ZeroMq IRC Log

Tuesday July 12, 2011

[Time] Name	Message
[00:31] gpfreitas	Can someone point me out to the closest example of the following: two clients, one server. Clients have a pile of integers that they send to the server. Main loop in the server: server gets on integer from client 1, one integer from client 2, adds them, and returns the sum to the clients.
[00:32] gpfreitas	By closest example, I mean code that is close to the application just described.
[00:33] whack	gpfreitas: look for examples of REQ/REP sockets
[00:34] gpfreitas	I tried to do this, but it did not work. Let me post the code:
[00:34] whack	sounds like you'll have two clients (req) and one server (rep), you'll need read one message each from the clients and reply to both clients at the same time
[00:34] whack	but I think you will need two rep sockets for that
[00:34] gpfreitas	Hmmmm... I thought the reply from the server would be a PUB
[00:35] whack	well, that can work too
[00:35] whack	it's up to you, clients can send with REQ/REP and receve the real result from a pubsub
[00:35] gpfreitas	Server code: http://codepad.org/14SBt7Nd
[00:36] gpfreitas	Clients code: http://codepad.org/nq2nVtbS
[00:37] gpfreitas	Server code ran fine, I don't know if it works, but it didn't crash.
[00:37] gpfreitas	Client's code crashed with the following message:
[00:37] gpfreitas	File "zmqclient.py", line 53, in client1out out_socket2.send(str(d)) File "socket.pyx", line 385, in zmq.core.socket.Socket.send (zmq/core/socket.c:3523) File "socket.pyx", line 438, in zmq.core.socket.Socket._send_copy (zmq/core/socket.c:4054) zmq.core.error.ZMQError: Operation cannot be accomplished in current state
[00:39] whack	gpfreitas: a few problems; you never send a reply to the request
[00:39] gpfreitas	Sorry, I know this must be a very newbie question. I'm not a programmer really, I am an economist, and I want to run experiments of my models (like auctions, etc.) at university, and I know Python... I saw a tutorial on ZMQ and it seemed simple enough.
[00:39] whack	(server)
[00:39] gpfreitas	(correction: I'm a graduate student in economics)
[00:39] gpfreitas	Ok, let me see.
[00:40] gpfreitas	whack: ok. So I should do something like send a reply like "received" to the client, at which point the client sends a new number. Is that all right?
[00:40] whack	gpfreitas: you have some copy paste errors, too
[00:40] whack	line 1 def client1out():
[00:41] whack	should be def client2out(): no?
[00:41] gpfreitas	Yes. Very sorry about that.
[00:41] whack	no worries, everybody makes typos :)
[00:42] gpfreitas	I just feel bad asking someone to "debug" code for me (as simple as it is) for free. So thanks.
[00:42] gpfreitas	Now,
[00:42] gpfreitas	when you said, you never send a reply to the request
[00:43] whack	yeah, req/rep. When you send a request with the client, server receives with a REP socket, you must reply always
[00:43] whack	even if it's an empty message
[00:43] whack	but that's a bug on your server, not the client, still reading your client code to see why it's crashing
[00:43] whack	oooh
[00:43] gpfreitas	Ok. I'll get back to that later.
[00:43] whack	hah yeah, what I said.
[00:43] whack	your data array has 5 elements
[00:43] gpfreitas	The lack of reply?
[00:43] whack	yeah
[00:44] whack	your server can just reply "OK" or something silly, have your client receive and drop the reply
[00:44] gpfreitas	That's the state thing that it is complaining about.
[00:44] whack	yup!
[00:44] gpfreitas	I see.
[00:44] whack	you are essentially doing two sends in a row on the same socket without processing a reply
[00:44] whack	and req/rep requires a request and reply each :)
[00:44] whack	hope this helps
[00:44] gpfreitas	thanks man
[00:45] gpfreitas	and an empty message is an empty string, or just nothing at all
[00:45] gpfreitas	like
[00:45] gpfreitas	socket.send('')
[00:45] gpfreitas	or socket.send()
[00:45] gpfreitas	?
[00:45] whack	I'd try empty string first
[00:45] whack	''
[00:45] gpfreitas	Ok.
[00:45] gpfreitas	If you don't mind, I'll ask some other questions!
[00:45] gpfreitas	:)
[00:45] whack	go ahead :)
[00:45] gpfreitas	Is it possible to send Python objects, instead of strings?
