redis-scripts

Script manager module for Redis Lua script functionality.

RedisScripts

Script manager module for Redis Lua script functionality.

Install

Simple installation with NPM

npm install redis-scripts

Usage

var redis = require("redis"),
    ScriptManager = require("redis-scripts"),
    client = redis.createClient();

client.on("error", function (err) {
    console.log("Error " + err);
});

client.on("ready", function (err) {
    var sm = new ScriptManager(client);

    // Load all Lua scripts in a directory into Redis
    sm.loadScriptsFromDirectory("./lua", function (err) {
         if (err) {
            console.log("Error " + err);
            process.exit(1);
         }

         // If your directory included a script called incrbyone.lua
         // you can now call it directly from the ScriptManager object
         sm.incrbyone('key');
    });
});

API

New Instance

You must first connect to a redis server using the redis client and pass the client instance to the constructor.

var redis = require("redis"),
    ScriptManager = require("redis-scripts");

//Connect to Redis
client = redis.createClient();

// Create the script manager instance using the redis client
client.on("ready", function (err) {
    var sm = new ScriptManager(client);
});

Keeping your script loading code on the ready event handler will reload all your scripts every time you reconect to redis.

scriptManager.load(command, scriptFile, callback)

Load a file containing a Lua script into Redis and create a new command in the script manager object. With the support for Lua server side scripting, and the fact that Lua scripts run atomically, as any native command would, we can easily add new behavior to Redis. Once loaded the scripts are cached in the server and do not need to be reloaded again, You can expect this to be true until a SCRIPT FLUSH command is issued.

If a script is not found on the server you will receive a NOSCRIPT error message, and need to call scriptManager.load() again. Suggestion is to use your script loading code in the Redis client "ready" event handler. This way whenever you reconnect to Redis the scripts will be reloaded.

Parameters:

• command name of the command that will be registered in the client
• scriptFile name of the file containing the script. If no extension is given .lua is used.
• callback optional callback

For more details on passing arguments to scripts and other important details about Lua scripting in general read the Redis EVAL command page at http://redis.io/commands/eval

After the script has been loaded you can call it as any native command, by using

scriptManager.command(key1, key2, ..., [callback]);

For example, imagine you need to implement a conditional increment command without using MULTI/EXEC/WATCH. Create a file called cincr.lua with the following content:

-- Conditional Increment
-- Increment Key if value is bigger than ARGV[1]
local value = tonumber(redis.call('get',KEYS[1]))
if value == nil then return {err="Value at key is not integer"} end
if value > tonumber(ARGV[1]) then
    value = value + 1
    redis.call('set',KEYS[1],value)
end
return value

Now from your application call:

scriptManager.Load('cincr', './cincr', 1, function(err, reply) {
    if( err ) {
        console.log( err );
        process.exit();
    }

    scriptManager.cincr('key1', 10, function (err, reply) {
        console.log(reply);
        process.exit();
    });
});

The load process will determine the number of Redis Keys your script needs by the number of elements in the KEYS lua table.

scriptManager.getNumberOfKeys(command)

Return the number of Redis Keys the command script needs to run properly. If command does not exist, returns -1.

scriptManager.calcNumberOfKeys(code)

Calculate the number of Redis Keys the passed Lua source code needs to run properly. Returns the number of keys the script needs.

scriptManager.loadScriptsFromDirectory(path, next)

Load all Lua scripts found in path into Redis. Scripts that start with _ or . are ignored. Scripts must have a .lua extension.

Testing

Tests require Node mocha and istanbul modules to be installed .

npm install mocha istanbul -g

Tests need to connect to a Redis server. By default it tries to connect to localhost:6376. So you must have a running Redis server or the tests will fail.

To run all module tests simply run:

npm test

or

make test

To obtain a test coverage report run

npm cover

#License

MIT License