[Info-vax] Accuweather new contract

[Craig A. Berry]

On 3/29/15 10:07 AM, Kerry Main wrote:
>> -----Original Message-----


> If it was Apache on OpenVMS, then I could see how another platform
> might outperform Apache on OpenVMS. As I understand it, Apache
> uses a model of a parent process controlling many child processes
> (one per request).

As far as I know, that hasn't been the case since Apache 1.x. I believe
the most common model now is to run it as a so-called pre-forking server
where multiple worker processes are created at start-up time and are all
ready to handle connections. There is a new thread (but not a new
process) started for each connection.

> WASD uses a dedicated server process  - not unlike what a transaction
> processing system uses i.e. dedicated processes that  handle many
> incoming connections in a more efficient model
>
>>From a past WASD presentation from Mark Daniel:
> "WASD uses a single process and ASTs to enable an event-driven
> (mainly I/O but with some timer queue) multiple request concurrency
> This model could be referred to as lightweight-threading.  These are
> very lightweight in the sense they are VMS' native threading model,
> almost negligible servicing cost and certainly containing none of the
> thread-management overhead of something like POSIX Threads or
> a process context. The WASD conservative approach to resource
> consumption in this respect is often a significant factor in preference
> over other approaches."

This is a great way to make efficient use of a single processor. It
appears that WASD also provides the ability to have multiple detached
processes coordinated via the DLM -- without that, the AST-driven model
wouldn't scale beyond one processor.

There are more details on how WASD actually works at performance
comparisons with Apache at:

<http://wasd.vsm.com.au/other/D215_WASD_Apache.ppt>