node tracer example

index.mjs

import express from "express";
import bodyParser from "body-parser";
import { trace, context } from "@opentelemetry/api";
import { BasicTracerProvider, ConsoleSpanExporter, SimpleSpanProcessor } from "@opentelemetry/sdk-trace-base";
import { AsyncLocalStorageContextManager } from '@opentelemetry/context-async-hooks';

const provider = new BasicTracerProvider();
provider.addSpanProcessor(new SimpleSpanProcessor(new ConsoleSpanExporter()));
trace.setGlobalTracerProvider(provider);

async function main() {
  const tracerContext = new AsyncLocalStorageContextManager();
  const tracer = trace.getTracer('service-foo');
  const app = express();
  const wrap = fn => async (req, res, next) => {
    try {
      await fn(req, res, next);
    } catch (error) {
      next(error);
    }
  };

  app.use(bodyParser.json());
  app.disable('etag');
  app.disable('x-powered-by');

  tracerContext.enable();
  context.setGlobalContextManager(tracerContext);

  const wrapSpan = (name, fn, { options, context } = {}) => {
    return function(...args) {
      const thisCtx = this;
      return tracer.startActiveSpan(name, options, context, (span) => {
        try {
          const result = fn.call(thisCtx, ...args);
          if (result instanceof Promise)
            result.finally(() => span.end());
          return result;
        } catch (error) {
          span.end();
          throw error;
        }
      });
    }
  }

  const dbQuery = wrapSpan('database', async (query) => {
    trace.getActiveSpan().setAttribute('db.query', query);
    await new Promise(resolve => setTimeout(resolve));
  });

  app.use(wrap(wrapSpan('request', async (req, res, next) => {
    trace.getActiveSpan().setAttribute('http.method', req.method);
    await next();
  })));

  app.get('/', wrap(wrapSpan('foo', async (req, res) => {
    await dbQuery(req.path);
    res.json({
      path: req.path
    });
  })));

  app.listen(3000, () => {
    console.log("Server started on port 3000");
  });
}

main();