There is a pretty good description of the extend/aside mode here (in
python, but it should be easily transferable)
http://aspn.activestate.com/ASPN/Cookbook/Python/Recipe/252494

You will still have the problem with one writer and simultaneous
readers though.

metaserver controls this by utilizing a metakit proxy that marshals
all read/view/write operations through a central server.  In practice
it has been really fast although it does have a problem with
transactions and rollbacks are kind of meaningless since any data no
commited by any user will be rolled back.  It is in python only
though, Jean-Claude and I are working on a standaridized mkrpc but
this is a little ways off.  Again the prototype is in python.

We are working on methods around this, in many ways the extend/aside
mode is a good start except that it needs to be extended to support
not just one aside file but many aside files (one for each user) but
this becomes tricky when you consider the need for table locking or
row locking so users don't clobber each other's data.

So in short, multiple readers can access the data using extend/aside
but you will have to marshall all data changes through the writer.  In
practice, this works very well for me because my frequency of data
committing is small compared to the number of reads.

I hope this helps.

Brian Kelley

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