Class: Datadog::Context

Inherits:
Object
  • Object
show all
Defined in:
lib/ddtrace/context.rb

Overview

Context is used to keep track of a hierarchy of spans for the current execution flow. During each logical execution, the same Context is used to represent a single logical trace, even if the trace is built asynchronously.

A single code execution may use multiple Context if part of the execution must not be related to the current tracing. As example, a delayed job may compose a standalone trace instead of being related to the same trace that generates the job itself. On the other hand, if it’s part of the same Context, it will be related to the original trace.

This data structure is thread-safe.

Instance Method Summary collapse

Constructor Details

#initialize ⇒ Context

Initialize a new thread-safe Context.



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# File 'lib/ddtrace/context.rb', line 18

def initialize
  @mutex = Mutex.new
  reset
end

Instance Method Details

#add_span(span) ⇒ Object

Add a span to the context trace list, keeping it as the last active span.



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# File 'lib/ddtrace/context.rb', line 41

def add_span(span)
  @mutex.synchronize do
    @current_span = span
    @sampled = span.sampled
    @trace << span
    span.context = self
  end
end

#close_span(span) ⇒ Object

Mark a span as a finished, increasing the internal counter to prevent cycles inside _trace list.



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# File 'lib/ddtrace/context.rb', line 52

def close_span(span)
  @mutex.synchronize do
    @finished_spans += 1
    # Current span is only meaningful for linear tree-like traces,
    # in other cases, this is just broken and one should rely
    # on per-instrumentation code to retrieve handle parent/child relations.
    @current_span = span.parent
    return if span.tracer.nil?
    return unless Datadog::Tracer.debug_logging
    if span.parent.nil? && !check_finished_spans
      opened_spans = @trace.length - @finished_spans
      Datadog::Tracer.log.debug("root span #{span.name} closed but has #{opened_spans} unfinished spans:")
      @trace.each do |s|
        Datadog::Tracer.log.debug("unfinished span: #{s}") unless s.finished?
      end
    end
  end
end

#current_span ⇒ Object

Return the last active span that corresponds to the last inserted item in the trace list. This cannot be considered as the current active span in asynchronous environments, because some spans can be closed earlier while child spans still need to finish their traced execution.



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# File 'lib/ddtrace/context.rb', line 34

def current_span
  @mutex.synchronize do
    return @current_span
  end
end

#finished? ⇒ Boolean

Returns if the trace for the current Context is finished or not. A Context is considered finished if all spans in this context are finished.

Returns:

  • (Boolean) 


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# File 'lib/ddtrace/context.rb', line 79

def finished?
  @mutex.synchronize do
    return check_finished_spans
  end
end

#get ⇒ Object

Returns both the trace list generated in the current context and if the context is sampled or not. It returns nil, nil if the “Context“ is not finished. If a trace is returned, the Context will be reset so that it can be re-used immediately.

This operation is thread-safe.



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# File 'lib/ddtrace/context.rb', line 99

def get
  @mutex.synchronize do
    return nil, nil unless check_finished_spans

    trace = @trace
    sampled = @sampled
    reset
    return trace, sampled
  end
end

#sampled? ⇒ Boolean

Returns true if the context is sampled, that is, if it should be kept and sent to the trace agent.

Returns:

  • (Boolean) 


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# File 'lib/ddtrace/context.rb', line 87

def sampled?
  @mutex.synchronize do
    return @sampled
  end
end

#to_s ⇒ Object

Return a string representation of the context.



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# File 'lib/ddtrace/context.rb', line 111

def to_s
  @mutex.synchronize do
    # rubocop:disable Metrics/LineLength
    "Context(trace.length:#{@trace.length},sampled:#{@sampled},finished_spans:#{@finished_spans},current_span:#{@current_span})"
  end
end