ZeroMq IRC Log

Sunday November 28, 2010

[Time] Name	Message
[01:24] shaun510	mikko: got a prototype running using XREP/XREQ. It was a little trickier than expected, mainly due to leaving out the empty frame indicating the end of the addressing frames
[01:24] shaun510	otherwise, fairly painless.
[01:26] mikko	are you reading the zguide?
[01:26] mikko	and good news
[01:26] mikko	thats quick movement
[01:29] shaun510	yeah, the zguide is pretty awesome.
[01:30] shaun510	anyway, I'm not entirely sure if the XREQ/XREP pair is the path I want to take on this. It seems like 1:1 bidirectional streaming might be a pattern common enough to formalize.
[01:32] mikko	well, PAIR is 1:1
[01:33] shaun510	yeah, I saw that, but it seems like those are missing some of the nicer bits (I think the zguide mentioned something about no auto reconnection, for instance)
[01:37] shaun510	I might just need to rethink how these components are talking to each other. 1:1 streaming makes sense if you're limited to TCP connections, but maybe it would be better to use one of the other patterns.
[10:56] Steve-o	looks like I'd better cut a new PGM 5.0 if you want a master release on monday
[10:57] Steve-o	backport the rate limiter fix from 5.1
[14:05] Gekz	hi guys.
[14:06] Gekz	I'm using pyzmq, and I'm getting an error when attempting the following
[14:06] Gekz	socket.connect("epgm://foo.bar:34343")
[14:06] Gekz	File "socket.pyx", line 342, in zmq.core.socket.Socket.connect (zmq/core/socket.c:3304)
[14:06] Gekz	zmq.core.error.ZMQError: Invalid argument
[14:08] Gekz	socket.bind("pgm://foo.bar:34343") on the other server works though
[14:08] Gekz	the host
[14:08] Gekz	the client is spitting the error.
[14:09] Gekz	it makes no difference whterh I use pgm or epgm.
[14:13] sustrik	you are specifying a wrong connection string
[14:14] sustrik	Gekz: check zmq_pgm(7)
[14:14] Gekz	I have tried specifying an interface, such as epgm://eth0;foo.bar:34343
[14:14] Gekz	it gives me the same error >_>
[14:14] sustrik	what's foo.bar?
[14:14] sustrik	there should be a multicast group there
[14:15] Gekz	a hostname.
[14:15] sustrik	you probably want to use TCP, not PGM
[14:15] Gekz	I'm writing a server/client to distribute 70Gb from one server to approximately 100 computers.
[14:16] Gekz	I'm thinking TCP wont suffice for that.
[14:16] sustrik	on LAN?
[14:16] Gekz	on LAN.
[14:17] Gekz	oh, I totally misunderstood how multicasting works.
[14:17] Gekz	I didn't realise there was an IP range specifically for it.
[14:17] sustrik	you should read some introductry article first
[14:18] sustrik	http://en.wikipedia.org/wiki/IP_multicast
[14:18] Gekz	haha, I did, I just _missed_ that integral part.
[14:21] Gekz	sustrik__: before I make another stupid rookie error, as I said, I will be broadcasting large amounts of data. Will using ZMQ_SNDMORE suffice, or will I need to implement my own checks?
[14:22] sustrik	you want to send only a single message?
[14:22] Gekz	well, I need to send it in chunks, in order, to write a file in order.
[14:23] sustrik	do so then
[14:23] sustrik	PUB/SUB paradigm
[14:23] Gekz	what I'm asking is whether or not using ZMQ_SNDMORE will affect that
[14:23] Gekz	yeah, I'm using PUB/SUB
[14:24] sustrik	SNDMORE sends only a single message, the only difference is you can compose it in chunks
[14:24] sustrik	thus the whole message must fit into memory etc.
[14:24] Gekz	oh ok
[14:25] Gekz	so the other side receives one message
[14:25] Gekz	but you're concatenating multiple into one on the host
[14:25] Gekz	I understand now.
[14:25] sustrik	right
[14:25] Gekz	do I need to do any checks to ensure the packets are received in order?
[14:25] sustrik	order should be ok
[14:25] Gekz	that was my basic worry.
