def checkSubs(seq_hash, msg_list):
incoming_msg = publishsubscribe.receive_message(sub_sockets)
# This assumes that the return is in the format [seq_num, message]
if incoming_msg[
1]: # If there was an incoming message from the subscribe ports
algorithm.add_seq_num(
seq_hash, incoming_msg[0][0]) # Adds the seq_num to the hash
msg_list.append(incoming_msg[0]) # Stores the message in the list
def running_loop():
try:
conn = boto.sqs.connect_to_region("us-west-2")
if conn == None:
sys.stderr.write(
"Could not connect to AWS region '{0}'\n".format("us-west-2"))
sys.exit(1)
# Assuming that the queues will have already been created elsewhere
q_in = conn.get_queue(args.in_queue)
q_out = conn.get_queue(args.out_queue)
except Exception as e:
sys.stderr.write("Exception connecting to SQS\n")
sys.stderr.write(str(e))
sys.exit(1)
global seq_num
seq_hash = []
last_performed_num = 0
stored_messages = []
print "Starting up instance: {0}".format(args.my_name)
# Actual work gets done here
while (1 < 2): # lol
# grab a message off SQS_IN
rs = q_in.get_messages(
message_attributes=["action", "id", "name", "activities"])
if (len(rs) < 1):
checkSubs(seq_hash, stored_messages) #Checks sub ports
calculated_num, next_in_seq = algorithm.compare_seq_num(
seq_hash, last_performed_num)
if next_in_seq: # If the next number is indeed last_performed_num + 1
last_performed_num = catchup(calculated_num, stored_messages,
last_performed_num)
time.sleep(
POLL_INTERVAL
) # wait before checking for messages again (in seconds)
continue
m = rs[0]
q_in.delete_message(
m) # remove message from queue so it's not read multiple times
print "Received message: " + m.get_body()
seq_num += 1 #increment
loc_seq_num = seq_num.last_set #store value to local variable
op_list = parse_sqs_msg(m)
publishsubscribe.send_message(pub_socket, [loc_seq_num, op_list])
algorithm.add_seq_num(seq_hash, loc_seq_num)
# Publish to pub_socket the seq_num and the message
# Runs the algorithm to check if the next number in hash is one above the last performed seq num
calculated_num, next_in_seq = algorithm.compare_seq_num(
seq_hash, last_performed_num)
# This is the catch-up loop, running until the number after last performed seq num is loc_seq_num
while (calculated_num < loc_seq_num):
checkSubs(seq_hash, stored_messages) #Checks sub ports
if next_in_seq: # If the next number is indeed last_performed_num + 1
last_performed_num = catchup(calculated_num, stored_messages,
last_performed_num)
calculated_num, next_in_seq = algorithm.compare_seq_num(
seq_hash, last_performed_num)
# NOTE: after it finally exits this loop, the seq_num should be equal to calculated_num
# This means that calculated_num == loc_seq_num, so it is the current operation
# If not, then something has gone wrong with the algorithm (Needs to be debugged)
# Actually perform the operation on the db here, grab the response,
# and put a message on the output queue
message_out = perform_operation_msg(m)
last_performed_num += 1
# Send out the message to the output queue
q_out.write(message_out)
def running_loop():
try:
conn = boto.sqs.connect_to_region("us-west-2")
if conn == None:
sys.stderr.write("Could not connect to AWS region '{0}'\n".format("us-west-2"))
sys.exit(1)
# Assuming that the queues will have already been created elsewhere
q_in = conn.get_queue(args.in_queue)
q_out = conn.get_queue(args.out_queue)
except Exception as e:
sys.stderr.write("Exception connecting to SQS\n")
sys.stderr.write(str(e))
sys.exit(1)
global seq_num
seq_hash = []
last_performed_num = 0
stored_messages = []
print "Starting up instance: {0}".format(args.my_name)
# Actual work gets done here
while (1 < 2): # lol
# grab a message off SQS_IN
rs = q_in.get_messages(message_attributes=["action", "id", "name", "activities"])
if (len(rs) < 1):
checkSubs(seq_hash, stored_messages) #Checks sub ports
calculated_num, next_in_seq = algorithm.compare_seq_num(seq_hash, last_performed_num)
if next_in_seq: # If the next number is indeed last_performed_num + 1
last_performed_num = catchup(calculated_num, stored_messages, last_performed_num)
time.sleep(POLL_INTERVAL) # wait before checking for messages again (in seconds)
continue
m = rs[0]
q_in.delete_message(m) # remove message from queue so it's not read multiple times
print "Received message: " + m.get_body()
seq_num += 1 #increment
loc_seq_num = seq_num.last_set #store value to local variable
op_list = parse_sqs_msg(m)
publishsubscribe.send_message(pub_socket, [loc_seq_num, op_list])
algorithm.add_seq_num(seq_hash, loc_seq_num)
# Publish to pub_socket the seq_num and the message
# Runs the algorithm to check if the next number in hash is one above the last performed seq num
calculated_num, next_in_seq = algorithm.compare_seq_num(seq_hash, last_performed_num)
# This is the catch-up loop, running until the number after last performed seq num is loc_seq_num
while (calculated_num < loc_seq_num):
checkSubs(seq_hash, stored_messages) #Checks sub ports
if next_in_seq: # If the next number is indeed last_performed_num + 1
last_performed_num = catchup(calculated_num, stored_messages, last_performed_num)
calculated_num, next_in_seq = algorithm.compare_seq_num(seq_hash, last_performed_num)
# NOTE: after it finally exits this loop, the seq_num should be equal to calculated_num
# This means that calculated_num == loc_seq_num, so it is the current operation
# If not, then something has gone wrong with the algorithm (Needs to be debugged)
# Actually perform the operation on the db here, grab the response,
# and put a message on the output queue
message_out = perform_operation_msg(m)
last_performed_num += 1
# Send out the message to the output queue
q_out.write(message_out)
def checkSubs(seq_hash, msg_list): incoming_msg = publishsubscribe.receive_message(sub_sockets) # This assumes that the return is in the format [seq_num, message] if incoming_msg[1]: # If there was an incoming message from the subscribe ports algorithm.add_seq_num(seq_hash, incoming_msg[0][0]) # Adds the seq_num to the hash msg_list.append(incoming_msg[0]) # Stores the message in the list
