Add option to have minion retry dns

If name resolution fails when the minion starts, allow the minion
to retry dns resolution after a configurable number of seconds.
Defaults to 30 seconds.

Add retry_dns option to minion config.

conf/minion.template

@@ -10,6 +10,11 @@
 # resolved, then the minion will fail to start.
 #master: salt
 
+# Set the number of seconds to wait before attempting to resolve
+# the master hostname if name resolution fails. Defaults to 30 seconds.
+# Set to zero if the minion should shutdown and not retry.
+# retry_dns: 30
+
 # Set the port used by the master reply and authentication server
 #master_port: 4506
 

salt/__init__.py

@@ -81,6 +81,7 @@ def start(self):
         '''
         Execute this method to start up a minion.
         '''
+        self.daemonize_if_required()
         self.parse_args()
 
         try:
@@ -113,7 +114,6 @@ def start(self):
         # waiting for it, if we daemonize later then the minion could halt
         # the boot process waiting for a key to be accepted on the master.
         # This is the latest safe place to daemonize
-        self.daemonize_if_required()
         try:
             minion = salt.minion.Minion(self.config)
             self.set_pidfile()

salt/config.py

@@ -212,6 +212,7 @@ def minion_config(path):
             'default_include': 'minion.d/*.conf',
             'update_url': False,
             'update_restart_services': [],
+            'retry_dns': 30,
             }
 
     if len(opts['sock_dir']) > len(opts['cachedir']) + 10:
@@ -229,7 +230,8 @@ def minion_config(path):
         opts['id'] = _append_domain(opts)
 
     try:
-        opts['master_ip'] = salt.utils.dns_check(opts['master'], True)
+        opts['master_ip'] = salt.utils.dns_check(opts['master'], True,
+                                                            opts['retry_dns'])
     except SaltClientError:
         opts['master_ip'] = '127.0.0.1'
 

salt/utils/__init__.py

@@ -310,7 +310,7 @@ def gen_mac(prefix='52:54:'):
     return mac[:-1]
 
 
-def dns_check(addr, safe=False):
+def dns_check(addr, safe=False, retry_dns=30):
     '''
     Return the ip resolved by dns, but do not exit on failure, only raise an
     exception.
@@ -325,6 +325,18 @@ def dns_check(addr, safe=False):
             err = ('This master address: \'{0}\' was previously resolvable '
                    'but now fails to resolve! The previously resolved ip addr '
                    'will continue to be used').format(addr)
+            if retry_dns:
+                msg = ('Hostname: \'{0}\' could not be reached.'
+                        'Waiting \'{1}\' seconds and then will try to'
+                        'resolve the name again.').format(addr, retry_dns)
+                import salt.log
+                if salt.log.is_console_configured():
+                    # If logging is not configured it also means that either
+                    # the master or minion instance calling this hasn't even
+                    # started running
+                    logging.getLogger(__name__).error(msg)
+                time.sleep(retry_dns)
+                self.dns_check(addr, safe, retry_dns)
             if safe:
                 import salt.log
                 if salt.log.is_console_configured():