How to get id of fiber/thread?

[lost22git]

(ev/spawn-thread (how to get current thread id?))

(fiber/current) # get id of the fiber?

[sogaiu]

I don't really understand what is being asked, but if this is about the task-id that gets reported in a supervisor channel, may be the following code snippets demonstrate how that might be used.

thread case [1]:

(def tc (ev/thread-chan 10))

(ev/thread (fn []
             (setdyn :task-id :id-for-thread-case)
             (error :from-thread))
           nil : tc)

(def [t-kwd t-val t-id] (ev/take tc))

(pp [:t-kwd t-kwd])
(pp [:t-val t-val])
# `t-id` should show up as `:id-for-thread-case`
(pp [:t-id t-id])

fiber case:

(def c (ev/chan 10))

(ev/go (fn []
         (setdyn :task-id :id-for-fiber-case)
         (error :from-fiber))
       nil c)

(def [f-kwd fib f-id] (ev/take c))

(pp [:f-kwd f-kwd])
(pp [:fib fib])
# `f-id` should show up as `:id-for-fiber-case`
(pp [:f-id f-id])

---

[1] For the thread case, it looks like one can specify a task-id when calling ev/thread:

* `:t` - set the task-id of the new thread to value. The task-id is 
  passed in messages to the supervisor channel.

In the text above, I think value refers to the first optional parameter for ev/thread:

(ev/thread main &opt value flags supervisor)

So instead of setting the task-id dynamic variable, the demo code might be adapted like:

(ev/thread (fn [] (error :hi))
           :id-for-thread :t tc)

[lost22git]

(let [ch (ev/chan)]
  (ev/go
    (fn [] (print "taskid: " (dyn *task-id*)))
    nil ch)
  (pp (ev/take ch)))

run result

taskid is nil?

taskid: 
(:ok <fiber 0x007A16BEAF00> nil)

[sogaiu]

Apparently so.

[lost22git]

Why¿

[sogaiu]

I don't know.

I may be mistaken, but the task-id in this setting is just an arbitrary keyword that a programmer gets to decide on in order to distinguish content that arrives on the supervisor channel [1]. IIUC, there isn't any intrinsic meaning apart from that. It's possible then that the default behavior is for the task-id to be nil for cases where a programmer isn't concerned with making certain distinctions.

Also, I'm not sure what you are trying to accomplish. May be you could elaborate a bit more on the background for this question?

---

[1] For example, since the supervisor channel is a parameter to ev/thread / ev/go, it's conceivable that multiple threads or fibers share a common supervisor channel (for that to happen the same supervisor channel just needs to be passed to the multiple invocations of ev/thread / ev/go). Under such conditions, one might be interested in telling apart the messages that arrive on the supervisor channel. This would be doable if a different task-id is set per thread or fiber.

[sogaiu]

As a follow-up, the current docstring of *task-id* is:

When spawning a thread or fiber, the task-id can be assigned for concurrency control.

May be that docstring was part of what prompted the original question...

If the code snippets above are valid, may be they (or something similar) can be added as examples to the website docs around here.