NSQ: Realtime distributed message processing at scale (in Go)

by matticakes • 14 years ago

108 44 14 years ago

wheaties• 14 years ago

I love seeing how people tackle these sorts of problems. Here, the trade-off is duplicate messages reaching a client. I know others have tried a no-"ack" approach. I'm still working in the land of RabbitMQ solving all my business needs and I like it.

I'd love to see some numbers, reasons for decisions made, and suggested best practices for this solution other than "manual de-dupe."

jehiah3• 14 years ago

Some of the background behind our decisions are on our blog post http://word.bitly.com/post/33232969144/nsq

In terms of manual de-duping, we strive internally for idempotent message processing so it's fairly irrelevant, but to handle cases where it matters, all of our messages have unique id's added to them outside of NSQ.

The actual cases where messages are handled multiple times is limited to when a client disappeared during message processing (a hard restart) or it passed the allowable time window to respond and was given to another client.

If there are any specific numbers you are curious about, please ask.

old_sound2• 14 years ago

When people say "billions of messages per day" do they realize that 1 billion messages =~ 11500 msgs/sec ? RabbitMQ as well as any self respecting message broker is able to handle that on a single machine

jordanlewis• 14 years ago

It's kind of like Storm. I'd love to see a comparison written by the authors.

matticakes7• 14 years ago

Agreed, a comparison would be helpful for highlighting the tradeoffs behind the choices we made.

We do talk about the evolution of our infrastructure and the genesis of NSQ in our blog post, http://word.bitly.com/post/33232969144/nsq.

jallmann2• 14 years ago

Was something like MQTT investigated prior to re-inventing the wheel with NSQ? From a cursory examination, I don't see any major advantages other than nice UI tools.

The wire protocol seems more complicated -- why distinct protocols for producers and consumers? Linebreak-delimited headers are error-prone and ought to be banished. Why transmit the hostname with sub requests -- is another system requesting jobs on behalf of workers?

Then the topic/channel distinction seems artificial when wildcards would suffice (and provide much more flexibility), eg topic/*/channels or topic/channels/# in the MQTT parlance. MQTT also has more fine-grained delivery guarantees via its QoS levels. All this with a header structure that's as small as two bytes.

edit: While MQTT is pubsub, as long as the system is under your control, you're free to change the semantics at the broker side from "broadcast messages to all consumers" to "rotate messages among consumers."

retrovirus• 14 years ago

Yes, it would be nice if someone from the team behind NSQ elaborates a bit on why they didn't go with an existing protocol like MQTT.

matticakes7• 14 years ago

one of the developers here...

The protocols that exist in NSQ now are designed to be the simplest implementation that worked.

You've correctly pointed out some of the issues. At this stage, the distinction of producer vs consumer was mostly so that you could publish at all without having to use the HTTP interface. For our use cases, in particular taking advantage of the /mput endpoint, we aren't even using the TCP based publishing protocol.

Re: your point on sending metadata with SUB commands. I agree its a bit ugly. We actually intend on improving that aspect by instead sending the data in the form of an IDENTIFY type command upon initial connection. That information is used in the various administrative UIs and endpoints.

I'm going to do a bit more reading on MQTT, thanks for the link.

old_sound2• 14 years ago

I'm really curious to know why would you build this tool instead of using, say, RabbitMQ?

DISCLAIMER: I wrote the RabbitMQ in Action book.

rabbitmq3• 14 years ago

shameless rabbitmq mqtt plug here :-) http://www.rabbitmq.com/blog/2012/09/12/mqtt-adapter/

arjn• 14 years ago

We use ActiveMQ at work and are investigating other MQs too. I dont see any info or performance graphs w.r.t message size. That would be a useful addition.

jehiah3• 14 years ago

Good idea, we will try to put together some numbers with regards to message size.

bgentry• 14 years ago

This ensures that the only edge case that would result in message loss is an unclean shutdown of an nsqd process. In that case, any messages that were in memory (or any buffered writes not flushed to disk) would be lost.

I don't understand how you can call it a message delivery "guarantee" when you're susceptible to losing messages when a node dies.

One solution is to stand up redundant nsqd pairs (on separate hosts) that receive copies of the same portion of messages.

OK, delivery is only guaranteed if I run multiple independent sets of NSQd and write messages to both.

