Should I use JanusGraph as main database to store all my data for a new project?

Question

I'm thinking about learn JanusGraph to use in my new big project but i can't understand some things.

Janus can be used like any database and supports "insert", "update", "delete" operations so JanusGraph will write data into Cassandra or other database to store these data, right?

Where JanusGraph store the Nodes, Edges, Attributes etc, it will write these into database, right?

These data should be loaded in memory by Janus or will be read from Cassandra all the time?

The data that JanusGraph read, must be load in JanusGraph in every query or it will do selects in database to retrieve the data I need?

The data retrieved in database is only what I need or Janus will read all records in database all the time?

Should I use JanusGraph in my project in production or should I wait until it becomes production ready?

I'm developing some kind of social network that need to store friendship, posts, comments, user blocks and do some elasticsearch too, in this case, what database backend should I use?

Answer 1

Janus will write data into Cassandra or other database to store these data, right?

Where Janus store the Nodes, Edges, Attributes etc, it will write these into database, right?

Janus Graph will write the data into whatever storage backend you configure it to use. This includes Cassandra. It writes this data into the underlaying database using the data model roughly outlined here

These data should be loaded in memory by Janus or will be read from Cassandra all the time?

The data retrieved in database is only what I need or Janus will read all records in database all the time?

Janus Graph will only load into memory vertices and edges which you touch during a query/traversal. So if you do something like:

graph.traversal().V().hasLabel("My Amazing Label");

Janus will read and load into memory only the vertices with that label. So you don't need to worry about initializing a graph connection and then waiting for the entire graph to be serialised into memory before you can query. Janus is a lazy reader.

Should I use Janus in my project in production or should I wait until it becomes production ready?

That is entirely up to you and your use case. Janus is being used in production already as can be seen here at the bottom of the page. Janus was forked from and improved on TitanDB which is also used in several production use cases. So if you wondering "is it ready" then I would say yes, it's clearly ready given it's existing uses.

what database backend should I use?

Again, that's entirely up to you. I use Cassandra because it can scale horizontally and I find it easier to work with. It also seems to suit all different sizes of data.

I have toyed with Google Big Table and that seems very powerful as well. However, it's only really suited for VERY big data and it's also only on the cloud where as Cassandra can be hosted locally very easily.

I have not used Janus with HBase or BerkeleyDB so I can't comment there.

It's very simple to change between backends though (all you need to do is adjust some configs and check your dependencies are in place) so during your development feel free to play around with the backends. You only really need to commit to a backend when you go production or are more sure of each backend.

Answer 2

When considering what storage backend to use for a new project it's important to consider what tradeoffs you'd like to make. In my personal projects, I've enjoyed using NoSQL graph databases due to the following advantages over relational dbs

• Not needing to migrate schemas increases productivity when rapidly iterating on a new project
• Traversing a heavily normalized data-model is not as expensive as with JOINs in an RDBMS
• Most include in-memory configurations which are great for experimenting & testing.
• Support for multi-machine clusters and Partition Tolerance.

Here are sample JanusGraph and Neo4j backends written in Kotlin:

• https://github.com/pm-dev/janusgraph-exploration
• https://github.com/pm-dev/neo4j-exploration

The main advantage with JanusGraph is the flexibility of pluging-in whichever storage backend you'd like.