Application Real-Time Monitoring Service:Report Ruby trace data with OpenTelemetry

Supported frameworks

Auto-instrumentation covers a wide range of Ruby libraries, including:

For the full list, see the OpenTelemetry Ruby contrib repository.

Step 1: Create a Rails project

Skip this step if you already have a Rails application.

gem install rails
rails new <your-project-name>
cd <your-project-name>

Replace <your-project-name> with your application name, for example rails new otel-demo.

If you see the error Rails is not currently installed on this system, close and reopen your terminal, then run the command again.

Step 2: Add OpenTelemetry gems

Add these lines to your project's Gemfile:

gem 'opentelemetry-sdk'
gem 'opentelemetry-exporter-otlp'
gem 'opentelemetry-instrumentation-all'

Then install the dependencies:

gem install bundler   # skip if Bundler is already installed
bundle install

Step 3: Configure the OpenTelemetry SDK

Create config/initializers/opentelemetry.rb:

# config/initializers/opentelemetry.rb
require 'opentelemetry/sdk'
require 'opentelemetry/exporter/otlp'
require 'opentelemetry/instrumentation/all'

OpenTelemetry::SDK.configure do |c|
  c.add_span_processor(
    OpenTelemetry::SDK::Trace::Export::BatchSpanProcessor.new(
      OpenTelemetry::Exporter::OTLP::Exporter.new(
        endpoint: '<endpoint>' # Replace with your OpenTelemetry HTTP endpoint.
      )
    )
  )
  c.resource = OpenTelemetry::SDK::Resources::Resource.create({
    OpenTelemetry::SemanticConventions::Resource::HOST_NAME => '<your-host-name>',
  })
  c.service_name = '<your-service-name>'
  c.use_all() # Enable auto-instrumentation for all supported libraries.
end

Replace the placeholders with your actual values:

Step 4: Start the application

rails server

Expected output:

* Puma version: 5.6.5 (ruby 2.7.2-p137) ("Birdie's Version")
*  Min threads: 5
*  Max threads: 5
*  Environment: development
*          PID: 79842
* Listening on http://127.0.0.1:3000
* Listening on http://[::1]:3000
Use Ctrl-C to stop

Step 5: Verify data reporting

Open http://127.0.0.1:3000 in a browser. If your terminal displays the following log output, trace data is being exported to Managed Service for OpenTelemetry:

Started GET "/" for 127.0.0.1 at 2023-01-01 10:00:00 +0800
Processing by Rails::WelcomeController#index as HTML
  Rendering /Users/username/.rvm/gems/ruby-2.7.2/gems/railties-7.0.4.3/lib/rails/templates/rails/welcome/index.html.erb
  Rendered /Users/username/.rvm/gems/ruby-2.7.2/gems/railties-7.0.4.3/lib/rails/templates/rails/welcome/index.html.erb (Duration: 0.8ms | Allocations: 665)
Completed 200 OK in 6ms (Views: 2.1ms | ActiveRecord: 0.0ms | Allocations: 5440)

Step 1: Install dependencies

Install the following OpenTelemetry dependencies:

gem install opentelemetry-api
gem install opentelemetry-sdk
gem install opentelemetry-exporter-otlp

Step 2: Initialize the SDK

Create a file (for example, manual.rb) and configure the OTLP exporter. BatchSpanProcessor buffers spans and sends them in batches for better performance:

require 'opentelemetry/sdk'
require 'opentelemetry-exporter-otlp'

OpenTelemetry::SDK.configure do |c|
  c.add_span_processor(
    OpenTelemetry::SDK::Trace::Export::BatchSpanProcessor.new(
      OpenTelemetry::Exporter::OTLP::Exporter.new(
        endpoint: '<endpoint>' # Replace with your OpenTelemetry HTTP endpoint.
      )
    )
  )
  c.resource = OpenTelemetry::SDK::Resources::Resource.create({
    OpenTelemetry::SemanticConventions::Resource::SERVICE_NAMESPACE => 'tracing',
    OpenTelemetry::SemanticConventions::Resource::SERVICE_NAME => '<your-service-name>',
    OpenTelemetry::SemanticConventions::Resource::SERVICE_VERSION => '0.0.1',
  })
end

Replace the placeholders:

Step 3: Create spans

Get a tracer and create a span:

tracer = OpenTelemetry.tracer_provider.tracer('<your-tracer-name>', '0.1.0')

tracer.in_span('parent_span') do |parent_span|
  # Your application logic here.
end

The tracer name identifies the instrumentation library in the ARMS console. Pick a name that describes the component being traced, for example 'order-service' or 'payment-processor'.

Step 4: Add attributes and read span context

Inside a span block, add attributes and retrieve the trace ID and span ID:

tracer.in_span('parent_span') do |parent_span|
  current_span = OpenTelemetry::Trace::current_span
  current_span.set_attribute('key', 'value')
  pp current_span.context.trace_id
  pp current_span.context.span_id
end

Step 5: Create nested spans

Nest in_span calls to represent parent-child relationships between operations:

tracer.in_span('parent_span') do |parent_span|
  # Parent span logic.
  tracer.in_span('child_span') do |child_span|
    current_span = OpenTelemetry::Trace::current_span
    pp current_span  # This is the child span.
  end
end

Complete example

This example covers span creation, attributes, events, nested spans, and error handling in a single script:

require 'opentelemetry/sdk'
require 'opentelemetry-exporter-otlp'

OpenTelemetry::SDK.configure do |c|
  c.add_span_processor(
    OpenTelemetry::SDK::Trace::Export::BatchSpanProcessor.new(
      OpenTelemetry::Exporter::OTLP::Exporter.new(
        endpoint: '<endpoint>' # Replace with your OpenTelemetry HTTP endpoint.
      )
    )
  )
  c.resource = OpenTelemetry::SDK::Resources::Resource.create({
    OpenTelemetry::SemanticConventions::Resource::SERVICE_NAMESPACE => 'tracing',
    OpenTelemetry::SemanticConventions::Resource::SERVICE_NAME => 'ruby_demo',
    OpenTelemetry::SemanticConventions::Resource::SERVICE_VERSION => '0.0.1',
  })

  # Alternatively, set the service name without the Resources API:
  # c.service_name = 'ruby_demo'
end

tracer = OpenTelemetry.tracer_provider.tracer('instrumentation_library_name', '0.1.0')

tracer.in_span('parent_span') do |parent_span|
  # Set span attributes.
  parent_span.set_attribute('language', 'ruby')
  parent_span.set_attribute("attribute_key", ["attribute_value1", "attribute_value1", "attribute_value1"])

  # Add a span event.
  parent_span.add_event("event", attributes: {
    "pid" => 1234,
    "signal" => "SIGHUP"
  })

  # Read the trace ID and span ID.
  current_span = OpenTelemetry::Trace::current_span
  pp current_span.context.trace_id
  pp current_span.context.span_id

  tracer.in_span('child_span') do |child_span|
    child_span.add_attributes({
      "key1" => "value1",
      "key2" => "value2"
    })

    child_span.add_event("mock exception here")

    begin
      raise 'An error has occurred'
    rescue
      # Mark the span as errored.
      child_span.status = OpenTelemetry::Trace::Status.error("error in child span")
    end

    pp child_span
  end
end

sleep 10

Run the application:

ruby manual.rb