port of prevayler

Marco Paga mail at marco-paga.de
Mon Feb 17 13:07:17 UTC 2003

You just can have a look at prevayler.com. It is a wiki where you can 
find information around the whole topic. The information is for a java 
prevalence layer, but it is suitable for other languages too.
There is not much to explain:

   1. A system (somethink like the database; where all persitent data is
      stored) gets serialized to disk.
   2. All commands that change the state of the system get logged to
      disk too.
   3. (From time to time the whole system gets serialized to disk again)

After a crash / restart the last known snapshot gets loaded. And after 
that every commandlog gets deserialized and is run on the system. (Every 
command contains the time when it was executed before the crash. (In 
prevayler for java  it is done by using the decorator pattern).
You see: the whole thing is very simple.

I just want to write my port new. My first port was just translating the 
java version, but i think that squeak can do it in a shorter and more 
robust way. I want to do it in the TDD manner.

    * Red: Writing a unit test.
    * Green : Making the test run
    * Refactor: Cleaning up.

This should result in a very clear and good code.
If there is anybody still interested, please mail.


Giovanni Giorgi wrote:

> What is it? where I can find more information about it?
> Marco Paga wrote:
>> Hi.
>> Is anybody out there who wants to port prevyler to squeak? I have a 
>> version aviable, but that one is badly designed. You can't extend it 
>> in any way.
>> So the next version NEEDS to be better.
>> If you are interested please let me know.
>> Marco

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