gRPC / Datadog / Open Tracing Interceptor

interceptor.ts

import * as tracer from 'dd-trace';
import * as opentracing from 'opentracing';
import { InterceptingCall } from 'grpc';

const TRACE_HEADER = 'x-datadog-trace-id';
const PARENT_HEADER = 'x-datadog-parent-id';

export default function gRPCInterceptor(options, nextCall) {
  return new InterceptingCall(nextCall(options), {
    start: (metadata, _listener, next) => {
      const parentScope = tracer.scopeManager().active();
      const parent = parentScope && parentScope.span();

      const path = options.method_definition.path;
      const service = path.split('/')[1].split('.').slice(-1)[0];
      const method = path.substring(1).replace(/[\/\.]/g, '_');

      const span = tracer.startSpan('grpc.client', {
        childOf: parent,
        tags: {
          'service.name': service,
          'resource.name': method,
          'span.type': 'grpc',
        },
      });

      const meta = {};
      tracer.scopeManager().activate(span);
      tracer.inject(span, opentracing.FORMAT_HTTP_HEADERS, meta);

      metadata.set(TRACE_HEADER, meta[TRACE_HEADER]);
      metadata.set(PARENT_HEADER, meta[PARENT_HEADER]);

      next(metadata, {
        onReceiveStatus: (status, next) => {
          span.finish();
          next(status);
        },
      });
    },
  });
}