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Node.js and Jaeger

Tracetest is a testing tool based on OpenTelemetry that allows you to test your distributed application. It allows you to use data from distributed traces generated by OpenTelemetry to validate and assert if your application has the desired behavior defined by your test definitions.

Jaeger is an open-source, end-to-end distributed tracing solution. It allows you to monitor and troubleshoot transactions in complex distributed systems. It was developed and then open sourced by Uber Technologies. Jaeger provides a distributed tracing solution to enable transactions across multiple heterogeneous systems or microservices to be tracked and displayed as a cascading series of spans.

Sample Node.js App with Jaeger, OpenTelemetry and Tracetest

This is a simple quick start on how to configure a Node.js app to use OpenTelemetry instrumentation with traces and Tracetest for enhancing your E2E and integration tests with trace-based testing. The infrastructure will use Jaeger as the trace data store, and OpenTelemetry Collector to receive traces from the Node.js app and send them to Jaeger.

Prerequisites

You will need Docker and Docker Compose installed on your machine to run this quick start app!

Project Structure

The project is built with Docker Compose. It contains two distinct docker-compose.yaml files.

1. Node.js App

The docker-compose.yaml file and Dockerfile in the root directory are for the Node.js app.

2. Tracetest

The docker-compose.yaml file, collector.config.yaml, tracetest-provision.yaml, and tracetest-config.yaml in the tracetest directory are for the setting up Tracetest, Jaeger, and the OpenTelemetry Collector.

The tracetest directory is self-contained and will run all the prerequisites for enabling OpenTelemetry traces and trace-based testing with Tracetest.

Docker Compose Network

All services in the docker-compose.yaml are on the same network and will be reachable by hostname from within other services. For example, jaeger:14250 in the collector.config.yaml will map to the jaeger service, where the port 14250 is the port where Jaeger accepts traces. And, jaeger:16685 in the tracetest-provision.yaml will map to the jaeger service and port 16685 where Tracetest will fetch trace data from Jaeger.

Node.js App

The Node.js app is a simple Express app contained in the app.js file.

The OpenTelemetry tracing is contained in the tracing.otel.grpc.js or tracing.otel.http.js files. Traces will be sent to the OpenTelemetry Collector.

Here's the content of the tracing.otel.grpc.js file:

const opentelemetry = require("@opentelemetry/sdk-node");
const {
getNodeAutoInstrumentations,
} = require("@opentelemetry/auto-instrumentations-node");
const {
OTLPTraceExporter,
} = require("@opentelemetry/exporter-trace-otlp-grpc");

const sdk = new opentelemetry.NodeSDK({
traceExporter: new OTLPTraceExporter({ url: "http://otel-collector:4317" }),
instrumentations: [getNodeAutoInstrumentations()],
});
sdk.start();

Depending on which of these you choose, traces will be sent to either the grpc or http endpoint.

The hostnames and ports for these are:

  • GRPC: http://otel-collector:4317
  • HTTP: http://otel-collector:4318/v1/traces

Enabling the tracer is done by preloading the trace file.

node -r ./tracing.otel.grpc.js app.js

In the package.json you will see two npm scripts for running the respective tracers alongside the app.js.

"scripts": {
"with-grpc-tracer":"node -r ./tracing.otel.grpc.js app.js",
"with-http-tracer":"node -r ./tracing.otel.http.js app.js"
},

To start the server, run this command:

npm run with-grpc-tracer
# or
npm run with-http-tracer

As you can see the Dockerfile uses the command above.

FROM node:slim
WORKDIR /usr/src/app
COPY package*.json ./
RUN npm install
COPY . .
EXPOSE 8080
CMD [ "npm", "run", "with-grpc-tracer" ]

And, the docker-compose.yaml contains just one service for the Node.js app.

version: "3"
services:
app:
image: quick-start-nodejs
build: .
ports:
- "8080:8080"

To start it, run this command:

docker compose build # optional if you haven't already built the image
docker compose up

This will start the Node.js app. But, you're not sending the traces anywhere.

Let's fix this by configuring Tracetest and OpenTelemetry Collector.

Tracetest

The docker-compose.yaml in the tracetest directory is configured with four services.

