module Gitlab module Metrics # Module for instrumenting methods. # # This module allows instrumenting of methods without having to actually # alter the target code (e.g. by including modules). # # Example usage: # # Gitlab::Metrics::Instrumentation.instrument_method(User, :by_login) module Instrumentation PROXY_IVAR = :@__gitlab_instrumentation_proxy def self.configure yield self end # Returns the name of the series to use for storing method calls. def self.series @series ||= "#{Metrics.series_prefix}method_calls" end # Instruments a class method. # # mod - The module to instrument as a Module/Class. # name - The name of the method to instrument. def self.instrument_method(mod, name) instrument(:class, mod, name) end # Instruments an instance method. # # mod - The module to instrument as a Module/Class. # name - The name of the method to instrument. def self.instrument_instance_method(mod, name) instrument(:instance, mod, name) end # Recursively instruments all subclasses of the given root module. # # This can be used to for example instrument all ActiveRecord models (as # these all inherit from ActiveRecord::Base). # # This method can optionally take a block to pass to `instrument_methods` # and `instrument_instance_methods`. # # root - The root module for which to instrument subclasses. The root # module itself is not instrumented. def self.instrument_class_hierarchy(root, &block) visit = root.subclasses until visit.empty? klass = visit.pop instrument_methods(klass, &block) instrument_instance_methods(klass, &block) klass.subclasses.each { |c| visit << c } end end # Instruments all public and private methods of a module. # # This method optionally takes a block that can be used to determine if a # method should be instrumented or not. The block is passed the receiving # module and an UnboundMethod. If the block returns a non truthy value the # method is not instrumented. # # mod - The module to instrument. def self.instrument_methods(mod) methods = mod.methods(false) + mod.private_methods(false) methods.each do |name| method = mod.method(name) if method.owner == mod.singleton_class if !block_given? || block_given? && yield(mod, method) instrument_method(mod, name) end end end end # Instruments all public and private instance methods of a module. # # See `instrument_methods` for more information. # # mod - The module to instrument. def self.instrument_instance_methods(mod) methods = mod.instance_methods(false) + mod.private_instance_methods(false) methods.each do |name| method = mod.instance_method(name) if method.owner == mod if !block_given? || block_given? && yield(mod, method) instrument_instance_method(mod, name) end end end end # Returns true if a module is instrumented. # # mod - The module to check def self.instrumented?(mod) mod.instance_variable_defined?(PROXY_IVAR) end # Returns the proxy module (if any) of `mod`. def self.proxy_module(mod) mod.instance_variable_get(PROXY_IVAR) end # Instruments a method. # # type - The type (:class or :instance) of method to instrument. # mod - The module containing the method. # name - The name of the method to instrument. def self.instrument(type, mod, name) return unless Metrics.enabled? name = name.to_sym target = type == :instance ? mod : mod.singleton_class if type == :instance target = mod label = "#{mod.name}##{name}" method = mod.instance_method(name) else target = mod.singleton_class label = "#{mod.name}.#{name}" method = mod.method(name) end unless instrumented?(target) target.instance_variable_set(PROXY_IVAR, Module.new) end proxy_module = self.proxy_module(target) # Some code out there (e.g. the "state_machine" Gem) checks the arity of # a method to make sure it only passes arguments when the method expects # any. If we were to always overwrite a method to take an `*args` # signature this would break things. As a result we'll make sure the # generated method _only_ accepts regular arguments if the underlying # method also accepts them. args_signature = if method.arity == 0 '' else '*args' end proxy_module.class_eval <<-EOF, __FILE__, __LINE__ + 1 def #{name}(#{args_signature}) if trans = Gitlab::Metrics::Instrumentation.transaction trans.method_call_for(#{label.to_sym.inspect}).measure { super } else super end end EOF target.prepend(proxy_module) end # Small layer of indirection to make it easier to stub out the current # transaction. def self.transaction Transaction.current end end end end