Lightweight RPC using Redis
by Nathan Farrington http://nathanfarrington.com
Redis is a powerful in-memory data structure server that is useful for building fast distributed systems. Redis implements message queue functionality with its use of list data structures and the LPOP, BLPOP, and RPUSH commands. RedisRPC implements a lightweight RPC mechanism using Redis message queues to temporarily hold RPC request and response messages. These messages are encoded as JSON strings for portability.
Many other RPC mechanisms are either programming language specific (e.g. Java RMI) or require boiler-plate code for explicit typing (e.g. Thrift). RedisRPC was designed to be extremely easy to use by eliminating boiler-plate code while also being programming language neutral. High performance was not an initial goal of RedisRPC and other RPC libraries are likely to have better performance. Instead, RedisRPC has better programmer performance; it lets you get something working immediately.
Here is a brief example using Python. The full source is in the examples/ directory.
redis_server = redis.Redis() calculator = redisrpc.RedisRPCClient(redis_server, 'calc') calculator.clr() calculator.add(5) calculator.sub(3) calculator.mul(4) calcaultor.div(2) assert calculator.val() == 4
redis_server = redis.Redis() server = redisrpc.RedisRPCServer(redis_server, 'calc', calc.Calculator()) server.run()
That’s all there is to it. The server wraps a local object, in this case a Calculator object. It listens for RPC requests from the ‘calc’ message queue. When it receives a request, it executes it on the calculator object and returns the result to the client. If an exception occurs then the exception is sent to the client.
Notice that the client doesn’t actually access the Calculator class. Instead its method invocations are intercepted and wrapped into RPC requests that are forwarded to the server. The return values embedded in the RPC responses are used for the values of the expressions.
Source code is available at http://github.com/nfarring/redisrpc.
This software is available under the GPLv3 or later. See the file LICENSE for more information.