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master.py
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master.py
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import threading
from xmlrpc.server import SimpleXMLRPCServer
from commons.loggers import default_logger, request_logger
from commons.metadata_manager import load_metadata, update_metadata, OplogActions
from commons.settings import CHUNK_SIZE, DEFAULT_MASTER_PORT, DEFAULT_IP, OP_LOG_FILENAME
from master.chunk_manager import ChunkManager
from master.namespace_manager import NamespaceManager
class Master:
__slots__ = 'my_addr', 'client_id', 'mutex', \
'metadata_file', 'namespace_manager', 'chunk_manager'
def __init__(self, my_addr, metadata_file):
self.my_addr = my_addr
self.client_id = 0 # counter to give next client ID
self.mutex = threading.Lock() # TODO: probably use a re entrant lock
self.metadata_file = metadata_file # File that contains masters metadata
self.namespace_manager = NamespaceManager()
self.chunk_manager = ChunkManager()
def __repr__(self):
return f"""Master(me={self.my_addr},
client_id={self.client_id},
namespace_manager={self.namespace_manager},
chunk_manager={self.chunk_manager})"""
def test_ok(self):
"""A quick test to see if server is working fine"""
return "Ok"
def unique_client_id(self):
"""
When a client is attached to the master,
it calls this function to get a unique client ID.
"""
rlog.info("Granting client id=%d", self.client_id + 1)
with self.mutex:
self.client_id += 1
# make client id persistent in metadata file
update_metadata(self.metadata_file, OplogActions.GRANT_CLIENT_ID, self.client_id)
return self.client_id
def create(self, path):
"""
Will be called by client to create a file in the namespace (in memory)
:param path: name of the file
:return: True if successful and errors if any.
"""
rlog.info("args: path=%s", path)
res, err = self.namespace_manager.create(path)
if not err:
# Log this operation to oplog
update_metadata(self.metadata_file, OplogActions.CREATE_FILE, path)
return res, err
def add_chunk(self, path, chunk_index):
"""
Client calls to get a new chunk.
:param path: name of the file
:param chunk_index:
:return: chunk_handle of the chunk created and address of chunkservers containing that chunk
"""
rlog.info("args: path=%s, chunk_index=%d", path, chunk_index)
info, err = self.chunk_manager.add_chunk(path, chunk_index)
if err:
return None, None, err
# Log this operation to oplog
update_metadata(self.metadata_file, OplogActions.ADD_CHUNK,
(path, chunk_index, info.chunk_handle, info.chunk_locations, info.chunk_handle))
return info.chunk_handle, info.chunk_locations, None
def find_locations(self, path, chunk_index):
"""
Returns CHUNK HANDLE and an array of CHUNK LOCATIONS for a given file name and chunk index.
:param path:
:param chunk_index:
:return: chunk_info {chunk_handle, chunk_locations} and errors.
"""
rlog.info("args: path=%s, chunk_index=%d", path, chunk_index)
chunk_locations, chunk_handle, err = self.chunk_manager.find_locations(path, chunk_index)
return chunk_locations, chunk_handle, err
def find_lease_holder(self, chunk_handle):
"""
Client calls to get the PRIMARY chunk server for a given chunk handle.
If there is no current lease holder, master will automatically select
one of the replicas to be the primary, and grant lease to that chunk server.
:param chunk_handle:
:return: lease holder, lease expiration timestamp, errors
"""
rlog.info("args: chunk_handle=%d", chunk_handle)
lease, err = self.chunk_manager.find_lease_holder(chunk_handle)
if err:
return None, None, err
return lease.primary, lease.expiration, None
def report_chunk(self, server, chunk_handle, chunk_index, length, path):
"""
Called by chunk servers to tell the master that they have a certain chunk and
the number of defined bytes in that chunk.
