Custom Caching

Anon

Hi,

I want to write some custom caching for a message board system I have written.

I want the cache file for a given subject to be updated upon someone posting a message. That way, I can cut down on database reads (i.e. a subject's page content only needs to be generated once per message posted).

This causes problems if a multiple messages are posted at the same time, as the cache file will become garbled if more that one process is writing to it at the same time.

What is the best way to handle this situation?

Anon

I'm not sure--won't the database have to be queried in
order to determine which page to display anyway? Or
are you talking about then having static links to
the content like this:

<a href="messages/msg0001.html">Previous Message</a>
<a href="messages/msg0003.html">Next Message</a>

If that's all you want, then surely the php script you post
to (i.e. which receives the content) could surely be the one
that writes the static html page.

Anon

There's an excellent essay on caching here:

http://www.mnot.net/cache_docs/

Anon

Kirk Parker wrote:

I'm not sure--won't the database have to be queried in
order to determine which page to display anyway?

Take a request to page.php?subject=125225 as an example. If a current cache file exists for subject 125225, it will include it, instead of generating the content from the database.

Kirk Parker wrote:

If that's all you want, then surely the php script you post
to (i.e. which receives the content) could surely be the one
that writes the static html page.

This is the point at which I want the static page created. My concern is if multiple posts are trying to update the static file at the exact same time. The static file would be all garbled.

I just need to know of a good way in PHP to lock access to a file.

Anon

Take a request to page.php?subject=125225

That's what I worried about in the first place. It's not just
that you'll have to do a directory lookup to see if you've got
a 'static/125225.html' available on disk, but that if you create
lots and lots of these, you'll have to worry about dir lookup
performance, and... How processor-intensive is the page
creation in the first place?

Anon

File locking can be done with the flock function. http://www.php.net/manual/function.flock.php

Trevor DeVore
Blue Mango Multimedia