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module OpenTracing
#:nodoc:
class Reference
CHILD_OF = 'child_of'.freeze
FOLLOWS_FROM = 'follows_from'.freeze
# @param context [SpanContext, Span] child_of context refers to a
# parent Span that caused *and* somehow depends upon the new child Span.
# Often (but not always), the parent Span cannot finish until the child
# Span does.
#
# An timing diagram for a child Span that is blocked on the new Span:
#
# [-Parent Span----------]
# [-Child Span----]
#
# See http://opentracing.io/documentation/pages/spec
#
# @return [Reference] a ChildOf reference
#
# @example
# root_span = OpenTracing.start_span('root operation')
# child_span = OpenTracing.start_span('child operation', references: [
# OpenTracing::Reference.child_of(root_span)
# ])
#
def self.child_of(context)
context = context.context if context.is_a?(Span)
Reference.new(CHILD_OF, context)
end
# @param context [SpanContext, Span] follows_from context refers to a
# parent Span that does not depend in any way on the result of the new
# child Span. For instance, one might use FollowsFrom Span to describe
# pipeline stages separated by queues, or a fire-and-forget cache insert
# at the tail end of a web request.
#
# A FollowsFrom Span is part of the same logical trace as the new Span:
# i.e., the new Span is somehow caused by the work of its FollowsFrom
# Span.
#
# All of the following could be valid timing diagrams for children that
# "FollowFrom" a parent:
#
# [-Parent Span--] [-Child Span-]
#
# [-Parent Span--]
# [-Child Span-]
#
# [-Parent Span-]
# [-Child Span-]
#
# See http://opentracing.io/documentation/pages/spec
#
# @return [Reference] a FollowsFrom reference
#
# @example
# context = OpenTracing.extract(OpenTracing::FORMAT_RACK, rack_env)
# span = OpenTracing.start_span('following operation', references: [
# OpenTracing::Reference.follows_from(context)
# ])
#
def self.follows_from(context)
context = context.context if context.is_a?(Span)
Reference.new(FOLLOWS_FROM, context)
end
def initialize(type, context)
@type = type
@context = context
end
# @return [String] reference type
attr_reader :type
# @return [SpanContext] the context of a span this reference is referencing
attr_reader :context
end
end
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