class Thread - Documentation for Ruby 4.0
Description: class Thread: Threads are the Ruby implementation for a concurrent programming model. Programs that require multiple threads of execution are a perfect candidate fo
Keywords: ruby,class,Thread

🔍

No recent searches

# class Thread

Threads are the Ruby implementation for a concurrent programming model.

Programs that require multiple threads of execution are a perfect candidate for Ruby’s `Thread` class.

For example, we can create a new thread separate from the main thread’s execution using `::new`.

    thr = Thread.new { puts "What's the big deal" }

Then we are able to pause the execution of the main thread and allow our new thread to finish, using `join`:

    thr.join #=> "What's the big deal"

If we don’t call `thr.join` before the main thread terminates, then all other threads including `thr` will be killed.

Alternatively, you can use an array for handling multiple threads at once, like in the following example:

    threads = []
    threads << Thread.new { puts "What's the big deal" }
    threads << Thread.new { 3.times { puts "Threads are fun!" } }

After creating a few threads we wait for them all to finish consecutively.

    threads.each { |thr| thr.join }

To retrieve the last value of a thread, use `value`

    thr = Thread.new { sleep 1; "Useful value" }
    thr.value #=> "Useful value"

### `Thread` initialization

In order to create new threads, Ruby provides `::new`, `::start`, and `::fork`. A block must be provided with each of these methods, otherwise a `ThreadError` will be raised.

When subclassing the `Thread` class, the `initialize` method of your subclass will be ignored by `::start` and `::fork`. Otherwise, be sure to call super in your `initialize` method.

### `Thread` termination

For terminating threads, Ruby provides a variety of ways to do this.

The class method `::kill`, is meant to exit a given thread:

    thr = Thread.new { sleep }
    Thread.kill(thr) # sends exit() to thr

Alternatively, you can use the instance method `exit`, or any of its aliases `kill` or `terminate`.

    thr.exit

### `Thread` status

Ruby provides a few instance methods for querying the state of a given thread. To get a string with the current thread’s state use `status`

    thr = Thread.new { sleep }
    thr.status # => "sleep"
    thr.exit
    thr.status # => false

You can also use `alive?` to tell if the thread is running or sleeping, and `stop?` if the thread is dead or sleeping.

### `Thread` variables and scope

Since threads are created with blocks, the same rules apply to other Ruby blocks for variable scope. Any local variables created within this block are accessible to only this thread.

#### Fiber-local vs. Thread-local

Each fiber has its own bucket for `Thread#[]` storage. When you set a new fiber-local it is only accessible within this `Fiber`. To illustrate:

    Thread.new {
      Thread.current[:foo] = "bar"
      Fiber.new {
        p Thread.current[:foo] # => nil
      }.resume
    }.join

This example uses `[]` for getting and `[]=` for setting fiber-locals, you can also use `keys` to list the fiber-locals for a given thread and `key?` to check if a fiber-local exists.

When it comes to thread-locals, they are accessible within the entire scope of the thread. Given the following example:

    Thread.new{
      Thread.current.thread_variable_set(:foo, 1)
      p Thread.current.thread_variable_get(:foo) # => 1
      Fiber.new{
        Thread.current.thread_variable_set(:foo, 2)
        p Thread.current.thread_variable_get(:foo) # => 2
      }.resume
      p Thread.current.thread_variable_get(:foo)   # => 2
    }.join

You can see that the thread-local `:foo` carried over into the fiber and was changed to `2` by the end of the thread.

This example makes use of `thread_variable_set` to create new thread-locals, and `thread_variable_get` to reference them.

There is also `thread_variables` to list all thread-locals, and `thread_variable?` to check if a given thread-local exists.

### `Exception` handling

When an unhandled exception is raised inside a thread, it will terminate. By default, this exception will not propagate to other threads. The exception is stored and when another thread calls `value` or `join`, the exception will be re-raised in that thread.

    t = Thread.new{ raise 'something went wrong' }
    t.value #=> RuntimeError: something went wrong

An exception can be raised from outside the thread using the `Thread#raise` instance method, which takes the same parameters as `Kernel#raise`.

Setting `Thread.abort_on_exception` = true, `Thread#abort_on_exception` = true, or $DEBUG = true will cause a subsequent unhandled exception raised in a thread to be automatically re-raised in the main thread.

With the addition of the class method `::handle_interrupt`, you can now handle exceptions asynchronously with threads.

### Scheduling

Ruby provides a few ways to support scheduling threads in your program.

The first way is by using the class method `::stop`, to put the current running thread to sleep and schedule the execution of another thread.

Once a thread is asleep, you can use the instance method `wakeup` to mark your thread as eligible for scheduling.

You can also try `::pass`, which attempts to pass execution to another thread but is dependent on the OS whether a running thread will switch or not. The same goes for `priority`, which lets you hint to the thread scheduler which threads you want to take precedence when passing execution. This method is also dependent on the OS and may be ignored on some platforms.

### Public Class Methods

abort_on_exception → true or false
Source

    static VALUE
    rb_thread_s_abort_exc(VALUE _)
    {
        return RBOOL(GET_THREAD()->vm->thread_abort_on_exception);
    }

Returns the status of the global “abort on exception” condition.

The default is `false`.

When set to `true`, if any thread is aborted by an exception, the raised exception will be re-raised in the main thread.

Can also be specified by the global $DEBUG flag or command line option `-d`.

See also `::abort_on_exception=`.

There is also an instance level method to set this for a specific thread, see `abort_on_exception`.

abort_on_exception= boolean → true or false
Source

    static VALUE
    rb_thread_s_abort_exc_set(VALUE self, VALUE val)
    {
        GET_THREAD()->vm->thread_abort_on_exception = RTEST(val);
        return val;
    }

When set to `true`, if any thread is aborted by an exception, the raised exception will be re-raised in the main thread. Returns the new state.

