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Hello everyone,

I'm in process of writing a distributed application and I'd like to use
SQLAlchemy as backend.

However, it's not performance that is my concern, but reliability.

Suppose I have n server nodes.

Writing:

I would like to be able to write on any node from 1 to n, and have write
results being sent to DB on every node.

Reading:

I would like to randomly select one of the n clean (up-to-date) nodes
and use it for reading objects (normal SA session handling).


Rationale: the write stream in my case is not going to be very large
(storing test results), while read stream is going to be heavy, so I can
afford this sort of architecture.

On the face of it, implementing such scenario manually should be simple:
just wrap around SA session and have the object sent to each backend in
turn (yes, I know, it's a performance hit but that's not a big problem
in this project).

However, suppose one of the nodes gets offline at some moment: it would
have to be marked as 'dirty' and synchronized somehow with other nodes
when returned to 'online' status. This gets complex and risky.

Alternatively, I could go with the "low tech" version: always assign
particular client to a particular server node, and back the DB up /
replicate it elsewhere. But this cuts into availability and makes me
maintain n backups / replicas.


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Regards,
mk

- --
Premature optimization is the root of all fun.
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