About
Trip is a concurrent tracer implemented with TracePoint and Fiber.
Examples
Concurrency
Fiber
Trip is a concurrent tracer that can pause and resume the code it is tracing. Trip yields control between two Fibers - typically the root Fiber and a Fiber that Trip creates. The process of yielding control back and forth between the two Fibers can be repeated until the the code being traced has finished and exits normally:
#!/usr/bin/env ruby
require "trip"
module Stdout
def self.write(message)
puts(message)
end
end
##
# Create a new Trip.
# Pause for events coming from "Stdout.write".
trip = Trip.new { Stdout.write("Ruby is") }
trip.pause_when { |event| event.self == Stdout && event.method_id == :write }
##
# Enter "Stdout.write" - then mutate a local
# variable while the tracer is paused.
event = trip.start
event.binding.eval("message << ' cool.'")
##
# Execute the "puts(message)" line, and pause
# for the return of "Stdout.write".
event = trip.resume
##
# Exit the "Stdout.write" method, and the
# tracer.
event = trip.resume
##
# Ruby is cool.
Filter
Events
Trip will listen for method call and return events from methods
implemented in either C or Ruby by default. The first argument given
to Trip.new can specify a list of event names to listen for other than
the defaults. All events can be included by using Trip.new('*') { ... }.
A full list of event names can be found in the
Trip::Event docs.
The following example listens for call and return events from Ruby methods,
and excludes methods implemented in C:
#!/usr/bin/env ruby
require "trip"
def add(x, y)
puts(x + y)
end
trip = Trip.new(%i[call return]) { add(20, 50) }
while event = trip.resume
print event.name, " ", event.method_id, "\n"
end
##
# call add
# 70
# return add
Pause
The Trip#pause_when method can configure when to pause the tracer.
For example – you might want to pause the tracer only when an event
originates from a certain file, class, or method. Note that the events
specified by the first argument given to Trip.new decide what events
will be made available to Trip#pause_when:
#!/usr/bin/env ruby
require "trip"
require "net/http"
trip = Trip.new do
uri = URI.parse("https://www.ruby-lang.org")
Net::HTTP.get_response(uri)
end
trip.pause_when { |event| File.basename(event.path) == "http.rb" }
print "Event".ljust(10), "Location".ljust(15), "Method", "\n"
while event = trip.resume
sigil = event.method_type == "singleton_method" ? "." : "#"
print "#{event.name}".ljust(10),
"#{File.basename(event.path)}:#{event.lineno}".ljust(15),
event.module_name, sigil, event.method_id,
"\n"
end
##
# Event Location Method
# call http.rb:470 Net::HTTP.get_response
# c_call http.rb:480 URI::HTTPS#port
# c_return http.rb:480 URI::HTTPS#port
# c_call http.rb:481 URI::HTTPS#scheme
# c_return http.rb:481 URI::HTTPS#scheme
# c_call http.rb:481 String#==
# c_return http.rb:481 String#==
# call http.rb:668 Net::HTTP.start
# ...
Analysis
Require
The Trip#to_a method can perform a trace from start to finish,
and then return an array of Trip::Event objects. The following
example returns the number of files that Pry v0.14.1 requires,
including duplicate calls to require, and without any plugins
being used. When we exclude require "pry" from the count,
the number is 165 rather than 166:
#!/usr/bin/env ruby
require "trip"
trip = Trip.new(%i[call]) { require "pry" }
trip.pause_when { _1.method_id == :require }
events = trip.to_a
##
# The number of calls to require
puts events.size
##
# The paths that were required
puts events.map { _1.binding.eval('name') }
##
# 166
# pry
# pry/version
# pry/last_exception
# pry/forwardable
# forwardable
# forwardable/impl
# pry/helpers/base_helpers
# pry/helpers/documentation_helpers
# pry/helpers
# pry/helpers/base_helpers
# pry/helpers/options_helpers
# ...
Rescue
IRB
Trip can listen for the raise event, and then pause the tracer when
it is encountered. Afterwards, an IRB session can be started in the
Binding
of where an exception was raised:
#!/usr/bin/env ruby
require "trip"
module Stdout
def self.write(message)
putzzz(message)
end
end
trip = Trip.new(%i[raise]) { Stdout.write("hello") }
event = trip.start
event.binding.irb
Install
trip.rb can be installed via rubygems.org:
gem install trip.rb