Now, Please Meander


    1.3.0 • Public • Published


    Build Status license 5cf

    • merkury ~ mercury => hermes
    • battle tested
    • test coverage 80%+
    • 100% promise api
    • super simple .on() and .emit() EventEmitter API
    • lightweight and fast
        npm install --save merkury

    how does it help?

    • (if got more time -> check "use case?" below)
    • before you implement some sort of database polling, check out merkury
    • just setup an instance of mercury in each service instance with the same topic name and redis configuration
    • listen for your event mk.on("my-event",..);
    • whenever you receive information and need to update other instances just call mk.emit("my-event",..); on one of your instances and every single one will receive the update

    simple api usage

        const Merkury = require("merkury");
        const ioRedisConfig = {
            host: "localhost",
            port: 6379
        const mk = new Merkury("unique-service-name", ioRedisConfig, true);
        //super easy API just like the usual event-emitter:
        mk.on("my-event", (arg1, arg2, arg3) => { .. });
        mk.emit("my-event", "arg1", {}, "arg3");
        //some advanced sugar available:
        mk.disconnect().then(_ => { .. });
        mk.setConfig() / mk.setTopic();
        mk.connect().then(_ => { .. }); //reconnect with topic switch
        mk.resume() //pause & resume handler
        //subscribe to error events
        mk.on("error", err => { .. });

    event race-lock mode

        mk1.on("my-event", arg1 => { console.write(arg1) });
        mk2.on("my-event", arg1 => { console.write(arg1) });
        mk3.on("my-event", arg1 => { console.write(arg1) });
        mk1.on("my-race-event", arg1 => { console.write(arg1) }, true);
        mk2.on("my-race-event", arg1 => { console.write(arg1) }, true);
        mk3.on("my-race-event", arg1 => { console.write(arg1) }, true);
        //with race mode disabled (usually)
        mk1.emit("my-event", 1); //output: 1\n1\n1\n
        //with race mode enabled
        mk1.emit("my-race-event", 1, 2, 3); //output: 1\n
        //race mode uses "redlock" algorithm to ensure only a single
        //Merkury{} instance will call its EventListener
        //merkury takes track of its race enabled events and is able
        //to remove them permanently when using e.g. mk1.removeListener(..)


    • imagine a world full of microservices
    • imagine you need high availabilty
    • the first thing you will do is scale your microservices to multiple instances or containers
    • imagine your instances run behind a load-balancer
    • your service/code will now only receive requests on single instances but you might need to do something with the received information on every instance - you have to notify all your instances about the updated information
    • you could implement some sort of polling..but what if you could simply notify the other instances? and what if that was just as easy as emitting a simple event


    npm i merkury

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