[00:46] gpfreitas	Well, that's probably a bad idea anyway. Better to send some representation of the object, right?
[00:46] whack	I believe you'll have to serialize it somehow
[00:46] gpfreitas	(For portability reasons, I guess.)
[00:46] gpfreitas	Ok.
[00:47] whack	well, if it's always python to python
[00:47] gpfreitas	JSON, YAML, something.
[00:47] whack	you can use python's marshal feature
[00:47] gpfreitas	marshal?
[00:47] gpfreitas	Ok, I'll check that
[00:47] whack	gpfreitas: yeah json or yaml will also suffice
[00:47] whack	http://docs.python.org/library/marshal.html
[00:47] gpfreitas	whack, thanks a lot.
[00:47] gpfreitas	Really.
[00:47] gpfreitas	I have found one nice pyzmq tutorial
[00:47] gpfreitas	and the examples in the zmq trunk, and the pyzmq trunk
[00:48] gpfreitas	(the nice tutorial was http://nichol.as/zeromq-an-introduction . This actually made me want to learn the thing.)
[00:48] whack	gpfreitas: yeah, marshal.dumps(some object) and send the resulting string; then marshal.loads(message) to load it up
[00:48] gpfreitas	whack: cool!
[00:48] gpfreitas	thanks again man.
[00:48] gpfreitas	Back to docs
[00:48] gpfreitas	the examples in the zmq and pyzmq trunks don't have a lot of comments
[00:48] gpfreitas	so they are not as helpful as they can be. Still very helpful, but, anyway.
[00:48] whack	nod. The ZMQ guide is pretty good about explaining how/why/what to do with zeromq
[00:49] gpfreitas	Ok. I'll check that.
[00:49] whack	most of the guide has examples in C, but the concepts are universal
[00:49] gpfreitas	Ok.
[00:49] whack	http://zguide.zeromq.org/page:all <-- guide
[00:49] whack	good luck :)
[00:49] gpfreitas	Thanks again.
[00:49] gpfreitas	I might come back to bother you guys again!
[00:49] gpfreitas	So far, I really like the simplicity of the whole thing, and I know I'm just scratching the surface.
[00:49] whack	soon you'll be conquering economic models before you know it
[00:49] gpfreitas	Haha
[00:50] whack	I was an econ minor :)
[00:50] gpfreitas	It's really cool to be able to implement an abstract concept like that of a "economic mechanism" in a bunch of server/clients... Really, really cool.
[00:50] gpfreitas	Cool.
[00:50] whack	the one econ class I wanted to take extra before graduation was game theory, but it was always over-full
[00:50] gpfreitas	Ah, pity.
[00:50] gpfreitas	It's really cool.
[00:51] whack	nod, I studied it briefly on my own; took labor and a bunch of other ones, too
[00:51] gpfreitas	I don't know labor econ at all. My field is mainly "reverse game theory" (mechanism design).
[00:51] gpfreitas	We design games so that the equilibria are what we want to happen.
[00:52] whack	cool :)
[00:52] gpfreitas	These games can be implemented in real life through things like ZMQ.
[00:52] gpfreitas	Like an auction.
[00:52] gpfreitas	Or a voting procedure.
[00:52] gpfreitas	Or a market.
[00:53] gpfreitas	And if I can implement these things quickly, then I don't have to rely on the programmers here, that are always so busy (and of course, the professors have priority over us when it comes to their time)
[00:53] gpfreitas	All right. whack, thanks once more. You are very helpful, man.
[00:53] gpfreitas	Take care.
[00:53] whack	later :)
[01:01] gpfreitas	whack: you still there?
[01:01] gpfreitas	New server code http://codepad.org/ttCkwfKA did not work. You can see I added the empty messages.
[01:01] whack	checking
[01:02] whack	did you update your clients to receive as well?
[01:02] gpfreitas	(client code, again: http://codepad.org/aV9zY1OY)
[01:02] gpfreitas	Oh.
[01:02] whack	you have this:
[01:02] whack	out_socket1.send(str(d))
[01:02] gpfreitas	I suppose they do not receive things automatically. :\|
[01:02] whack	but need to out_socket1.recv() or whatnot :)
[01:02] gpfreitas	Gosh. Sorry.
[01:02] whack	no worries
[01:02] gpfreitas	Thanks, gain man.
[01:03] gpfreitas	again
[01:03] whack	this particular model might fit best without req/rep
[01:03] gpfreitas	how would the clients send the result then?
