Flask OpenTelemetry Instrumentation

This document contains instructions on how to set up OpenTelemetry instrumentation in your Flask applications. OpenTelemetry, also known as OTel for short, is an open source observability framework that can help you generate and collect telemetry data - traces, metrics, and logs from your Flask application.

Requirements

• Python 3.8 or newer

Send Traces to SigNoz Cloud

Based on your application environment, you can choose the setup below to send traces to SigNoz Cloud.

python3 -m venv .venv
source .venv/bin/activate

pip install opentelemetry-distro==0.43b0
pip install opentelemetry-exporter-otlp==1.22.0

opentelemetry-bootstrap --action=install

OTEL_RESOURCE_ATTRIBUTES=service.name=<service_name> \
OTEL_EXPORTER_OTLP_ENDPOINT="https://ingest.{region}.signoz.cloud:443" \
OTEL_EXPORTER_OTLP_HEADERS="signoz-access-token=SIGNOZ_INGESTION_KEY" \
OTEL_EXPORTER_OTLP_PROTOCOL=grpc \
opentelemetry-instrument <your_run_command>

python3 -m venv .venv
source .venv/bin/activate

pip install opentelemetry-distro==0.43b0
pip install opentelemetry-exporter-otlp==1.22.0

opentelemetry-bootstrap --action=install

OTEL_RESOURCE_ATTRIBUTES=service.name=<service_name> \
OTEL_EXPORTER_OTLP_ENDPOINT="http://localhost:4317" \
OTEL_EXPORTER_OTLP_PROTOCOL=grpc opentelemetry-instrument <your run command>

Send Traces to Self-Hosted SigNoz

There are three major steps to using OpenTelemetry:

• Instrumenting your Flask application with OpenTelemetry
• Configuring exporter to send data to SigNoz
• Validating that configuration to ensure that data is being sent as expected.

Let’s understand how to download, install, and run OpenTelemetry in Flask.

You can use OpenTelemetry to send your traces directly to SigNoz. OpenTelemetry provides a handy distro in Python that can help you get started with automatic instrumentation. We recommend using it to get started quickly.

Steps to auto-instrument Flask app for traces

1. Create a virtual environment
   

   python3 -m venv .venv
   source .venv/bin/activate
   

2. Install the OpenTelemetry dependencies
   

   pip install opentelemetry-distro==0.43b0
   pip install opentelemetry-exporter-otlp==1.22.0
   

   The dependencies included are briefly explained below:

   opentelemetry-distro - The distro provides a mechanism to automatically configure some of the more common options for users. It helps to get started with OpenTelemetry auto-instrumentation quickly.

   opentelemetry-exporter-otlp - This library provides a way to install all OTLP exporters. You will need an exporter to send the data to SigNoz.

   📝 Note

   💡 The opentelemetry-exporter-otlp is a convenience wrapper package to install all OTLP exporters. Currently, it installs:

   • opentelemetry-exporter-otlp-proto-http

   • opentelemetry-exporter-otlp-proto-grpc

   • (soon) opentelemetry-exporter-otlp-json-http

   The opentelemetry-exporter-otlp-proto-grpc package installs the gRPC exporter which depends on the grpcio package. The installation of grpcio may fail on some platforms for various reasons. If you run into such issues, or you don't want to use gRPC, you can install the HTTP exporter instead by installing the opentelemetry-exporter-otlp-proto-http package. You need to set the OTEL_EXPORTER_OTLP_PROTOCOL environment variable to http/protobuf to use the HTTP exporter.

3. Add automatic instrumentation
   The below command inspects the dependencies of your application and installs the instrumentation packages relevant for your Flask application.

   opentelemetry-bootstrap --action=install
   

   📝 Note

   Please make sure that you have installed all the dependencies of your application before running the above command. The command will not install instrumentation for the dependencies which are not installed.

4. Run your application
   In the final run command, you can configure environment variables and flags. Flags for exporters:
   

   For running your application, there are a few things that you need to keep in mind. Below are the notes:

   📝 Note

   Don’t run app in reloader/hot-reload mode as it breaks instrumentation. For example, if you use export Flask_ENV=development, it enables the reloader mode which breaks OpenTelemetry instrumentation.

