This article was originally posted on SigNoz blog, and is written by Selvaganesh.

In this article, we will implement distributed tracing for a nodejs application based on microservices architecture. To implement distributed tracing, we will be using open-source solutions - SigNoz and OpenTelemetry, so you can easily follow the tutorial.

In modern microservices-based applications, it is difficult to understand how requests are performing across multiple services, infrastructure, and protocols. As companies began moving to distributed systems, they realized they needed a way to track requests in their entirety for debugging applications. Distributed tracing is a technology that was born out of this need.
Let’s have a brief overview of distributed tracing.

What is distributed tracing?

In a microservices architecture, a user request travels through hundreds, even thousands of services before serving the user what they need. Engineering teams often responsible for maintaining single services have no visibility over how the system performs as a whole.

Distributed tracing gives insights into how a particular service is performing as part of the whole in a distributed software system. It involves passing a trace context with each user request which is then passed across hosts, services, and protocols to track the user request.

In this article, we will use OpenTelemetry and SigNoz to enable distributed tracing in a sample nodejs application.

OpenTelemetry and SigNoz

OpenTelemetry is a vendor-agnostic set of tools, APIs, and SDKs used to instrument applications to create and manage telemetry data(Logs, metrics, and traces). It aims to make telemetry data(logs, metrics, and traces) a built-in feature of cloud-native software applications.

OpenTelemetry provides the instrumentation layer to generate and export your telemetry data to a backend. Then, you need to choose a backend tool that will provide the data storage and visualization for your telemetry data. That’s where SigNoz comes into the picture.

SigNoz is a full-stack open-source APM tool that provides metrics monitoring and distributed tracing.

We will demonstrate implementing distributed tracing in a nodejs application in two sections:

• Running a sample nodejs application with OpenTelemetry
• Visualizing traces data with SigNoz dashboards

Running a sample nodejs application with OpenTelemetry

The sample nodejs application will have three microservices:

• user-service
• orders-service
• payment-service

Here’s the architecture of the sample application along with OpenTelemetry and SigNoz.

Pre-requisites

• Node JS 14 or newer Download the latest version.
• MySql 8
• SigNoz

Installing SigNoz

SigNoz can be installed on macOS or Linux computers in just three steps by using a simple install script.

The install script automatically installs Docker Engine on Linux. However, on macOS, you must manually install Docker Engine before running the install script.

git clone -b main https://github.com/SigNoz/signoz.git
cd signoz/deploy/
./install.sh

You can visit our documentation for instructions on how to install SigNoz using Docker Swarm and Helm Charts.

When you are done installing SigNoz, you can access the UI at http://localhost:3301

Installing MySql

Download MySQL community version from here based on your operating system.

Once installation is complete, run the below commands to create a database for our sample nodejs app.

➜  ~ mysql -u root
mysql> create database signoz;
mysql> use signoz;

Running sample application

Below are the steps to run the sample nodejs application with OpenTelemetry:

Clone sample nodejs app repository and go to the root folder
We will be using a sample nodejs app at this GitHub repo.

git clone git@github.com:SigNoz/distributed-tracing-nodejs-sample.git
cd distributed-tracing-nodejs-sample

Install the required dependencies
You can check out the depencies required from package.json file. Install all the required dependencies for the sample application using npm

npm install

OpenTelemetry needs the following packages to instrument the nodejs app.

"@opentelemetry/api": "^1.0.3",
"@opentelemetry/auto-instrumentations-node": "^0.25.0",
"@opentelemetry/exporter-collector": "0.25.0",
"@opentelemetry/exporter-collector-grpc": "^0.25.0",
"@opentelemetry/exporter-otlp-grpc": "^0.26.0",
"@opentelemetry/resources": "^0.24.0",
"@opentelemetry/sdk-trace-base": "^1.0.1",
"@opentelemetry/sdk-trace-node": "^1.0.1",
"@opentelemetry/semantic-conventions": "^0.24.0",

tracer.ts file
In order to instrument our services, we will create a single tracer.ts file and use it to instrument all three services.

