[ZDP] BackTalk to Document Zope Developer's Guide (2.4 edition)/ZODB Persistent Components

nobody@nowhere.com nobody@nowhere.com
Fri, 13 Sep 2002 11:20:26 -0400

A comment to the paragraph below was recently added via http://www.zope.org/Documentation/Books/ZDG/current/Persistence.stx#2-54


    If a conflict happens, you have two choices. The first choice is
    that you live with the error and you try again. Statistically,
    conflicts are going to happen, but only in situations where objects
    are "hot-spots".  Most problems like this can be "designed away";
    if you can redesign your application so that the changes get
    spread around to many different objects then you can usually get
    rid of the hot spot.

      % Anonymous User - Sep. 12, 2002 7:09 pm:
       This is totally retarded.  Why can't we get a mutex instead?

      % Anonymous User - Sep. 12, 2002 7:18 pm:
       Code talks.  Write code or shut the hell up.

      % Anonymous User - Sep. 13, 2002 11:20 am:
       Although the comment above was not very nice, this might be a good place
       to explain why a mutex is not appropriate.
       A mutex would have to span multiple ZEO servers and would
       serialize all Zope application threads.  Conflicts are one of the prices
       of scalability, but in practice conflicts are rare enough that
       few applications need to deal with them directly.