Using GraphDB to manage dynamic subscription

Recently we added functionalities for users to subscribe to their sports of interest so we can send them more personalized content. Given the dynamic nature of sports / match / fixture , I wanted the subscription topics flexible but still hierarchical. The idea was to enable someone to get each and every notification that happens on cricket or to choose a particular team / player etc and get more granular notification.

After trying to model the hierarchy into a RDBMS & document DB , we quickly realized traditional DB is just a bad fit for such recursive model design and the data retrieval queries will be too expensive.

This is finally the big enough problem when you can sell / justify introducing a completely new tool to address the issue. And my chance to use graph-db in production. I was introduced to the graph db concept to a previous project of mine and was really impressed by the ease of natural domain model mapping into the DB via the graph concept.

After some basic R & D, we decided to go with Orientdb. Having used elasticsearch cluster products , Orientdb clustering model seemed more natural compared to neo4j. Having said that, having a graph on a distributed cluster is not a easy problem which we realized later the hard way.

We could easily map our model in a graph schema like the following:


Notice how easily the concept of an unregistered device / user , and a user with multiple device fits into the domain. A user can subscribe to any node on the Tree that is Topic and the events automatically flows through the Subscriber.

This is how it looks like on Database:



With the default setup & no special tuning, the system is looking up 10,000 device-id to push the notification in < 500 ms , which is quite good for us. however, the orientdb-support tells us that it can be made even faster.

Lessons Learned:

>     We went with latest major production release 2.1 (which was released only 1 week ago) , and got burnt by many bugs / corner cases. It took upto 2.1.7 to finally have it stable.

>     Use TinkerPop (think jdbc for database) apis so you can switch between orientdb / neo4j

> If coding in java, use Frames api to maintain the Domain mapping

> Frames api is not properly tuned. I had to re-write most of my queries in gremlin . I am not sure about neo4j but orientdb recommends using gremlin / sql to run the search queries.

> Partition your clusters appropriately, it will result in proper utilization of all nodes in your cluster.

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