class Communicator(object):
'''
Communicator talks to the client and receives commands from the client
in terms of HTTP GET, PUT and DETELE verbs.
Uses the HEAD verb as a control channel signaling the nodes to perform clean ups,
remove dead peers from the key ring etc
see utils package for sample standalone commands
'''
base_file_path = os.path.abspath('.')
#------------------------------------------------------------------------------
# Logging setup
#------------------------------------------------------------------------------
logger = LogHelper.getLogger()
def __init__(self, config):
'''
Constructor
'''
#=======================================================================
# By this time, topology has configured itself based on the config file
# or the defaults
#=======================================================================
self.config = config
self.topology = Topology(config)
self.cache = Cache(reconstruct=self.config.local_reconstruct)
self.logger.info('setup up communicator for node: ' + str(self.config.node_id) + '\n')
def GET(self, key, origin='client'):
if origin == 'client':
self.logger.info("Request from client")
else:
if str(origin) == self.config.node_address:
self.logger.error("Houston, we have a problem. Cycle detected. Have to fail...")
return None
node = self.topology.key_manager.get_node(key)
# for node in node_gen:
self.logger.info("Key requested: " + key)
self.logger.info("Node responsible: " + node)
if node == self.config.node_address: #we are responsible for fetching this key from the cache
return self.cache.fetch(key)
else: #tell our peer to handle this key
return self.topology.instructPeer(node, 'GET', cherrypy.serving.request.path_info) #TODO change faux get/post to auto route
#else:
#===============================================================================
# ideally there should be a for loop at the commented for node in node_gen where node_gen
# is a generator that loops over the set of possible peers
# need to figure out a way to update underlying datastructure over which the generator rotates
# this is against the laws of a generator, so will have to think of some other clever trick.
# This means the node we contacted was down. It was removed from the key ring
# since node_gen is a generator, we will sping until we hit next node who will
# assume responsibility for this key
#===============================================================================
def PUT(self, key, value, origin='client'):
if origin == 'client':
self.logger.info("Request from client")
else:
if str(origin) == self.config.node_address:
self.logger.error("Houston, we have a problem. Cycle detected. Have to fail...")
return None
node = self.topology.key_manager.get_node(key)
# for node in node_gen:
if node == self.config.node_address: #we are responsible for storing this key in the cache
#also forward the request to mirrors
print "mirroring"
self.topology.mirror('PUT', cherrypy.serving.request.path_info)
return self.cache.store(key, value)
else: #tell our peer to handle this key
return self.topology.instructPeer(node, 'PUT', cherrypy.serving.request.path_info) #TODO change faux get/post to auto route
#===============================================================================
# This means the node we contacted was down. It was removed from the key ring
# since node_gen is a generator, we will sping until we hit next node who will
# assume responsibility for this key
#===============================================================================
def DELETE(self, key, origin='client'):
if origin == 'client':
self.logger.info("Request from Client")
else:
if str(origin) == self.config.node_address:
self.logger.error("Houston, we have a problem. Cycle detected. Have to fail...")
return None
node = self.topology.key_manager.get_node(key)
if node == self.config.node_address: #we are responsible for deleting this key from the cache
#also forward the request to mirrors
self.topology.mirror('DELETE', cherrypy.serving.request.path_info)
return self.cache.erase(key)
else: #tell our peer to handle this key
return self.topology.instructPeer(node, 'DELETE', cherrypy.serving.request.path_info) #TODO change faux get/post to auto route
def HEAD(self, key=None, value=None):
print "head called"
print key
print value
if key is None:
#===================================================================
# This is a simple heartbeat check, do nothing
#===================================================================
return "alive"
if not isinstance(key, NoneType) and not isinstance(value, NoneType):
if key == 'connect':
self.topology.connect(value)
elif key == 'dead':
print '%s is dead' % value
self.topology.key_manager.remove_node(value)
elif not isinstance(key, NoneType) and key == 'reconstruct':
#===================================================================
# Need to work on this functionality
#===================================================================
self.cache.data_map = self.cache.diskCache.reconstruct() or LRUDict()
#===============================================================================
# Need to tell the CherryPy engine to expose this class as a web-servlet definition
#===============================================================================
exposed = True
