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running-python-app-with-opentelemetry-collector-and-tracetest
Python with OpenTelemetry manual instrumention
Quick start how to configure a Python app to use OpenTelemetry instrumentation with traces, and Tracetest for enhancing your e2e and integration tests with trace-based testing.
false
tracetest
trace-based testing
observability
distributed tracing
testing

:::note Check out the source code on GitHub here. :::

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.

Sample Python app with OpenTelemetry Collector and Tracetest

This is a simple quick start on how to configure a Python app to use OpenTelemetry instrumentation with traces, and Tracetest for enhancing your e2e and integration tests with trace-based testing.

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. Python app

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

2. Tracetest

The docker-compose.yaml file, collector.config.yaml, tracetest-provision.yaml, and tracetest-config.yaml in the tracetest directory are for setting up Tracetest 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. E.g. tracetest:4317 in the collector.config.yaml will map to the tracetest service, where the port 4317 is the port where Tracetest accepts traces.

Python app

The Python app is a simple Flask app, contained in the app.py file.

The code below imports all the Flask, and OpenTelemetry libraries and configures both manual and automatic OpenTelemetry instrumentation.

from flask import Flask, request
import json

from opentelemetry import trace
from opentelemetry.sdk.resources import Resource
from opentelemetry.sdk.trace import TracerProvider
from opentelemetry.sdk.trace.export import BatchSpanProcessor
from opentelemetry.sdk.trace.export import ConsoleSpanExporter

provider = TracerProvider()
processor = BatchSpanProcessor(ConsoleSpanExporter())
provider.add_span_processor(processor)
trace.set_tracer_provider(provider)
tracer = trace.get_tracer(__name__)

There are 3 endpoints in the Flask app. For seeing manual instrumentation trigger the "/manual" endpoint. For seeing the automatic instrumentation trigger the "/automatic" endpoint respectively.

app = Flask(__name__)

@app.route("/manual")
def manual():
    with tracer.start_as_current_span(
        "manual", 
        attributes={ "endpoint": "/manual", "foo": "bar" } 
    ):
        return "App works with a manual instrumentation."

@app.route('/automatic')
def automatic():
    return "App works with automatic instrumentation."

@app.route("/")
def home():
    return "App works."

The Dockerfile includes bootstrapping the needed OpenTelemetry packages. As you can see it does not have the CMD command. Instead, it's configured in the docker-compose.yaml below.

FROM python:3.10.1-slim
WORKDIR /opt/app
COPY . .
RUN pip install --no-cache-dir -r requirements.txt
RUN opentelemetry-bootstrap -a install
EXPOSE 8080

The docker-compose.yaml contains just one service for the Python app. The service is stared with the command parameter.

version: '3'
services:
  app:
    image: quick-start-python
    platform: linux/amd64
    extra_hosts:
      - "host.docker.internal:host-gateway"
    build: .
    ports:
      - "8080:8080"
    # using the command here instead of the Dockerfile
    command: opentelemetry-instrument --traces_exporter otlp --service_name app --exporter_otlp_endpoint otel-collector:4317 --exporter_otlp_insecure true flask run --host=0.0.0.0 --port=8080
    depends_on:
      tracetest:
        condition: service_started

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 Python 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 three 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.
  • Tracetest - Trace-based testing that generates end-to-end tests automatically from traces.
version: "3"
services:
  tracetest:
    image: kubeshop/tracetest: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/provisioning.yaml
    ports:
      - 11633:11633
    command: --provisioning-file /app/provisioning.yaml
    depends_on:
      postgres:
        condition: service_healthy
      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

Tracetest depends on both Postgres 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.

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

The tracetest-provision.yaml file provisions the trace data store and polling to store in the Postgres database. The data store is set to OTLP meaning the traces will be stored in Tracetest itself.

---
type: DataStore
spec:
  name: OpenTelemetry Collector
  type: otlp
  isdefault: true

But how are traces sent to Tracetest?

The collector.config.yaml explains that. It receives traces via either grpc or http. Then, exports them to Tracetest's otlp endpoint tracetest:4317.

receivers:
  otlp:
    protocols:
      grpc:
      http:

processors:
  batch:
    timeout: 100ms

exporters:
  logging:
    loglevel: debug
  otlp/1:
    endpoint: tracetest:4317
    # Send traces to Tracetest.
    # Read more in docs here: https://docs.tracetest.io/configuration/connecting-to-data-stores/opentelemetry-collector
    tls:
      insecure: true

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

Run both the Python app and Tracetest

To start both the Python 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/. Go ahead and open it up.

Start creating tests! Make sure to use the http://app:8080/ url in your test creation, because your Python 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!