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// tracing.js
const initTracer = require('jaeger-client').initTracer;
const opentracing = require('opentracing');

const initJaegerTracer = (serviceName) => {
  const config = {
    serviceName: serviceName,
    sampler: {
      type: 'const',
      param: 1
    },
    reporter: {
      logSpans: true,
      agentHost: process.env.JAEGER_AGENT_HOST || 'localhost',
      agentPort: process.env.JAEGER_AGENT_PORT || 6831
    }
  };

  return initTracer(config, {});
};

const tracer = initJaegerTracer('api-service');
module.exports = { tracer };

// middleware.js
const { tracer } = require('./tracing');
const opentracing = require('opentracing');

const tracingMiddleware = (req, res, next) => {
  const wireCtx = tracer.extract(
    opentracing.FORMAT_HTTP_HEADERS,
    req.headers
  );

  const span = tracer.startSpan(req.path, {
    childOf: wireCtx,
    tags: {
      [opentracing.Tags.SPAN_KIND]: opentracing.Tags.SPAN_KIND_RPC_SERVER,
      [opentracing.Tags.HTTP_METHOD]: req.method,
      [opentracing.Tags.HTTP_URL]: req.url
    }
  });

  req.span = span;

  res.on('finish', () => {
    span.setTag(opentracing.Tags.HTTP_STATUS_CODE, res.statusCode);
    span.finish();
  });

  next();
};

module.exports = tracingMiddleware;

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// propagation.js
const axios = require('axios');
const { tracer } = require('./tracing');
const opentracing = require('opentracing');

async function callDownstreamService(span, url, data) {
  const headers = {};

  // Inject trace context
  tracer.inject(span, opentracing.FORMAT_HTTP_HEADERS, headers);

  try {
    const response = await axios.post(url, data, { headers });
    span.setTag('downstream.success', true);
    return response.data;
  } catch (error) {
    span.setTag(opentracing.Tags.ERROR, true);
    span.log({
      event: 'error',
      message: error.message
    });
    throw error;
  }
}

module.exports = { callDownstreamService };

// zipkin-setup.js
const CLSContext = require('zipkin-context-cls');
const { Tracer, BatchRecorder, HttpLogger } = require('zipkin');
const zipkinMiddleware = require('zipkin-instrumentation-express').expressMiddleware;

const recorder = new BatchRecorder({
  logger: new HttpLogger({
    endpoint: 'http://localhost:9411/api/v2/spans',
    headers: { 'Content-Type': 'application/json' }
  })
});

const ctxImpl = new CLSContext('zipkin');
const tracer = new Tracer({ recorder, ctxImpl });

module.exports = {
  tracer,
  zipkinMiddleware: zipkinMiddleware({
    tracer,
    serviceName: 'api-service'
  })
};

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response = requests.get('http://localhost:16686/api/traces', params=params)
return response.json()['data']

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