Make it possible to tell paramiko to not record new host keys, which can be slow…

Make it possible to tell paramiko to not record new host keys, which can be slow with a large number of hosts.
-c ssh is preferred in most cases if you have ControlPersist available, otherwise if you are comfortable you
can turn off recording while leaving host key checking on, etc.

examples/ansible.cfg

@@ -94,7 +94,11 @@ filter_plugins     = /usr/share/ansible_plugins/filter_plugins
 
 [paramiko_connection]
 
-# nothing to configure yet
+# uncomment this line to cause the paramiko connection plugin to not record new host
+# keys encountered.  Increases performance.  Setting works independently of the
+# host key checking setting above.
+
+#record_host_keys=False
 
 [ssh_connection]
 

lib/ansible/constants.py

@@ -126,7 +126,8 @@ DEFAULT_LOG_PATH               = shell_expand_path(get_config(p, DEFAULTS, 'log_
 
 ANSIBLE_NOCOWS                 = get_config(p, DEFAULTS, 'nocows', 'ANSIBLE_NOCOWS', None)
 ANSIBLE_SSH_ARGS               = get_config(p, 'ssh_connection', 'ssh_args', 'ANSIBLE_SSH_ARGS', None)
-ZEROMQ_PORT                    = int(get_config(p, 'fireball', 'zeromq_port', 'ANSIBLE_ZEROMQ_PORT', 5099))
+PARAMIKO_RECORD_HOST_KEYS      = get_config(p, 'paramiko_connection', 'record_host_keys', 'ANSIBLE_PARAMIKO_RECORD_HOST_KEYS', True, boolean=True)
+ZEROMQ_PORT                    = int(get_config(p, 'fireball_connection', 'zeromq_port', 'ANSIBLE_ZEROMQ_PORT', 5099))
 
 HOST_KEY_CHECKING              = get_config(p, DEFAULTS, 'host_key_checking',  'ANSIBLE_HOST_KEY_CHECKING',    True, boolean=True)
 

lib/ansible/runner/connection_plugins/paramiko_ssh.py

@@ -303,9 +303,14 @@ class Connection(object):
         if self.sftp is not None:
             self.sftp.close()
 
-        if self._any_keys_added():
+        if C.PARAMIKO_RECORD_HOST_KEYS and self._any_keys_added():
+
             # add any new SSH host keys -- warning -- this could be slow
             lockfile = self.keyfile.replace("known_hosts",".known_hosts.lock") 
+            dirname = os.path.dirname(self.keyfile)
+            if not os.path.exists(dirname):
+                os.makedirs(dirname)
+
             KEY_LOCK = open(lockfile, 'w')
             fcntl.lockf(KEY_LOCK, fcntl.LOCK_EX)
             try: