I'm trying to create a simple echo server that can handle multiple connections, I am using select and need to use non blocking sockets but I get an error saying 'BlockingIOError: [Errno 35] Resource temporarily unavailable' on the line where I receive the data.
Here's the server and client code
inputs = [server]
while True:
inready, outready, excready = select.select(inputs, [], [])
for s in inready:
if s == server:
client, address = server.accept()
client.setblocking(0)
print(address)
inready.append(client)
else:
data = s.recv(1024);
if data:
s.send(data)
else:
inputs.remove(s)
s.close()
This little error took me also a while to find:
inready.append(client)
Correct is, of course:
inputs.append(client)
Since inready was accidentally modified, the else block was executed when it shouldn't have been.
Related
I had using pika to make a connection to RabbitMQ and consume message, once I start the script on ubuntu prod environment it is working as expected but is opening mysql connection and never closes them and ends up in Too many connection on mysql server.
Will appreciate any recommendation on the code below, as well can not understand what is going wrong. Thanking you in advance.
The flow is the following
Starting pika on Python3
Subscribe to a channel and waiting for messages
In callback i do various validation and save or update data inside MySql
The result that is showing the problem is the at the end of question a screenshot from ubuntu htop, that is showing new connection on MySql and keep adding them on the top
Pika Verion = 0.13.0
For MySql I use pymysql.
Pika Script
def main():
credentials = pika.PlainCredentials(tunnel['queue']['name'], tunnel['queue']['password'])
while True:
try:
cp = pika.ConnectionParameters(
host=tunnel['queue']['host'],
port=tunnel['queue']['port'],
credentials=credentials,
ssl=tunnel['queue']['ssl'],
heartbeat=600,
blocked_connection_timeout=300
)
connection = pika.BlockingConnection(cp)
channel = connection.channel()
def callback(ch, method, properties, body):
if 'messageType' in properties.headers:
message_type = properties.headers['messageType']
if events.get(message_type):
result = Descriptors._reflection.ParseMessage(events[message_type]['decode'], body)
if result:
result = protobuf_to_dict(result)
model.write_response(external_response=result, message_type=message_type)
else:
app_log.warning('Message type not in allowed list = ' + str(message_type))
app_log.warning('continue listening...')
channel.basic_consume(callback, queue=tunnel['queue']['name'], no_ack=True)
try:
channel.start_consuming()
except KeyboardInterrupt:
channel.stop_consuming()
connection.close()
break
except pika.connection.exceptions.ConnectionClosed as e:
app_log.error('ConnectionClosed :: %s' % str(e))
continue
except pika.connection.exceptions.AMQPChannelError as e:
app_log.error('AMQPChannelError :: %s' % str(e))
continue
except Exception as e:
app_log.error('Connection was closed, retrying... %s' % str(e))
continue
if __name__ == '__main__':
main()
Inside the script i have a model that doing inserts or updated in the database, code below
def write_response(self, external_response, message_type):
table_name = events[message_type]['table_name']
original_response = external_response[events[message_type]['response']]
if isinstance(original_response, list):
external_response = []
for o in original_response:
record = self.map_keys(o, message_type, events[message_type].get('values_fix', {}))
external_response.append(self.validate_fields(record))
else:
external_response = self.map_keys(original_response, message_type, events[message_type].get('values_fix', {}))
external_response = self.validate_fields(external_response)
if not self.mysql.open:
self.mysql.ping(reconnect=True)
with self.mysql.cursor() as cursor:
if isinstance(original_response, list):
for e in external_response:
id_name = events[message_type]['id_name']
filters = {id_name: e[id_name]}
self.event(
cursor=cursor,
table_name=table_name,
filters=filters,
external_response=e,
message_type=message_type,
event_id=e[id_name],
original_response=e # not required here
)
else:
id_name = events[message_type]['id_name']
filters = {id_name: external_response[id_name]}
self.event(
cursor=cursor,
table_name=table_name,
filters=filters,
external_response=external_response,
message_type=message_type,
event_id=external_response[id_name],
original_response=original_response
)
cursor.close()
self.mysql.close()
return
On ubuntu i use systemd to run the script and restart in case something goes wrong, below is systemd file
[Unit]
Description=Pika Script
Requires=stunnel4.service
Requires=mysql.service
Requires=mongod.service
[Service]
User=user
Group=group
WorkingDirectory=/home/pika_script
ExecStart=/home/user/venv/bin/python pika_script.py
Restart=always
[Install]
WantedBy=multi-user.target
Image from ubuntu htop, how the MySql keeps adding in the list and never close it
Error
tornado_mysql.err.OperationalError: (1040, 'Too many connections')
i have found the issue, posting if will help somebody else.
the problem was that mysqld went into infinite loop trying to create indexing to a specific database, after found to which database was trying to create the indexes and never succeed and was trying again and again.
solution was to remove the database and recreate it, and the mysqld process went back to normal. and the infinite loop to create indexes dissapeared as well.
I would say increasing connection may solve your problem temperately.
1st find out why the application is not closing the connection after completion of task.
2nd Any slow queries/calls on the DB and fix them if any.
3rd considering no slow queries/calls on DB and also application is closing the connection/thread after immediately completing the task, then consider playing with "wait_timeout" on mysql side.
According to this answer, if you have MySQL 5.7 and 5.8 :
It is worth knowing that if you run out of usable disc space on your
server partition or drive, that this will also cause MySQL to return
this error. If you're sure it's not the actual number of users
connected then the next step is to check that you have free space on
your MySQL server drive/partition.
From the same thread. You can inspect and increase number of MySQL connections.
I have a weird issue. After reading about websocket-client, it seems easy enough, send data via websocket.send() and receive via recv().
I have setup my websocket to read and send a binary file. The codes are below
ws = websocket.WebSocket()
ws.connect(uri)
text_list = list()
# setup the receiving portion
receiving_tread = threading.Thread(target=thread_receiving, args=(ws, text_list))
receiving_tread.start()
ws.send_binary([48]) # telling server file has started
f = open(binary_file, 'rb')
chunk = f.read(8000)
while chunk != b'':
ws.send(chunk)
time.sleep(0.5)
chunk = f.read(8000)
ws.send_binary([49]) # tell server file has ended
The process to receive the data:
def thread_receiving(ws, text_list):
data = json.loads(ws.recv())
text_list.append(data)
I know the data gets sent because I get the first part of the data returned, then it stops. So I get only 1 return and somehow the recv() stops listening. Note: I have no access to the server or the server websocket so I have to troubleshoot from the client side.
Can anyone tell me, what it is I'm doing wrong?
Okay, I've found the answer, it seems that the receiving function exits after it runs. So we need to keep it running.
Therefore,
def thread_receiving(ws, text_list):
data = json.loads(ws.recv())
while len(data) > 0
text_list.append(data)
data = json.loads(ws.recv())
So I'm connected to an IRC chat using socket.connec
I log in by passing my variables via socket.send
The log in is successful and then I sit in a while true loop using
Socket.recv(1024)
If I just continually print the response everything looks fine, but let's say I want to add to the end of the string... I noticed that socket.recv doesn't always get the full message (only grabs up to 1024 as expected) and the remainder of the message is in the next iteration of the loop.
This makes its it impossible to process the feedback line by line.
Is there a better way to constantly read the data without it getting trunked? Is it possible to figure out the size of the response before receiving it so the buffer can be set dynamically?
TCP is a stream-based protocol. Buffer the bytes received and only extract complete messages from the stream.
For complete lines, look for newline characters in the buffer.
Example server:
import socket
class Client:
def __init__(self,socket):
self.socket = socket
self.buffer = b''
def getline(self):
# if there is no complete line in buffer,
# add to buffer until there is one.
while b'\n' not in self.buffer:
data = self.socket.recv(1024)
if not data:
# socket was closed
return ''
self.buffer += data
# break the buffer on the first newline.
# note: partition(n) return "left of n","n","right of n"
line,newline,self.buffer = self.buffer.partition(b'\n')
return line + newline
srv = socket.socket()
srv.bind(('',5000))
srv.listen(1)
conn,where = srv.accept()
client = Client(conn)
print(f'Client connected on {where}')
while True:
line = client.getline()
if not line:
break
print(line)
Example client:
s=socket()
s.connect(('127.0.0.1',5000))
s.sendall(b'line one\nline two\nline three\nincomplete')
s.close()
Output on server:
Client connected on ('127.0.0.1', 2667)
b'line one\n'
b'line two\n'
b'line three\n'
This question is two-fold.
1. So I need to run code for a socket server that's all defined and created in another.py, Clicking run on PyCharm works just fine, but if you exec() the file it just runs the bottom part of the code.
There are a few answers here but they are conflicting and for Python 2.
From what I can gather there are three ways:
- Execfile(), Which I think is Python 2 code.
- os.system() (But I've seen it be said that it's not correct to pass to the OS for this)
- And subprocess.Popen (unsure how to use this either)
I need this to run in the background, it is used to create threads for sockets for the recv portion of the overall program and listen on those ports so I can input commands to a router.
This is the complete code in question:
import sys
import socket
import threading
import time
QUIT = False
class ClientThread(threading.Thread): # Class that implements the client threads in this server
def __init__(self, client_sock): # Initialize the object, save the socket that this thread will use.
threading.Thread.__init__(self)
self.client = client_sock
def run(self): # Thread's main loop. Once this function returns, the thread is finished and dies.
global QUIT # Need to declare QUIT as global, since the method can change it
done = False
cmd = self.readline() # Read data from the socket and process it
while not done:
if 'quit' == cmd:
self.writeline('Ok, bye. Server shut down')
QUIT = True
done = True
elif 'bye' == cmd:
self.writeline('Ok, bye. Thread closed')
done = True
else:
self.writeline(self.name)
cmd = self.readline()
self.client.close() # Make sure socket is closed when we're done with it
return
def readline(self): # Helper function, read up to 1024 chars from the socket, and returns them as a string
result = self.client.recv(1024)
if result is not None: # All letters in lower case and without and end of line markers
result = result.strip().lower().decode('ascii')
return result
def writeline(self, text): # Helper func, writes the given string to the socket with and end of line marker at end
self.client.send(text.strip().encode("ascii") + b'\n')
class Server: # Server class. Opens up a socket and listens for incoming connections.
def __init__(self): # Every time a new connection arrives, new thread object is created and
self.sock = None # defers the processing of the connection to it
self.thread_list = []
def run(self): # Server main loop: Creates the server (incoming) socket, listens > creates thread to handle it
all_good = False
try_count = 0 # Attempt to open the socket
while not all_good:
if 3 < try_count: # Tried more than 3 times without success, maybe post is in use by another program
sys.exit(1)
try:
self.sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM) # Create the socket
port = 80
self.sock.bind(('127.0.0.1', port)) # Bind to the interface and port we want to listen on
self.sock.listen(5)
all_good = True
break
except socket.error:
print('Socket connection error... Waiting 10 seconds to retry.')
del self.sock
time.sleep(10)
try_count += 1
print('Server is listening for incoming connections.')
print('Try to connect through the command line with:')
print('telnet localhost 80')
print('and then type whatever you want.')
print()
print("typing 'bye' finishes the thread. but not the server",)
print("eg. you can quit telnet, run it again and get a different ",)
print("thread name")
print("typing 'quit' finishes the server")
try:
while not QUIT:
try:
self.sock.settimeout(0.500)
client = self.sock.accept()[0]
except socket.timeout:
time.sleep(1)
if QUIT:
print('Received quit command. Shutting down...')
break
continue
new_thread = ClientThread(client)
print('Incoming Connection. Started thread ',)
print(new_thread.getName())
self.thread_list.append(new_thread)
new_thread.start()
for thread in self.thread_list:
if not thread.isAlive():
self.thread_list.remove(thread)
thread.join()
except KeyboardInterrupt:
print('Ctrl+C pressed... Shutting Down')
except Exception as err:
print('Exception caught: %s\nClosing...' % err)
for thread in self.thread_list:
thread.join(1.0)
self.sock.close()
if "__main__" == __name__:
server = Server()
server.run()
print('Terminated')
Notes:
This is created in Python 3.4
I use Pycharm as my IDE.
One part of a whole.
2. So I'm creating a lightning detection system and this is how I expect it to be done:
- Listen to the port on the router forever
The above is done, but the issue with this is described in question 1.
- Pull numbers from a text file for sending text message
Completed this also.
- Send http get / post to port on the router
The issue with this is that i'm unsure how the router will act if I send this in binary form, I suspect it wont matter, the input commands for sending over GSM are specific. Some clarification may be needed at some point.
- Recieve reply from router and exception manage
- Listen for relay trip for alarm on severe or close strike warning.
- If tripped, send messages to phones in storage from text file
This would be the http get / post that's sent.
- Wait for reply from router to indicate messages have been sent, exception handle if it's not the case
- Go back to start
There are a few issues I'd like some background knowledge on that is proving hard to find via the old Google and here on the answers in stack.
How do I grab the receive data from the router from another process running in another file? I guess I can write into a text file and call that data but i'd rather not.
How to multi-process and which method to use.
How to send http get / post to socket on router, post needed occording to the router manual is as follows: e.g. "http://192.168.1.1/cgi-bin/sms_send?number=0037061212345&text=test"
Notes: Using Sockets, threading, sys and time on Python 3.4/Pycharm IDE.
Lightning detector used is LD-250 with RLO Relay attached.
RUT500 Teltonica router used.
Any direction/comments, errors spotted, anything i'm drastically missing would be greatly appreciated! Thank you very much in advance :D constructive criticism is greatly encouraged!
Okay so for the first part none of those suggested in the OP were my answer. Running the script as is from os.system(), exec() without declaring a new socket object just ran from __name__, this essentially just printed out "terminated", to get around this was simple. As everything was put into a classes already, all I had to do is create a new thread. This is how it was done:
import Socketthread2
new_thread = Socketthread2.Server() # Effectively declaring a new server class object.
new_thread.run()
This allowed the script to run from the beginning by initialising the code from the start in Socket, which is also a class of Clientthread, so that was also run too. Running this at the start of the parent program allowed this to run in the background, then continue with the new code in parent while the rest of the script was continuously active.
I want to establish publish subscribe communication between to machines.
The two machines, that I have, are ryu-primary and ryu-secondary
The steps I follow in each of the machines are as follows.
In the initializer for ryu-primary (IP address is 192.168.241.131)
self.context = zmq.Context()
self.sub_socket = self.context.socket(zmq.SUB)
self.pub_socket = self.context.socket(zmq.PUB)
self.pub_port = 5566
self.sub_port = 5566
def establish_zmq_connection(self): # Socket to talk to server
print( "Connection to ryu-secondary..." )
self.sub_socket.connect( "tcp://192.168.241.132:%s" % self.sub_port )
def listen_zmq_connection(self):
print( 'Listen to zmq connection' )
self.pub_socket.bind( "tcp://*:%s" % self.pub_port )
def recieve_messages(self):
while True:
try:
string = self.sub_socket.recv( flags=zmq.NOBLOCK )
print( 'flow mod messages recieved {}'.format(string) )
return string
except zmq.ZMQError:
break
def push_messages(self,msg):
self.pub_socket.send( "%s" % (msg) )
From ryu-secondary (IP address - 192.168.241.132)
In the initializer
self.context = zmq.Context()
self.sub_socket = self.context.socket(zmq.SUB)
self.pub_socket = self.context.socket(zmq.PUB)
self.pub_port = 5566
self.sub_port = 5566
def establish_zmq_connection(self): # Socket to talk to server
print( "Connection to ryu-secondary..." )
self.sub_socket.connect( "tcp://192.168.241.131:%s" % self.sub_port )
def listen_zmq_connection(self):
print( 'Listen to zmq connection' )
self.pub_socket.bind( "tcp://*:%s" % self.pub_port )
def recieve_messages(self):
while True:
try:
string = self.sub_socket.recv( flags=zmq.NOBLOCK )
print( 'flow mod messages recieved {}'.format(string) )
return string
except zmq.ZMQError:
break
def push_messages(self,msg):
print( 'pushing message to publish socket' )
self.pub_socket.send( "%s" % (msg) )
These are the functions that I have.
I am calling on ryu-secondary:
establish_zmq_connections()
push_messages()
But I am not recieving those messages on ryu-primary, when I call
listen_zmq_connection()
recieve_messages()
Can someone point out to me what I am doing wrong?
Repair the PUB/SUB messaging pattern setup
There are several important steps in making the PUB/SUB pattern work.
All this is well described in the ZeroMQ documentation.
You need not repeat both pub & sub parts of code on both sides, the more that it masks, as A side-effect thereof, the case if you mix the pub and sub socket addresses/ports/calls/etc in an "opposite" node code and you do not see such a principal collision.
your code defines the initial form of PUB-archetype, that is expected to .push_messages()
your code defines the initial form of SUB-archetype, that is expected to .receive_messages()
your code does not show, how do you control who goes first on a connection setup -- whether .bind() or .connect() appears at random or before/after the other
your code does not show any subscription setup, after the SUB-archetype was instantiated. A default value upon a socket instantiation does need to be modified via a .setsockopt( zmq.SUBSCRIBE = '') method, otherwise there is a prohibitive filter that does not allow any ( yet unsubscribed ) message to pass through and got-output ( "received" ) on the SUB-side
Must modify a default SUB-side subscription filter, it is prohibitive
You may have noticed from the ZeroMQ documentation, that until setup otherwise, the sub-side does filter-out all incoming messages.
http://api.zeromq.org/2-1:zmq-setsockopt
"The ZMQ_SUBSCRIBE option shall establish a new message filter on a ZMQ_SUB socket. Newly created ZMQ_SUB sockets shall filter out all incoming messages, therefore you should call this option to establish an initial message filter.
An empty option_value of length zero shall subscribe to all incoming messages. A non-empty option_value shall subscribe to all messages beginning with the specified prefix. Multiple filters may be attached to a single ZMQ_SUB socket, in which case a message shall be accepted if it matches at least one filter."
Class-method pre-configuration of a Context instance possible
There is another possibility for a python code using pyzmq 13.0+. There you may also setup this via a Context class-method .setsockopt( zmq.SUBSCRIBE, "" ) et al, but such call has to precede the new socket instantiation from a Context-instance pre-configured this way.