    Thread.abort_on_exception = true
    t1 = Thread.new do
      puts  "In new thread"
      raise "Exception from thread"
    end
    sleep(1)
    puts "not reached"

This will produce:

    In new thread
    prog.rb:4: Exception from thread (RuntimeError)
     from prog.rb:2:in `initialize'
     from prog.rb:2:in `new'
     from prog.rb:2

See also `::abort_on_exception`.

There is also an instance level method to set this for a specific thread, see `abort_on_exception=`.

current → thread
Source

    static VALUE
    thread_s_current(VALUE klass)
    {
        return rb_thread_current();
    }

Returns the currently executing thread.

    Thread.current   #=> #<Thread:0x401bdf4c run>

each_caller_location(...) { |loc| ... } → nil
Source

    static VALUE
    each_caller_location(int argc, VALUE *argv, VALUE _)
    {
        rb_execution_context_t *ec = GET_EC();
        long n, lev = ec_backtrace_range(ec, argc, argv, 1, 1, &n);
        if (lev >= 0 && n != 0) {
            rb_ec_partial_backtrace_object(ec, lev, n, NULL, FALSE, TRUE);
        }
        return Qnil;
    }

Yields each frame of the current execution stack as a backtrace location object.

exit → thread
Source

    static VALUE
    rb_thread_exit(VALUE _)
    {
        rb_thread_t *th = GET_THREAD();
        return rb_thread_kill(th->self);
    }

Terminates the currently running thread and schedules another thread to be run.

If this thread is already marked to be killed, `::exit` returns the `Thread`.

If this is the main thread, or the last thread, exit the process.

start([args]*) {|args| block } → thread
fork([args]*) {|args| block } → thread
Source

    static VALUE
    thread_start(VALUE klass, VALUE args)
    {
        struct thread_create_params params = {
            .type = thread_invoke_type_proc,
            .args = args,
            .proc = rb_block_proc(),
        };
        return thread_create_core(rb_thread_alloc(klass), &params);
    }

Basically the same as `::new`. However, if class `Thread` is subclassed, then calling `start` in that subclass will not invoke the subclass’s `initialize` method.

handle_interrupt(hash) { ... } → result of the block
Source

    static VALUE
    rb_thread_s_handle_interrupt(VALUE self, VALUE mask_arg)
    {
        VALUE mask = Qundef;
        rb_execution_context_t * volatile ec = GET_EC();
        rb_thread_t * volatile th = rb_ec_thread_ptr(ec);
        volatile VALUE r = Qnil;
        enum ruby_tag_type state;

        if (!rb_block_given_p()) {
            rb_raise(rb_eArgError, "block is needed.");
        }

        mask_arg = rb_to_hash_type(mask_arg);

        if (OBJ_FROZEN(mask_arg) && rb_hash_compare_by_id_p(mask_arg)) {
            mask = Qnil;
        }

        rb_hash_foreach(mask_arg, handle_interrupt_arg_check_i, (VALUE)&mask);

        if (UNDEF_P(mask)) {
            return rb_yield(Qnil);
        }

        if (!RTEST(mask)) {
            mask = mask_arg;
        }
        else if (RB_TYPE_P(mask, T_HASH)) {
            OBJ_FREEZE(mask);
        }

        rb_ary_push(th->pending_interrupt_mask_stack, mask);
        if (!rb_threadptr_pending_interrupt_empty_p(th)) {
            th->pending_interrupt_queue_checked = 0;
            RUBY_VM_SET_INTERRUPT(th->ec);
        }

        EC_PUSH_TAG(th->ec);
        if ((state = EC_EXEC_TAG()) == TAG_NONE) {
            r = rb_yield(Qnil);
        }
        EC_POP_TAG();

        rb_ary_pop(th->pending_interrupt_mask_stack);
        if (!rb_threadptr_pending_interrupt_empty_p(th)) {
            th->pending_interrupt_queue_checked = 0;
            RUBY_VM_SET_INTERRUPT(th->ec);
        }

        RUBY_VM_CHECK_INTS(th->ec);

        if (state) {
            EC_JUMP_TAG(th->ec, state);
        }

        return r;
    }

Changes asynchronous interrupt timing.

interrupt means asynchronous event and corresponding procedure by `Thread#raise`, `Thread#kill`, signal trap (not supported yet) and main thread termination (if main thread terminates, then all other thread will be killed).

The given `hash` has pairs like `ExceptionClass => :TimingSymbol`. Where the ExceptionClass is the interrupt handled by the given block. The TimingSymbol can be one of the following symbols:

`:immediate`

  Invoke interrupts immediately.

`:on_blocking`

  Invoke interrupts while BlockingOperation.

`:never`

  Never invoke all interrupts.

BlockingOperation means that the operation will block the calling thread, such as read and write. On CRuby implementation, BlockingOperation is any operation executed without GVL.

Masked asynchronous interrupts are delayed until they are enabled. This method is similar to sigprocmask(3).

### NOTE

Asynchronous interrupts are difficult to use.

If you need to communicate between threads, please consider to use another way such as `Queue`.

Or use them with deep understanding about this method.

### Usage

In this example, we can guard from `Thread#raise` exceptions.

Using the `:never` TimingSymbol the `RuntimeError` exception will always be ignored in the first block of the main thread. In the second `::handle_interrupt` block we can purposefully handle `RuntimeError` exceptions.

    th = Thread.new do
      Thread.handle_interrupt(RuntimeError => :never) {
        begin
          # You can write resource allocation code safely.
          Thread.handle_interrupt(RuntimeError => :immediate) {
            # ...
          }
        ensure
          # You can write resource deallocation code safely.
        end
      }
    end
    Thread.pass
    # ...
    th.raise "stop"

While we are ignoring the `RuntimeError` exception, it’s safe to write our resource allocation code. Then, the ensure block is where we can safely deallocate your resources.

#### Stack control settings

It’s possible to stack multiple levels of `::handle_interrupt` blocks in order to control more than one ExceptionClass and TimingSymbol at a time.

