[Zope-dev] DA changes needed for Zpe 2

[Jim Fulton]

Thread safety of DAs will be a significant issue in Zope 2, since Zope 2
wants to be multi-threaded, although it can still be run in a multi-threaded
mode.  

Here's the scoop:

  If an underlying database API is thread safe and allows
  multiple connections in multiple threads, then nothing needs
  to be done.  Database connections will be automatically 
  pooled as part of the Zope database connection pooling mechanism.
  RDBMS database connections will be established as needed and kept
  only as long as needed to satisfy load.  This will be very cool.

  Unfortunately, I fear that many of the database APIs (or
  possibly the Python database interfaces to them) are not thread
  safe.  In the short term, I'll come up with a mechanism for
  assuring that only one thread is using a database at one time.
  This will allow some (most?) databases to limp along.

  I fear that some DAs will never work with a multi-threaded zope
  due to limitations in the underlying APIs.

  There are probably a number of DAs that can and should be updated
  to work correctly in a multi-threaded environment, in which 
  multiple threads may have connections to the same database.

People working on DAs should start thinking about this.

Jim

--
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