Beam is a library to turn your application into a collection of loosely coupled micro-services. It implements an ultra-lightweight hub for the different components of an application to discover and consume each other, either in-memory or across the network.
Beam can be embedded with very little overhead by using Go channels. It also implements an efficient http2/tls transport which can be used to securely expose and consume any micro-service across a distributed system.
Because remote Beam sessions are regular HTTP2 over TLS sessions, they can be used in combination with any standard proxy or authentication middleware. This means Beam, when configured propely, can be safely exposed on the public Internet. It can also be embedded in an existing rest API using an http1 and websocket fallback.
Modern micro-services are not a great fit for classical RPC or REST protocols because they often rely heavily on events, bi-directional communication, stream multiplexing, and some form of data synchronization. Sometimes these services have a component which requires raw socket access, either for performance (file transfer, event firehose, database access) or simply because they have their own protocol (dns, smtp, sql, ssh, zeromq, etc). These components typically need a separate set of tools because they are outside the scope of the REST and RPC tools. If there is also a websocket or ServerEvents transport, those require yet another layer of tools.
Instead of a clunky patchwork of tools, Beam implements in a single minimalistic library all the primitives needed by modern micro-services:
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Request/response with arbitrary structured data
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Asynchronous events flowing in real-time in both directions
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Requests and responses can flow in any direction, and can be arbitrarily nested, for example to implement a self-registering worker model
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Any request or response can include any number of streams, multiplexed in both directions on the same session.
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Any message serialization format can be plugged in: json, msgpack, xml, protobuf.
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As an optional convenience a minimalist key-value format is implemented. It is designed to be extremely fast to serialize and parse, dead-simple to implement, and suitable for both one-time data copy, file storage, and real-time synchronization.
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Raw file descriptors can be "attached" to any message, and passed under the hood using the best method available to each transport. The Go channel transport just passes os.File pointers around. The unix socket transport uses fd passing which makes it suitable for high-performance IPC. The tcp transport uses dedicated http2 streams. And as a bonus extension, a built-in tcp gateway can be used to proxy raw network sockets without extra overhead. That means Beam services can be used as smart gateways to a sql database, ssh or file transfer service, with unified auth, discovery and tooling and without performance penalty.
An explicit goal of Beam is simplicity of implementation and clarity of spec. Porting it to any language should be as effortless as humanly possible.
Solomon Hykes
Code and documentation copyright 2013-2014 Docker, inc. Code released under the Apache 2.0 license. Docs released under Creative commons.