Re: Relieving some ClassLoader contention in PreferredClassProvider

On Fri, Jan 05, 2007 at 10:33:44AM -0600, Gregg Wonderly wrote:
>
> Peter Jones wrote:
>>
>> On Thu, Jan 04, 2007 at 04:56:41PM -0600, Gregg Wonderly wrote:
>>
>>> Peter Jones wrote:
>>>
>>>> Just to be clear, is the network activity that you are concerned about
>>>> only the name->address resolution done by SocketPermission.implies
>>>> during PreferredClassProvider.createClassLoader?  Or is it also the
>>>> resolution potentially done by URL.equals during the table lookup and
>>>> the "boomerang" search (PreferredClassProvider.findOriginLoader)?
>>>
>>> I am interested in acceptable behavior in both cases.  The
>>> .implies() is one thing that causes all URLs to be queried (one
>>> optimization I added was to check for an HttpURLConnection instance
>>> and request a "HEAD" instead of "GET").  A non operating codebase
>>> host, will hang all threads for at least the TCP timeout period
>>> foreach URL.openConnection() at least.  So, I am really concerned
>>> overall about minimizing the impact any particular failure has on
>>> unrelated threads.
>>
>> Wait, are you suggesting that an actual HTTP request is attempted
>> during the process of getting the permission for each codebase URL?
>
> Yes, my vhttp handler serves streams from multiple possible locations
> (cache or net) and its returns from openConnection() either a file: URL
> openConnection() value or a deferred http: URL openConnection() value.
>
> This is a detail associated with my implementation of that handler.

I'm confused: if it returns a "deferred http: URL openConnection()
value", I still wouldn't expect an HTTP request to be attempted here?

And separate from the primary topic of this discussion: I don't recall
exactly what your vhttp handler does, but I wonder if the right
permission is getting returned.  If an HTTP URL is always the original
source from which the data will have been obtained, then permission to
connect to it would seem to be what should count, regardless of
whether data cached in the file system will be used.

-- Peter

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