Question:
Summary: you can rotate and change WEB and Rochade servers and RoAccess
won't miss a beat!
>
> Question 2: Can RoAccess access the Rochade Repository across the
network?
> (I thought I had the answer earlier as I browsed your very informative
web
> site, but then I lost it and could not find it again. I read about
multiple
> instances and load balancing, but I do not recall what role the Rochade
> Repository played in this.)
>
RoAccess is stateless. That is, you can look at a RoAccess page
that has links to other RoAccess pages or screens or has buttons, reboot
the RoAccess server machine, reboot the Rochade server, then click a hyperlink
or button on the RoAccess page and it will continue to work as if nothing
had happened. This surprises many because they are used to session
keys expiring or reboots losing session keys or entire sessions.
But RoAccess was designed to be fault tolerant and be a part of scalable
systems.
For instance, suppose you would like to have 10 parallel Rochade Servers
accessed by 50 RoAccess WEB servers. You want to make sure not matter
even if 90 % of all the servers are down, then the users continue as usual.
Or you want to do load balancing on all these machines. where if several
Rochade servers are loaded, the query goes to an idle Rochade server.
Here the relationship between users, which WEB server is hit and which
Rochade server accessed changes every time you click a button or access
a page. For example if you originally use WEB server
2 and Rochade Server 5, if you hit "refresh" your request may be sent to
WEB Server 10 and Rochade Server 8. If you hit a Rochade server,
but that server then dies, you merely hit reload, and a new Rochade server
is substituted.
This also means if you have an "IP rotation box", then every time a
request for a WEB service comes in, the box either sends the request to
other WEB servers machines on a simple rotating basis (dumb load sharing)
or based on intelligent statistics based load sharing. Since RoAccess
does not depend upon state information saved on any RoAccess or Rochade
server or WEB server (like files or session keys), this "IP rotation box"
works perfectly. This also means you can bring up and down various
parts of the system and network, and the "IP rotation box" can merely exclude
them until they are up again. This also means you can also
put a "IP rotation box" in front of several Rochade servers, and RoAccess
will continue to function perfectly.
RoAccess can also be taught to rotate between multiple Rochade servers
to load balance the Rochade servers. (Note: the Rochade servers are
used in Read-Only mode in this case, since
Rochade does not support replication required for data update.
But that is not a limitation, because manual replication in Rochade is
extremely fast. You do data update in the "master repository".)
So you can load balance both RoAccess WEB and
Rochade servers only if you use RoAccess! This is not true with other
WEB systems and approaches.
RoAccess also has a stateless page caching system, where even if the
RoAccess and WEB server machines are rebooted, the cache remains!
Most caching systems lose the cache if they are rebooted. Not RoAccess.
So you have a lot of options. And in general, usually the more
options you have, the better off you are.
(Note: August does not sell the IP rotation or load sharing boxes,
but we would be glad to give you the names of some. What is important,
is that RoAccess can be used seamlessly with them.)
