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First, I want to thank everyone on the development team. I have
brought in some pretty unusual ideas and requests, and the team has
always been willing to engage whether they make sense and how to
make these work. This doesn't happen all the time and I wanted to
say how much easier (and more fun) it makes my work.<br>
<br>
<br>
This is what happens when a marketing person carelessly steps into
the how rather than the what. :)<br>
<br>
Mickal's idea makes sense to me for a different reason. I was
concerned that at each possible point of interest there would be a
subroutine call that did nothing in 99% of all installations. I was
worried about the performace impact when we are trying to squeeze
every qps possible out of the code. With the list idea, a single "if
(list) ..." test (with a predictive miss) would have far less impact
to the normal processing case.<br>
<br>
One minor consequence (and a huge win for BIND 10's modular design)
is that you will need to restart the processing module when a change
is made to either the list of needed external routines or their
code. Being able to start the new instance, let it get to full
functioning state and then have it take over the query processing
means that these changes are possible without the down time of a
BIND 9 restart.<br>
<br>
There will be some fun figuring out the best way to connect these
external functions to the binary only server and how to make it
manageable.<br>
<br>
warmly,<br>
jerry<br>
<br>
On 01/21/2011 06:04 AM, Michal 'vorner' Vaner wrote:
<blockquote cite="mid:20110121140425.GA9300@hydra" type="cite">
<pre wrap="">Hello
On Fri, Jan 21, 2011 at 11:24:24AM +0000, Stephen Morris wrote:
</pre>
<blockquote type="cite">
<pre wrap="">For performance reasons, I don't think these could be done by external modules. The way I was thinking of would be to load a dynamic library at run-time. So we supply a default library in the distribution directory, each function comprising nothing more than a return statement. This is loaded at run-time unless a configuration option is set, in which case we load a user-supplied one. (As Michal pointed out, we might want to enable this feature by a compile-time option to avoid the overhead of calling empty functions.)
</pre>
</blockquote>
<pre wrap="">
Well, this has two problems. One is you can have only one callback. Then you
can't combine the hooks together. Another is, call to dynamic library is more
expensive (though not by much), so having an empty function in different library
seems odd.
If I was to design a callback system, I would have a list/chain of functions to be
called at given point of execution. Each function could modify the ongoing
packet (or, whatever was there) and return status (pass to next function, abort,
say it is handled). Then the „usual“ behaviour would be just the only one in
default list. If we want an extension, a library would be loaded and it would
add its own functions to the front of whatever lists it would like, intercepting
all places it is interested in. So it could effectively modify the packets,
handle them itself in a different ways, abort the whole process, count
statistics, completely replace the logic, etc. And the only think it would
require from us is to split the logic in parts, decide interfaces and have a
template for the chained call. It seems simpler (or, at last, equally simple)
and more powerful.
Of course, this is just unfinished, unpolished, idea.
What do you think about it?
Have a nice day
</pre>
<pre wrap="">
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