    Thread.handle_interrupt(FooError => :never) {
      Thread.handle_interrupt(BarError => :never) {
         # FooError and BarError are prohibited.
      }
    }

#### Inheritance with ExceptionClass

All exceptions inherited from the ExceptionClass parameter will be considered.

    Thread.handle_interrupt(Exception => :never) {
      # all exceptions inherited from Exception are prohibited.
    }

For handling all interrupts, use `Object` and not `Exception` as the ExceptionClass, as kill/terminate interrupts are not handled by `Exception`.

ignore_deadlock → true or false
Source

    static VALUE
    rb_thread_s_ignore_deadlock(VALUE _)
    {
        return RBOOL(GET_THREAD()->vm->thread_ignore_deadlock);
    }

Returns the status of the global “ignore deadlock” condition. The default is `false`, so that deadlock conditions are not ignored.

See also `::ignore_deadlock=`.

ignore_deadlock = boolean → true or false
Source

    static VALUE
    rb_thread_s_ignore_deadlock_set(VALUE self, VALUE val)
    {
        GET_THREAD()->vm->thread_ignore_deadlock = RTEST(val);
        return val;
    }

Returns the new state. When set to `true`, the VM will not check for deadlock conditions. It is only useful to set this if your application can break a deadlock condition via some other means, such as a signal.

    Thread.ignore_deadlock = true
    queue = Thread::Queue.new

    trap(:SIGUSR1){queue.push "Received signal"}

    # raises fatal error unless ignoring deadlock
    puts queue.pop

See also `::ignore_deadlock`.

kill(thread) → thread
Source

    static VALUE
    rb_thread_s_kill(VALUE obj, VALUE th)
    {
        return rb_thread_kill(th);
    }

Causes the given `thread` to exit, see also `Thread::exit`.

    count = 0
    a = Thread.new { loop { count += 1 } }
    sleep(0.1)       #=> 0
    Thread.kill(a)   #=> #<Thread:0x401b3d30 dead>
    count            #=> 93947
    a.alive?         #=> false

list → array
Source

    static VALUE
    thread_list(VALUE _)
    {
        return rb_thread_list();
    }

Returns an array of `Thread` objects for all threads that are either runnable or stopped.

    Thread.new { sleep(200) }
    Thread.new { 1000000.times {|i| i*i } }
    Thread.new { Thread.stop }
    Thread.list.each {|t| p t}

This will produce:

    #<Thread:0x401b3e84 sleep>
    #<Thread:0x401b3f38 run>
    #<Thread:0x401b3fb0 sleep>
    #<Thread:0x401bdf4c run>

main → thread
Source

    static VALUE
    rb_thread_s_main(VALUE klass)
    {
        return rb_thread_main();
    }

Returns the main thread.

new { ... } → thread
new(*args, &proc) → thread
new(*args) { |args| ... } → thread
Source

    static VALUE
    thread_s_new(int argc, VALUE *argv, VALUE klass)
    {
        rb_thread_t *th;
        VALUE thread = rb_thread_alloc(klass);

        if (GET_RACTOR()->threads.main->status == THREAD_KILLED) {
            rb_raise(rb_eThreadError, "can't alloc thread");
        }

        rb_obj_call_init_kw(thread, argc, argv, RB_PASS_CALLED_KEYWORDS);
        th = rb_thread_ptr(thread);
        if (!threadptr_initialized(th)) {
            rb_raise(rb_eThreadError, "uninitialized thread - check '%"PRIsVALUE"#initialize'",
                     klass);
        }
        return thread;
    }

Creates a new thread executing the given block.

Any `args` given to `::new` will be passed to the block:

    arr = []
    a, b, c = 1, 2, 3
    Thread.new(a,b,c) { |d,e,f| arr << d << e << f }.join
    arr #=> [1, 2, 3]

A `ThreadError` exception is raised if `::new` is called without a block.

If you’re going to subclass `Thread`, be sure to call super in your `initialize` method, otherwise a `ThreadError` will be raised.

pass → nil
Source

    static VALUE
    thread_s_pass(VALUE klass)
    {
        rb_thread_schedule();
        return Qnil;
    }

Give the thread scheduler a hint to pass execution to another thread. A running thread may or may not switch, it depends on OS and processor.

pending_interrupt?(error = nil) → true/false
Source

    static VALUE
    rb_thread_s_pending_interrupt_p(int argc, VALUE *argv, VALUE self)
    {
        return rb_thread_pending_interrupt_p(argc, argv, GET_THREAD()->self);
    }

Returns whether or not the asynchronous queue is empty.

Since `Thread::handle_interrupt` can be used to defer asynchronous events, this method can be used to determine if there are any deferred events.

If you find this method returns true, then you may finish `:never` blocks.

For example, the following method processes deferred asynchronous events immediately.

    def Thread.kick_interrupt_immediately
      Thread.handle_interrupt(Object => :immediate) {
        Thread.pass
      }
    end

If `error` is given, then check only for `error` type deferred events.

### Usage

    th = Thread.new{
      Thread.handle_interrupt(RuntimeError => :on_blocking){
        while true
          ...
          # reach safe point to invoke interrupt
          if Thread.pending_interrupt?
            Thread.handle_interrupt(Object => :immediate){}
          end
          ...
        end
      }
    }
    ...
    th.raise # stop thread

This example can also be written as the following, which you should use to avoid asynchronous interrupts.

    flag = true
    th = Thread.new{
      Thread.handle_interrupt(RuntimeError => :on_blocking){
        while true
          ...
          # reach safe point to invoke interrupt
          break if flag == false
          ...
        end
      }
    }
    ...
    flag = false # stop thread

report_on_exception → true or false
Source

    static VALUE
    rb_thread_s_report_exc(VALUE _)
    {
        return RBOOL(GET_THREAD()->vm->thread_report_on_exception);
    }

Returns the status of the global “report on exception” condition.

