Instrumenting Python Apps with OpenTelemetry

Auto Instrumentation

This section shows a working example of a Python application auto-instrumented with OpenTelemetry.

Prerequisite

• A VMware Aria Operations for Applications (formerly known as Tanzu Observability by Wavefront) account, which gives you access to a cluster. If you don’t have a cluster, sign up for a free trial.
• Clone the OpenTelemetry Examples repository.
• Install the Wavefront proxy.
  Note: When running the Wavefront proxy:
  • Make sure that the WAVEFRONT_PROXY_ARGS environment variable contains --otlpGrpcListenerPorts 4317.
  • And expose the OpenTelemetry port via -p 4317:4317.
• Set up an OpenTelemetry Collector:
  1. Download the otelcol-contrib binary from the latest release of the OpenTelemetry Collector project.
  2. In the same directory, create a file named otel_collector_config.yaml.
  3. Copy the configurations in the preconfigured YAML file to the file you just created. For details on OpenTelemetry configurations, see OpenTelemetry Collector Configuration.
  4. On your console, navigate to the directory you downloaded in the step above and run the following command to start OpenTelemetry Collector:

      ./otelcol-contrib --config otel_collector_config.yaml
     

Tip: We recommend trying virtualenv to create an isolated Python environment.

Step 1: Create or Download a Sample Application

Any application can be easily instrumented, for this walk through we will refer to a locally hosted application that responds with “Hello, World!“ each time it is accessed.

from flask import Flask

app = Flask(__name__)


@app.route('/')
def index():
    return 'Hello World'


app.run(host='0.0.0.0', port=80)

Let’s save this file as server.py.

Step 2: Install OpenTelemetry Packages

The following OpenTelemetry packages are required to auto-instrument an application:

• Flask
• opentelemetry-distro
• opentelemetry-instrumentation
• opentelemetry-bootstrap
• opentelemetry-exporter-otlp

To install these packages, run the following commands from the application directory:

pip3 install Flask

pip3 install opentelemetry-distro

pip3 install opentelemetry-instrumentation

opentelemetry-bootstrap --action=install

pip3 install opentelemetry-exporter-otlp

Step 3: Configuring the OpenTelemetry Exporter

Now, configure the OpenTelemetry Exporter to send traces from our application to the required endpoint on our local machine:

export OTEL_TRACES_EXPORTER=otlp

export OTEL_EXPORTER_OTLP_ENDPOINT="http://localhost:4317"

Note: Change the value of my_service_name and my_application_name attribute as per application’s requirements.

export OTEL_RESOURCE_ATTRIBUTES="service.name=<my_service_name>,application=<my_application_name>"

In the above configuration, we export our trace data using OpenTelemetry Protocol (OTLP). In addition, we set the export endpoint as localhost:4317 and assign the name my_application_name to our tracing service as a resource attribute.

Step 4: Run the Application and Generate a Trace

The collector is now running and listening to incoming traces on port 4317. Now we’re ready to generate traces.

• Start the application

  opentelemetry-instrument python3 server.py
  

• Visit http://localhost and refresh the page. The application generates and emits a trace of that transaction. When the trace data collected from the OpenTelemetry collector are ingested, we can examine them in our user interface.

Manual-Instrumentation

Automation is great, but eventually we want to add detail. This section shows a working example of a Python application manually-instrumented with OpenTelemetry.

Prerequisite

• An Aria Operations for Applications account, which gives you access to a cluster. If you don’t have a cluster, sign up for a free trial.
• Clone the OpenTelemetry Examples repository.
• Install the Wavefront proxy.
  Note: When running the Wavefront proxy:
  • Make sure that the WAVEFRONT_PROXY_ARGS environment variable contains --otlpGrpcListenerPorts 4317.
  • And expose the OpenTelemetry port via -p 4317:4317.
• Set up an OpenTelemetry Collector:
  1. Download the otelcol-contrib binary from the latest release of the OpenTelemetry Collector project.
  2. In the same directory, create a file named otel_collector_config.yaml.
  3. Copy the configurations in the preconfigured YAML file to the file you just created. For details on OpenTelemetry configurations, see OpenTelemetry Collector Configuration.
  4. On your console, navigate to the directory you downloaded in the step above and run the following command to start OpenTelemetry Collector:

      ./otelcol-contrib --config otel_collector_config.yaml
     

Tip: We recommend trying virtualenv to create an isolated Python environment. Please do not use the same virtual environment if it is already used in auto-instrumentation.

Step 1: Install OpenTelemetry Packages

To install OpenTelemetry packages for Python, run this command:

pip3 install -r requirements.txt

Tip: We’ve put all the dependencies in the requirements.txt file.

Step 2: Instrument the Application

To keep things simple, this example creates a basic “Hello World” application using Flask.

• Activate Flask Instrumentation

  • First, install the instrumentation package. already taken care of.
  • To activate flask instrumentation, run following code in the application:

      app = Flask(__name__)
      FlaskInstrumentor().instrument_app(app)
    

• Resource Attributes

  Note: Change the value of my_service_name and my_application_name attribute as per application’s requirements.

        resource = Resource(attributes={
          "service.name": "<my_service_name>",
          "application": "<my_application_name>"
        })
  

• OTLPSpanExporter Configuration

  Note: These are default values, changing this is optional.

    span_exporter = OTLPSpanExporter(
        # endpoint="localhost:4317",
        # credentials=ChannelCredentials(credentials),
        # headers=(("metadata", "metadata")),
        )
  

• Setup Tracer

  Tracer, an object that tracks the currently active span and allows us to create (or activate) new spans.

      trace.set_tracer_provider(tracer_provider)
      span_processor = BatchSpanProcessor(span_exporter)
      tracer_provider.add_span_processor(span_processor)
      
      tracer = trace.get_tracer_provider().get_tracer(__name__)
  

• Creating a Child Span

  A span represents a distinct operation - not an individual function, but an entire operation, such as a database query. Generally, this means we shouldn’t be creating spans in our application code, they should be managed as part of the framework or library we are using. But, that said, here is how we do it. Span management has two parts - the span lifetime and the span context. The lifetime is managed by starting the span with a tracer, and adding it to a trace by assigning it a parent.

    @app.route('/')
    def index():
        # add latency to the parent span
        sleep(20 / 1000)
  
      # always create a new context when starting a span
      with tracer.start_as_current_span("child_span") as span:
        # add an event to the child span
        span.add_event("event message",
                       {"event_attributes": 1})
        # get_current_span will now return the same span
        trace.get_current_span().set_attribute("http.route", "some route")
        # add latency to the child span
        sleep(30 / 1000)
        return "Hello World"
  

• Recording Errors

  Exceptions are reported as events, but they should be properly formatted. As a convenience, OpenTelemetry provides a record_exception method for capturing them correctly.

      @app.route("/exception")
      def exception():
          try:
              1 / 0
          except ZeroDivisionError as error:
              span = trace.get_current_span()
              # record an exception
              span.record_exception(error)
              # fail the operation
              span.set_status(Status(StatusCode.ERROR, "error happened"))
          return "Some Exception"
  

Step 3: Run the Application

• Start the application

  opentelemetry-instrument python3 server.py
  

• Visit http://localhost:8080 or http://localhost:8080/exception and refresh the page. The application generates and emits a trace of that transaction. When the trace data collected from the OpenTelemetry collector are ingested, we can examine them in our user interface.