Regardless, it looks like an interesting project.

jlgreco2• 14 years ago

How would you design a system that didn't have this problem at the individual node level?

dclusin2• 14 years ago

Sequence numbers on messages sent by producers coupled with some sort of persistence by the sender. This way when a gap is detected some sort of resend protocol can be implemented to achieve the delivery guarantee.

philjr• 14 years ago

A similar design to TCP/IP - sequence numbers, acknowledgements & resending capability on sender side

onetwothreefour• 14 years ago

This is a solved problem in most messaging protocols.

matan_a• 14 years ago

We're currently using Apache Kafka which is working out great, but does include a broker as a middleman. This is good for us since it's designed to accumulate unconsumed data (or even roll it back) and still provide good performance - rather than having that happen on the producers or consumers.

It would be cool to see some stats on throughput and latency relative to # of producers / consumers and amount of data currently accumulated in the producers (since there is no middleman).

knodi3• 14 years ago

Does this have gob interface?

matticakes7• 14 years ago

it is data format agnostic so you can certainly serialize using the gob package.

knodi3• 14 years ago

Amazing, with this my whole infrastructure will be 100% Go.

jasonmoo• 14 years ago

Hey it's awesome to see you guys tackling a larger project in Go. I've been writing some smaller services/tools with it in my day job, and I like it a lot.

Thanks for sharing your work.

andreypopp• 14 years ago

Interesting if bitly guys had a look at beanstalkd before implementing nsqd.

matticakes7• 14 years ago

beanstalkd is a great project and it certainly inspired some of our thinking. I think of beanstalkd as a more fully functional alternative to simplequeue (what we built/used prior to NSQ - more details in our blog post http://word.bitly.com/post/33232969144/nsq).

Some of the goals of NSQ transcended just replacing our specific daemon that buffered and delivered messages (most importantly the interactions with the lookup service). Because of that, we felt that owning that piece would make it easier to achieve those goals.

Additionally, one of the most important properties of nsqd (the queue component of NSQ) is that data is pushed to the client rather than polled (like in beanstalkd).

knodi3• 14 years ago

Beanstalkd is not stable it has a lot issues even in it current version. If you doing to be sending couple million messages per day beanstalkd is not for you.

interg12• 14 years ago

Anyone at Disqus care to weigh in on this?

overbroad2• 14 years ago

I'm too lazy to install Go just to try this (I would need to, right?) but reading through the docs this looks far more appealing to me than tent.io. Nice work, at least with respect to the general design. Flexible.

jehiah3• 14 years ago

Thanks for the reminder. Getting binary builds up is on our to-do list, so check back soon for those.

In the mean time, installing Go is pretty easy (you can use brew, or the official OSX package (assuming you are on OSX) http://golang.org/doc/install) and we've tried to leave clear steps for building NSQ here https://github.com/bitly/nsq/blob/master/INSTALLING.md (there really are very few dependencies other than go itself)

overbroad2• 14 years ago

Cheers. I have installed Go before and messed around with it. I agree it's pretty good as far as being self-contained and straightforward. I just don't have the energy to keep chasing a moving target. For my purposes, I'm more interested in stuff that is stable and rarely changes.

If you can produce binaries for UNIX (Linux, BSD, etc), OSX and Windows, I'll be impressed. That's something I was interested in doing with Go (is it possible to cross-compile?) but never managed to learn.

dikbrouwer3• 14 years ago

How does this compare to ZeroMQ?

jeremyjh• 14 years ago

ZeroMQ is a library, it is embedded in the application code and can support a peer-to-peer messaging topology. It also has support for Broker patterns but you have to develop the Broker application yourself; you could build a solution such as this one using it, but the zmq library itself really handles lower-level concerns with a high degree of flexibility but no out-of-the-box functionality. zmq can be thought of as something as simple as an improved socket library but with support for async, storing & high-water marks when there are no attached consumers, various distribution strategies, queues and lots more.

dikbrouwer3• 14 years ago

Right, I guess my question more specifically is: ZeroMQ allows you to built applications like this in (seemingly) just a few lines of code. Did you guys consider building it on top of ZeroMQ, and if so, what made your decide to not use it? Nothing against what you've built btw, it looks great, but am just curious

stevvooe• 14 years ago

Where is the guy with the comment about generics? Disappointing.

NSQ: Realtime distributed message processing at scale (in Go)

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