[14:25] sustrik	what you need to check is whether packets are missing
[14:26] Gekz	ah.
[14:26] sustrik	when network is overloaded, some of them may be dropped
[14:26] sustrik	but you can set the reliability parameters for PGM
[14:26] sustrik	check ZMQ_RATE, ZMQ_REOCVERY_IVL socket options
[14:27] Gekz	if they're dropped, does it NAK and request a resend?
[14:27] sustrik	that's happening behind the scenes automatically
[14:27] sustrik	when you see packet missing
[14:27] Gekz	yeah, that's what I'm asking
[14:27] sustrik	what happened was that the congestion was that bad there was no way to repair
[14:28] Gekz	so I should do non-blocking recv and check for errors?
[14:28] sustrik	no, just number the messages and check for missing messages then
[14:28] sustrik	do not ask for resend on the application level
[14:28] Gekz	ok
[14:29] sustrik	if message is missing the state of network is so bad that trying to recover would actually make the congestion even worse
[14:29] Gekz	so I need to know how it recovers. let's say it sends 1234, and the receiver receives 124.
[14:29] sustrik	?
[14:29] Gekz	I'd have implemented something that noticed that 4 is in fact not after 3
[14:30] sustrik	yes
[14:30] Gekz	would the third packet be resent?
[14:30] Gekz	or am I simply aware of the failure
[14:30] Gekz	and need to start again?
[14:30] sustrik	behind the scenes
[14:30] sustrik	you won't see that
[14:30] Gekz	ok
[14:30] Gekz	so it just drops 4, and waits to see 3?
[14:30] sustrik	if packet is missing
[14:30] sustrik	something went terribly wrong
[14:30] sustrik	you alert the admin then
[14:30] sustrik	blow the siren
[14:31] sustrik	start the red alert mode
[14:31] sustrik	auto-destruct
[14:31] sustrik	watever
[14:31] Gekz	lol
[14:31] Gekz	so basically, that should never happen
[14:31] Gekz	I should catch the error, abort, and work out the problem before attempting again?
[14:31] sustrik	it can, but there's no way to recover from it
[14:32] sustrik	for example, if the consumer is too slow
[14:32] sustrik	it cannot keep with the publisher
[14:32] sustrik	and finally blows up
[14:32] sustrik	the problem is there's no way to solve the problem
[14:32] Gekz	yep
[14:33] sustrik	maybe buy better box or something
[14:33] Gekz	so basically, dont publish at 1Gbit if you have 100Mbit subscribers haha
[14:33] sustrik	exactly
[14:33] Gekz	I'm actually trying to rig up a small application to distribute hdd images for a small job I have.
[14:34] sustrik	try with TCP first
[14:34] Gekz	I'm currently using novell zenworks, but that is just not feasible right now.
[14:34] sustrik	multicast is a complex topic
[14:34] Gekz	multicast is indeed more complex than I had expected.
[14:34] Gekz	but I was told that using TCP was a no-no for this.
[14:34] sustrik	you haven't heard all yet :)
[14:34] sustrik	you need adequate network hardware to deal with it
[14:35] sustrik	otherwise you can kill your network with it
[14:35] Gekz	many procurve switches >_>
[14:35] Gekz	many 1GBit switches
[14:35] sustrik	also, the network has to be set up correctly
[14:35] sustrik	etc.
[14:35] Gekz	but yes, I'm not in control of the infrastructure (which based on my experience, is probably a good thing :P)
[14:35] Gekz	but sadly, the guy in charge seems to know less
[14:35] Gekz	which is a scarier though
[14:35] Gekz	thought*
[14:35] sustrik	anyway, start with TCP
[14:36] sustrik	use multicast only if you are 100% sure the TCP won't fly
[14:36] Gekz	let me pastebin the code I have for my host, I'm not entirely sure if it's right
[14:36] Gekz	because when I test it with the client, it gets approximately half the packets before it just stops receiving.
