Hello all,

I have two fundamental questions regarding the requirements for
a Berkeley DB replication transport protocol:

- is out-of-order reception of messages permitted?
- is loss of messages permitted?

To be concrete: would it be sufficient to use plain UDP, maybe augmented
with a good message authenticator, without regard to retransmission and
sequencing?

best regards
Patrick

mailer-daemon (AT) bof (DOT) de (Patrick Schaaf) wrote in message news:<3f55cf78$0$31866$9b622d9e (AT) news (DOT) freenet.de>...
Yes, and yes.

Berkeley DB replication was carefully designed to be transport mechanism
agnostic, that is, we wanted to be able to run using TCP/IP, UDP, backplane
message passing protocol, or carrier pigeon.

Obviously, this has serious implications for the application's transactional
guarantees: if the message didn't arrive at the replica, should the master
return to the application that the transaction has committed? This means
applications requiring serious transactional guarantees will have to do more
work when using transport protocols that are lossy, for example.

Regards,
--keith

=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
Keith Bostic bostic (AT) sleepycat (DOT) com
Sleepycat Software Inc. keithbosticim (ymsgid)
118 Tower Rd. +1-781-259-3139
Lincoln, MA 01773 http://www.sleepycat.com

bostic (AT) sleepycat (DOT) com (Keith Bostic) writes:

Great! Thanks, Keith. That's what I hoped for.

I'm roughly aware of that; for my application, the most important thing
will be that master and replicas eventually catch up to a common state,
after network and node failures, and after possible master changes.
Right now, I checkpoint & copy over the whole database, then manually
feed data changed during the copying into the new machine. Works for the
rarely changed ~30000 entries now, won't work well when things get more
frequent.

As my application happens to be UDP based, a pure UDP transport seems
to fit me very well. Good to hear it should work.

best regards
Patrick

mailer-daemon (AT) bof (DOT) de (Patrick Schaaf) wrote in message news:<3f56d2de$0$1584$9b622d9e (AT) news (DOT) freenet.de>...

Patrick, just a side note. We have been building a high-load
replication app (we happen to use TCP/IP), and are extremely happy
with the library. However, if you are using replication you should
ask support (AT) sleepycat (DOT) com for the latest v4.2.x pre-release snapshot.
Replication in 4.1.24/25 had a number of bugs, but 4.2.x is looking
very solid indeed in our stress tests.

regards,

Chris