  • Postgres - Postgres is a prerequisite for Tracetest to work. It stores trace data when running the trace-based tests.
  • OpenTelemetry Collector - A vendor-agnostic implementation of how to receive, process and export telemetry data.
  • Jaeger - A trace data store.
  • Tracetest - Trace-based testing that generates end-to-end tests automatically from traces.
version: "3"
services:
tracetest:
image: kubeshop/tracetest:${TAG:-latest}
platform: linux/amd64
volumes:
- type: bind
source: ./tracetest/tracetest.config.yaml
target: /app/tracetest.yaml
- type: bind
source: tracetest/tracetest-provision.yaml
target: /app/provision.yaml
command: --provisioning-file /app/provision.yaml
ports:
- 11633:11633
depends_on:
postgres:
condition: service_healthy
jaeger:
condition: service_started
otel-collector:
condition: service_started
healthcheck:
test: ["CMD", "wget", "--spider", "localhost:11633"]
interval: 1s
timeout: 3s
retries: 60
environment:
TRACETEST_DEV: ${TRACETEST_DEV}

postgres:
image: postgres:14
environment:
POSTGRES_PASSWORD: postgres
POSTGRES_USER: postgres
healthcheck:
test: pg_isready -U "$$POSTGRES_USER" -d "$$POSTGRES_DB"
interval: 1s
timeout: 5s
retries: 60

otel-collector:
image: otel/opentelemetry-collector-contrib:0.59.0
command:
- "--config"
- "/otel-local-config.yaml"
volumes:
- ./tracetest/collector.config.yaml:/otel-local-config.yaml

jaeger:
image: jaegertracing/all-in-one:latest
restart: unless-stopped
ports:
- "16686:16686"
healthcheck:
test: ["CMD", "wget", "--spider", "localhost:16686"]
interval: 1s
timeout: 3s
retries: 60

Tracetest depends on Postgres, Jaeger and the OpenTelemetry Collector. Both Tracetest and the OpenTelemetry Collector require config files to be loaded via a volume. The volumes are mapped from the root directory into the tracetest directory and the respective config files.

To start both the Node.js app and Tracetest we will run this command:

docker-compose -f docker-compose.yaml -f tracetest/docker-compose.yaml up # add --build if the images are not built already

The tracetest-config.yaml file contains the basic setup of connecting Tracetest to the Postgres instance.

postgres:
host: postgres
user: postgres
password: postgres
port: 5432
dbname: postgres
params: sslmode=disable

telemetry:
exporters:
collector:
serviceName: tracetest
sampling: 100 # 100%
exporter:
type: collector
collector:
endpoint: otel-collector:4317

server:
telemetry:
exporter: collector

The tracetest.provision.yaml file defines the trace data store, set to Jaeger, meaning the traces will be stored in Jaeger and Tracetest will fetch them from Jaeger when running tests.

But how does Tracetest fetch traces?

Tracetest uses jaeger:16685 to connect to Jaeger and fetch trace data.

---
type: PollingProfile
spec:
name: Default
strategy: periodic
default: true
periodic:
retryDelay: 5s
timeout: 10m

---
type: DataStore
spec:
name: Jaeger
type: jaeger
default: true
jaeger:
endpoint: jaeger:16685
tls:
insecure: true

How do traces reach Jaeger?

The collector.config.yaml explains that. It receives traces via either grpc or http. Then, exports them to Jaegers's model.proto endpoint jaeger:14250.

receivers:
otlp:
protocols:
grpc:
http:

processors:
batch:
timeout: 100ms

exporters:
logging:
loglevel: debug
jaeger:
endpoint: jaeger:14250
tls:
insecure: true

service:
pipelines:
traces/1:
receivers: [otlp]
processors: [batch]
exporters: [jaeger]

Run Both the Node.js App and Tracetest

To start both the Node.js app and Tracetest, we will run this command:

docker-compose -f docker-compose.yaml -f tracetest/docker-compose.yaml up # add --build if the images are not built already

This will start your Tracetest instance on http://localhost:11633/.

Open the URL and start creating tests! Make sure to use the http://app:8080/ URL in your test creation, because your Node.js app and Tracetest are in the same network.

Learn More

Feel free to check out our examples in GitHub and join our Slack Community for more info!