ZEO responsiveness improvement

[Dieter Maurer]

For huge transactions ZEO spends a long time (in the order of minutes)
in the call to "vote". This makes it irresponsive for other requests,
e.g. probes by monitoring software.

This has been discussed in Dez. 2004 on "zodb-dev" with Jeremy Hylton.

The attached patch (against ZODB 3.2)
lets '_restart' (which causes the long irresponsiveness
periods) execute in a separate thread for huge transactions.

Note that I expect serious problems when an originally delayed operation
results in an exception. If formerly any exceptional case during
execution of the delayed operation including connection close was
handled perfectly, then the execution in a separate thread should
work, too. However, if there were wholes, then formerly
problems simply caused a client disconnected while
now the server may end up not releasing the commit lock.

[Andreas Jung (ajung)]

Is this still an open issue for the most current ZODB version?

[Tim Peters (tim-one)]

Status: Pending => Accepted

 Supporters added: tim_one

[Tim Peters (tim-one)]

Unassigned myself -- I haven't done ZODB work in nearly 3 years :-(

[Jim Fulton (jim-zope)]

Now (in 3.10) that ZEO servers are multi-threaded, this is far less of an issue. Each clients will get it's own thread.

Multi-threaded clients might still benefit from running huge transactions in a separate thread, but I'm not sure I care that much at this point. :)