[erlang-questions] Kill a process tree

June Kim <>
Sun Apr 22 17:06:49 CEST 2007


2007/4/22, June Kim <>:
> My original purpose of all this is, to make a test runner, which runs
> a given function, which in turn might create a group of
> processes(which may not be linked to each other) and then kill all of
> them after a certain amount of time. The function under test could be
> written without the specific consideration of being run with the test
> runner.
>
> Okay. There seems to be a way out.
>
> I happened to learn that there is a way of compile-time code AST
> modification in Erlang. Maybe I could do something like...:
>  * replace all spawn/* calls with my reg_spawn/* in a specific module
> we want to run (and kill at once)
>  * In reg_spawn, we spawn a process and register the pid to a global dictionary
>  * after running the module, we kill all the processes that are
> registered in the global dictionary.
>
> So no source code modification manually. Does it sound right?

This may work when the function only calls functions inside the
module. It has no control over the functions residing in other
modules.

One possible solution, that I tested now, is using(or is it abusing?)
group_leader.

-module(runner).
-export([run/3]).

run(Mod,Fun,Arg)->
    Pid=spawn(fun run_loop/0),
    group_leader(Pid,Pid),
    Pid!{run,{Mod,Fun,Arg}},
    Pid.

run_loop()->
    receive
        {run, {Mod,Fun,Arg}} ->
            apply(Mod,Fun,Arg),
            run_loop()
    end.

Now I can call the tested function with run/3 and all the children and
grand-children processes' group_leader will be the Pid returned from
run/3. Then I can later kill the process group with exit(Pid,kill).
One undesirable side effect is all io acitivty doesn't occur. Any
other issues to consider?


>
> Where can I get more info on that "parse transform"?
>
> 2007/4/21, June Kim <>:
> > Sorry for my mistake,
> >
> > 2007/4/21, June Kim <>:
> > > If only I could programmatically replace(not search and replace on the
> > > source code) spawn calls in the code with spawn_link... then I may
> > > kill the originator process and kill all the family.
> >
> > In this case, there would be unexpected side effects: since the
> > processes are linked to each other, one process' death would affect
> > other processes, which wouldn't with the original code.
> >
> > It's more complexed.
> >
> > >
> > > 2007/4/21, June Kim <>:
> > > > 2007/4/21, Ulf Wiger (TN/EAB) <>:
> > > > >
> > > > > If the processes were linked to each other and
> > > > > not trapping exits, then killing the root should
> > > > > kill the others as well.
> > > > >
> > > > > But you claim that they are not linked...
> > > > > I wonder what makes it a tree, then.
> > > > >
> > > > > You could call processes(), and traverse the list
> > > > > looking for some common element, perhaps
> > > > > initial_call?
> > > > >
> > > > > E.g.
> > > > >
> > > > > 1> [P || {P,{initial_call,IC}} <-
> > > > >   [{P1,process_info(P1,initial_call)} ||
> > > > >     P1 <- processes()],
> > > > >     IC == {proc_lib,init_p,5}].
> > > > > [<0.4.0>,
> > > > >  <0.7.0>,
> > > > >  <0.9.0>,
> > > > >  <0.10.0>,
> > > > >  <0.11.0>,
> > > > >  <0.14.0>,
> > > > >  <0.16.0>,
> > > > >  <0.17.0>,
> > > > >  <0.19.0>,
> > > > >  <0.24.0>,
> > > > >  <0.25.0>,
> > > > >  <0.28.0>,
> > > > >  <0.30.0>,
> > > > >  <0.31.0>,
> > > > >  <0.32.0>,
> > > > >  <0.33.0>,
> > > > >  <0.34.0>]
> > > > >
> > > > > Without knowing anything about how the processes
> > > > > relate to each other, it's a bit difficult to
> > > > > give advice.
> > > > >
> > > > > BR,
> > > > > Ulf W
> > > >
> > > > Thank you for the tip but it won't work.
> > > >
> > > > What I want to do is take a abitrary function and run it as a new
> > > > process inside a sandbox containment and then kill all the processes
> > > > that originated from the function after a while.
> > > >
> > > > Maybe I'm looking for a wrong path in Erlang?
> > > >
> > > > >
> > > > > > -----Original Message-----
> > > > > > From: 
> > > > > > [mailto:] On Behalf Of June Kim
> > > > > > Sent: den 20 april 2007 18:30
> > > > > > To: 
> > > > > > Subject: [erlang-questions] Kill a process tree
> > > > > >
> > > > > > Suppose I spawned a process and let's call it "root".
> > > > > >
> > > > > > root will probably spawn a few children, and those children,
> > > > > > in turn, would spawn a few grand-children.
> > > > > >
> > > > > > Now, I want to kill the process tree starting from root. How
> > > > > > can I achieve it?
> > > > > >
> > > > > > Limitation: the thing is that all the code is written using
> > > > > > plain spawn and no consideration was done in the code for
> > > > > > this kind of case(such as link). Moreover, you can't change
> > > > > > the code. The code for root and so on were written without
> > > > > > any regard for this process tree kill. (well, suppose the
> > > > > > root and its descendant codes were written by a third-party)
> > > > > >
> > > > > > How can I do it?
> > > > > >
> > > > > > June
> > > > > > _______________________________________________
> > > > > > erlang-questions mailing list
> > > > > > 
> > > > > > http://www.erlang.org/mailman/listinfo/erlang-questions
> > > > > >
> > > > >
> > > >
> > >
> >
>



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