[bug] fail gracefully when sync fails

With new soledad async api, we need to catch errors using errbacks instead of
catching exceptions explicitelly. This commit fixed the api sync() call to
intercept sync failures, log them, and do not propagate them down the callback
chain.

1 files changed, 15 insertions, 12 deletions

diff --git a/client/src/leap/soledad/client/api.py b/client/src/leap/soledad/client/api.py
index b8409cbe..35b44ac8 100644
--- a/client/src/leap/soledad/client/api.py
+++ b/client/src/leap/soledad/client/api.py
@@ -44,6 +44,7 @@ from u1db.remote.ssl_match_hostname import match_hostname
 from zope.interface import implements
 
 from twisted.python import log
+from twisted.internet import defer
 
 from leap.common.config import get_path_prefix
 
@@ -654,18 +655,20 @@ class Soledad(object):
             return local_gen
 
         sync_url = urlparse.urljoin(self._server_url, 'user-%s' % self.uuid)
-        try:
-            d = self._dbsyncer.sync(
-                sync_url,
-                creds=self._creds, autocreate=False,
-                defer_decryption=defer_decryption)
-
-            d.addCallbacks(on_sync_done, lambda err: log.err(err))
-            return d
-
-        # TODO catch the exception by adding an Errback
-        except Exception as e:
-            logger.error("Soledad exception when syncing: %s" % str(e))
+        d = self._dbsyncer.sync(
+            sync_url,
+            creds=self._creds, autocreate=False,
+            defer_decryption=defer_decryption)
+
+        # prevent sync failures from crashing the app by adding an errback
+        # that logs the failure and does not propagate it down the callback
+        # chain
+        def _errback(failure):
+            log.err(failure)
+            logger.error("Soledad exception when syncing: %s" % str(failure))
+
+        d.addCallbacks(on_sync_done, _errback)
+        return d
 
     def stop_sync(self):
         self._dbsyncer.stop_sync()