Fix handling of connection timeouts in outgoing http requests (#8400)

* Remove `on_timeout_cancel` from `timeout_deferred`

The `on_timeout_cancel` param to `timeout_deferred` wasn't always called on a
timeout (in particular if the canceller raised an exception), so it was
unreliable. It was also only used in one place, and to be honest it's easier to
do what it does a different way.

* Fix handling of connection timeouts in outgoing http requests

Turns out that if we get a timeout during connection, then a different
exception is raised, which wasn't always handled correctly.

To fix it, catch the exception in SimpleHttpClient and turn it into a
RequestTimedOutError (which is already a documented exception).

Also add a description to RequestTimedOutError so that we can see which stage
it failed at.

* Fix incorrect handling of timeouts reading federation responses

This was trapping the wrong sort of TimeoutError, so was never being hit.

The effect was relatively minor, but we should fix this so that it does the
expected thing.

* Fix inconsistent handling of `timeout` param between methods

`get_json`, `put_json` and `delete_json` were applying a different timeout to
the response body to `post_json`; bring them in line and test.

Co-authored-by: Patrick Cloke <clokep@users.noreply.github.com>
Co-authored-by: Erik Johnston <erik@matrix.org>

1 files changed, 43 insertions, 12 deletions

diff --git a/synapse/http/matrixfederationclient.py b/synapse/http/matrixfederationclient.py
index b02c74ab2d..c23a4d7c0c 100644
--- a/synapse/http/matrixfederationclient.py
+++ b/synapse/http/matrixfederationclient.py
@@ -171,7 +171,7 @@ async def _handle_json_response(
         d = timeout_deferred(d, timeout=timeout_sec, reactor=reactor)
 
         body = await make_deferred_yieldable(d)
-    except TimeoutError as e:
+    except defer.TimeoutError as e:
         logger.warning(
             "{%s} [%s] Timed out reading response - %s %s",
             request.txn_id,
@@ -655,10 +655,14 @@ class MatrixFederationHttpClient:
             long_retries (bool): whether to use the long retry algorithm. See
                 docs on _send_request for details.
 
-            timeout (int|None): number of milliseconds to wait for the response headers
-                (including connecting to the server), *for each attempt*.
+            timeout (int|None): number of milliseconds to wait for the response.
                 self._default_timeout (60s) by default.
 
+                Note that we may make several attempts to send the request; this
+                timeout applies to the time spent waiting for response headers for
+                *each* attempt (including connection time) as well as the time spent
+                reading the response body after a 200 response.
+
             ignore_backoff (bool): true to ignore the historical backoff data
                 and try the request anyway.
             backoff_on_404 (bool): True if we should count a 404 response as
@@ -704,8 +708,13 @@ class MatrixFederationHttpClient:
             timeout=timeout,
         )
 
+        if timeout is not None:
+            _sec_timeout = timeout / 1000
+        else:
+            _sec_timeout = self.default_timeout
+
         body = await _handle_json_response(
-            self.reactor, self.default_timeout, request, response, start_ms
+            self.reactor, _sec_timeout, request, response, start_ms
         )
 
         return body
@@ -734,10 +743,14 @@ class MatrixFederationHttpClient:
             long_retries (bool): whether to use the long retry algorithm. See
                 docs on _send_request for details.
 
-            timeout (int|None): number of milliseconds to wait for the response headers
-                (including connecting to the server), *for each attempt*.
+            timeout (int|None): number of milliseconds to wait for the response.
                 self._default_timeout (60s) by default.
 
+                Note that we may make several attempts to send the request; this
+                timeout applies to the time spent waiting for response headers for
+                *each* attempt (including connection time) as well as the time spent
+                reading the response body after a 200 response.
+
             ignore_backoff (bool): true to ignore the historical backoff data and
                 try the request anyway.
 
@@ -801,10 +814,14 @@ class MatrixFederationHttpClient:
             args (dict|None): A dictionary used to create query strings, defaults to
                 None.
 
-            timeout (int|None): number of milliseconds to wait for the response headers
-                (including connecting to the server), *for each attempt*.
+            timeout (int|None): number of milliseconds to wait for the response.
                 self._default_timeout (60s) by default.
 
+                Note that we may make several attempts to send the request; this
+                timeout applies to the time spent waiting for response headers for
+                *each* attempt (including connection time) as well as the time spent
+                reading the response body after a 200 response.
+
             ignore_backoff (bool): true to ignore the historical backoff data
                 and try the request anyway.
 
@@ -840,8 +857,13 @@ class MatrixFederationHttpClient:
             timeout=timeout,
         )
 
+        if timeout is not None:
+            _sec_timeout = timeout / 1000
+        else:
+            _sec_timeout = self.default_timeout
+
         body = await _handle_json_response(
-            self.reactor, self.default_timeout, request, response, start_ms
+            self.reactor, _sec_timeout, request, response, start_ms
         )
 
         return body
@@ -865,10 +887,14 @@ class MatrixFederationHttpClient:
             long_retries (bool): whether to use the long retry algorithm. See
                 docs on _send_request for details.
 
-            timeout (int|None): number of milliseconds to wait for the response headers
-                (including connecting to the server), *for each attempt*.
+            timeout (int|None): number of milliseconds to wait for the response.
                 self._default_timeout (60s) by default.
 
+                Note that we may make several attempts to send the request; this
+                timeout applies to the time spent waiting for response headers for
+                *each* attempt (including connection time) as well as the time spent
+                reading the response body after a 200 response.
+
             ignore_backoff (bool): true to ignore the historical backoff data and
                 try the request anyway.
 
@@ -900,8 +926,13 @@ class MatrixFederationHttpClient:
             ignore_backoff=ignore_backoff,
         )
 
+        if timeout is not None:
+            _sec_timeout = timeout / 1000
+        else:
+            _sec_timeout = self.default_timeout
+
         body = await _handle_json_response(
-            self.reactor, self.default_timeout, request, response, start_ms
+            self.reactor, _sec_timeout, request, response, start_ms
         )
         return body