Re: How to programatically limit the number of threads in a java

Posted by Joerg... on 13. May 2015

On Tue, 12 May 2015 21:19:33 +0200, Marcel Mueller wrote:



Disclaimer: I only just now looked into this topic, so my answers may not
be the end all.




On 12.05.15 17.49, Ajay Paul wrote:




How to programatically limit the number of threads in a java.
Simply do not start more threads than wanted. :-)
Java will not start more than one thread automatically.





Java might start (at least) three threads on its own (main, edt and garbage
collection).





but how do we do it programatically.
Not at all.





You can certainly prevent new threads being created programmatically.
Simply subclass SecurityManager, configure it to override checkAccess, and
implement restrictions on how new Thread objects are allowed to be created
in whatever fashion you deem apropriate. And don't forget to actually
install the SecurityManager.



I have demonstrated described solution here: http://ideone.com/edhsyF




Even if the JVM could control that what should be the action when the
application requests another thread?
Throw a NoMoreThreadsException? This exception could not be reasonably




AccessControlException.



If the goal is to prevent untrusted code from creating new threads, this
may be a valid approach, otherwise, it will probably just make stuff break.



Alternatively, this could also be prohibited by setting the
SecurityConstants.MODIFYTHREADGROUPPERMISSION and
SecurityConstants.MODIFYTHREADPERMISSION permissions to false, but
changing permissions is less easy to demonstrate.



Now, all of this took me about 20 minutes to research, because I thought it
was an interesting problem. I don't mean to be rude, but if you don't know
the answer to a question, instead of making one up, consider simply not
responding with a statement that looks like a fact.



Liebe Gruesse,
Joerg





Ich lese meine Emails nicht, replies to Email bleiben also leider
ungelesen.


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