I’m currently documenting an application that uses RabbitMQ extensively. I want to show the routing topology within the broker, but I want the bulk generated automatically because there are a lot of entities to deal with. Given that I can export the broker definitions into JSON, it seemed like it would be fairly straightforward to generate something using Graphviz.
The internet does reliability end to end. That is, when a node A sends a message to node B, the message travels through many other nodes. These intervening nodes make a best effort at delivery, but if they don’t succeed, they just forget about it. B must confirm receipt, and A must try again if it doesn’t.
Communicating securely requires the same approach. We should not guarantee each step is secure, and hence the whole path is secure, but design a system in which only the design of A and B matters.
The more we do our computing in the cloud, the more true this becomes. Simply put, the security of our communications depends on too many people, and the chances of failure multiply.
For example, we might use a messaging service, provided in the cloud. A and B could authenticate to the message server, and ensure privacy by connecting using SSL. The server could implement access controls, to ensure other users of the service won’t receive messages they are not entitled to receive. In this arrangement, you are making some assumptions:
Alternatively, A could encrypt messages using B’s private encryption key, and sign them with its private signing key. Then we are assuming:
Unfortunately good excuses abound:
I’ve recently designed a solution which uses end to end encryption of messages, and a message server to minimise the attack surface of the solution, and ensure privacy while transferring data over the internet. The attack surface is minimised to the extent that the nodes are behind firewalls that allow no incoming connections. Because messages must have valid signatures to be accepted, an attacker cannot use specific payloads in messages to attack the system. They are limited to attacking the code which parses the envelope. This code is extremely simple.
To do this efficiently, we have designed our own cryptographic suite, based on the NSA Suite B specification. Because this specification does not specify an encoding, we have designed our own envelope for messages. The resulting library also includes a sophisticated, extensible trust model. We plan to publish the result as open source.
We see lots of sites that use RabbitMQ, and other message servers, and would benefit from the security this architecture provides. Either these sites allow clients to interact with services via a message server, or use cloud based messaging services. Using cloud based messaging services has significant cost benefits over hosting your own message server, and in this architecture, the decision to do this has no security implications.
SpringSource, a division of VMware, Inc. today announced the acquisition by VMware of Rabbit Technologies, Ltd, a company set up by LShift and partners Monadic and CohesiveFT.
A worker pool is a very common pattern, and they exist in the standard libraries for many languages. The idea is simple: submit some sort of closure to a service which commits to running the closure in the future in some thread. Normally the work is shared out among many different threads and in the absence of anything fancier, one assumes a first-come-first-served queue of closures.
Erlang, with its light-weight process model is not a language which you would expect would require such an approach: processes are dirt cheap, and the scheduler maps processes onto threads when they are ready to be run — in many ways, the ErlangVM is a glorified implementation of a worker pool, only one that does pre-emption and other fancy features, in a very similar way to an OS kernel. However, we recently found in RabbitMQ a need for a worker pool. (more…)
People tend to like certain software packages to be scalable. This can have a number of different meanings but mostly it means that as you throw more work at the program, it may require some more resources, in terms of memory or CPU, but it nevertheless just keeps on working. Strangely enough, it’s fairly difficult to achieve this with finite resources. With things like memory, the classical hierarchy applies: as you use up more and more faster memory, you start to spill to slower memory — i.e. spilling to disk. The assumption tends to be that one always has enough disk space.
Other resources are even more limited, and are harder to manage. One of these is file descriptors. (more…)
Some time ago we got an interesting bug report for RabbitMQ. Surprisingly, unlike other complex bugs, this one is easy to describe:
At some point basic.get suddenly starts being very slow – about 9 times slower!(more…)
In several applications, it’s very useful to be able to take messages out of one RabbitMQ broker, and insert them into another. Many people on our mailing list have being asking for such a shovel, and we’ve recently been able to devote some time to writing one. This takes the form of a plugin for Rabbit, and whilst it hasn’t been through QA just yet, we’re announcing it so people who would like to play and even suggest further features for inclusion can do so sooner rather than later.
The shovel is written on top of the Erlang client. It supports both direct and network connections to nodes, SSL support, the ability to declare resources on nodes it connects to, basic round-
robinrabbit balancing of both source and destination nodes, and allows you to configure many parameters controlling how messages are consumed from the source, and how they’re published to the destination. Multiple shovels can be specified, their statuses queried, and shovels can repeatedly reconnect to nodes in the event of failure.
The plugin is available from http://hg.rabbitmq.com/rabbitmq-shovel/, and is released under the MPL v1.1. There is a README included which contains full documentation. This is replicated below. (more…)
An obvious extension point for an AMQP broker is the addition of new types of exchange. An exchange type essentially represents an algorithm for dispatching messages to queues, usually based on the message’s routing key, given how the queues are bound to the exchange — it’s a message routing algorithm.
At a minimum, supporting new exchange types requires only some scaffolding to plug in to (an exchange type registry) and a hook for routing messages. However, this wouldn’t support some more interesting use cases, and in particular it didn’t support our motivating use case. Exchange types that want to keep their own state need to be initialised, and be notified about other lifecycle events. (more…)
Tokyo Cabinet is a rather excellent key-value store, with the ability to write to disk in a sane way (i.e. not just repeatedly dumping the same data over and over again), operate in bounded memory, and go really fast. I like it a lot, and there’s a likelihood that there’ll be a RabbitMQ plugin fairly soon that’ll use Tokyo Cabinet to improve the new persister yet further. Toke is an Erlang linked-in driver that allows you to use Tokyo Cabinet from Erlang. (more…)
Today I was lucky enough to give a talk at the Skills Matter Functional Programming Exchange. I talked about resource management in RabbitMQ and how we’re improving this in upcoming versions of RabbitMQ. All the sessions were videotaped and it would seem that a podcast will be going up shortly. In the mean time you can have a look at the slides if you want to.
The attendance was really good and the talks well received. There was a good range of talks, from some very practical and pragmatic such as my own, to slightly more theoretical talks. It was great to see Haskell, Erlang and F# being discussed outside of a purely academic setting and great to see so many companies and organisations getting really interested in functional programming and coming along to see how other people were making the most of it.
The Park Bench session was also good fun, with a good range of questions and experience being demonstrated by all. A good, fun atmosphere, and I’m sure all enjoyed the day.
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