The legacy event handler signature (payload, sender, eventName) has been removed. You must now use the Context based signature. Access payload via ctx.params, the sender via ctx.nodeID, metadata via ctx.meta, and the event name via ctx.eventName.

module.exports = {
    name: "accounts",
    events: {
        "user.created"(
            ctx
        ) {
            console.log("Payload:", ctx.params);
            console.log("Sender:", ctx.nodeID);
            console.log("We have also metadata:", ctx.meta);
            console.log("The called event name:", ctx.eventName);

            // ...
        }
    }
};

You can install the Moleculer framework using npm or yarn.

$ npm i moleculer

or

$ yarn add moleculer

Action streaming has been rewritten. The Stream instance is no longer passed in ctx.params.

Sending a stream: Pass the stream in the calling options under the stream property. This allows ctx.params to be used for regular action parameters.

Receiving a stream: Access the stream directly via ctx.stream instead of ctx.params.

// Sending a stream
ctx.call("file.save", { filename: "as.txt" }, { stream: fs.createReadStream() });

// Receiving a stream
// file.service.js
module.exports = {
    name: "file",
    actions: {
        save(ctx) {
            const stream = ctx.stream;
            const s = fs.createWriteStream(ctx.params.filename);
            stream.pipe(s);
        }
    }
};

The broker.use method is deprecated and removed in version 0.14.x. Instead of calling broker.use(middleware), define middlewares within the middlewares array in your broker configuration object.

// moleculer.config.js
module.exports = {
    middlewares: [
        myMiddleware1,
        myMiddleware2,
    ]
};

Middleware can no longer be defined as a simple function. ServiceBroker now requires middleware to be an Object with a name and a localAction method.

// moleculer.config.js
module.exports = {
    middlewares: [
        {
            name: "MyMiddleware",
            localAction(handler) {
                // My logic
            }
        }
    ]
}

You can use the Chrome DevTools to inspect and profile your Node.js application by starting it with the --inspect flag. Adding --expose-gc allows you to manually trigger garbage collection from the inspector.

node --inspect --expose-gc benchmark/perf-runner.js

You can use the built-in Node.js profiler to identify performance bottlenecks. This involves running your application with the --prof flag to generate an isolate log file, and then processing that file into a human-readable text format.

1. Run your application in profiler mode: node --prof main.js This generates a file named something like isolate-0xnnnnnnnnnnnn-v8.log.

2. Convert the isolate file to text: node --prof-process isolate-0xnnnnnnnnnnnn-v8.log > processed.txt

$ node --prof main.js
$ node --prof-process isolate-0xnnnnnnnnnnnn-v8.log > processed.txt

IR Hydra provides deep insights into V8's internal processes. You can run it using the following command structure to trace hydrogen, phases, and de-optimizations while redirecting code traces to an assembly file.

$ node --trace-hydrogen --trace-phase=Z --trace-deopt --code-comments --hydrogen-track-positions --redirect-code-traces --redirect-code-traces-to=code.asm index.js

To use Zipkin as a trace exporter for Moleculer, run the following Docker command to start a Zipkin instance on port 9411.

docker run -d -p 9411:9411 --name=zipkin openzipkin/zipkin

To use Jaeger as a trace exporter for Moleculer, you can run the Jaeger all-in-one image using Docker. This exposes the necessary ports for receiving traces and provides a web UI for visualization.

UI Access: http://<docker-ip>:16686/

docker run -d --name jaeger -p 5775:5775/udp -p 6831:6831/udp -p 6832:6832/udp -p 5778:5778 -p 16686:16686 -p 14250:14250 -p 14268:14268 -p 14269:14269 jaegertracing/all-in-one:latest