[Zope] - pcgi and multi concurrent access

[Jim Fulton]

Service Informatique CHSR wrote:
> 
> >In the future, the application itself will be able to
> >handle multiple requests simultaneously.  This will be
> >especially emportant if there are requests that consume alot
> >of application time, like indexing large databases.
> i suppose this mean that with this new version of pcgi,
> one has to write thread-safe code (although I still have to
> lean what thread-safe code is :-)). For example, one wouldn't
> write this:
> 
> class MyData:
>     """give access to my data"""
>     def __init__(self):
>         self.curs=db.cursor() # shared data -- bad
>     def request0(self):
>         """list the table0 content"""
>         self.curs.execute("select * from table0")
>         return self.curs.fetchall()
>     def request1(self):
>         """list the table1 content"""
>         self.curs.execute("select * from table1")
>         return self.curs.fetchall()
> bobo_application=MyData()
> 
> One would write this instead:
> 
> class MyData:
>     """give access to my data"""
>     def request0(self):
>         """list the table0 content"""
>         curs=db.cursor()
>         curs.execute("select * from table0")
>         return curs.fetchall()
>     def request1(self):
>         """list the table1 content"""
>         curs=db.cursor()
>         curs.execute("select * from table1")
>         return curs.fetchall()
> bobo_application=MyData()
> 
> Am i right?

Right.

> (about the fact that one should write thread-safe code
> *now* to support the new pcgi way of doing)

Right.

> Of course, this code is just an example, it is not what i intend to do.

Note that the database in Zope 2.0 will make writing thread-safe
applications much easier.  This is because each application thread
will have a separate "connection" to the database and it's own
copy of objects. So for example, if the first version of MyData
above was changed to use a database object, it would be thread safe
(using the database that will be included in Zope 2).

Jim

--
Jim Fulton           mailto:jim@digicool.com
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