Well explained. Sounds brilliant. I'm all in favor. Let me know how if I
can help.
-----Original Message-----
From: Berin Loritsch [mailto:[EMAIL PROTECTED]]
Sent: Wednesday, August 15, 2001 1:08 PM
To: Avalon Development
Subject: Re: New Monitor framework
Laran Coates wrote:
>
> I've just started digging into Avalon and Cocoon. I've read all the docs
> and looked over a lot of the source code. I'm curious to know more about
> how you think the Monitor framework would emulate, if not override Cocoon.
> Could you either explain a bit or point me to packages that perform the
role
> of monitoring now?
Currently, Cocoon asks a File or class if it has been modified since time X
for each request. This is a little bit of overhead, and adds a little bit
of
stress to the filesystem in that it must be queried for the current
timestamp.
If the test returns true, then Cocoon must do whatever is required to update
that information.
The Monitor Framework is an active entity that handles the tests separate
from
the request framework. In other words, the request only needs to get the
contents
of the resource, and the filesystem is spared the extra overhead. The logic
to handle a changed resource does not change, but it is initiated by the
Monitor,
not the request system.
To bring it in the real world, a production web server can see upwards of
1000
requests per second--each with a test for the timestamp of the file
resource.
This overhead is not necessary, and possibly even harmful. Most modern
operating
systems cache such information so that you are really getting the
information
from the cache anyway. However, the lower the number of system calls from
the
JVM, the better.
With the afforementioned example, the ActiveMonitor can poll all its
resources
once every minute. If the resource has changed durring that time, we can
easily
handle that. This limits the number of filesystem calls to 1 per minute
(60000
times less than before).
In fact, the ActiveMonitor approach can handle changes to resources as often
or as little as you like.
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