Monitoring your Flask application using OpenTelemetry

In this article, we will use OpenTelemetry to instrument a sample Flask app. Flask is one of the most popular web application frameworks of Python. It consists of Werkzeug WSGI toolkit and Jinja2 template engine.

Instrumentation is one of the biggest challenge engineering teams face when starting out with observability. Instrumenting a distributed application architecture is not easy. Applications now have distributed services as well as distributed teams that might be using multiple programming languages and numerous frameworks and libraries.

OpenTelemetry is the leading open-source standard that is solving the problem of instrumentation. It is currently an incubating project under the Cloud Native Computing Foundation.

It is a 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.

Why use OpenTelemetry?

As might be clear by now that OpenTelemetry helps you to generate telemetry data. You still need a backend to analyze, store and visualize that data. By design, OpenTelemetry is vendor-agnostic. And that's one of the biggest advantages of using OpenTelemetry. It can export data in multiple formats which you can send to a backend of your choice.

In this article, we will use SigNoz as a backend. SigNoz is an open-source APM that can be used for both metrics and distributed tracing.

Let's get started and see how to use OpenTelemetry for a Flask application.

Running a Flask application with OpenTelemetry

OpenTelemetry is a set of tools, APIs, and SDKs used to instrument applications to create and manage telemetry data(logs, metrics, and traces).

Installing SigNoz

You can get started with SigNoz using just three commands at your terminal.

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

For detailed instructions, you can visit our documentation.

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

The application list shown in the dashboard is from a sample app called HOT R.O.D that comes bundled with the SigNoz installation package.

SigNoz Dashboard

Getting a sample Flask application

Prerequisites

1. Python 3.4 or newer
   Download the latest version of Python.
2. MongoDB
   Below are the download links for different OS:
   MacOS
   Linux
   Windows
   Ubuntu
   

Running sample Flask app
We will be using the Flask app at this Github repo.

1. Clone sample Flask app repository and go to the root folder
   

   git clone https://github.com/SigNoz/sample-flask-app.git
   cd sample-flask-app

2. Check if the app is running

   python3 app.py

   You can now access the UI of the app on your local host: http://localhost:5002/

Sample flask application running on local host

To capture data with OpenTelemetry, you need to configure some environment variables and run the app with OpenTelemetry packages. Once you ensure your app is running, stop the app with ctrl + c on a mac. So let us see how to run the app with OpenTelemetry packages.

Instrumenting the Flask application with OpenTelemetry

1. Opentelemetry Python instrumentation installation
   The app folder contains a file called requirements.txt, which contains all the necessary requirements to set up OpenTelemetry Python instrumentation. Make sure your path is updated to the root directory of your sample app and run the following command:

   pip3 install -r requirements.txt

   If it hangs while installing grpcio during pip3 install opentelemetry-exporter-otlp then follow below steps as suggested in this stackoverflow link.

   • pip3 install --upgrade pip
   • python3 -m pip install --upgrade setuptools
   • pip3 install --no-cache-dir --force-reinstall -Iv grpcio

2. Install application-specific packages
   This step is required to install packages specific to the application. Make sure to run this command in the root directory of your installed application. This command figures out which instrumentation packages the user might want to install and installs it for them:

   opentelemetry-bootstrap --action=install

3. Passing the necessary environment variables
   You're almost done. In the last step, you just need to configure a few environment variables for your OTLP exporters. Environment variables that need to be configured:

   • service.name- application service name (you can name it as you like)
   • OTEL_EXPORTER_OTLP_ENDPOINT - In this case, IP of the machine where SigNoz is installed

   You need to put these environment variables in the below command.

   note

   Don’t run app in reloader/hot-reload mode as it breaks instrumentation.

   OTEL_RESOURCE_ATTRIBUTES=service.name=<service_name> OTEL_EXPORTER_OTLP_ENDPOINT="http://<IP of SigNoz>:4317" opentelemetry-instrument python3 app.py

   As we are running SigNoz on local host, IP of SigNoz can be replaced with localhost in this case. And, for service_name let's use Flask_App. Hence, the final command becomes:
   Final Command

   OTEL_RESOURCE_ATTRIBUTES=service.name=Flask_App OTEL_METRICS_EXPORTER=none OTEL_EXPORTER_OTLP_ENDPOINT="http://localhost:4317" opentelemetry-instrument python3 app.py

   And congratulations! You have now instrumented your flask application with OpenTelemetry.

   Below you can find your Flask_app in the list of applications being monitored on SigNoz dashboard.

   

   Flask app in the list of applications monitored by SigNoz

Troubleshooting

The debug mode can break instrumentation from happening because it enables a reloader. To run instrumentation while the debug mode is enabled, set the use_reloader option to False:

if __name__ == "__main__":
    app.run(host='0.0.0.0', port=5002, debug=True, use_reloader=False)

If you face any problem in instrumenting with OpenTelemetry, refer to docs at https://signoz.io/docs/instrumentation/python

Open-source tool to visualize telemetry data

SigNoz makes it easy to visualize metrics and traces captured through OpenTelemetry instrumentation.

SigNoz comes with out of box RED metrics charts and visualization. RED metrics stands for:

• Rate of requests
• Error rate of requests
• Duration taken by requests

Measure things like application latency, requests per sec, error percentage and see your top endpoints with SigNoz.

You can then choose a particular timestamp where latency is high to drill down to traces around that timestamp.

View of traces at a particular timestamp

You can use flamegraphs to exactly identify the issue causing the latency.

View of traces at a particular timestamp

You can also build custom metrics dashboard for your infrastructure.

You can also build a custom metrics dashboard for your infrastructure

Conclusion

OpenTelemetry makes it very convenient to instrument your Flask application. You can then use an open-source APM tool like SigNoz to analyze the performance of your app. As SigNoz offers a full-stack observability tool, you don't have to use multiple tools for your monitoring needs.

You can try out SigNoz by visiting its GitHub repo 👇

If you are someone who understands more from video, then you can watch the below video tutorial on the same with SigNoz.

 

 

If you have any questions or need any help in setting things up, join our slack community and ping us in #support channel.

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If you want to read more about SigNoz 👇

Golang Aplication Monitoring with OpenTelemetry and SigNoz

OpenTelemetry collector - complete guide