What is the proper way (or ways) to use Objectify 4.0 with the
<threadsafe>true</threadsafe> setting in an AppEngine app? The following is
in the "Caching" Wiki page, but what else should we be aware of?
The session cache is *not* thread-safe. You should never share an Objectify instance
between threads.

 - Also, on a side-note: is there a way to temporarily disable the session
cache for our own testing purposes - not involving ofy().clear()?

(Love Objectify, btw.)

Just don't share an Objectify instance between multiple requests (eg, put
it in a static context).  This is just normal programming in a servlet
environment.  Very few parts of the GAE SDK are officially thread-safe, so
this shouldn't be an unusual pattern.

Not at present.  Because of the way @Load works, it's not a trivial change.

Jeff

Ok. Follow-up questions...

Given the following code:
Objectify objectifyInstance = ObjectifyService.factory().begin();

1) The javadoc for begin() indicates:

The default options are:

   - Do NOT begin a transaction.
   - *Do NOT use a session cache. *
   - DO use a global cache.
   - Use STRONG consistency.
   - Apply no deadline to calls.

But the wiki page says the session cache is enabled automatically. Is the
javadoc just out-of-date?

2) And just to double-check, is the above code the proper way to start a
new session (e.g. in a servlet's doPost() method) when running in
threadsafe-mode?

3) When using multiple Objectify instances, is there anything
(resource-wise) we need to deal with when an instance is about to be
discarded (e.g. at the end of a doPost() method)?

Ooops, obsolete javadoc.  Fixed.

2) And just to double-check, is the above code the proper way to start a

The proper way is to always call ofy(), the static method on
ObjectifyService.  You will always get the right session.  You should not
call begin() directly in your code.

All of the current documentation examples show the ofy() pattern.

3) When using multiple Objectify instances, is there anything

No, there is nothing you need to do to close session.  But unless you
really know what you're doing (say, running two transactions in parallel)
you shouldn't even be asking this question - just use ofy() every time you
want to access Objectify.  If you need to escape a transaction temporarily,
use ofy().transactionless().load()...etc

Jeff
BTW:  4.0 beta 1 should be in Maven Central tomorrow.  Just waiting for
sonatype to approve the release.

Thanks for clearing that up.

I was peeking around in the Objectify source, and I understand how it works
internally now...
static final ThreadLocal<Deque<Objectify>> STACK = new
ThreadLocal<Deque<Objectify>>();

I have peace of mind.

Keep up the great work, Jeff. Objectify is awesome!