[ZODB-Dev] Read only ZEO instances

[Tim Hoffman]

Hi

I am trying to get a config working where I have read only and read 
write instances
of the Zeo Client talking to a single ZSS instance.

I have tried the -r flag in the ZEO instance, but I believe that flag in 
traditional zope just causes
the Data.fs to be opened "ro" rather than mucking around with the 
transactions, and so it doesn't work
with Zeo.

My thoughts are that I will have to patch StorageServer.ZEOConnection
and put the smarts in there, to check whether a connection can write etc.
My goal is to be able to control whether the Zeo client can write to the 
ZSS in the ZSS. Probably a control file or command line, which says 
whether a Zeo Client connection is read/write or readonly based on IP 
address
to start with.

I have only just started looking at the Zeo code and
ZODB stuff, so am feeling my way at the moment.

What I need to work out is, do all of the transaction types go through a 
single method first
(I think not, otherwise why do tpc_begin, storea etc all do the same 
test on self._transaction?)

Is there a UML depiction of ZEO/ZSS interaction?

If anyone can give me some pointers or ideas it would be greatly 
appreciated, alternately if anyone
has already done this already you will save me heaps of time, if you can 
point to an RTFM ... ;-)

TIA

Tim Hoffman

P.S. I am having trouble subscribing to ZODB-dev so at the moment, I can 
get any of the posts,
so could you reply directly as well - Thanks