Got response headers: %d %s",
request.txn_id,
request.destination,
response.code,
response.phrase.decode('ascii', errors='replace'),
)
if 200 <= response.code < 300:
pass
else:
# :'(
# Update transactions table?
d = treq.content(response)
d = timeout_deferred(
d,
timeout=_sec_timeout,
reactor=self.hs.get_reactor(),
)
body = yield make_deferred_yieldable(d)
raise HttpResponseException(
response.code, response.phrase, body
)
except Exception as e:
logger.warn(
"{%s} [%s] Request failed: %s %s: %s",
request.txn_id,
request.destination,
request.method,
url_str,
_flatten_response_never_received(e),
)
raise
defer.returnValue(response)