Class: Phronomy::Tracing::LangfuseTracer

Inherits:
Base
  • Object
show all
Defined in:
lib/phronomy/tracing/langfuse_tracer.rb

Overview

Langfuse tracer adapter.

Sends spans to Langfuse via the batch ingestion REST API (+POST /api/public/ingestion+). No external gem is required — only Ruby standard-library network primitives are used.

Ingestion errors are silently swallowed so that a Langfuse outage never breaks the application.

Examples:

Configure globally

Phronomy.configure do |c|
  c.tracer = Phronomy::Tracing::LangfuseTracer.new(
    public_key: ENV.fetch("LANGFUSE_PUBLIC_KEY"),
    secret_key: ENV.fetch("LANGFUSE_SECRET_KEY"),
    host:       ENV.fetch("LANGFUSE_HOST", "https://cloud.langfuse.com")
  )
end

Constant Summary collapse

DEFAULT_HOST =

Default Langfuse cloud host.

"https://cloud.langfuse.com"

Instance Method Summary collapse

Methods inherited from Base

#trace

Constructor Details

#initialize(public_key:, secret_key:, host: DEFAULT_HOST) ⇒ LangfuseTracer

Returns a new instance of LangfuseTracer.

Parameters:

  • public_key (String) —

    Langfuse project public key

  • secret_key (String) —

    Langfuse project secret key

  • host (String) (defaults to: DEFAULT_HOST) —

    Langfuse host URL (override for self-hosted instances)



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# File 'lib/phronomy/tracing/langfuse_tracer.rb', line 34

def initialize(public_key:, secret_key:, host: DEFAULT_HOST)
  @public_key = public_key
  @secret_key = secret_key
  @host = host.chomp("/")
end

Instance Method Details

#finish_span(span, output: nil, usage: nil, error: nil) ⇒ Object

Serialises the span and fires it to Langfuse via the ingestion API.



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# File 'lib/phronomy/tracing/langfuse_tracer.rb', line 55

def finish_span(span, output: nil, usage: nil, error: nil)
  body = {
    id: span[:id],
    traceId: span[:trace_id],
    name: span[:name],
    startTime: span[:start_time].utc.iso8601(3),
    endTime: Time.now.utc.iso8601(3),
    input: span[:input],
    output: error ? nil : output,
    metadata: span[:meta]
  }
  body[:level] = "ERROR" if error
  body[:statusMessage] = error.message if error
  if usage
    body[:usage] = {
      input: usage.input,
      output: usage.output,
      total: (usage.input || 0) + (usage.output || 0)
    }
  end
  ingest([{type: "span-create", body: body}])
end

#start_span(name, input: nil, **meta) ⇒ Hash

Returns a plain Hash that records the span start state.

Returns:



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# File 'lib/phronomy/tracing/langfuse_tracer.rb', line 43

def start_span(name, input: nil, **meta)
  {
    id: SecureRandom.uuid,
    trace_id: SecureRandom.uuid,
    name: name,
    input: input,
    start_time: Time.now,
    meta: meta
  }
end