From 4084a774a89f0d02406eebda8279c2b8aab89812 Mon Sep 17 00:00:00 2001
From: Erik Johnston <erik@matrix.org>
Date: Wed, 12 Sep 2018 09:59:15 +0100
Subject: [PATCH 1/2] Timeout reading body for outbound HTTP requests

---
 synapse/http/matrixfederationclient.py | 52 ++++++++++++++++++++++----
 1 file changed, 45 insertions(+), 7 deletions(-)

diff --git a/synapse/http/matrixfederationclient.py b/synapse/http/matrixfederationclient.py
index 6a1fc8ca55..f9a1fbf95d 100644
--- a/synapse/http/matrixfederationclient.py
+++ b/synapse/http/matrixfederationclient.py
@@ -280,7 +280,10 @@ class MatrixFederationHttpClient(object):
                 # :'(
                 # Update transactions table?
                 with logcontext.PreserveLoggingContext():
-                    body = yield treq.content(response)
+                    body = yield self._timeout_deferred(
+                        treq.content(response),
+                        timeout,
+                    )
                 raise HttpResponseException(
                     response.code, response.phrase, body
                 )
@@ -394,7 +397,10 @@ class MatrixFederationHttpClient(object):
             check_content_type_is_json(response.headers)
 
         with logcontext.PreserveLoggingContext():
-            body = yield treq.json_content(response)
+            body = yield self._timeout_deferred(
+                treq.json_content(response),
+                timeout,
+            )
         defer.returnValue(body)
 
     @defer.inlineCallbacks
@@ -444,7 +450,10 @@ class MatrixFederationHttpClient(object):
             check_content_type_is_json(response.headers)
 
         with logcontext.PreserveLoggingContext():
-            body = yield treq.json_content(response)
+            body = yield self._timeout_deferred(
+                treq.json_content(response),
+                timeout,
+            )
 
         defer.returnValue(body)
 
@@ -496,7 +505,10 @@ class MatrixFederationHttpClient(object):
             check_content_type_is_json(response.headers)
 
         with logcontext.PreserveLoggingContext():
-            body = yield treq.json_content(response)
+            body = yield self._timeout_deferred(
+                treq.json_content(response),
+                timeout,
+            )
 
         defer.returnValue(body)
 
@@ -543,7 +555,10 @@ class MatrixFederationHttpClient(object):
             check_content_type_is_json(response.headers)
 
         with logcontext.PreserveLoggingContext():
-            body = yield treq.json_content(response)
+            body = yield self._timeout_deferred(
+                treq.json_content(response),
+                timeout,
+            )
 
         defer.returnValue(body)
 
@@ -585,8 +600,10 @@ class MatrixFederationHttpClient(object):
 
         try:
             with logcontext.PreserveLoggingContext():
-                length = yield _readBodyToFile(
-                    response, output_stream, max_size
+                length = yield self._timeout_deferred(
+                    _readBodyToFile(
+                        response, output_stream, max_size
+                    ),
                 )
         except Exception:
             logger.exception("Failed to download body")
@@ -594,6 +611,27 @@ class MatrixFederationHttpClient(object):
 
         defer.returnValue((length, headers))
 
+    def _timeout_deferred(self, deferred, timeout_ms=None):
+        """Times the deferred out after `timeout_ms` ms
+
+        Args:
+            deferred (Deferred)
+            timeout_ms (int|None): Timeout in milliseconds. If None defaults
+                to 60 seconds.
+
+        Returns:
+            Deferred
+        """
+
+        add_timeout_to_deferred(
+            deferred,
+            timeout_ms / 1000. if timeout_ms else 60,
+            self.hs.get_reactor(),
+            cancelled_to_request_timed_out_error,
+        )
+
+        return deferred
+
 
 class _ReadBodyToFileProtocol(protocol.Protocol):
     def __init__(self, stream, deferred, max_size):

From 649c647955dee037e9f7d0d0d81341cac020a901 Mon Sep 17 00:00:00 2001
From: Erik Johnston <erik@matrix.org>
Date: Wed, 12 Sep 2018 10:10:32 +0100
Subject: [PATCH 2/2] Newsfile

---
 changelog.d/3845.bugfix | 1 +
 1 file changed, 1 insertion(+)
 create mode 100644 changelog.d/3845.bugfix

diff --git a/changelog.d/3845.bugfix b/changelog.d/3845.bugfix
new file mode 100644
index 0000000000..5b7e8f1934
--- /dev/null
+++ b/changelog.d/3845.bugfix
@@ -0,0 +1 @@
+Fix outbound requests occasionally wedging, which can result in federation breaking between servers.