Getting Started with OpenTelemetry Python v1.0.0

Since the OpenTelemetry Tracing Specification reached 1.0.0 —  guaranteeing long-term stability for the tracing portion of the OpenTelemetry clients, the community has been busy working to get the SDKs and APIs for popular programming language ready to be GA.

Next in our ‘Getting Started with OpenTelemetry’ Series, we’ll walk you through instrumenting a Python application and install both the OpenTelemetry API and SDK. 

Hello World: Emit a Trace to Your Console

To get started, install both the OpenTelemetry API and SDK:

pip install opentelemetry-api

pip install opentelemetry-sdk

The API package provides the interfaces required by the application owner, as well as some helper logic to load implementations.

The SDK provides an implementation of those interfaces. The implementation is designed to be generic and extensible enough that in many situations, the SDK is sufficient.

Once installed, you can use the packages to emit spans from your application. A span represents an action within your application that you want to instrument, such as an HTTP request or a database call. Once instrumented, you can extract helpful information such as how long the action took. You can also add arbitrary attributes to the span that provide more insight for debugging.

The following example script emits a trace containing three named spans: “foo”, “bar”, and “baz”:

# tracing.py

from opentelemetry import trace

from opentelemetry.sdk.trace import TracerProvider

from opentelemetry.sdk.trace.export import (

    ConsoleSpanExporter,

    SimpleSpanProcessor,

)

trace.set_tracer_provider(TracerProvider())

trace.get_tracer_provider().add_span_processor(

    SimpleSpanProcessor(ConsoleSpanExporter())

)

tracer = trace.get_tracer(__name__)

with tracer.start_as_current_span("foo"):

    with tracer.start_as_current_span("bar"):

        with tracer.start_as_current_span("baz"):

            print("Hello world from OpenTelemetry Python!")

When you run the script you can see the traces printed to your console:

$ python tracing_example.py

{

    "name": "baz",

    "context": {

        "trace_id": "0xb51058883c02f880111c959f3aa786a2",

        "span_id": "0xb2fa4c39f5f35e13",

        "trace_state": "{}"

    },

    "kind": "SpanKind.INTERNAL",

    "parent_id": "0x77e577e6a8813bf4",

    "start_time": "2020-05-07T14:39:52.906272Z",

    "end_time": "2020-05-07T14:39:52.906343Z",

    "status": {

        "status_code": "OK"

    },

    "attributes": {},

    "events": [],

    "links": []

}

{

    "name": "bar",

    "context": {

        "trace_id": "0xb51058883c02f880111c959f3aa786a2",

        "span_id": "0x77e577e6a8813bf4",

        "trace_state": "{}"

    },

    "kind": "SpanKind.INTERNAL",

    "parent_id": "0x3791d950cc5140c5",

    "start_time": "2020-05-07T14:39:52.906230Z",

    "end_time": "2020-05-07T14:39:52.906601Z",

    "status": {

        "status_code": "OK"

    },

    "attributes": {},

    "events": [],

    "links": []

}

{

    "name": "foo",

    "context": {

        "trace_id": "0xb51058883c02f880111c959f3aa786a2",

        "span_id": "0x3791d950cc5140c5",

        "trace_state": "{}"

    },

    "kind": "SpanKind.INTERNAL",

    "parent_id": null,

    "start_time": "2020-05-07T14:39:52.906157Z",

    "end_time": "2020-05-07T14:39:52.906743Z",

    "status": {

        "status_code": "OK"

    },

    "attributes": {},

    "events": [],

    "links": []

}

Each span typically represents a single operation or unit of work. Spans can be nested, and have a parent-child relationship with other spans. While a given span is active, newly-created spans inherit the active span’s trace ID, options, and other attributes of its context. A span without a parent is called the root span, and a trace is comprised of one root span and its descendants.

In this example, the OpenTelemetry Python library creates one trace containing three spans and prints it to STDOUT.