[01:03] whack	pubsub from client->server would fit your model, maybe; depending on where you are taking this program
[01:04] gpfreitas	I mean, in general, the model I have in mind is: each client `i` sends a message `m_i` and server applies a function `f` on `(m_1, ..., m_n)` obtaining a result `r` that it broadcasts to all the clients.
[01:05] whack	nod, what you have now (assuming you handle empty replies and such) is fine; alternately you can have each client publish m_i with pubsub
[01:05] whack	totally your call; try both and maybe see what fits you better
[01:08] gpfreitas	pubsub does not require this "you need to reply" bureaucracy?
[01:09] whack	yup
[01:09] whack	your clients would simply send each number (publish) to the server
[01:09] whack	and server would pull one message from each client (like it does now), do some computation, then publish result to all clients
[01:09] gpfreitas	Ok. That's better.
[01:09] gpfreitas	I'll try that.
[01:10] whack	you'll still need one 'sub' on the server per client
[01:10] whack	just so you can identify which messages are from what client
[01:10] gpfreitas	yeah
[01:11] gpfreitas	whack: well, thank you very much. Again!
[01:11] gpfreitas	I'll work on this later. Need to go to a meeting. Thanks, whack.
[01:11] gpfreitas	See you later!
[01:11] whack	later :)
[02:10] xristos	does zmq use select or epoll internally?
[02:10] xristos	i'm hitting the select fd > 1024 issue
[02:11] whack	xristos: strace will show you
[02:16] xristos	well it shouldn't matter, the question is why is it having issues with > fds open
[02:16] xristos	*1024
[02:40] Silly	I thought 1024 was a limitation of the linux kernel from the last time I looked into opening more than that...
[02:40] Silly	maybe I just had a weird system...
[02:52] reuben	Silly, it is, you can change that limit
[02:52] reuben	xristos, ^
[03:08] xristos	reuben: you mean FD_SETSIZE?
[03:09] xristos	that needs kernel recompilation
[03:23] reuben	xristos, nono, it's a runtime configuration
[03:24] reuben	xristos, /etc/sysctl.conf
[03:24] reuben	fs.file-max
[03:26] xristos	i have that changed to 500k
[03:26] reuben	xristos, or just ulimit -n NUM
[03:26] reuben	on bash
[03:26] xristos	ulimit -n
[03:26] xristos	is 1 100k
[03:26] xristos	so thats not it
[03:27] xristos	if zeromq is using select then it's a known problem
[03:27] xristos	i call zmq_poll
[03:27] xristos	don't know what that does underneath
[03:28] xristos	but the way it manifests is i have a pull socket
[03:28] xristos	> 1024 clients connect and do push
[03:28] xristos	and i've called poll
[03:29] xristos	well actually it's more like 500 clients
[03:29] xristos	so one client connection uses more than 1 fd
[03:51] sustrik	xristos: what OS are you on?
[03:51] sustrik	select is being used only for windows and openvms iirc
[03:52] xristos	linux 2.6
[03:52] sustrik	hm
[03:52] sustrik	what's the actual assert?
[03:54] xristos	dont have it right now, i'm at home
[03:55] sustrik	write an email to the list later on then
[03:55] sustrik	or fill in a bug report
[03:55] sustrik	with test program attached
[03:55] xristos	i'll ask here tomorrow
[03:55] xristos	from work
[03:56] sustrik	ok
[07:33] minsa	I am reading the zmq internal paper.
[07:33] minsa	when objects inside an I/O threads register a file descriptor, does it use the poller_t in the io_thread_t ?
[07:34] minsa	I know that poller_t in the io_thread_t receives commands from other threads.
[07:35] minsa	but I wasn't sure whether that is the same poller_t used for the file descriptors from the objects inside that I/O thread.
[08:28] sustrik	minsa: yes, it's the same poller
[10:28] pieter_hintjens	sustrik: hi
[10:29] pieter_hintjens	just doing some tests on 3.0...
[10:29] sustrik	morning
[10:29] sustrik	any problems?
[10:29] pieter_hintjens	getsockopt doesn't seem to return consistent results in some cases
[10:29] pieter_hintjens	if I set the rcvhwm on a dealer socket and then try to get it back that works
[10:30] pieter_hintjens	if I do the same on a sub socket, it doesn't work
[10:30] pieter_hintjens	if I set affinity and try to get it back I don't get the same value back
[10:30] pieter_hintjens	this used to work in 3.0, something's changed
[10:31] sustrik	strange
[10:31] sustrik	do you have a test program?
