Hey Harry, Etherpad uses a node.js module called ueberDB [1] which abstracts multiple databases in key-value stores. We’ve written a driver for Cassandra [2] which allows etherpad to store it’s data in Cassandra. Thanks to ueberDB, etherpad can be run on MySQL, Redis, Mongo, Postgres, Cassandra, ..
Although etherpad is now backed by Cassandra, it can only be scaled out for “performance" and not for failover/reliability. This means that if an etherpad server goes down, a portion of collaborative documents will be unavailable to users. Here is an example: We’re currently running 3 etherpad servers in the production environment. If one were to go down, roughly 1/3 of collaborative documents would be inaccessible in write-mode and they would *not* fail over to the remaining two (without some intervention by us [3]). However, if more and more people were going to start using collab docs, we can simply add an extra server and the load would be shared across all servers (somewhat) evenly. This is due to an inherit design decision of Etherpad. Work is under way to resolve this by the etherpad team. I hope that clarifies it a bit. Kind regards, Simon [1] https://github.com/Pita/ueberDB [2] https://github.com/Pita/ueberDB/pull/42 [3] In reality, we can simply flip a setting in our nginx config and all users would be redirected to a live etherpad server. It would take about 2 minutes to do this On 18 Nov 2013, at 03:14, Harry Wang <harryjw...@gmail.com> wrote: > Hi, > > I have a question on Etherpad integration with OAE. The README at > https://github.com/ether/etherpad-lite shows that MySQL is the production DB > for Etherpad, while OAE is using Cassandra. > > I am not sure about how Etherpad is integrated with OAE: did the project team > configure Etherpad to work with Cassandra or is Etherpad in OAE still > supported by MySQL? If MySQL is used, how can Etherpad scale out as OAE does? > > This question related other future possible integrations with Node.js based > applications that are running on relational databases or other non-Cassandra > NoSQL databases. > > Thanks for your help. > > Harry > _______________________________________________ > oae-dev mailing list > oae-dev@collab.sakaiproject.org > http://collab.sakaiproject.org/mailman/listinfo/oae-dev
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