Handle (dis|re)connect more appropriately.

This code was reconnecting via ssh on every iteration of the loop,
which is completely unnecessary.  It should use the existing
connection and only reconnect if there was an SSH error when exeuting
a command.  The code should also explicitly close the connection when
its done.

Change-Id: I2545a1ca5e0cd39a8b453445ea25927756b1fd19

reviewstats/utils.py

@@ -122,6 +122,7 @@ def get_changes(projects, ssh_user, ssh_key, only_open=False, stable='',
     client = paramiko.SSHClient()
     client.load_system_host_keys()
     client.set_missing_host_key_policy(paramiko.AutoAddPolicy())
+    connected = False
 
     for project in projects:
         changes = {}
@@ -146,6 +147,8 @@ def get_changes(projects, ssh_user, ssh_key, only_open=False, stable='',
         while True:
             connect_attempts = 3
             for attempt in range(connect_attempts):
+                if connected:
+                    break
                 try:
                     client.connect(server, port=29418,
                                    key_filename=ssh_key,
@@ -161,7 +164,7 @@ def get_changes(projects, ssh_user, ssh_key, only_open=False, stable='',
                             raise
                         time.sleep(3)
                         continue
-                # Connected successfully
+                connected = True
                 break
 
             cmd = ('gerrit query %s --all-approvals --patch-sets '
@@ -176,7 +179,16 @@ def get_changes(projects, ssh_user, ssh_key, only_open=False, stable='',
                 # Get a small set the first time so we can get to checking
                 # againt the cache sooner
                 cmd += ' limit:5'
-            stdin, stdout, stderr = client.exec_command(cmd)
+            try:
+                stdin, stdout, stderr = client.exec_command(cmd)
+            except paramiko.SSHException:
+                try:
+                    client.close()
+                except Exception:
+                    pass
+                connected = False
+                time.sleep(5)
+                continue
             end_of_changes = False
             for l in stdout:
                 new_change = json.loads(l)
@@ -204,6 +216,12 @@ def get_changes(projects, ssh_user, ssh_key, only_open=False, stable='',
 
         all_changes.update(changes)
 
+    if connected:
+        try:
+            client.close()
+        except Exception:
+            pass
+
     # changes used to be a list, but is now a dict.  Convert it back to a list
     # for the sake of not having to change all the code that calls this
     # function (yet, anyway).