ask-opentelemetry

OpenTelemetry tracing for the ask-rb ecosystem. Subscribes to ask-instrumentation events and creates OpenTelemetry spans for chat completions, tool calls, embeddings, and image generation.

Works with any OpenTelemetry-compatible backend: Langfuse, Datadog, Honeycomb, Jaeger, Arize Phoenix, and more.

Installation

gem "ask-opentelemetry"
gem "ask-instrumentation"

Quick Start

require "ask/open_telemetry"

# Subscribe to all ask events and create OpenTelemetry spans
Ask::OpenTelemetry.install

In Rails

The Railtie auto-installs — no manual setup required:

# Gemfile
gem "ask-opentelemetry"
gem "ask-instrumentation"

That's it. Spans are created automatically for every LLM operation.

Spans Created

Event	Span Name	Key Attributes
chat.ask	llm.chat	provider, model, input_tokens, output_tokens, duration_ms
chat.stream.ask	llm.chat	provider, model, input_tokens, output_tokens, duration_ms
tool.ask	llm.tool	provider, tool, tool_args
embedding.ask	llm.embedding	provider, model, input_tokens
image.ask	llm.image	provider, model, image.size, duration_ms

Standard Attributes

All spans include:

• llm.provider — The LLM provider (e.g., openai, anthropic)
• llm.model — The model identifier (e.g., gpt-4, claude-3)
• llm.duration_ms — The duration of the LLM operation in milliseconds
• llm.input_tokens — Input token count (when available)
• llm.output_tokens — Output token count (when available)

Metadata Attributes

Any context set via Ask::Instrumentation.with_metadata is forwarded as llm.metadata.* attributes:

Ask::Instrumentation.with_metadata(user_id: 42, session_id: "abc") do
  # The resulting span has:
  #   llm.metadata.user_id = 42
  #   llm.metadata.session_id = "abc"
end

Backend Examples

Langfuse

Langfuse provides LLM observability (cost tracking, evaluations, prompt management) via OpenTelemetry.

Using Langfuse Cloud:

require "ask/open_telemetry"
require "opentelemetry-sdk"
require "opentelemetry-exporter-otlp"

OpenTelemetry::SDK.configure do |c|
  c.service_name = "my-app"
  c.add_span_processor(
    OpenTelemetry::SDK::Trace::Export::BatchSpanProcessor.new(
      OpenTelemetry::Exporter::OTLP::Exporter.new(
        endpoint: "https://cloud.langfuse.com/api/public/otel/v1/traces",
        headers: {
          "Authorization" => "Basic #{Base64.strict_encode64("#{LANGFUSE_PUBLIC_KEY}:#{LANGFUSE_SECRET_KEY}")}"
        }
      )
    )
  )
end

Ask::OpenTelemetry.install

Using Langfuse Self-Hosted:

OpenTelemetry::SDK.configure do |c|
  c.service_name = "my-app"
  c.add_span_processor(
    OpenTelemetry::SDK::Trace::Export::BatchSpanProcessor.new(
      OpenTelemetry::Exporter::OTLP::Exporter.new(
        endpoint: "https://your-instance.langfuse.com/api/public/otel/v1/traces",
        headers: {
          "Authorization" => "Basic #{Base64.strict_encode64("#{LANGFUSE_PUBLIC_KEY}:#{LANGFUSE_SECRET_KEY}")}"
        }
      )
    )
  )
end

Datadog

require "ask/open_telemetry"
require "opentelemetry-sdk"
require "opentelemetry-exporter-otlp"

OpenTelemetry::SDK.configure do |c|
  c.service_name = "my-app"
  c.add_span_processor(
    OpenTelemetry::SDK::Trace::Export::BatchSpanProcessor.new(
      OpenTelemetry::Exporter::OTLP::Exporter.new(
        endpoint: "https://otlp.datadoghq.com",
        headers: { "DD-API-KEY" => ENV["DD_API_KEY"] }
      )
    )
  )
end

Ask::OpenTelemetry.install

Honeycomb

require "ask/open_telemetry"
require "opentelemetry-sdk"
require "opentelemetry-exporter-otlp"

OpenTelemetry::SDK.configure do |c|
  c.service_name = "my-app"
  c.add_span_processor(
    OpenTelemetry::SDK::Trace::Export::BatchSpanProcessor.new(
      OpenTelemetry::Exporter::OTLP::Exporter.new(
        endpoint: "https://api.honeycomb.io:443",
        headers: { "x-honeycomb-team" => ENV["HONEYCOMB_API_KEY"] }
      )
    )
  )
end

Ask::OpenTelemetry.install

API

.install

Subscribe to all .ask events and start creating spans. Idempotent — calling multiple times only subscribes once.

Ask::OpenTelemetry.install

Development

git clone https://github.com/ask-rb/ask-opentelemetry.git
cd ask-opentelemetry
bundle install
bundle exec rake test

License

MIT