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September 10, 2025 20:34
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Using MethodTrace to identify where Memoizing might be helpful.
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| # | |
| # With reference to | |
| # Just a run-down of TracePoint | |
| # | |
| # https://medium.com/@baweaver/exploring-tracepoint-in-ruby-part-one-example-code-2cf9b1a1b956 | |
| # Rotoscope tracks method invocations but not arguments | |
| # | |
| # https://github.com/Shopify/rotoscope | |
| # | |
| # Rack::MethodTrace - allows us to see which methods are called more than once and which are memoized | |
| # | |
| if ActiveModel::Type::Boolean.new.cast(ENV["METHOD_TRACE"]) | |
| module Rack | |
| class MethodTrace | |
| ROOTS_REGEXP = %r{^(#{Rails.root}|#{Gem::Specification.find_by_name("memery").gem_dir})} | |
| def initialize(app) | |
| @app = app | |
| end | |
| def call(env) | |
| trace.enable do | |
| status, headers, response = @app.call(env) | |
| log(env["REQUEST_URI"]) | |
| [status, headers, response] | |
| end | |
| end | |
| private | |
| def trace | |
| TracePoint.new(:call) do |tp| | |
| next unless ROOTS_REGEXP.match?(tp.path) | |
| # memoized = (tp.defined_class.try(:memoized_methods) || []).map(&:memoized_method).include?(tp.method_id) | |
| store.concat(Rover::DataFrame.new([{ | |
| class: tp.defined_class.name, | |
| object_id: tp.binding.eval("object_id"), | |
| method: tp.method_id.to_s, | |
| # memoized: memoized, | |
| lineno: "#{tp.path.sub(ROOTS_REGEXP, "")}:#{tp.lineno}", | |
| args: extract_args(tp).to_s | |
| }])) | |
| end | |
| end | |
| def log(path) | |
| grouped = store.group(:class, :object_id, :method, :lineno, :args).count | |
| results = grouped[grouped["count"] > 1].to_a | |
| return if results.empty? | |
| table = Text::Table.new | |
| table.head = ["Class", "ObjectId", "Method", "Line No.", "Args", "Count"] | |
| results.each do |row| | |
| table.rows << [row[:class], row[:object_id], row[:method], row[:lineno], row[:args][0..20], row["count"]] | |
| end | |
| logger.info([path, table.to_s].join("\n")) | |
| end | |
| def store | |
| RequestStore.store[:methods] ||= Rover::DataFrame.new([]) | |
| end | |
| def logger | |
| @logger ||= ::Logger.new(Rails.root.join("log", "method_trace.log"), formatter: proc { |severity, datetime, progname, msg| | |
| "#{datetime}\n#{msg}\n" | |
| }) | |
| end | |
| def extract_args(tp) | |
| tp.parameters.map do |f, v| | |
| next if f == :rest || f == :keyrest || f == :block | |
| [v, tp.binding.eval(v.to_s).to_s] | |
| end.compact.to_h | |
| end | |
| Rails.application.config.middleware.insert_after(ActionDispatch::Static, self) | |
| end | |
| end | |
| end |
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