:param server:
:param chunk_handle:
:param chunk_index:
:param length:
:param path:
:return:
"""
rlog.debug(
f"received request from chunk server:{server} with args: "
f"chunk_handle={chunk_handle}, length={length}, chunk_index={chunk_index}, path={path}")
# FIXME: path_index looks unnecessary :/
path_index, err = self.chunk_manager.get_path_index_from_handle(chunk_handle)
if err:
return None, err
assert path_index.index == chunk_index
self.chunk_manager.set_chunk_location(chunk_handle, server)
# Update file size information
file_length, err = self.namespace_manager.get_file_length(path_index.path)
new_length = CHUNK_SIZE * path_index.index + length
log.debug(f"new calculated file size= {new_length}, "
f"old_file_size={file_length}, "
f"this chunk's size={length}, "
f"chunk index={path_index.index}")
if new_length > file_length:
self.namespace_manager.set_file_length(path_index.path, new_length)
return None
def create_dir(self, path):
"""Will be called by client to create a dir in the namespace"""
rlog.info("CREATE DIR API called")
res, err = self.namespace_manager.create_dir(path)
if not err:
update_metadata(self.metadata_file, OplogActions.CREATE_DIR, path)
return res, err
def list_allfiles(self, path):
"""Will be called by client to list all files present in given directory path"""
rlog.info("LIST FILES API called")
res, err = self.namespace_manager.list_allfiles(path)
return res, err
def delete(self, path):
"""Will be called by client to delete a specific file"""
rlog.info("DELETE FILE API called")
self.chunk_manager.update_deletechunk_list(path)
err = self.namespace_manager.delete(path)
if not err:
update_metadata(self.metadata_file, OplogActions.DELETE_FILE, path)
return err
def get_file_length(self, path):
"""Will be called by client to get the file length"""
rlog.info("GET FILE LENGTH API Called")
file_length, err = self.namespace_manager.get_file_length(path)
return file_length, err
def notify_master(self, chunksrv_addr, chunk_handles):
"""
When a chunk server is created,
it calls this function to notify master of its presence.
Then master adds this address to its chunkserver list
:param chunk_handles: list of chunk handles at that chunk server
:param chunksrv_addr: http://<ip_addr>:<port>
:return: None
"""
rlog.info("Received registration request from chunk server at: %s", chunksrv_addr)
self.chunk_manager.update_chunkserver_list(chunksrv_addr)
for chunk_handle in chunk_handles:
self.chunk_manager.set_chunk_location(chunk_handle, chunksrv_addr)
# Log this operation to oplog
update_metadata(self.metadata_file, OplogActions.NOTIFY_MASTER, chunksrv_addr)
def heartbeat(self):
import threading
bg_thread = threading.Thread(target=self.chunk_manager.beat, args=())
# Run the thread in daemon mode.
# This allows the main application to exit even though the thread is running.
# It will also (therefore) make it possible to use ctrl+c to terminate the application.
bg_thread.daemon = True
bg_thread.start()
def start_master(ip, port):
m = Master(f'http://{ip}:{port}', OP_LOG_FILENAME)
# restore previous launch's meta data
load_metadata(m)
# one time polling to get the list of chunks from each chunk server
m.chunk_manager.poll_chunkservers()
# call heartbeat
m.heartbeat()
master_server = SimpleXMLRPCServer((ip, port),
logRequests=True,
allow_none=True)
# Read: https://gist.github.com/abnvanand/199cacf6c8f45258ff096b842b77b216
master_server.register_introspection_functions()
# register all methods to be available to client
# can either use register_function(<function's_name>)
# or register_instance(<class's_instance>) # All the methods of the instance are published as XML-RPC methods
master_server.register_instance(m)
print("Master running at: ", m.my_addr)
master_server.serve_forever()
# TODO: launch background tasks (eg. gc, heartbeat) in a separate thread
if __name__ == '__main__':
log = default_logger
rlog = request_logger
import argparse
parser = argparse.ArgumentParser()
parser.add_argument('--ip', default=DEFAULT_IP)
parser.add_argument('--port', type=int, default=DEFAULT_MASTER_PORT)
args = parser.parse_args()
start_master(args.ip, args.port)