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authorErik Johnston <erik@matrix.org>2015-04-27 13:59:37 +0100
committerErik Johnston <erik@matrix.org>2015-04-27 13:59:37 +0100
commit1c82fbd2eb99d689d8fe835eca9f394518e25316 (patch)
tree387651aa71c3cffd4e6e0dde3012636df50db576 /synapse/util
parentAdd note about updating your signing keys (ie. "the auto thing") (diff)
downloadsynapse-1c82fbd2eb99d689d8fe835eca9f394518e25316.tar.xz
Implement create_observer.
`create_observer` takes a deferred and create a new deferred that
*observers* the original deferred. Any callbacks added to the observing
deferred will *not* affect the origin deferred.
Diffstat (limited to 'synapse/util')
-rw-r--r--synapse/util/async.py19
1 files changed, 19 insertions, 0 deletions
diff --git a/synapse/util/async.py b/synapse/util/async.py
index c4fe5d522f..d8febdb90c 100644
--- a/synapse/util/async.py
+++ b/synapse/util/async.py
@@ -32,3 +32,22 @@ def run_on_reactor():
     iteration of the main loop
     """
     return sleep(0)
+
+
+def create_observer(deferred):
+    """Creates a deferred that observes the result or failure of the given
+     deferred *without* affecting the given deferred.
+    """
+    d = defer.Deferred()
+
+    def callback(r):
+        d.callback(r)
+        return r
+
+    def errback(f):
+        d.errback(f)
+        return f
+
+    deferred.addCallbacks(callback, errback)
+
+    return d