def copyFromDFS(address, fname, path):
""" Contact the metadata server to ask for the file blocks of
the file fname. Get the data blocks from the data nodes.
Saves the data in path.
"""
# Contact the metadata server to ask for information of fname
# Create socket and connect to metadata server
metaSock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
metaSock.connect(address)
# Create get packet and send request to metadata server
p = Packet()
p.BuildGetPacket(fname)
metaSock.sendall(p.getEncodedPacket())
# Recieve chunk list
msg = b""
while True:
buffer = metaSock.recv(2048)
msg += buffer
if getsizeof(buffer) < 2048:
break
# If file not found, exit, if file found, decode packet
if msg != b"NFOUND":
p.DecodePacket(msg)
else:
exit("File not found, exiting...")
# If there is no error response Retreive the data blocks
# Get blocks
blocks = p.getDataNodes()
# Open file
fd = open(path, "wb+")
for ip, addr, blockId in blocks:
# Create socket and connect to node
nodeSock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
nodeSock.connect((ip, addr))
# Build packet and send request to data node
p.BuildGetDataBlockPacket(blockId)
nodeSock.send(p.getEncodedPacket())
# Recieve block and write to file named path
fd.write(nodeSock.recv(16384))
# Close socket
nodeSock.close()
