Path: csiph.com!v102.xanadu-bbs.net!xanadu-bbs.net!eternal-september.org!feeder.eternal-september.org!mx04.eternal-september.org!.POSTED!not-for-mail From: Eric Sosman Newsgroups: comp.lang.java.programmer Subject: Re: Proposed new Java feature Date: Sun, 27 May 2012 15:30:49 -0400 Organization: A noiseless patient Spider Lines: 53 Message-ID: References: <8Euwr.47425$On2.20024@newsfe16.iad> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Injection-Date: Sun, 27 May 2012 19:30:56 +0000 (UTC) Injection-Info: mx04.eternal-september.org; posting-host="03ebLEozl+tXCe7JS60Feg"; logging-data="1925"; mail-complaints-to="abuse@eternal-september.org"; posting-account="U2FsdGVkX18pV4Mxs68kZyrN+XKpAyD0" User-Agent: Mozilla/5.0 (Windows NT 5.1; rv:12.0) Gecko/20120428 Thunderbird/12.0.1 In-Reply-To: Cancel-Lock: sha1:3WpSHe4pcK0iYv/B8jMdWrUR0Po= Xref: csiph.com comp.lang.java.programmer:14838 On 5/27/2012 3:04 PM, Mike Schilling wrote: > "Daniel Pitts" wrote in message > news:8Euwr.47425$On2.20024@newsfe16.iad... >> On 5/27/12 11:00 AM, Mike Schilling wrote: >>> "markspace"<-@.> wrote in message news:jptkmp$vbg$1@dont-email.me... >>>> On 5/26/2012 4:11 PM, Mike Schilling wrote: >>>> >>>>> Proposed feature: a static method on Thread that clears all >>>>> ThreadLocals >>>>> for >>>>> the current thread. >>>>> >>>> >>>> >>>> I can see your points. However, I don't have any real experience with >>>> ThreadLocal, and when a neophyte agrees with your argument, that's a red >>>> flag. >>>> >>>> Here's a blog where someone seems to have the same issue as you. >>>> >>>> >>>> >>>> At the end of the comments, there's a suggestion to use >>>> ThreadLocal::remove(), with the implication that it allows the thread >>>> local variable to be garbage collection. Is there a reason that doesn't >>>> work for you? >>> >>> That acts on an individual ThreadLocal (and works quite well), but it >>> doens't allow removing all ThreadLocals that might have been accumlated. >> You're basically saying "This type of resource can leak if not cleared >> appropriately, so there should be a 'Release all resources' method." >> >> When paraphrased that way, does that make it clearer why it isn't a good >> idea? It would be about the same as a "File.closeAll()" or a >> "Socket.closeAll()" call. Extremely dangerous and only a crutch for not >> doing the right thing to begin with. > > Or a "collect all unused memory" call . Clearly, that's a crutch for not > keeping track of memory allocation properly in the first place. And the > fact that files and sockets are closed when a process exits is yet another > crutch. I'm with Daniel. Your code uses classes that you wrote, and classes you got from somewhere else -- Sioux Unusuals, perhaps. And if those classes use ThreadLocals for their own purposes, and you blithely destroy them all, what happens then? Or what about the class that invoked your code, passing an InheritableThreadLocal? Is it a good idea to change parts of your invoker's state that you don't understand, that you aren't even aware of? -- Eric Sosman esosman@ieee-dot-org.invalid