[14:39] Gekz	http://paste2.org/p/1114829
[14:39] Gekz	sustrik__: ^
[14:40] Gekz	erm, except change epgm to tcp, I forgot to change it back xD
[14:42] sustrik	it's ok
[14:43] sustrik	keep in mind though that the subscribers may miss the beginning of the transmission
[14:43] sustrik	it they are started after it have begun
[14:44] Gekz	I start them first, this is just a test app
[14:45] sustrik	but it takes some time to connect
[14:45] sustrik	so you start the publisher
[14:45] sustrik	it starts publishing
[14:46] sustrik	the subscribers connect after 1/100 sec
[14:46] sustrik	but they've missed some messages already
[14:46] Gekz	no no
[14:46] Gekz	I bind on the server, then I start the client, then I hit enter on the server to start sending
[14:46] sustrik	then it should work fine
[14:46] Gekz	but it doesnt :<
[14:47] sustrik	then report a bug
[14:47] Gekz	I'm not sure where the bug is
[14:47] Gekz	because it stops printing numbers part way
[14:47] Gekz	280 281 282 28
[14:47] Gekz	it never prints the 3 in 283 which confuses me.
[14:47] sustrik	heh
[14:47] sustrik	a deadlock in python?
[14:48] sustrik	report the bug to pyzmq project IMO
[14:50] Gekz	I changed how I test it
[14:50] Gekz	and it worked.
[14:50] Gekz	I made it send a count, instead of counting itself.
[14:51] Gekz	ie, filled the buffer with 1 to 9999
[14:51] Gekz	it worked.
[14:51] Gekz	so it's probably just a crappy python bug
[14:52] Gekz	haha that crashed my terminal
[14:52] Gekz	damn you python, you're ruining my day
[14:53] Gekz	haha, it's still sending packets
[14:59] Gekz	anyway, thanks very much sustrik__
[14:59] Gekz	you've guided my efforts well :P
[14:59] Gekz	and now i shall sleep.
[16:09] mikko	sustrik__: http://build.valokuva.org/job/ZeroMQ2-core-master_mingw32/28/console
[16:52] sustrik	mikko: yes, seen it
[16:52] sustrik	sorry
[18:31] magicblaze007	will there be a zeromq python installation system for windows (.msi/.exe) sometime?
[18:33] magicblaze007	seems like there used to be an msi installer -- http://lists.zeromq.org/pipermail/zeromq-dev/2009-January/000321.html (but the link doesnt have anything)
[18:43] Guthur	magicblaze007, Probably a matter of no one being willing to maintain it
[18:43] Guthur	you could ask on the mailing list and maybe volunteer
[18:44] sustrik	Guthur: right
[18:44] sustrik	it's just a matter of someone actually doing it :)
[18:46] Guthur	mikko, The building of clrzmq2 seems to be stuck
[18:46] Guthur	says that it has taken over 2.5 days so fatr
[18:46] Guthur	far*
[18:47] Guthur	http://build.valokuva.org/
[18:50] mikko	added a timeout
[18:50] mikko	it now fails after 5 mins
[18:57] magicblaze007	Guthur: are these zeromq builds that are maintained regularly?
[18:58] magicblaze007	I guess i should be looking at this: http://build.valokuva.org/view/pyzmq/?
[18:58] mikko	magicblaze007: those are daily builds for zeromq and bindings
[18:59] mikko	magicblaze007: MSI installer is slightly different
[19:00] magicblaze007	all thats stopping me from using zeromq in my project is a windows msi installer. I wish i was any good in writing installers..
[19:00] Guthur	magicblaze007, You could just build it...
[19:01] magicblaze007	Guthur: I tried. I guess I only have VS 2010. Didnt work
[19:01] mikko	magicblaze007: why do you need msi installer?
[19:01] magicblaze007	because my users can easily install it?
[19:01] Guthur	magicblaze007, build instructions are here [
[19:01] Guthur	oops
[19:01] mikko	why dont you ship it with your project?
[19:01] Guthur	here http://www.zeromq.org/bindings:python
[19:02] magicblaze007	Guthur: for pyzmq installation, zmq should be installed...which is the problem
[19:03] Guthur	It seemed to mention building libzmq from scratch
[19:03] mikko	magicblaze007: you can ship the .dlls with your project
[19:03] mikko	i dont think anything prevents you from doing that
[19:04] mikko	libzmq.dll should be enough afaik
[19:04] magicblaze007	so pyzmq just needs one dll file?