[10:32] pieter_hintjens	it's in czmq but I can make a plain one, sure
[10:32] pieter_hintjens	30 secs...
[10:39] pieter_hintjens	sustrik: minimal test case is here: https://gist.github.com/1077756
[10:39] sustrik	let me see
[10:41] sustrik	pieter_hintjens: works ok here
[10:41] sustrik	what computer is that on?
[10:41] sustrik	32bit one?
[10:41] pieter_hintjens	ubuntu
[10:41] pieter_hintjens	64-bit one
[10:41] sustrik	hm, same here
[10:41] pieter_hintjens	it returns zero
[10:42] pieter_hintjens	i'll do some more checking... just built & installed 3.0 from master
[10:42] sustrik	testing on master as well...
[10:43] sustrik	does getsockopt succeed??
[10:43] sustrik	the result is not checked
[10:43] pieter_hintjens	have checked that, getsockopt succeeds fine
[10:43] sustrik	hm
[10:44] pieter_hintjens	I'll debug it, can't be so difficult
[10:44] sustrik	ok
[10:47] pieter_hintjens	sustrik: it never seems to call getsockopt (in options.cpp) at all
[10:47] pieter_hintjens	sorry
[10:47] sustrik	just step into the function
[10:47] pieter_hintjens	I meant, it never calls setsockopt
[10:48] pieter_hintjens	it does call getsockopt and the value is (still) zero
[10:48] sustrik	zmq_setsocopt?
[10:48] pieter_hintjens	int zmq::options_t::setsockopt
[10:48] pieter_hintjens	that is never called
[10:48] sustrik	try stepping inside the function
[10:48] sustrik	in gdb
[10:48] pieter_hintjens	ok
[10:48] sustrik	it should look like this:
[10:49] sustrik	zmq_setsockopt()
[10:49] sustrik	zmq::socket_t::setsockopt()
[10:49] sustrik	zmq::options_t::setsockopt()
[10:49] pieter_hintjens	agh, doorbell & meeting, will have to continue later
[10:51] sustrik	cya
[11:02] sustrik	pieter_hintjens: found the proble
[11:03] sustrik	let me fix it
[11:07] CIA-32	libzmq: 03Martin Sustrik 07master * r57c1342 10/ src/sub.cpp : Bug with setting options on SUB socket fixed ...
[11:11] sustrik	done
[11:29] mpales	just a quick question about REP sockets
[11:30] mpales	i bind one, start polling and receive an event right away, although no REQ is connected yet
[11:30] mpales	is it ok?
[11:31] mpales	recv on the socket then blocks
[11:32] sustrik	mpales: no
[11:32] reuben	no, that's not ok...
[11:32] sustrik	it's a bug
[11:33] sustrik	mpales: what version of 0mq is that?
[11:56] mpales	sustrik: it's 2.1.7
[12:20] sustrik	ok, let me try
[12:20] sustrik	mpalse: ah, btw, what event is that?
[12:20] sustrik	POLLOUT
[12:20] sustrik	?
[12:20] sustrik	that should be ok
[12:28] mpales	it's POLLIN
[12:29] mpales	i use a normal system select on socket's fd
[12:29] mpales	not zmq::poll
[13:15] pieter_hintjens	re
[13:16] sustrik	pieter_hintjens: the problem is fixed
[13:16] sustrik	try the new version
[13:16] pieter_hintjens	sustrik: yes, saw that, will retest now... thanks!
[13:19] pieter_hintjens	sustrik: fix confirmed, thanks!
[13:27] pieter_hintjens	sustrik: question, why is ZMQ_AFFINITY a uint64_t?
[13:42] sustrik	pieter_hintjens: it's the biggest interger type availble
[13:42] sustrik	should be a bitmap of course
[13:42] sustrik	TODO
[13:42] pieter_hintjens	sustrik: ah, bitmap
[13:43] pieter_hintjens	stupid of me, I missed that, but eventually it should be a blob, yes
[13:43] pieter_hintjens	also MAXMSGSIZE might better be an int
[13:43] sustrik	yeah, the API is capable of that
[13:43] sustrik	but the implementation is lousy
[13:44] pieter_hintjens	perhaps just an 8-byte blob?