Configure Exporters to Emit Spans Elsewhere

The previous example does emit information about all spans, but the output is a bit hard to read. In most cases, you can instead export this data to an application performance monitoring backend to be visualized and queried. It’s also common to aggregate span and trace information from multiple services into a single database so that actions requiring multiple services can still all be visualized together.

This concept of aggregating span and trace information is known as distributed tracing. One such distributed tracing backend is known as Jaeger. The Jaeger project provides an all-in-one Docker container with a UI, database, and consumer.

Run the following command to start Jaeger:

docker run -p 16686:16686 -p 6831:6831/udp jaegertracing/all-in-one

This command starts Jaeger locally on port 16686 and exposes the Jaeger thrift agent on port 6831. You can visit Jaeger here.

After you spin up the backend, your application needs to export traces to this system. Although opentelemetry-sdk doesn’t provide an exporter for Jaeger, you can install it as a separate package with the following command:

pip install opentelemetry-exporter-jaeger

After you install the exporter, update your code to import the Jaeger exporter and use that instead:

# jaeger_example.py

from opentelemetry import trace

from opentelemetry.exporter.jaeger.thrift import JaegerExporter

from opentelemetry.sdk.resources import SERVICE_NAME, Resource

from opentelemetry.sdk.trace import TracerProvider

from opentelemetry.sdk.trace.export import BatchSpanProcessor

trace.set_tracer_provider(

    TracerProvider(

        resource=Resource.create({SERVICE_NAME: "my-helloworld-service"})

    )

)

jaeger_exporter = JaegerExporter(agent_host_name="localhost", agent_port=6831,)

trace.get_tracer_provider().add_span_processor(

    BatchSpanProcessor(jaeger_exporter)

)

tracer = trace.get_tracer(__name__)

with tracer.start_as_current_span("foo"):

    with tracer.start_as_current_span("bar"):

        with tracer.start_as_current_span("baz"):

            print("Hello world from OpenTelemetry Python!")

Finally, run the Python script:

python jaeger_example.py

Instrumentation Example with Flask

While the example in the previous section is great, it’s very manual. The following are common actions you might want to track and include as part of your distributed tracing.

• HTTP responses from web services
• HTTP requests from clients
• Database calls
  
  

To track these common actions, OpenTelemetry has the concept of instrumentations. Instrumentations are packages designed to interface with a specific framework or library, such as Flask and psycopg2. You can find a list of the currently curated extension packages in the Contrib repository.

Instrument a basic Flask application that uses the requests library to send HTTP requests. First, install the instrumentation packages themselves:

pip install opentelemetry-instrumentation-flask

pip install opentelemetry-instrumentation-requests

The following small Flask application sends an HTTP request and also activates each instrumentation during its initialization:

# flask_example.py

import flask

import requests

from opentelemetry import trace

from opentelemetry.instrumentation.flask import FlaskInstrumentor

from opentelemetry.instrumentation.requests import RequestsInstrumentor

from opentelemetry.sdk.trace import TracerProvider

from opentelemetry.sdk.trace.export import (

    ConsoleSpanExporter,

    SimpleSpanProcessor,

)

trace.set_tracer_provider(TracerProvider())

trace.get_tracer_provider().add_span_processor(

    SimpleSpanProcessor(ConsoleSpanExporter())

)

app = flask.Flask(__name__)

FlaskInstrumentor().instrument_app(app)

RequestsInstrumentor().instrument()

@app.route("/")

def hello():

    tracer = trace.get_tracer(__name__)

    with tracer.start_as_current_span("example-request"):

        requests.get("http://www.example.com")

    return "hello"

app.run(debug=True, port=5000)

Now run the script, hit the root URL (http://localhost:5000/) a few times, and watch your spans be emitted!

python flask_example.py

Configure Your HTTP propagator (b3, Baggage)

A major feature of distributed tracing is the ability to correlate a trace across multiple services. However, those services need to propagate information about a trace from one service to the other.

