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cassandrajanusgraph
Gilad
Gilad

Reputation: 77

Janusgraph components that scale

If I understand right multiple gremlin servers don't communicate with each other. The scale is in the cassandra/ES only.

If that is true how many vertexes can each gremlin server support?

When the graph is updated by one gremlin server when will the other gremlin servers see that change?

Thanks!

Upvotes: 2

Views: 120

Answers (1)

Rebecca Nelson
Rebecca Nelson

Reputation: 1296

The number of vertices supported is 500 trillion (2^59)

The storage backend is the sole source of state between multiple Gremlin servers. The number of vertices will not be increased by adding additional Gremlin servers.

The limitations on the number of vertices is outlined in the Technical Limitations Page in the JanusGraph Manual.

When one Gremlin Server sees changes made by another is determined by the storage backend choice, but it's still tricky to answer

As far as when the other Gremlin servers will see changes, that is a bit tricky to answer. If you are using a consistent data backend, the answer will generally be as soon as Gremlin finishes its transaction.

But Cassandra is a different beast.

Using an eventually consistent storage backend

Cassandra is what's known as an eventually-consistent database. This means that it trades transactional consistency for availability and partition tolerance; even if you started to lose nodes in the cluster, it will continue to function and serve requests.

The downside to this is that mutations in Cassandra do not instantly become available to consumers; you can even have the case where a client writes a change to Cassandra and that very same client doesn't see the change if they immediately try to read that data.

Chapter 31 in the JanusGraph Manual covers dealing with an eventually consistent storage backend like Cassandra.

Realistically, the amount of time between a mutation and all clients being able to see the mutation in Cassandra depends entirely upon the data load, the nature of the write, and the read/write consistency levels that JanusGraph is configured to read and write to Cassandra with.

Upvotes: 3

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