The default is `true` since Ruby 2.5.

All threads created when this flag is true will report a message on $stderr if an exception kills the thread.

    Thread.new { 1.times { raise } }

will produce this output on $stderr:

    #<Thread:...> terminated with exception (report_on_exception is true):
    Traceback (most recent call last):
            2: from -e:1:in `block in <main>'
            1: from -e:1:in `times'

This is done to catch errors in threads early. In some cases, you might not want this output. There are multiple ways to avoid the extra output:

- If the exception is not intended, the best is to fix the cause of the exception so it does not happen anymore.

- If the exception is intended, it might be better to rescue it closer to where it is raised rather then let it kill the `Thread`.

- If it is guaranteed the `Thread` will be joined with `Thread#join` or `Thread#value`, then it is safe to disable this report with `Thread.current.report_on_exception = false` when starting the `Thread`. However, this might handle the exception much later, or not at all if the `Thread` is never joined due to the parent thread being blocked, etc.

See also `::report_on_exception=`.

There is also an instance level method to set this for a specific thread, see `report_on_exception=`.

report_on_exception= boolean → true or false
Source

    static VALUE
    rb_thread_s_report_exc_set(VALUE self, VALUE val)
    {
        GET_THREAD()->vm->thread_report_on_exception = RTEST(val);
        return val;
    }

Returns the new state. When set to `true`, all threads created afterwards will inherit the condition and report a message on $stderr if an exception kills a thread:

    Thread.report_on_exception = true
    t1 = Thread.new do
      puts  "In new thread"
      raise "Exception from thread"
    end
    sleep(1)
    puts "In the main thread"

This will produce:

    In new thread
    #<Thread:...prog.rb:2> terminated with exception (report_on_exception is true):
    Traceback (most recent call last):
    prog.rb:4:in `block in <main>': Exception from thread (RuntimeError)
    In the main thread

See also `::report_on_exception`.

There is also an instance level method to set this for a specific thread, see `report_on_exception=`.

start([args]*) {|args| block } → thread
fork([args]*) {|args| block } → thread
Source

    static VALUE
    thread_start(VALUE klass, VALUE args)
    {
        struct thread_create_params params = {
            .type = thread_invoke_type_proc,
            .args = args,
            .proc = rb_block_proc(),
        };
        return thread_create_core(rb_thread_alloc(klass), &params);
    }

Basically the same as `::new`. However, if class `Thread` is subclassed, then calling `start` in that subclass will not invoke the subclass’s `initialize` method.

stop → nil
Source

    static VALUE
    thread_stop(VALUE _)
    {
        return rb_thread_stop();
    }

Stops execution of the current thread, putting it into a “sleep” state, and schedules execution of another thread.

    a = Thread.new { print "a"; Thread.stop; print "c" }
    sleep 0.1 while a.status!='sleep'
    print "b"
    a.run
    a.join
    #=> "abc"

### Public Instance Methods

thr[sym] → obj or nil
Source

    static VALUE
    rb_thread_aref(VALUE thread, VALUE key)
    {
        ID id = rb_check_id(&key);
        if (!id) return Qnil;
        return rb_thread_local_aref(thread, id);
    }

Attribute Reference—Returns the value of a fiber-local variable (current thread’s root fiber if not explicitly inside a `Fiber`), using either a symbol or a string name. If the specified variable does not exist, returns `nil`.

    [
      Thread.new { Thread.current["name"] = "A" },
      Thread.new { Thread.current[:name]  = "B" },
      Thread.new { Thread.current["name"] = "C" }
    ].each do |th|
      th.join
      puts "#{th.inspect}: #{th[:name]}"
    end

This will produce:

    #<Thread:0x00000002a54220 dead>: A
    #<Thread:0x00000002a541a8 dead>: B
    #<Thread:0x00000002a54130 dead>: C

`Thread#[]` and `Thread#[]=` are not thread-local but fiber-local. This confusion did not exist in Ruby 1.8 because fibers are only available since Ruby 1.9. Ruby 1.9 chooses that the methods behaves fiber-local to save following idiom for dynamic scope.

    def meth(newvalue)
      begin
        oldvalue = Thread.current[:name]
        Thread.current[:name] = newvalue
        yield
      ensure
        Thread.current[:name] = oldvalue
      end
    end

The idiom may not work as dynamic scope if the methods are thread-local and a given block switches fiber.

    f = Fiber.new {
      meth(1) {
        Fiber.yield
      }
    }
    meth(2) {
      f.resume
    }
    f.resume
    p Thread.current[:name]
    #=> nil if fiber-local
    #=> 2 if thread-local (The value 2 is leaked to outside of meth method.)

For thread-local variables, please see `thread_variable_get` and `thread_variable_set`.

thr[sym] = obj → obj
Source

    static VALUE
    rb_thread_aset(VALUE self, VALUE id, VALUE val)
    {
        return rb_thread_local_aset(self, rb_to_id(id), val);
    }

Attribute Assignment—Sets or creates the value of a fiber-local variable, using either a symbol or a string.

See also `Thread#[]`.

For thread-local variables, please see `thread_variable_set` and `thread_variable_get`.

abort_on_exception → true or false
Source

    static VALUE
    rb_thread_abort_exc(VALUE thread)
    {
        return RBOOL(rb_thread_ptr(thread)->abort_on_exception);
    }

Returns the status of the thread-local “abort on exception” condition for this `thr`.

The default is `false`.

See also `abort_on_exception=`.

There is also a class level method to set this for all threads, see `::abort_on_exception`.

abort_on_exception= boolean → true or false
Source

    static VALUE
    rb_thread_abort_exc_set(VALUE thread, VALUE val)
    {
        rb_thread_ptr(thread)->abort_on_exception = RTEST(val);
        return val;
    }

When set to `true`, if this `thr` is aborted by an exception, the raised exception will be re-raised in the main thread.