To enable this propagation, OpenTelemetry has the concept of propagators, which provide a common method to encode and decode span information from a request and response, respectively.

By default, opentelemetry-python is configured to use the W3C Trace Context and W3C Baggage HTTP headers for HTTP requests, but you can configure it to leverage different propagators. Here’s an example using Zipkin’s b3 propagation:

pip install opentelemetry-propagator-b3

Following the installation of the package containing the b3 propagator, configure the propagator as follows:

from opentelemetry.propagate import set_global_textmap

from opentelemetry.propagators.b3 import B3Format

set_global_textmap(B3Format())

Use the OpenTelemetry Collector for Traces

Although it’s possible to directly export your telemetry data to specific backends, you might have more complex use cases such as the following:

A single telemetry sink shared by multiple services, to reduce overhead of switching exporters.

• A single telemetry sink shared by multiple services, to reduce overhead of switching exporters.
• Aggregating traces across multiple services, running on multiple hosts.
  
  

To enable a broad range of aggregation strategies, OpenTelemetry provides the opentelemetry-collector. The Collector is a flexible application that can consume trace data and export to multiple other backends, including to another instance of the Collector.

Start the Collector locally to see how the Collector works in practice. Write the following file:

receivers:

    opencensus:

        endpoint: 0.0.0.0:55678

exporters:

    logging:

        loglevel: debug

processors:

    batch:

    queued_retry:

service:

    pipelines:

        traces:

            receivers: [opencensus]

            exporters: [logging]

            processors: [batch, queued_retry]

Then start the Docker container:

docker run -p 55678:55678 \

    -v /tmp/otel-collector-config.yaml:/etc/otel-collector-config.yaml \

    omnition/opentelemetry-collector-contrib:latest \

    --config=/etc/otel-collector-config.yaml

Install the OpenTelemetry Collector exporter:

pip install opentelemetry-exporter-otlp

Finally, execute the following script:

# otcollector.py

import time

from opentelemetry import trace

from opentelemetry.exporter.otlp.proto.grpc.trace_exporter import (

    OTLPSpanExporter,

)

from opentelemetry.sdk.trace import TracerProvider

from opentelemetry.sdk.trace.export import BatchSpanProcessor

span_exporter = OTLPSpanExporter(

    # optional

    # endpoint:="myCollectorURL:55678",

    # credentials=ChannelCredentials(credentials),

    # headers=(("metadata", "metadata")),

)

tracer_provider = TracerProvider()

trace.set_tracer_provider(tracer_provider)

span_processor = BatchSpanProcessor(span_exporter)

tracer_provider.add_span_processor(span_processor)

# Configure the tracer to use the collector exporter

tracer = trace.get_tracer_provider().get_tracer(__name__)

with tracer.start_as_current_span("foo"):

    print("Hello world!")

Congratulations! You’re up and running with OpenTelemetry Python v1.0.0!

You can find more elaborate examples on Github and the complete documentation here.

What’s Next?

OpenTelemetry Javascript v1.0.0 will be GA soon. Check back here or the OpenTelemetry blog for updates. 

ICYMI

• Getting started instructions for OpenTelemetry .NET and OpenTelemetry Java
  
  

What Does This Mean for Splunk Customers?

Whether you build your own OpenTelemetry SDKs or Collectors or use our pre-packaged and supported distribution, you can have confidence that the 1.0 releases contain stable tracing APIs and tracing-related functionality, and that even more integrations are on the way. You can use the .Net, Java, and Python SDKs today with Splunk APM by sending traces to an OpenTelemetry Collector that then exports the traces to Splunk. 

You can read more about this exciting announcement and what’s next with the project in the blog below. 

Splunk is a contributor to OpenTelemetry and committed to accelerating the adoption of the project. For more information about Splunk and OpenTelemetry, you can check out our latest OpenTelemetry blog posts.