From: "Adrian Crum" <[email protected]>
Jacques Le Roux wrote:
Hi Deyan,
Thanks for your clear explanation and suggestion. As I'm busy with another
stuff, I have quickly put your comment as a quote in
OFBIZ-3333 .
There is however a major issue that CAN NOT be fixed in the current
implementation: the list and sequence of entities to be
synchronized gets created by entities' timestamp - date_created_tx and
last_update_tx. It works as long as the clocks of all the
syncing parties are in sync. You can easily achieve this by using NTP for
example - reliable enough. But if the clock of one of
the parties gets un-synced for just few minutes, and during those few minutes
records get inserted or updated than you are in
trouble. Syncing the clock back won't help you because you won't be able to
sync the broken records due to foreign key constraint
issues. Examples I could give but I guess you could think of such by yourselves
:)
So IMHO the best approach for synchronization is not the timestamp but the
TRANSACTION LOG. This approach is used in all major
databases - m$ $ql, oracle.
The problem with that approach is that it is database-specific. As an
alternative, you could query the other servers for their
current time and generate a set of offsets to adjust the timing.
Why asking from one to the others? Using NTP on all of them should be enough,
or do I miss something (looks like it's used telecom,
air control, videoconferences, etc.). Of course the timezone needs to be set
equally on each.
Googling for NTP related stuff I found http://en.wikipedia.org/wiki/SyncML.
Looks like there are a lot of solutions out there
(Funambol being unfortunately AGPL licenced)?
Deyan has also suggested to create a new way with "entity triggers", based on
what he did with Postres. I'm not quite sure of what
"entity triggers" should be, I guess EECAs. But of course this means more work,
and maybe NTP is enough...
PS: why mean Re: JUNK-> ?
-Adrian