See also `abort_on_exception`.

There is also a class level method to set this for all threads, see `::abort_on_exception=`.

add_trace_func(proc) → proc
Source

    static VALUE
    thread_add_trace_func_m(VALUE obj, VALUE trace)
    {
        thread_add_trace_func(GET_EC(), rb_thread_ptr(obj), trace);
        return trace;
    }

Adds proc as a handler for tracing.

See `Thread#set_trace_func` and `Kernel#set_trace_func`.

alive? → true or false
Source

    static VALUE
    rb_thread_alive_p(VALUE thread)
    {
        return RBOOL(!thread_finished(rb_thread_ptr(thread)));
    }

Returns `true` if `thr` is running or sleeping.

    thr = Thread.new { }
    thr.join                #=> #<Thread:0x401b3fb0 dead>
    Thread.current.alive?   #=> true
    thr.alive?              #=> false

See also `stop?` and `status`.

backtrace → array or nil
Source

    static VALUE
    rb_thread_backtrace_m(int argc, VALUE *argv, VALUE thval)
    {
        return rb_vm_thread_backtrace(argc, argv, thval);
    }

Returns the current backtrace of the target thread.

backtrace_locations(*args) → array or nil
Source

    static VALUE
    rb_thread_backtrace_locations_m(int argc, VALUE *argv, VALUE thval)
    {
        return rb_vm_thread_backtrace_locations(argc, argv, thval);
    }

Returns the execution stack for the target thread—an array containing backtrace location objects.

See `Thread::Backtrace::Location` for more information.

This method behaves similarly to `Kernel#caller_locations` except it applies to a specific thread.

exit → thr

Terminates `thr` and schedules another thread to be run, returning the terminated `Thread`. If this is the main thread, or the last thread, exits the process. Note that the caller does not wait for the thread to terminate if the receiver is different from the currently running thread. The termination is asynchronous, and the thread can still run a small amount of ruby code before exiting.

Alias for: kill
fetch(sym) → obj
fetch(sym) { } → obj
fetch(sym, default) → obj
Source

    static VALUE
    rb_thread_fetch(int argc, VALUE *argv, VALUE self)
    {
        VALUE key, val;
        ID id;
        rb_thread_t *target_th = rb_thread_ptr(self);
        int block_given;

        rb_check_arity(argc, 1, 2);
        key = argv[0];

        block_given = rb_block_given_p();
        if (block_given && argc == 2) {
            rb_warn("block supersedes default value argument");
        }

        id = rb_check_id(&key);

        if (id == recursive_key) {
            return target_th->ec->local_storage_recursive_hash;
        }
        else if (id && target_th->ec->local_storage &&
                 rb_id_table_lookup(target_th->ec->local_storage, id, &val)) {
            return val;
        }
        else if (block_given) {
            return rb_yield(key);
        }
        else if (argc == 1) {
            rb_key_err_raise(rb_sprintf("key not found: %+"PRIsVALUE, key), self, key);
        }
        else {
            return argv[1];
        }
    }

Returns a fiber-local for the given key. If the key can’t be found, there are several options: With no other arguments, it will raise a `KeyError` exception; if default is given, then that will be returned; if the optional code block is specified, then that will be run and its result returned. See `Thread#[]` and `Hash#fetch`.

group → thgrp or nil
Source

    VALUE
    rb_thread_group(VALUE thread)
    {
        return rb_thread_ptr(thread)->thgroup;
    }

Returns the `ThreadGroup` which contains the given thread.

    Thread.main.group   #=> #<ThreadGroup:0x4029d914>

inspect
Alias for: to_s
join → thr
join(limit) → thr
Source

    static VALUE
    thread_join_m(int argc, VALUE *argv, VALUE self)
    {
        VALUE timeout = Qnil;
        rb_hrtime_t rel = 0, *limit = 0;

        if (rb_check_arity(argc, 0, 1)) {
            timeout = argv[0];
        }

        // Convert the timeout eagerly, so it's always converted and deterministic
        /*
         * This supports INFINITY and negative values, so we can't use
         * rb_time_interval right now...
         */
        if (NIL_P(timeout)) {
            /* unlimited */
        }
        else if (FIXNUM_P(timeout)) {
            rel = rb_sec2hrtime(NUM2TIMET(timeout));
            limit = &rel;
        }
        else {
            limit = double2hrtime(&rel, rb_num2dbl(timeout));
        }

        return thread_join(rb_thread_ptr(self), timeout, limit);
    }

The calling thread will suspend execution and run this `thr`.

Does not return until `thr` exits or until the given `limit` seconds have passed.

If the time limit expires, `nil` will be returned, otherwise `thr` is returned.

Any threads not joined will be killed when the main program exits.

If `thr` had previously raised an exception and the `::abort_on_exception` or $DEBUG flags are not set, (so the exception has not yet been processed), it will be processed at this time.

    a = Thread.new { print "a"; sleep(10); print "b"; print "c" }
    x = Thread.new { print "x"; Thread.pass; print "y"; print "z" }
    x.join # Let thread x finish, thread a will be killed on exit.
    #=> "axyz"

The following example illustrates the `limit` parameter.

    y = Thread.new { 4.times { sleep 0.1; puts 'tick... ' }}
    puts "Waiting" until y.join(0.15)

This will produce:

    tick...
    Waiting
    tick...
    Waiting
    tick...
    tick...

key?(sym) → true or false
Source

    static VALUE
    rb_thread_key_p(VALUE self, VALUE key)
    {
        VALUE val;
        ID id = rb_check_id(&key);
        struct rb_id_table *local_storage = rb_thread_ptr(self)->ec->local_storage;

        if (!id || local_storage == NULL) {
            return Qfalse;
        }
        return RBOOL(rb_id_table_lookup(local_storage, id, &val));
    }

Returns `true` if the given string (or symbol) exists as a fiber-local variable.

