Class: Datadog::Tracing::Distributed::Propagation

Inherits:
Object
  • Object
show all
Defined in:
lib/datadog/tracing/distributed/propagation.rb

Overview

Provides extraction and injection of distributed trace data.

Instance Method Summary collapse

Constructor Details

#initialize(propagation_styles:) ⇒ Propagation

DEV: This class should receive the value for DEV: ‘Datadog.configuration.tracing.distributed_tracing.propagation_inject_style` DEV: at initialization time, instead of constantly reading global values. DEV: This means this class should be reconfigured on `Datadog.configure` calls, thus DEV: singleton instances should not used as they will become stale.

Parameters:

  • propagation_styles (Hash<String,Object>) 


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# File 'lib/datadog/tracing/distributed/propagation.rb', line 19

def initialize(propagation_styles:)
  @propagation_styles = propagation_styles
end

Instance Method Details

#extract(data) ⇒ Object

extract returns TraceDigest containing the distributed trace information. sampling priority defined in data.

This method will never raise errors, but instead log them to ‘Datadog.logger`.

Parameters:

  • data (Hash) 


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# File 'lib/datadog/tracing/distributed/propagation.rb', line 74

def extract(data)
  trace_digest = nil
  dd_trace_digest = nil

  ::Datadog.configuration.tracing.distributed_tracing.propagation_extract_style.each do |style|
    propagator = @propagation_styles[style]
    next if propagator.nil?

    begin
      extracted_trace_digest = propagator.extract(data)
    rescue => e
      ::Datadog.logger.error(
        'Error extracting distributed trace data. ' \
      "Cause: #{e} Location: #{Array(e.backtrace).first}"
      )
    end

    # Skip if no valid data was found
    next if extracted_trace_digest.nil?

    # Keep track of the Datadog extracted digest, we want to return it if we have it.
    if extracted_trace_digest && style == Tracing::Configuration::Ext::Distributed::PROPAGATION_STYLE_DATADOG
      dd_trace_digest = extracted_trace_digest
    end

    # No previously extracted trace data, use the one we just extracted
    if trace_digest.nil?
      trace_digest = extracted_trace_digest
    else
      unless trace_digest.trace_id == extracted_trace_digest.trace_id \
            && trace_digest.span_id == extracted_trace_digest.span_id
        # We have two mismatched propagation contexts
        ::Datadog.logger.debug do
          'Cannot extract distributed trace data: extracted styles differ, ' \
          "#{trace_digest.trace_id} != #{extracted_trace_digest.trace_id} && " \
          "#{trace_digest.span_id} != #{extracted_trace_digest.span_id}"
        end

        # It's safer to create a new context than to attach ourselves to the wrong context
        return TraceDigest.new # Early return from the whole method
      end
    end
  end

  # Return the extracted trace digest if we found one or else a new empty digest.
  # Always return the Datadog trace digest if one exists since it has more
  # information than the B3 digest, e.g. origin, priority sampling values.
  dd_trace_digest || trace_digest || nil
end

#inject!(digest, data) ⇒ Boolean?

inject! populates the env with span ID, trace ID and sampling priority

This method will never raise errors, but instead log them to ‘Datadog.logger`.

DEV-2.0: inject! should work without arguments, injecting the active_trace’s digest DEV-2.0: and returning a new Hash with the injected data. DEV-2.0: inject! should also accept either a ‘trace` or a `digest`, as a `trace` DEV-2.0: argument is the common use case, but also allows us to set error tags in the `trace` DEV-2.0: if needed. DEV-2.0: Ideally, we’d have a separate stream to report tracer errors and never DEV-2.0: touch the active span.

Parameters:

Returns:

  • (Boolean) —

    ‘true` if injected successfully, `false` if no propagation style is configured

  • (nil) —

    in case of error, see ‘Datadog.logger` output for details.



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# File 'lib/datadog/tracing/distributed/propagation.rb', line 39

def inject!(digest, data)
  if digest.nil?
    ::Datadog.logger.debug('Cannot inject distributed trace data: digest is nil.')
    return nil
  end

  digest = digest.to_digest if digest.respond_to?(:to_digest)

  result = false

  # Inject all configured propagation styles
  ::Datadog.configuration.tracing.distributed_tracing.propagation_inject_style.each do |style|
    propagator = @propagation_styles[style]
    begin
      if propagator
        propagator.inject!(digest, data)
        result = true
      end
    rescue => e
      result = nil
      ::Datadog.logger.error(
        "Error injecting distributed trace data. Cause: #{e} Location: #{Array(e.backtrace).first}"
      )
    end
  end

  result
end