Issue 121 in walkaround: Apply and commit: Write changes to the datastore after broadcasting them to clients

[walka...@googlecode.com]

Status: New
Owner: ----
Labels: Type-Defect Priority-Medium

New issue 121 by i...@goodow.com: Apply and commit: Write changes to the
datastore after broadcasting them to clients
http://code.google.com/p/walkaround/issues/detail?id=121

The wave server should be responsible for two steps when a delta is
submitted by a user:
First, apply the delta and immediately sent a onAck message to client.
Second, commit the delta: write the delta to persistent storage and then
sent a onCommit message to client.

The Design Overview page said:
"Walkaround writes changes to the datastore before broadcasting them to
other clients; this avoids the need for complicated rollback protocols."

To process the rollback, I guess most of the work will be done in
GenericOperationChannel. When rollback occurs, the channel should try to
resend the missing operations, so that the server side can silently ignore
the corresponding commit fails.

The more complicated two step process is really a killer feature, please
consider it.