    me = Thread.current
    me[:oliver] = "a"
    me.key?(:oliver)    #=> true
    me.key?(:stanley)   #=> false

keys → array
Source

    static VALUE
    rb_thread_keys(VALUE self)
    {
        struct rb_id_table *local_storage = rb_thread_ptr(self)->ec->local_storage;
        VALUE ary = rb_ary_new();

        if (local_storage) {
            rb_id_table_foreach(local_storage, thread_keys_i, (void *)ary);
        }
        return ary;
    }

Returns an array of the names of the fiber-local variables (as Symbols).

    thr = Thread.new do
      Thread.current[:cat] = 'meow'
      Thread.current["dog"] = 'woof'
    end
    thr.join   #=> #<Thread:0x401b3f10 dead>
    thr.keys   #=> [:dog, :cat]

kill → thr
Source

    VALUE
    rb_thread_kill(VALUE thread)
    {
        rb_thread_t *target_th = rb_thread_ptr(thread);

        if (target_th->to_kill || target_th->status == THREAD_KILLED) {
            return thread;
        }
        if (target_th == target_th->vm->ractor.main_thread) {
            rb_exit(EXIT_SUCCESS);
        }

        RUBY_DEBUG_LOG("target_th:%u", rb_th_serial(target_th));

        if (target_th == GET_THREAD()) {
            /* kill myself immediately */
            rb_threadptr_to_kill(target_th);
        }
        else {
            threadptr_check_pending_interrupt_queue(target_th);
            rb_threadptr_pending_interrupt_enque(target_th, RUBY_FATAL_THREAD_KILLED);
            rb_threadptr_interrupt(target_th);
        }

        return thread;
    }

Terminates `thr` and schedules another thread to be run, returning the terminated `Thread`. If this is the main thread, or the last thread, exits the process. Note that the caller does not wait for the thread to terminate if the receiver is different from the currently running thread. The termination is asynchronous, and the thread can still run a small amount of ruby code before exiting.

Also aliased as: terminate, exit
name → string
Source

    static VALUE
    rb_thread_getname(VALUE thread)
    {
        return rb_thread_ptr(thread)->name;
    }

show the name of the thread.

name=(name) → string
Source

    static VALUE
    rb_thread_setname(VALUE thread, VALUE name)
    {
        rb_thread_t *target_th = rb_thread_ptr(thread);

        if (!NIL_P(name)) {
            rb_encoding *enc;
            StringValueCStr(name);
            enc = rb_enc_get(name);
            if (!rb_enc_asciicompat(enc)) {
                rb_raise(rb_eArgError, "ASCII incompatible encoding (%s)",
                         rb_enc_name(enc));
            }
            name = rb_str_new_frozen(name);
        }
        target_th->name = name;
        if (threadptr_initialized(target_th) && target_th->has_dedicated_nt) {
            native_set_another_thread_name(target_th->nt->thread_id, name);
        }
        return name;
    }

set given name to the ruby thread. On some platform, it may set the name to pthread and/or kernel.

native_thread_id → integer
Source

    static VALUE
    rb_thread_native_thread_id(VALUE thread)
    {
        rb_thread_t *target_th = rb_thread_ptr(thread);
        if (rb_threadptr_dead(target_th)) return Qnil;
        return native_thread_native_thread_id(target_th);
    }

Return the native thread ID which is used by the Ruby thread.

The ID depends on the OS. (not POSIX thread ID returned by pthread_self(3))

- On Linux it is TID returned by gettid(2).

- On macOS it is the system-wide unique integral ID of thread returned by pthread_threadid_np(3).

- On FreeBSD it is the unique integral ID of the thread returned by pthread_getthreadid_np(3).

- On Windows it is the thread identifier returned by GetThreadId().

- On other platforms, it raises `NotImplementedError`.

NOTE: If the thread is not associated yet or already deassociated with a native thread, it returns nil. If the Ruby implementation uses M:N thread model, the ID may change depending on the timing.

pending_interrupt?(error = nil) → true/false
Source

    static VALUE
    rb_thread_pending_interrupt_p(int argc, VALUE *argv, VALUE target_thread)
    {
        rb_thread_t *target_th = rb_thread_ptr(target_thread);

        if (!target_th->pending_interrupt_queue) {
            return Qfalse;
        }
        if (rb_threadptr_pending_interrupt_empty_p(target_th)) {
            return Qfalse;
        }
        if (rb_check_arity(argc, 0, 1)) {
            VALUE err = argv[0];
            if (!rb_obj_is_kind_of(err, rb_cModule)) {
                rb_raise(rb_eTypeError, "class or module required for rescue clause");
            }
            return RBOOL(rb_threadptr_pending_interrupt_include_p(target_th, err));
        }
        else {
            return Qtrue;
        }
    }

Returns whether or not the asynchronous queue is empty for the target thread.

If `error` is given, then check only for `error` type deferred events.

See `::pending_interrupt?` for more information.

priority → integer
Source

    static VALUE
    rb_thread_priority(VALUE thread)
    {
        return INT2NUM(rb_thread_ptr(thread)->priority);
    }

Returns the priority of thr. Default is inherited from the current thread which creating the new thread, or zero for the initial main thread; higher-priority thread will run more frequently than lower-priority threads (but lower-priority threads can also run).

This is just hint for Ruby thread scheduler. It may be ignored on some platform.

    Thread.current.priority   #=> 0

priority= integer → thr
Source

    static VALUE
    rb_thread_priority_set(VALUE thread, VALUE prio)
    {
        rb_thread_t *target_th = rb_thread_ptr(thread);
        int priority;

    #if USE_NATIVE_THREAD_PRIORITY
        target_th->priority = NUM2INT(prio);
        native_thread_apply_priority(th);
    #else
        priority = NUM2INT(prio);
        if (priority > RUBY_THREAD_PRIORITY_MAX) {
            priority = RUBY_THREAD_PRIORITY_MAX;
        }
        else if (priority < RUBY_THREAD_PRIORITY_MIN) {
            priority = RUBY_THREAD_PRIORITY_MIN;
        }
        target_th->priority = (int8_t)priority;
    #endif
        return INT2NUM(target_th->priority);
    }

Sets the priority of thr to integer. Higher-priority threads will run more frequently than lower-priority threads (but lower-priority threads can also run).