   For running applications with application servers which are based on pre fork model, like Gunicorn, uWSGI you have to add a post_fork hook or a @postfork decorator in your configuration.

   To start sending data to SigNoz, use the following run command:

   OTEL_RESOURCE_ATTRIBUTES=service.name=<service_name> OTEL_EXPORTER_OTLP_ENDPOINT="http://<IP of SigNoz Backend>:4317" OTEL_EXPORTER_OTLP_PROTOCOL=grpc opentelemetry-instrument <your run command>
   

   <service_name> is the name of service you want

   <your_run_command> can be python3 app.py or flask run

   IP of SigNoz backend is the IP of the machine where you installed SigNoz. If you have installed SigNoz on localhost, the endpoint will be http://localhost:4317 for gRPC exporter and http://localhost:4318 for HTTP exporter.

   📝 Note

   The port numbers are 4317 and 4318 for the gRPC and HTTP exporters respectively. Remember to allow incoming requests to port 4317/4318 of machine where SigNoz backend is hosted.

   In case you encounter an issue where all applications do not get listed in the services section then please refer to the troubleshooting section.

Validating instrumentation by checking for traces

With your application running, you can verify that you’ve instrumented your application with OpenTelemetry correctly by confirming that tracing data is being reported to SigNoz.

To do this, you need to ensure that your application generates some data. Applications will not produce traces unless they are being interacted with, and OpenTelemetry will often buffer data before sending. So you need to interact with your application and wait for some time to see your tracing data in SigNoz.

Validate your traces in SigNoz:

1. Trigger an action in your app that generates a web request. Hit the endpoint a number of times to generate some data. Then, wait for some time.
2. In SigNoz, open the Services tab. Hit the Refresh button on the top right corner, and your application should appear in the list of Applications.
3. Go to the Traces tab, and apply relevant filters to see your application’s traces.

You might see other dummy applications if you’re using SigNoz for the first time. You can remove it by following the docs here.

Database Instrumentation

Make sure that the DB client library you are using has the corresponding instrumentation library, and the version of the DB client library is supported by OpenTelemetry.

MongoDB Database Instrumentation

You can use opentelemetry-distro to initialize instrumentation for your MongoDB database calls. You need to ensure that the version of your DB client library is supported by OpenTelemetry. For MongoDB, the instrumentation library is opentelemetry-instrumentation-pymongo.

You can check the supported versions here.

Redis Database Instrumentation

You can use opentelemetry-distro to initialize instrumentation for your Redis database calls. You need to ensure that the version of your DB client library is supported by OpenTelemetry. For Redis, the instrumentation library is opentelemetry-instrumentation-redis.

You can check the supported versions here.

MySQL Database Instrumentation

You can use opentelemetry-distro to initialize instrumentation for your MySQL database calls. You need to ensure that the version of your DB client library is supported by OpenTelemetry. For MySQL, we have two isntrumentation libraries:

• opentelemetry-instrumentation-mysql
• opentelemetry-instrumentation-pymysql

You can check the supported versions here.

Postgres Database Instrumentation

You can use opentelemetry-distro to initialize instrumentation for your PostgreSQL database calls. You need to ensure that the version of your DB client library is supported by OpenTelemetry. For Postgres, the instrumentation library is opentelemetry-instrumentation-psycopg2.

You can check the supported versions here.

Running applications with Gunicorn, uWSGI

For application servers which are based on pre fork model like Gunicorn, uWSGI you have to add a post_fork hook or a @postfork decorator in your configuration.

Check this documentation from OpenTelemetry on how to set it up.

Here's a working example where we have configured a gunicorn server with post_fork hook.

Troubleshooting your installation

Spans are not being reported

If spans are not being reported to SigNoz, try enabling debug exporter which writes the JSON formatted trace data to the console by setting env var OTEL_TRACES_EXPORTER=console.

