Added ClientStorage option to wait for a connection to the server

on start up, with the default being to wait for the server.

The intent was that it should be possible to bring a client up even
if it can't talk to the server, however, this is a little bit risky if
we need to start them both.  Eventually, we need to be the start-up
code be smart enough to wait if we can't serve data requests during
startup, but to proceed if we can.

src/ZEO/ClientStorage.py

@@ -84,7 +84,7 @@
 ##############################################################################
 """Network ZODB storage client
 """
-__version__='$Revision: 1.19 $'[11:-2]
+__version__='$Revision: 1.20 $'[11:-2]
 
 import struct, time, os, socket, string, Sync, zrpc, ClientCache
 import tempfile, Invalidator, ExtensionClass, thread
@@ -117,7 +117,8 @@ class ClientStorage(ExtensionClass.Base, BaseStorage.BaseStorage):
 
     def __init__(self, connection, async=0, storage='1', cache_size=20000000,
                  name='', client='', debug=0, var=None,
-                 min_disconnect_poll=5, max_disconnect_poll=300):
+                 min_disconnect_poll=5, max_disconnect_poll=300,
+                 wait_for_server_on_starup=1):
 
         # Decide whether to use non-temporary files
         client=client or os.environ.get('ZEO_CLIENT','')
@@ -125,6 +126,7 @@ class ClientStorage(ExtensionClass.Base, BaseStorage.BaseStorage):
         self._connection=connection
         self._storage=storage
         self._debug=debug
+        self._wait_for_server_on_starup=wait_for_server_on_starup
 
         self._info={'length': 0, 'size': 0, 'name': 'ZEO Client',
                     'supportsUndo':0, 'supportsVersions': 0,
@@ -194,7 +196,7 @@ class ClientStorage(ExtensionClass.Base, BaseStorage.BaseStorage):
 
     def _startup(self):
 
-        if not self._call.connect():
+        if not self._call.connect(not self._wait_for_server_on_starup):
 
             # If we can't connect right away, go ahead and open the cache
             # and start a separate thread to try and reconnect.