We need to initialize OpenTelemetry before our application gets loaded. If your application begins requiring packages before OpenTelemetry is set up, it can create issues. You can initialize OpenTelemetry by using the code as shown below:

import init from './tracer'
const { sdk } = init('order-service') // provide service name to view in signoz dashboard

You can check out the code sample here.

Setting up SigNoz as the OpenTelemetry backend
To set up OpenTelemetry to collect and export telemetry data, you need to specify OTLP (OpenTelemetry Protocol) endpoint. It consists of the IP of the machine where SigNoz is installed and the port number at which SigNoz listens.

OTLP endpoint for SigNoz - <IP of the machine>:4317

If you have installed SigNoz on your local machine, then your endpoint is 127.0.0.0:4317.

Ports are setup in the .env file as shown below:

OTEL_EXPORTER_OTLP_ENDPOINT="127.0.0.0:4317"
ORDER_PORT=8082
USERS_PORT=8081
PAYMENT_PORT=8080

You can check the file in the cloned repo.

Run the microservices
From the root folder of your application on your terminal, run each microservice. Run users service:

npm run users

Open a new tab of your terminal, and run payment service:

npm run payment

Open a new tab of your terminal, and run orders service:

npm run orders

Ensure that the microservices are running on different ports. As earlier mentioned, you can set ports using the .env file.

Confirm table creation
After running the services, check if the tables ORDERS and USERS are created using the commands below:

mysql> use signoz;
mysql> show tables;

Visualizing traces data with SigNoz dashboards

To visualize the traces data with SigNoz, we first need to generate some user data by interacting with the sample nodejs application.

Generating user data by interacting with the sample app

You need to generate some user data to see how it appears in the SigNoz dashboard.

Create a new user

Call the below endpoint to create a new user in the MySQL db with autogenerated id. Make a note of the id.

curl --location --request POST 'localhost:8081/user/create' \
--header 'Content-Type: application/json' \
--data-raw '{
"USER_NAME": "Abishek",
"ACCOUNT": "ABC12345"
}'

This will create a user in our users table. Make a note of the ID as you will need it for further API calls.

Transfer some amount
Transfer some amount by calling the below API. The param id is the userid that was generated from the previous service.

curl --location --request GET 'localhost:8080/payment/transfer/id/2?amount=5000'

Place an order
Place an order using below API:

curl --location --request POST 'localhost:8082/order/create' \
--header 'Content-Type: application/json' \
--data-raw '{
       "USER_ID":2,
       "PRODUCT_NAME":"Mac Mini",
       "PRICE":"1299"
       }'

Now go to SigNoz dashboard, you will notice the list of service names that we configured:

• user-service
• order-service
• payment-service

You can play around with the dashboard to see what data is captured. Below is a handy guide on how to use the SigNoz dashboard to see the captured data.

How to use SigNoz dashboard to analyze traces

The traces tab of SigNoz dashboard provides powerful filters to analyze the traces data. You can use a number of filters to see traces data across many dimensions.

See the count of requests by service and HTTP Status code

Identify latency issues with Flamegraphs and Gantt charts

You can inspect each event in the table with flamegraphs and Gantt charts to see a complete breakdown of the request. Establishing a sequential flow of the user request along with info on time taken by each part of the request can help identify latency issues quickly. Let’s see how it works in case of our sample nodejs app.

Go to operation filter on the left navigation apply two filters GET /payment/transfer/:id and service name payment-service . Click on the single event listed in the table as shown below:

You will be able to see the flamegraph of the selected event which shows how the request traveled between the payment and the user-service. You can also use the Gantt chart to analyze each event in detail.

SigNoz also provides a detailed view of common semantic conventions like HTTP, network, and other attributes.

The end-to-end tracing of user requests can help you to identify latency issues quickly.

Conclusion

Distributed tracing is a powerful and critical toolkit for developers creating applications based on microservices architecture. For nodejs applications based on microservices architecture, distributed tracing can enable a central overview of how requests are performing across services which is needed for quick debugging.

OpenTelemetry and SigNoz provides a great open-source solution to implement distributed tracing for your applications. You can check out SigNoz by visiting its GitHub repo 👇

Read more about distributed tracing from SigNoz blog 👇

Spans - a key concept of distributed tracing

Context Propagation in distributed tracing