This is just hint for Ruby thread scheduler. It may be ignored on some platform.

    count1 = count2 = 0
    a = Thread.new do
          loop { count1 += 1 }
        end
    a.priority = -1

    b = Thread.new do
          loop { count2 += 1 }
        end
    b.priority = -2
    sleep 1   #=> 1
    count1    #=> 622504
    count2    #=> 5832

raise(exception, message = exception.to_s, backtrace = nil, cause: $!)
raise(message = nil, cause: $!)
Source

    static VALUE
    thread_raise_m(int argc, VALUE *argv, VALUE self)
    {
        rb_thread_t *target_th = rb_thread_ptr(self);
        const rb_thread_t *current_th = GET_THREAD();

        threadptr_check_pending_interrupt_queue(target_th);

        if (rb_threadptr_dead(target_th)) {
            return Qnil;
        }

        VALUE exception = rb_exception_setup(argc, argv);
        rb_threadptr_pending_interrupt_enque(target_th, exception);
        rb_threadptr_interrupt(target_th);

        /* To perform Thread.current.raise as Kernel.raise */
        if (current_th == target_th) {
            RUBY_VM_CHECK_INTS(target_th->ec);
        }
        return Qnil;
    }

Raises an exception from the given thread. The caller does not have to be `thr`. See `Kernel#raise` for more information on arguments.

    Thread.abort_on_exception = true
    a = Thread.new { sleep(200) }
    a.raise("Gotcha")

This will produce:

    prog.rb:3: Gotcha (RuntimeError)
     from prog.rb:2:in `initialize'
     from prog.rb:2:in `new'
     from prog.rb:2

report_on_exception → true or false
Source

    static VALUE
    rb_thread_report_exc(VALUE thread)
    {
        return RBOOL(rb_thread_ptr(thread)->report_on_exception);
    }

Returns the status of the thread-local “report on exception” condition for this `thr`.

The default value when creating a `Thread` is the value of the global flag `Thread.report_on_exception`.

See also `report_on_exception=`.

There is also a class level method to set this for all new threads, see `::report_on_exception=`.

report_on_exception= boolean → true or false
Source

    static VALUE
    rb_thread_report_exc_set(VALUE thread, VALUE val)
    {
        rb_thread_ptr(thread)->report_on_exception = RTEST(val);
        return val;
    }

When set to `true`, a message is printed on $stderr if an exception kills this `thr`. See `::report_on_exception` for details.

See also `report_on_exception`.

There is also a class level method to set this for all new threads, see `::report_on_exception=`.

run → thr
Source

    VALUE
    rb_thread_run(VALUE thread)
    {
        rb_thread_wakeup(thread);
        rb_thread_schedule();
        return thread;
    }

Wakes up `thr`, making it eligible for scheduling.

    a = Thread.new { puts "a"; Thread.stop; puts "c" }
    sleep 0.1 while a.status!='sleep'
    puts "Got here"
    a.run
    a.join

This will produce:

    a
    Got here
    c

See also the instance method `wakeup`.

set_trace_func(proc) → proc
set_trace_func(nil) → nil
Source

    static VALUE
    thread_set_trace_func_m(VALUE target_thread, VALUE trace)
    {
        rb_execution_context_t *ec = GET_EC();
        rb_thread_t *target_th = rb_thread_ptr(target_thread);

        rb_threadptr_remove_event_hook(ec, target_th, call_trace_func, Qundef);

        if (NIL_P(trace)) {
            return Qnil;
        }
        else {
            thread_add_trace_func(ec, target_th, trace);
            return trace;
        }
    }

Establishes proc on thr as the handler for tracing, or disables tracing if the parameter is `nil`.

See `Kernel#set_trace_func`.

status → string, false or nil
Source

    static VALUE
    rb_thread_status(VALUE thread)
    {
        rb_thread_t *target_th = rb_thread_ptr(thread);

        if (rb_threadptr_dead(target_th)) {
            if (!NIL_P(target_th->ec->errinfo) &&
                !FIXNUM_P(target_th->ec->errinfo)) {
                return Qnil;
            }
            else {
                return Qfalse;
            }
        }
        else {
            return rb_str_new2(thread_status_name(target_th, FALSE));
        }
    }

Returns the status of `thr`.

`"sleep"`

  Returned if this thread is sleeping or waiting on I/O

`"run"`

  When this thread is executing

`"aborting"`

  If this thread is aborting

`false`

  When this thread is terminated normally

`nil`

  If terminated with an exception.

    a = Thread.new { raise("die now") }
    b = Thread.new { Thread.stop }
    c = Thread.new { Thread.exit }
    d = Thread.new { sleep }
    d.kill                  #=> #<Thread:0x401b3678 aborting>
    a.status                #=> nil
    b.status                #=> "sleep"
    c.status                #=> false
    d.status                #=> "aborting"
    Thread.current.status   #=> "run"

See also the instance methods `alive?` and `stop?`

stop? → true or false
Source

    static VALUE
    rb_thread_stop_p(VALUE thread)
    {
        rb_thread_t *th = rb_thread_ptr(thread);

        if (rb_threadptr_dead(th)) {
            return Qtrue;
        }
        return RBOOL(th->status == THREAD_STOPPED || th->status == THREAD_STOPPED_FOREVER);
    }

Returns `true` if `thr` is dead or sleeping.

    a = Thread.new { Thread.stop }
    b = Thread.current
    a.stop?   #=> true
    b.stop?   #=> false

See also `alive?` and `status`.

terminate → thr

Terminates `thr` and schedules another thread to be run, returning the terminated `Thread`. If this is the main thread, or the last thread, exits the process. Note that the caller does not wait for the thread to terminate if the receiver is different from the currently running thread. The termination is asynchronous, and the thread can still run a small amount of ruby code before exiting.