[13:44] sustrik	random sized blob
[13:44] sustrik	not a big problem
[13:44] pieter_hintjens	later then
[13:44] sustrik	yes
[13:44] pieter_hintjens	I'm removing the debian packaging as mato requested
[13:44] sustrik	sure
[13:44] pieter_hintjens	ok
[14:13] pieter_hintjens	zeromq/3.0.0 has been officially packaged & released
[14:13] pieter_hintjens	go break it, guys!
[14:15] mikko	as a stable?
[14:16] pieter_hintjens	heh, sure
[14:16] pieter_hintjens	I spent all night writing comprehensive test ... oh, hang on, that was a dream
[14:16] pieter_hintjens	no mikko, as unstable...
[14:17] pieter_hintjens	mikko: you'll be real happy to know I cloned the repo again
[14:55] sustrik	pieter_hintjens: you should announce it on zeromq-dev as well
[14:56] pieter_hintjens	sustrik: did that
[14:56] pieter_hintjens	did the email not show up?
[14:56] sustrik	ah, there it is
[14:56] sustrik	sorry, missed it
[14:56] pieterh	its pretty simple, the packaging process...
[14:56] pieterh	one thing we might do, remove the old tags from master
[14:57] sustrik	you mean pre 2-1?
[14:57] pieterh	yes
[14:57] sustrik	they should be somewhere
[14:57] sustrik	given there's no 2-9
[14:57] sustrik	2=0
[14:57] pieterh	they're in the zeromq2-0 repo
[14:57] sustrik	i see
[14:57] sustrik	no idea how to remove them though
[14:57] pieterh	https://github.com/zeromq/zeromq2-0
[14:57] pieterh	all there
[14:57] pieterh	well, I'll remove them if you approve
[14:58] sustrik	sure, go on
[14:58] pieterh	great, that'll help, there's always this risk now of fetching all the tags by mistake
[14:59] pieterh	a\|i: yes, afaik
[14:59] pieterh	there are a lot of Lua examples in the Guide
[14:59] pieterh	including examples of polling (which is what you want)
[15:00] pieterh	search for poll
[15:00] pieterh	it applies to sub sockets as well as other types
[15:04] pieterh	a\|i: poll works by waiting for a socket to be ready (for input, or output as you specify), then telling you
[15:05] pieterh	sustrik: done, removed, the tags will remain in cloned copies of the repo until manually deleted there
[15:05] pieterh	a\|i: the question makes little sense... please read the Guide a little more...
[15:06] sustrik	pieterh: thanks
[15:06] sustrik	any idea how to remove outdated topic branches btw?
[15:06] pieterh	a\|i: it's not a coroutine, your thread is suspended until there's activity for it to work on
[15:06] pieterh	sustrik: kind of the same, you remove locally and/or remotely as separate operations
[15:07] pieterh	a\|i: yes... but if you read the Guide as I suggest you would know all this
[15:07] pieterh	sustrik: to delete a remote branch is the same as deleting a remote tag, you push 'nothing' to it...
[15:08] pieterh	git push origin :branchname
[15:08] sustrik	ok, let me try
[15:08] pieterh	to delete a local branch, git branch -d branchname
[15:10] sustrik	works!
[15:10] pieterh	:-)
[15:11] pieterh	yes, much cleaner now
[15:11] pieterh	we can delete the maint branch too IMO
[15:11] pieterh	it's not used, not maintained
[15:11] sustrik	true
[15:12] sustrik	done
[15:12] pieterh	i really like this process we're using, it's light and simple
[15:54] sustrik	mpales: still there?
[15:54] sustrik	i've created following test program:
[15:54] sustrik	https://gist.github.com/1078259
[15:54] sustrik	it seems to work ok
[15:54] sustrik	can you give it a try?
[19:42] fintler	does anyone know of anyone doing a compare and contrast of zeromq to mrnet?
[19:43] fintler	or anyone using zeromq in HPC for that matter?
[19:46] fintler	on another note, the zeromq examples kick ass
[19:46] fintler	amazing work
[21:46] mikko	pieterh: here?
[22:05] mikko	or sustrik
[23:59] smanek	hi there. I have a a server which creates a 0mq PUB socket, and several clients connect to the socket. Things work well, but well for the first few minutes, but then all the clients stop seeing any messages (even though the server logs show that it is 'sending' them over the socket). Both the server and clients are using pyzmq. Any ideas?