OTEL_RESOURCE_ATTRIBUTES=service.name=python_app OTEL_TRACES_EXPORTER=console opentelemetry-instrument <your run command>

{
    "name": "alice",
    "context": {
        "trace_id": "0xedb7caf0c8b082a9578460a201759193",
        "span_id": "0x57cf7eee198e1fed",
        "trace_state": "[]"
    },
    "kind": "SpanKind.INTERNAL",
    "parent_id": null,
    "start_time": "2022-03-27T14:55:18.804758Z",
    "end_time": "2022-03-27T14:55:18.804805Z",
    "status": {
        "status_code": "UNSET"
    },
    "attributes": {},
    "events": [],
    "links": [],
    "resource": {
        "telemetry.sdk.language": "python",
        "telemetry.sdk.name": "opentelemetry",
        "telemetry.sdk.version": "1.10.0",
        "service.name": "my-service"
    }
}

Sample Flask Application

• Working example where we have configured a gunicorn server with post_fork hook.

• We have included a sample Flask application with README.md at Sample Flask App Github Repo.

Frequently Asked Questions

1. How to find what to use in IP of SigNoz if I have installed SigNoz in Kubernetes cluster?

   Based on where you have installed your application and where you have installed SigNoz, you need to find the right value for this. Please use this grid to find the value you should use for IP of SigNoz

2. I am sending data from my application to SigNoz, but I don't see any events or graphs in the SigNoz dashboard. What should I do?

   This could be because of one of the following reasons:

   1. Your application is generating telemetry data, but not able to connect with SigNoz installation

      Please use this troubleshooting guide to find if your application is able to access SigNoz installation and send data to it.

   2. Your application is not actually generating telemetry data

      Please check if the application is generating telemetry data first. You can use Console Exporter to just print your telemetry data in console first. Join our Slack Community if you need help on how to export your telemetry data in console

   3. Your SigNoz installation is not running or behind a firewall

      Please double check if the pods in SigNoz installation are running fine. docker ps or kubectl get pods -n platform are your friends for this.

What Cloud Endpoint Should I Use?

The primary method for sending data to SigNoz Cloud is through OTLP exporters. You can either send the data directly from your application using the exporters available in SDKs/language agents or send the data to a collector agent, which batches/enriches telemetry and sends it to the Cloud.

My Collector Sends Data to SigNoz Cloud

Using gRPC Exporter

The endpoint should be ingest.{region}.signoz.cloud:443, where {region} should be replaced with in, us, or eu. Note that the exporter endpoint doesn't require a scheme for the gRPC exporter in the collector.

# Sample config with `us` region
exporters:
    otlp:
        endpoint: "ingest.us.signoz.cloud:443"
        tls:
            insecure: false
        headers:
            "signoz-access-token": "<SIGNOZ_INGESTION_KEY>"

Using HTTP Exporter

The endpoint should be https://ingest.{region}.signoz.cloud:443, where {region} should be replaced with in, us, or eu. Note that the endpoint includes the scheme https for the HTTP exporter in the collector.

# Sample config with `us` region
exporters:
    otlphttp:
        endpoint: "https://ingest.us.signoz.cloud:443"
        tls:
            insecure: false
        headers:
            "signoz-access-token": "<SIGNOZ_INGESTION_KEY>"

My Application Sends Data to SigNoz Cloud

The endpoint should be configured either with environment variables or in the SDK setup code.

Using Environment Variables

Using gRPC Exporter

Examples with us region

• OTEL_EXPORTER_OTLP_PROTOCOL=grpc OTEL_EXPORTER_OTLP_ENDPOINT=https://ingest.us.signoz.cloud:443 OTEL_EXPORTER_OTLP_HEADERS=signoz-access-token=<SIGNOZ_INGESTION_KEY>

Using HTTP Exporter

• OTEL_EXPORTER_OTLP_PROTOCOL=http/protobuf OTEL_EXPORTER_OTLP_ENDPOINT=https://ingest.us.signoz.cloud:443 OTEL_EXPORTER_OTLP_HEADERS=signoz-access-token=<SIGNOZ_INGESTION_KEY>

Configuring Endpoint in Code

Please refer to the agent documentation.

Sending Data from a Third-Party Service

The endpoint configuration here depends on the export protocol supported by the third-party service. They may support either gRPC, HTTP, or both. Generally, you will need to adjust the host and port. The host address should be ingest.{region}.signoz.cloud:443, where {region} should be replaced with in, us, or eu, and port 443 should be used.