Alias for: kill
thread_variable?(key) → true or false
Source

    static VALUE
    rb_thread_variable_p(VALUE thread, VALUE key)
    {
        VALUE locals;
        VALUE symbol = rb_to_symbol(key);

        if (LIKELY(!THREAD_LOCAL_STORAGE_INITIALISED_P(thread))) {
            return Qfalse;
        }
        locals = rb_thread_local_storage(thread);

        return RBOOL(rb_hash_lookup(locals, symbol) != Qnil);
    }

Returns `true` if the given string (or symbol) exists as a thread-local variable.

    me = Thread.current
    me.thread_variable_set(:oliver, "a")
    me.thread_variable?(:oliver)    #=> true
    me.thread_variable?(:stanley)   #=> false

Note that these are not fiber local variables. Please see `Thread#[]` and `Thread#thread_variable_get` for more details.

thread_variable_get(key) → obj or nil
Source

    static VALUE
    rb_thread_variable_get(VALUE thread, VALUE key)
    {
        VALUE locals;
        VALUE symbol = rb_to_symbol(key);

        if (LIKELY(!THREAD_LOCAL_STORAGE_INITIALISED_P(thread))) {
            return Qnil;
        }
        locals = rb_thread_local_storage(thread);
        return rb_hash_aref(locals, symbol);
    }

Returns the value of a thread local variable that has been set. Note that these are different than fiber local values. For fiber local values, please see `Thread#[]` and `Thread#[]=`.

`Thread` local values are carried along with threads, and do not respect fibers. For example:

    Thread.new {
      Thread.current.thread_variable_set("foo", "bar") # set a thread local
      Thread.current["foo"] = "bar"                    # set a fiber local

      Fiber.new {
        Fiber.yield [
          Thread.current.thread_variable_get("foo"), # get the thread local
          Thread.current["foo"],                     # get the fiber local
        ]
      }.resume
    }.join.value # => ['bar', nil]

The value “bar” is returned for the thread local, where nil is returned for the fiber local. The fiber is executed in the same thread, so the thread local values are available.

thread_variable_set(key, value)
Source

    static VALUE
    rb_thread_variable_set(VALUE thread, VALUE key, VALUE val)
    {
        VALUE locals;

        if (OBJ_FROZEN(thread)) {
            rb_frozen_error_raise(thread, "can't modify frozen thread locals");
        }

        locals = rb_thread_local_storage(thread);
        return rb_hash_aset(locals, rb_to_symbol(key), val);
    }

Sets a thread local with `key` to `value`. Note that these are local to threads, and not to fibers. Please see `Thread#thread_variable_get` and `Thread#[]` for more information.

thread_variables → array
Source

    static VALUE
    rb_thread_variables(VALUE thread)
    {
        VALUE locals;
        VALUE ary;

        ary = rb_ary_new();
        if (LIKELY(!THREAD_LOCAL_STORAGE_INITIALISED_P(thread))) {
            return ary;
        }
        locals = rb_thread_local_storage(thread);
        rb_hash_foreach(locals, keys_i, ary);

        return ary;
    }

Returns an array of the names of the thread-local variables (as Symbols).

    thr = Thread.new do
      Thread.current.thread_variable_set(:cat, 'meow')
      Thread.current.thread_variable_set("dog", 'woof')
    end
    thr.join               #=> #<Thread:0x401b3f10 dead>
    thr.thread_variables   #=> [:dog, :cat]

Note that these are not fiber local variables. Please see `Thread#[]` and `Thread#thread_variable_get` for more details.

to_s → string
Source

    static VALUE
    rb_thread_to_s(VALUE thread)
    {
        VALUE cname = rb_class_path(rb_obj_class(thread));
        rb_thread_t *target_th = rb_thread_ptr(thread);
        const char *status;
        VALUE str, loc;

        status = thread_status_name(target_th, TRUE);
        str = rb_sprintf("#<%"PRIsVALUE":%p", cname, (void *)thread);
        if (!NIL_P(target_th->name)) {
            rb_str_catf(str, "@%"PRIsVALUE, target_th->name);
        }
        if ((loc = threadptr_invoke_proc_location(target_th)) != Qnil) {
            rb_str_catf(str, " %"PRIsVALUE":%"PRIsVALUE,
                        RARRAY_AREF(loc, 0), RARRAY_AREF(loc, 1));
        }
        rb_str_catf(str, " %s>", status);

        return str;
    }

Dump the name, id, and status of thr to a string.

Also aliased as: inspect
value → obj
Source

    static VALUE
    thread_value(VALUE self)
    {
        rb_thread_t *th = rb_thread_ptr(self);
        thread_join(th, Qnil, 0);
        if (UNDEF_P(th->value)) {
            // If the thread is dead because we forked th->value is still Qundef.
            return Qnil;
        }
        return th->value;
    }

Waits for `thr` to complete, using `join`, and returns its value or raises the exception which terminated the thread.

    a = Thread.new { 2 + 2 }
    a.value   #=> 4

    b = Thread.new { raise 'something went wrong' }
    b.value   #=> RuntimeError: something went wrong

wakeup → thr
Source

    VALUE
    rb_thread_wakeup(VALUE thread)
    {
        if (!RTEST(rb_thread_wakeup_alive(thread))) {
            rb_raise(rb_eThreadError, "killed thread");
        }
        return thread;
    }

Marks a given thread as eligible for scheduling, however it may still remain blocked on I/O.

Note: This does not invoke the scheduler, see `run` for more information.

    c = Thread.new { Thread.stop; puts "hey!" }
    sleep 0.1 while c.status!='sleep'
    c.wakeup
    c.join
    #=> "hey!"