node-gearman is an extremely simple Gearman client/worker module for Node.JS. You can register workers and you can submit jobs, that's all about it.
Install through npm
npm install node-gearman
See examples folder for sample scripts
Set up connection data and create a new Gearman object
var Gearman = require("node-gearman");
var gearman = new Gearman(hostname, port);
Where hostname defaults to "localhost" and port to 4730
This doesn't actually create the connection yet. Connection is created when needed but you can force it with gearman.connect()
var gearman = Gearman(hostname, port);
gearman.connect();
The following events can be listened for a Gearman object:
- connected - when the connection has been successfully established to the server
- idle - when a there's no jobs available for workers
- close - connection closed
- error - an error occured. Connection is automatically closed.
Example:
var gearman = new Gearman(hostname, port);
gearman.on("connected", function(){
console.log("Connected to the server!");
});
gearman.connect();
Jobs can be submitted with gearman.submitJob(name, payload) where name is the name of the function and payload is a string or a Buffer. The returned object (Event Emitter) can be used to detect job status and has the following events:
- error - if the job failed, has parameter error
- data - contains a chunk of data as a Buffer
- end - when the job has been completed, has no parameters
Example:
var gearman = Gearman(hostname, port);
var job = gearman.submitJob("reverse", "test string");
job.on("data", function(data){
console.log(data.toString("utf-8")); // gnirts tset
});
job.on("end", function(){
console.log("Job completed!");
});
job.on("error", function(error){
console.log(error.message);
});
Workers can be set up with gearman.registerWorker(name, callback) where name is the name of the function and callback is the function to be run when a job is received.
Worker function callback gets two parameters - payload (received data as a Buffer) and worker which is a helper object to communicate with the server. worker object has following methods:
- write(data) - for sending data chunks to the client
- end([data]) for completing the job
- error() to indicate that the job failed
Example:
var gearman = Gearman(hostname, port);
gearman.registerWorker("reverse", function(payload, worker){
if(!payload){
worker.error();
return;
}
var reversed = payload.toString("utf-8").split("").reverse().join("");
worker.end(reversed);
});
Worker and job objects also act as Stream objects (workers are writable and jobs readable streams), so you can stream data with pipe from a worker to a client (but not the other way round). This is useful for zipping/unzipping etc.
NB! Streaming support is experimental, do not send very large files as the data tends to clutter up (workers stream interface lacks support for pausing etc.).
Streaming worker
gearman.registerWorker("stream_file", function(payload, worker){
var input = fs.createReadStream(filepath);
// stream file to client
input.pipe(worker);
});
Streaming client
var job = gearman.submitJob("stream", null),
output = fs.createWriteStream(filepath);
// save incoming stream to file
job.pipe(output);
MIT