Feature #17853


Add Thread#thread_id

Added by komamitsu (Mitsunori Komatsu) 5 months ago. Updated 4 months ago.

Target version:



New method Thread#thread_id to get associated native thread id (LWP.) It might return nil if OS doesn't support thread id or equivalent.


When I tried to investigate which Ruby thread of an application is busy, I did the following steps

  • checked the CPU usage of the Ruby application's threads using ps -eLf or top (with H key) and got which thread is busy
  • dumped all the threads of the application using
  • tried to find a busy thread in the thread dump result, but the thread dump doesn't contain thread id...

Thread class itself has no method to get associated thread id. If the class has #thread_id or something, I can create a PR on sigdump project to add thread id in thread dump output to make investigations with thread dump much easier.

Thread#name may seem an alternative to Thread#thread_id, but Thread#name just returns a value that's set through Thread#name= while Thread#thread_id returns a thread id that OS or something has assigned.

In case of Java, thread dump created by jcmd ${pid} Thread.print contains nid field which is an associated native thread id

"http-bio-80-exec-77" daemon prio=6 tid=0x0000000026f29000 nid=0xbd0 runnable [0x0000000020c7f000]
   java.lang.Thread.State: RUNNABLE
    at Method)
    at Source)
    at Source)
    at org.apache.coyote.http11.InternalInputBuffer.fill(
    at org.apache.coyote.http11.InternalInputBuffer.fill(
    at org.apache.coyote.http11.Http11Processor.setRequestLineReadTimeout(
    at org.apache.coyote.http11.AbstractHttp11Processor.process(
    at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(
    - locked <0x00000007b16e3e88> (a
    at java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source)
    at java.util.concurrent.ThreadPoolExecutor$ Source)
    at Source)

Related issues

Related to Ruby master - Feature #11251: Thread#name and Thread#name=ClosedActions
Actions #1

Updated by naruse (Yui NARUSE) 5 months ago

Actions #2

Updated by komamitsu (Mitsunori Komatsu) 5 months ago

  • Description updated (diff)
Actions #3

Updated by komamitsu (Mitsunori Komatsu) 5 months ago

  • Description updated (diff)

Updated by yui-knk (Kaneko Yuichiro) 5 months ago

I investigated Python for reference. Current CPython supports threading.get_native_id ( which returns native Thread ID.

Implementation details are

This method can be used as below

# cat
import threading
import time
import os
def p():
    while True:
thread1 = threading.Thread(target=p)
thread2 = threading.Thread(target=p)
# python
15 # <- pid
16 # <- Thread id
17 # <- Thread id

# ps -efL
root         1     0     1  0    1 07:28 pts/0    00:00:00 /bin/bash
root         9     0     9  0    1 07:29 pts/1    00:00:00 /bin/bash
root        15     1    15  0    3 07:30 pts/0    00:00:00 python
root        15     1    16  0    3 07:30 pts/0    00:00:00 python
root        15     1    17  0    3 07:30 pts/0    00:00:00 python
root        19     9    19  0    1 07:30 pts/1    00:00:00 ps -efL

Updated by ivoanjo (Ivo Anjo) 4 months ago

+1 This would be useful for Datadog's ddtrace gem as well: currently we need to do quite a bit of hackery and monkey-patching to get the per-thread cpu clock information, and if we had the native id, we could use that instead to call Process.clock_gettime.

Updated by ko1 (Koichi Sasada) 4 months ago

Two concerns.

(1) name should include native, os or something to represent it is platform value. Maybe native_id same as Python's API is enough. Ruby can set internal ID for threads.
(2) In future the thread model can be changed (1:1 -> M:N). In this case, native_id should be changed (or nil if the ruby thread is not running on native thread).

Updated by komamitsu (Mitsunori Komatsu) 4 months ago

native_id sounds better to me. I agree with it.

As for m:n thread model, in my opinion, either volatile value or nil (this can happen when it's waiting an event in select/epoll/kqueue without assigning any thread?) sounds good to me since what I want to do is just mapping the result of Ruby Thread information to native thread resource. current_native_id might be better since it sounds like the attribute/property can be easily changed.

Actions #9

Updated by naruse (Yui NARUSE) 4 months ago

  • Status changed from Open to Closed

Applied in changeset git|46655156dcc37509dcb69fcd0717c110eb1c624a.

Add Thread#native_thread_id [Feature #17853]

Updated by ivoanjo (Ivo Anjo) 4 months ago

Thanks a lot for building this, naruse (Yui NARUSE)!

If I can ask for a tiny addition, it would be really cool to get the native_thread_id, if available, in Thread#inspect :)

Updated by nobu (Nobuyoshi Nakada) 4 months ago

diff --git i/thread.c w/thread.c
index cbef44a9d4a..c627e5c8f2a 100644
--- i/thread.c
+++ w/thread.c
@@ -3456,6 +3456,14 @@ rb_thread_to_s(VALUE thread)
     if (!NIL_P(target_th->name)) {
         rb_str_catf(str, "@%"PRIsVALUE, target_th->name);
+    if (!rb_threadptr_dead(target_th)) {
+        VALUE native_id = native_thread_native_thread_id(target_th);
+        if (!NIL_P(native_id)) {
+            rb_str_catf(str, "(%"PRIsVALUE")", native_id);
+        }
+    }
     if ((loc = threadptr_invoke_proc_location(target_th)) != Qnil) {
         rb_str_catf(str, " %"PRIsVALUE":%"PRIsVALUE,
                     RARRAY_AREF(loc, 0), RARRAY_AREF(loc, 1));

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