Module: Tins::ThreadLocal

Included in:
Object, Deflect, HashBFS, HashSymbolizeKeysRecursive
Defined in:
lib/tins/thread_local.rb

Overview

Provides thread-local storage capabilities for classes and modules. Thread-local variables are scoped to individual threads, allowing each thread to maintain its own copy of the variable value.

Examples:

Basic usage with a class

class MyClass
  extend Tins::ThreadLocal

  thread_local :counter, 0
  thread_local :name, "default"
end

# Each thread gets its own copy of the variables
t1 = Thread.new { puts MyClass.new.counter }  # => 0
t2 = Thread.new { puts MyClass.new.counter }  # => 0
t1.join; t2.join

Usage with default blocks

class Config
  extend Tins::ThreadLocal

  thread_local :database_url do
    ENV['DATABASE_URL'] || 'sqlite3://default.db'
  end
end

Instance-level thread local variables

class MyClass
  include Tins::ThreadLocal

  instance_thread_local :user_id, 0
end

Constant Summary collapse

@@cleanup =

Cleanup lambda that removes thread-local data when objects are garbage collected

lambda do |my_object_id|
  my_id = "__thread_local_#{my_object_id}__"
  for t in Thread.list
    t[my_id] = nil if t[my_id]
  end
end

Instance Method Summary collapse

Instance Method Details

#instance_thread_local(name, default_value = nil) {|void| ... } ⇒ self

Define a thread local variable for the current instance with name name. If the value value is given, it is used to initialize the variable.

Examples:

Basic usage

class MyClass
  include Tins::ThreadLocal

  instance_thread_local :user_id, 0
end

Parameters:

  • name (Symbol, String) —

    The name of the thread-local variable

  • default_value (Object) (defaults to: nil) —

    Optional default value for the variable

Yields:

  • (void) —

    Optional block that returns the default value

Returns:

  • (self) 


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# File 'lib/tins/thread_local.rb', line 106

def instance_thread_local(name, default_value = nil, &default)
  class << self
    extend Tins::ThreadLocal
    self
  end.thread_local name, default_value, &default

  self
end

#thread_local(name, default_value = nil) {|void| ... } ⇒ self

Define a thread local variable named name in this module/class. If the value value is given, it is used to initialize the variable.

Examples:

With static default value

thread_local :counter, 0

With dynamic default value via block

thread_local :timestamp do
  Time.now
end

Parameters:

  • name (Symbol, String) —

    The name of the thread-local variable

  • default_value (Object) (defaults to: nil) —

    Optional default value for the variable

Yields:

  • (void) —

    Optional block that returns the default value

Returns:

  • (self)

Raises:

  • (TypeError) —

    If receiver is not a Module

  • (ArgumentError) —

    If both default_value and default block are provided



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# File 'lib/tins/thread_local.rb', line 61

def thread_local(name, default_value = nil, &default)
  is_a?(Module) or raise TypeError, "receiver has to be a Module"

  default_value && default and raise ArgumentError,
    "require either default_value or default block"

  if default_value
    default = -> * { default_value }
  end

  name = name.to_s
  my_id = "__thread_local_#{__id__}__"

  ObjectSpace.define_finalizer(self, @@cleanup)

  define_method(name) do
    values = Thread.current[my_id] ||= {}
    if default && !values.key?(name)
      values[name] = default.call
    end
    values[name]
  end

  define_method("#{name}=") do |value|
    Thread.current[my_id] ||= {}
    Thread.current[my_id][name] = value
  end

  self
end