zerorpc

zerorpc-node

ZeroRPC is a communication layer for distributed systems. zerorpc-node is a port of the original ZeroRPC for node.js. We have full client and server support for version 3 of the protocol, and clients/servers written in the Python version can communicate transparently with those written in node.js. This project is in alpha.

To install the package:

Make sure you have ZeroMQ installed.

Then:

npm install zerorpc

If you get the error Package libzmq was not found after making sure ZeroMQ is installed, take a look at the fix for zeromq.node. If you get the error Unable to load shared library <<path to zeromq.node>>/binding.node, make sure you run ldconfig. If that still doesn't work, check out this ticket.

Servers

To create a new server:

var zerorpc = require("zerorpc");
var server = new zerorpc.Server(context [, heartbeat]);

The constructor takes in a context object with the functions to expose over RPC. Only functions that do not have a leading underscore will be exposed. Each exposed method must take in a callback as the last argument. This callback is called as callback(error, response, more) when there is a new update, where error is an error object or string, response is the new update, and more is a boolean specifying whether new updates will be available later. error, response, and more default to falsy values, so e.g. simply calling callback() closes an open stream, since more is false by default. Constructor also takes a heartbeat parameter that specifies the interval that the server should ping clinets to let them know it is active.

Events:

• error - When an error occurs.

Methods:

• bind(endpoint) - Binds the server to the specified ZeroMQ endpoint.
• connect(endpoint) - Connects the server to the specified ZeroMQ endpoint.
• close() - Closes the ZeroMQ socket.

Full example:

var zerorpc = require("zerorpc");

var server = new zerorpc.Server({
    addMan: function(sentence, reply) {
        reply(null, sentence + ", man!");
    },

    add42: function(n, reply) {
        reply(null, n + 42);
    },

    iter: function(from, to, step, reply) {
        for(i=from; i<to; i+=step) {
            reply(null, i, true);
        }

        reply();
    }
});

server.bind("tcp://0.0.0.0:4242");

server.on("error", function(error) {
    console.error("RPC server error:", error);
});

Clients

To create a new client:

var zerorpc = require("zerorpc");
var client = new zerorpc.Client(options);

The constructor optionally takes in an options object. Allowable options:

• timeout (number) - Sets the number of seconds to wait for a response before considering the call timed out. Defaults to 30.
• heartbeatInterval (number) - Sets the number of miliseconds to send send heartbeats to connected servers. Defaults to 5000ms.

Events:

• error - When an error occurs.

Methods:

• bind(endpoint) - Binds the client to the specified ZeroMQ endpoint.
• connect(endpoint) - Connects the client to the specified ZeroMQ endpoint.
• close() - Closes the ZeroMQ socket.
• invoke(method, arguments..., callback) - Invokes a remote method.
  • method is the method name.
  • arguments are a list of arguments passed to the method, if there are no arguments then this argument is ommitted
  • callback is a method to call when there is an update. This callback is called as callback(error, response, more), where error is an error object, response is the new update, and more is a boolean specifying whether new updates will be available later (i.e. whether the response is streaming).

Full example:

var zerorpc = require("zerorpc");

var client = new zerorpc.Client();
client.connect("tcp://127.0.0.1:4242");

client.on("error", function(error) {
    console.error("RPC client error:", error);
});

client.invoke("iter", 10, 20, 2, function(error, res, more) {
    if(error) {
        console.error(error);
    } else {
        console.log("UPDATE:", res);
    }

    if(!more) {
        console.log("Done.");
    }
});