ee-resource-pool

resource pool for managing shared resources

installation

npm install ee-resource-pool

build status

usage

example of a pool of connections, there may never be more than 50 connections open.

var ResourcePool = require( "ee-resource-pool" );


var pool = new ResourcePool( {
	  max: 50 					// max 50 connections
	, maxWaitingRequests: 1000 	// fail requests for a connection when there are already more then 1'000 requests waiting
	, timeout: 5000 			// fail requests for a connection after waiting 5 seconds
	, idle: 600000 				// close conenctions if they weren't used in the last 10 minutes
	, prefetch: 10 				// create always 10% more connections currently used, so we neevr have to wait for aconnection to be created
} );


// the pool can request more resources, but if you don't need 
// special resources you dont listen for the event and the pool 
// will create its own resource representation 
// -> this is entirely optional
pool.on( "resourceRequest", function( callback ){
	callback( new Connection() );
} );


// if the pool gets a free resource which isn't used by the queue it emits the «resource» event
pool.on( "resource", function(){
	pool.get( function( err, resource ){
		// you should get that exact resource which triggered the event

	} );
} );


// this code is placed where you request the connections
pool.get( function( err, connection ){
	if ( err ){
		if ( err.name === "CapacityOverloadException" ) {
			console.log( "the resource pool is over capacity ...", err );
		}
		else if ( err.name === "RequestTimeoutException" ){
			console.log( "timeout while waiting for a free connection ...", err );
		}
	}
	else {
		// use the connection
		// IMPORTANT: if you are finished using ti you have to call the «freeResource» or «closeResource» method 

		connection.query( "whatever", function( err, data ){
			if ( err ){
				console.log( "crap, my query failed" );
				connection.closeResource();
				connection.close();
			}
			else {
				console.log( "got some data :)" );
				connection.freeResource();
			}
		} );
	}
} );

example of an image uploader which never should upload more than 5 images at the same time

var ResourcePool = require( "ee-resource-pool" );


var pool = new ResourcePool( {
	  timeout: 3600000 			// fail if we cannot upload an image within the next hour
	, ratelLimit: 5 			// max 5 uploads / second
} );


// the pool can request more resources
pool.on( "resourceRequest", function( callback ){
	callback( new Uploader() );
} );


// this code is placed where you uploader your imges, it will rate liimit your request...
pool.get( function( err, uploader ){
	if ( err ){
		if ( err.name === "RequestTimeoutException" ){
			console.log( "timeout while waiting for a free uploader ...", err );
		}
	}
	else {
		// use the uploader
		// IMPORTANT: if you are finished using ti you have to call the «freeResource» or «closeResource» method 

		uploader.upload.query( data, function( err ){
			if ( err ){
				console.log( "crap, the upload failed" );
				uploader.closeResource();
			}
			else {
				console.log( "upload finished :)" );
				uploader.freeResource();
			}
		} );
	}
} );