Implement default timeout for slap communication.

Currently slap library was coded with optimistic assumption, that remote system
are not failing. But in order not to block library caller it is required to
setup timeout on socket operations, with default different than infinity.

slapos/slap/slap.py

@@ -413,13 +413,14 @@ class ConnectionHelper:
 check given master-url argument, and make sure that IPv6 is enabled on \
 your machine and that the server is available. The original error was:"
   def __init__(self, connection_wrapper, host, path, key_file=None,
-      cert_file=None, master_ca_file=None):
+      cert_file=None, master_ca_file=None, timeout=None):
     self.connection_wrapper = connection_wrapper
     self.host = host
     self.path = path
     self.key_file = key_file
     self.cert_file = cert_file
     self.master_ca_file = master_ca_file
+    self.timeout = timeout
 
   def getComputerInformation(self, computer_id):
     self.GET('/getComputerInformation?computer_id=%s' % computer_id)
@@ -437,6 +438,9 @@ your machine and that the server is available. The original error was:"
     self.connection = self.connection_wrapper(**connection_dict)
 
   def GET(self, path):
+    try:
+      default_timeout = socket.getdefaulttimeout()
+      socket.setdefaulttimeout(self.timeout)
       try:
         self.connect()
         self.connection.request('GET', self.path + path)
@@ -455,9 +459,14 @@ your machine and that the server is available. The original error was:"
         message = 'Server responded with wrong code %s with %s' % \
                                            (self.response.status, path)
         raise ServerError(message)
+    finally:
+      socket.setdefaulttimeout(default_timeout)
 
   def POST(self, path, parameter_dict,
       content_type="application/x-www-form-urlencoded"):
+    try:
+      default_timeout = socket.getdefaulttimeout()
+      socket.setdefaulttimeout(self.timeout)
       try:
         self.connect()
         header_dict = {'Content-type': content_type}
@@ -478,18 +487,20 @@ your machine and that the server is available. The original error was:"
         message = 'Server responded with wrong code %s with %s' % \
                                            (self.response.status, path)
         raise ServerError(message)
+    finally:
+      socket.setdefaulttimeout(default_timeout)
 
 class slap:
 
   zope.interface.implements(interface.slap)
 
   def initializeConnection(self, slapgrid_uri, key_file=None, cert_file=None,
-      master_ca_file=None):
+      master_ca_file=None, timeout=60):
     self._initialiseConnectionHelper(slapgrid_uri, key_file, cert_file,
-        master_ca_file)
+        master_ca_file, timeout)
 
   def _initialiseConnectionHelper(self, slapgrid_uri, key_file, cert_file,
-      master_ca_file):
+      master_ca_file, timeout):
     SlapDocument._slapgrid_uri = slapgrid_uri
     scheme, netloc, path, query, fragment = urlparse.urlsplit(
         SlapDocument._slapgrid_uri)
@@ -509,7 +520,7 @@ class slap:
         connection_wrapper = httplib.HTTPSConnection
     slap._connection_helper = \
       SlapDocument._connection_helper = ConnectionHelper(connection_wrapper,
-          netloc, path, key_file, cert_file, master_ca_file)
+          netloc, path, key_file, cert_file, master_ca_file, timeout)
 
   def _register(self, klass, *registration_argument_list):
     if len(registration_argument_list) == 1 and type(