Add support for TCP keep alive in gerritlib

Clients using gerritlib behind NAT/firewall
can be stuck when the NAT/firewall discard
packets belong to the TCP connection after extended
silent periods thinking the connection is dead.

This change allows clients using gerritlib to set
keep alive interval to a non zero value. This will
enable TCP keep alive packets to be sent in
configured intervals keeping the TCP connections alive.

Change-Id: I588706bb51ce41810cd2243f4969763d193d1d55

doc/source/usage.rst

@@ -5,7 +5,7 @@ Usage
 Example usage::
 
     import gerritlib.gerrit as gerrit
-    g = gerrit.Gerrit('gerrit_host', 'username', keyfile='/home/username/.ssh/id_rsa.pub')
+    g = gerrit.Gerrit('gerrit_host', 'username', keyfile='/home/username/.ssh/id_rsa.pub', keep_alive_interval=60)
 
     # manage projects
     g.createProject('test', description='a test project')
@@ -18,4 +18,4 @@ Example usage::
     print(groups)
 
 
-Look at the :doc:`api` for more details.
+Look at the :doc:`api` for more details.

gerritlib/gerrit.py

@@ -40,7 +40,8 @@ class GerritConnection(object):
     log = logging.getLogger("gerrit.GerritConnection")
 
     def __init__(self, username=None, hostname=None, port=29418,
-                 keyfile=None, connection_attempts=-1, retry_delay=5):
+                 keyfile=None, keep_alive=0, connection_attempts=-1,
+                 retry_delay=5):
 
         assert retry_delay >= 0, "Retry delay must be >= 0"
         self.username = username
@@ -49,6 +50,7 @@ class GerritConnection(object):
         self.keyfile = keyfile
         self.connection_attempts = int(connection_attempts)
         self.retry_delay = float(retry_delay)
+        self.keep_alive = keep_alive
 
     def connect(self):
         """Attempts to connect and returns the connected client."""
@@ -85,6 +87,8 @@ class GerritConnection(object):
                                username=self.username,
                                port=self.port,
                                key_filename=self.keyfile)
+                if self.keep_alive:
+                    client.get_transport().set_keepalive(self.keep_alive)
                 return client
             except (IOError, paramiko.SSHException) as e:
                 self.log.exception("Exception connecting to %s:%s",
@@ -108,7 +112,7 @@ class GerritWatcher(threading.Thread):
 
     def __init__(
             self, gerrit, username=None, hostname=None, port=None,
-            keyfile=None, connection_attempts=-1, retry_delay=5):
+            keyfile=None, keep_alive=0, connection_attempts=-1, retry_delay=5):
         """Create a GerritWatcher.
 
         :param gerrit: A GerritConnection instance to pass events to.
@@ -122,6 +126,7 @@ class GerritWatcher(threading.Thread):
             hostname or gerrit.connection.hostname,
             port or gerrit.connection.port,
             keyfile or gerrit.connection.keyfile,
+            keep_alive or gerrit.connection.keep_alive,
             connection_attempts,
             retry_delay
         )
@@ -194,8 +199,10 @@ class GerritWatcher(threading.Thread):
 class Gerrit(object):
     log = logging.getLogger("gerrit.Gerrit")
 
-    def __init__(self, hostname, username, port=29418, keyfile=None):
-        self.connection = GerritConnection(username, hostname, port, keyfile)
+    def __init__(self, hostname, username, port=29418, keyfile=None,
+                 keep_alive_interval=0):
+        self.connection = GerritConnection(username, hostname, port, keyfile,
+                                           keep_alive=keep_alive_interval)
         self.client = None
         self.watcher_thread = None
         self.event_queue = None

test-requirements.txt

@@ -1,4 +1,4 @@
-hacking>=0.5.6,<0.11
+hacking
 sphinx>=1.1.2,<1.2
 python-subunit
 stestr<3.0.0;python_version<'3.5'