def findPred(self, key):
if (self.fingerTable is None or len(self.fingerTable) == 0):
raise ttypes.SystemException(
"No finger table present for this node")
if (key > self.id and key >= self.fingerTable[0].id
and self.fingerTable[0].id < self.id):
#This means key is between the largest node and the smallest node but it is larger than the largest node
return self.node
elif (key < self.id and key <= self.fingerTable[0].id
and self.fingerTable[0].id < self.id):
#this means key is between the largest node and the smallest node but it is smaller than the smallest node
return self.node
elif (key <= self.id or key > self.fingerTable[0].id):
#ask the closest known pred node
predNode = self.closestPred(key)
if (predNode.id != self.id):
#ask the pred node for the actual pred node
transport = TSocket.TSocket(predNode.ip, int(predNode.port))
transport = TTransport.TBufferedTransport(transport)
protocol = TBinaryProtocol.TBinaryProtocol(transport)
client = FileStore.Client(protocol)
transport.open()
pred = client.findPred(key)
transport.close()
return pred
else:
return self.node
else:
return self.node
def writeFile(self, rfile):
'''
Writes the file to the server dictionary, such that filename is key and RFile object is data.
input : RFile rfile
'''
# contentHash is useful in error detecting no use here.
# saving dict{file_name_hash : RFile object} this will be usefull in locating files efficiently
file_name_hash = _hl.sha256(rfile.meta.filename).hexdigest()
test_node = self.findSucc(file_name_hash)
#print("\nin server write : test_node"+str(test_node)+"self.node : "+str(self.node))
#print(test_node == self.node)
if test_node == self.node:
if file_name_hash not in self.dht_files:
#if file already not in memory, save it with version = 0
meta = _tt.RFileMetadata()
meta = rfile.meta
meta.version= 0
meta.contentHash = _hl.sha256(rfile.content).hexdigest()
w_file = _tt.RFile()
w_file.meta = meta
w_file.content = rfile.content
self.dht_files[file_name_hash] = w_file
else:
# else if file already in memory version += 1 amd replace the content
self.dht_files[file_name_hash].meta.version += 1
self.dht_files[file_name_hash].meta.content = rfile.content
# requirements pdf doesn't say this. mention in the documentation
self.dht_files[file_name_hash].meta.contentHash = _hl.sha256(rfile.content).hexdigest()
else:
raise _tt.SystemException(message="Server : "+str(self.node)+" doesn't own this file id.")
def findPred(self, file_id):
'''
returns the preceding node of the node which keeps the file_id.
input : sha256(file_name) file_id
output: NodeID n
'''
if not self.node_list:
raise _tt.SystemException(message="Fingertable not set for the server : "+str(self.node))
# comparison between strings work(sha256().hexdigest()), check again with more examples.
#print("\nin pred : "+str(self.node)+"\n\n")
if self.node.id > self.node_list[0].id:
if file_id > self.node.id or file_id <= self.node_list[0].id:
return self.node
# else can be removed but eases the readding.
else:
if file_id > self.node.id and file_id <= self.node_list[0].id:
return self.node
pred_node = None
for i in reversed(range(-256, 0, 1)):
if self.node_list[i].id > self.node.id:
if self.node_list[i].id > self.node.id and self.node_list[i].id <= file_id:
pred_node = self.node_list[i]
break
else:
if file_id > self.node_list[i].id and file_id < self.node.id:
pred_node = self.node_list[i]
break
if not pred_node:
return self.node
#print("\n\n=========After calculating pred_node===="+str(pred_node)+"\n\n")
pred_node = create_pred_client(pred_node).findPred(file_id)
return pred_node
def readFile(self, filename):
if (filename not in self.files):
raise ttypes.SystemException(
"Given filename not present in this node")
sha256 = hashlib.sha256()
sha256.update(filename.encode('utf-8'))
fileid = sha256.hexdigest()
if (fileid <= self.pred.id or fileid > self.id):
raise ttypes.SystemException(
"Given filename not present in this node")
readFile = open(filename, "r")
content = readFile.read()
readFile.close()
metadata = ttypes.RFileMetadata(filename, self.files[filename])
rFile = ttypes.RFile(metadata, content)
return rFile
def getNodeSucc(self):
'''
returns the next active node in the DHT chord.
output: NodeID n
'''
if not self.node_list:
raise _tt.SystemException(message="Fingertable not set for the server : "+str(self.node))
# this should work but the printed node list didn't seem like it
return self.node_list[0]
def readFile(self, file_name):
'''
Reads file from the server dictionary.
input : string file_name
output: RFile file_name
'''
# inside the if rfile exists on this node block.
file_name_hash = _hl.sha256(file_name).hexdigest()
test_node = self.findSucc(file_name_hash)
# __eq__ is implemented in init so it should work
if test_node == self.node:
if file_name_hash not in self.dht_files:
ex = _tt.SystemException(message="No such file with this filename exists on this server!"+
str(self.node))
raise ex
return self.dht_files[file_name_hash]
raise _tt.SystemException(message="Server : "+str(self.node)+" doesn't own this file.")
def findSucc(self, key):
if (self.fingerTable is None or len(self.fingerTable) == 0):
raise ttypes.SystemException(
"No finger table present for this node")
if (key == self.id):
return self.node
pred = self.findPred(key)
if (pred.id == self.id):
return self.getNodeSucc()
else:
#ask pred node for its succesor and return it
transport = TSocket.TSocket(pred.ip, int(pred.port))
transport = TTransport.TBufferedTransport(transport)
protocol = TBinaryProtocol.TBinaryProtocol(transport)
client = FileStore.Client(protocol)
transport.open()
succ = client.getNodeSucc()
transport.close()
return succ
def writeFile(self, rFile):
rFileMeta = rFile.meta
filename = rFileMeta.filename
sha256 = hashlib.sha256()
sha256.update(filename.encode('utf-8'))
fileid = sha256.hexdigest()
if (self.pred == None):
self.pred = self.findPred(self.id)
if (fileid <= self.pred.id or fileid > self.id):
raise ttypes.SystemException(
"File id does not belong to this node")
if (filename in self.files):
self.files[filename] += 1
else:
self.files[filename] = 0
fileWrite = open(filename, "w")
fileWrite.write(rFile.content)
fileWrite.flush()
fileWrite.close()
def setFingertable(self, node_list):
'''
Sets server's finger table to node_list.
input : list<NodeID> node_list
'''
try:
self.node_list = node_list
#print self.node_list
except:
ex = _tt.SystemException(message="Could not set finger table for node : "+
str(self.node))
raise ex
# If you want to have a better look at fingertables of all nodes uncomment the following if else block
if 'nodes.txt' not in os.listdir(os.getcwd()):
test_file = open('nodes.txt', 'w+')
test_file.write("\n\n----begin----\n\n"+str(self.node_list)+"\n\n----END---\n\n")
test_file.close()
else:
test_file = open('nodes.txt', 'a')
test_file.write("\n\n----"+str(self.node)+"----\n\n"+str(self.node_list)+"\n\n----END---\n\n")
test_file.close()
def getNodeSucc(self):
if (self.fingerTable is None or len(self.fingerTable) == 0):
raise ttypes.SystemException(
"No finger table present for this node")
return self.fingerTable[0]
