Module: BrainzLab::Pulse::Propagation

Defined in:
lib/brainzlab/pulse/propagation.rb

Overview

Distributed tracing context propagation using W3C Trace Context format www.w3.org/TR/trace-context/

Defined Under Namespace

Classes: Context

Constant Summary collapse

TRACEPARENT_HEADER =

W3C Trace Context header names

'traceparent'
TRACESTATE_HEADER = 
'tracestate'
HTTP_TRACEPARENT =

HTTP header versions (with HTTP_ prefix for Rack env)

'HTTP_TRACEPARENT'
HTTP_TRACESTATE = 
'HTTP_TRACESTATE'
B3_TRACE_ID =

Also support B3 format for compatibility

'X-B3-TraceId'
B3_SPAN_ID = 
'X-B3-SpanId'
B3_SAMPLED = 
'X-B3-Sampled'
B3_PARENT_SPAN_ID = 
'X-B3-ParentSpanId'

Class Method Summary collapse

Class Method Details

.child_context(parent: nil) ⇒ Object

Create a child context for a new span



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# File 'lib/brainzlab/pulse/propagation.rb', line 122

def child_context(parent: nil)
  parent ||= current
  return Context.new unless parent&.valid?

  Context.new(
    trace_id: parent.trace_id,
    parent_span_id: parent.span_id,
    sampled: parent.sampled,
    tracestate: parent.tracestate
  )
end

.clear! ⇒ Object

Clear current context



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# File 'lib/brainzlab/pulse/propagation.rb', line 78

def clear!
  Thread.current[:brainzlab_propagation_context] = nil
end

.current ⇒ Object

Get current propagation context from thread local



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# File 'lib/brainzlab/pulse/propagation.rb', line 60

def current
  Thread.current[:brainzlab_propagation_context]
end

.current=(context) ⇒ Object

Set current propagation context



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# File 'lib/brainzlab/pulse/propagation.rb', line 65

def current=(context)
  Thread.current[:brainzlab_propagation_context] = context
end

.extract(headers) ⇒ Context?

Extract trace context from incoming HTTP headers (Rack env or plain headers)

Parameters:

  • headers (Hash) —

    the headers to extract from

Returns:

  • (Context, nil) —

    the extracted context or nil



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# File 'lib/brainzlab/pulse/propagation.rb', line 106

def extract(headers)
  # Try W3C format first
  ctx = extract_w3c(headers)
  return ctx if ctx

  # Fall back to B3 format
  extract_b3(headers)
end

.extract!(headers) ⇒ Object

Extract and set as current context Returns the context for chaining



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# File 'lib/brainzlab/pulse/propagation.rb', line 117

def extract!(headers)
  self.current = extract(headers)
end

.inject(headers, context: nil, format: :w3c) ⇒ Object

Inject trace context into outgoing HTTP headers

Parameters:

  • headers (Hash) —

    the headers hash to inject into

  • context (Context) (defaults to: nil) —

    optional context (defaults to current)

  • format (Symbol) (defaults to: :w3c) —

    :w3c (default), :b3, or :all



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# File 'lib/brainzlab/pulse/propagation.rb', line 86

def inject(headers, context: nil, format: :w3c)
  ctx = context || current
  return headers unless ctx&.valid?

  case format
  when :w3c
    inject_w3c(headers, ctx)
  when :b3
    inject_b3(headers, ctx)
  when :all
    inject_w3c(headers, ctx)
    inject_b3(headers, ctx)
  end

  headers
end

.start(trace_id: nil, parent_span_id: nil) ⇒ Object

Create new context and set as current



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# File 'lib/brainzlab/pulse/propagation.rb', line 70

def start(trace_id: nil, parent_span_id: nil)
  self.current = Context.new(
    trace_id: trace_id,
    parent_span_id: parent_span_id
  )
end