[19:10] sustrik	i think so
[19:19] andrewvc	cremes: you around at all?
[19:19] andrewvc	or I guess actually someone else might, know, I've got a question about zmq fds
[19:20] andrewvc	basically, http://www.mail-archive.com/zeromq-dev@lists.zeromq.org/msg03131.html
[19:20] andrewvc	says that you'd monitor the file descriptor you get with ZMQ_FD, and figure out what to do based on ZMQ_EVENTS
[19:21] andrewvc	but, if you're using the FD with say 'select', should readable and writable be determined by select
[19:21] andrewvc	why do you need ZMQ_EVENTS ?
[20:03] cremes	andrewvc: i'm around for a bit...
[20:03] cremes	i don't have an answer for your question ^^
[20:03] cremes	i spent a lot of time messing around with 0mq FDs yesterday in Ruby and had very little luck treating it like a real FD
[20:04] cremes	btw, jruby returns EBADF for 0mq FDs
[20:06] mikko	andrewvc: because a full message might not be there
[20:06] mikko	andrewvc: 0mq handles "messages" and activity on the socket doesn't mean that a message is ready
[20:15] andrewvc	hi
[20:15] andrewvc	ah, gotcha
[20:16] andrewvc	yeah, the FDs are problematic as real FDs
[20:16] andrewvc	jruby doesn't like them instantiated as IOs
[20:16] andrewvc	but EM doesn't mind being passed the raw FD
[20:16] cremes	interesting
[20:17] andrewvc	yeah, I got issues instantiated FDs as IOs as well
[20:17] andrewvc	*instantiating
[20:17] andrewvc	mikko: thanks btw
[20:17] cremes	yeah, i'm trying to cook up another way of confirming the FD is good in the ruby env
[20:17] cremes	no luck so far
[20:22] cremes	andrewvc: that might be a bug
[20:22] andrewvc	cremes: thanks. Can do
[20:23] cremes	andrewvc: want to collaborate on zmqmachine too? alternately, once EM goes 1.0 we might be able to get 0mq sockets into it and then i can drop the zmqmachine project
[20:24] andrewvc	sure, definitely, was working on adding EM support to it today
[20:24] andrewvc	had rudimentary, support kinda working
[20:24] andrewvc	brb, gtg for ~ 45 min
[20:24] cremes	neat!
[20:24] cremes	ttyl; i'm out the remainder of the day
[21:13] mgc	Hmm, doing pub/sub with epgm, when a subscriber gets too far behind it get permanently blacklisted. Is there any way to handle/recover from this other than just consuming faster and manually reconnecting?
[23:11] Guthur	mgc: I assume you can set a higher ZMQ_RECOVERY_IVL
[23:12] Guthur	that has memory issues though see -> http://api.zeromq.org/zmq_setsockopt.html
[23:19] mgc	I've tried that, but no luck. I think I'm being bitten by https://github.com/zeromq/zeromq2/issues#issue/104
[23:19] mgc	I only see the subscribers dropping off when they are all on the same box
[23:20] mgc	when I load test between two boxes it doesnt seem to happen
[23:20] mgc	so I tried delaying the subscriber connects, but no luck.
[23:24] magicblaze007	how is activemq different from zeromq?
[23:27] mgc	magicblaze007: http://stackoverflow.com/questions/731233/activemq-or-rabbitmq-or-zeromq-or
[23:29] magicblaze007	thanks
[23:30] magicblaze007	where can i find the zeromq-dll for windows for download. Cant compile the source on windows
[23:35] mgc	http://www.coastrd.com/download/ZMQClientServer.zip?attredirects=0
[23:38] magicblaze007	thanks mgc
[23:38] magicblaze007	now does anyone know how i can use this dll file and use pyzeromq on a windows machine?
[23:40] mgc	sorry :)
[23:42] mgc	Guthur: ugh, nevermind, I get the dead subscriber then between two boxes as well. 4,000 msgs/s, hwm recoveryivl buffer sizes all cranked way up, after several minutes one or more subscribers just stops getting messages.
[23:42] Guthur	mgc: Sorry I had tuned out there
[23:42] Guthur	just reading the backlog