Running multiple Dgraph alpha pod and zeros in single host

[MichelDiz]

@micky_mics

replicas: 3

This is K8s replica. But in the context with Dgraph, means about the same thing. K8s will spin up 3 Alphas and 3 Zeros pods. In the RAFT they will become (the alphas) Dgraph replicas.

@micky_mics

Then how all these three alphas create a single alpha group?

They will talk to the Zero Group leader and ask to join the cluster. The zero will ask them to create an election. They will elect a leader. Based on the Zero configs they will organize themselves as replicas. Done.

@micky_mics

Hi @MichelDiz, I understood the best practice says to run each alpha or alpha group to run in dedicated hosts but this is for development purpose. Thanks for your reply.

It is fine to run like this in a dev environment. Avoid doing this in prod.

@micky_mics

But my confusion is, If, we don’t mention the replica settings for Dgraph RAFT group while deploying Dgraph zero, ideally every alpha node should creates it’s own alpha group right?

Yes. If you don’t set the replication factor in the replica flag(for the zeros). Each Alpha will be a group. So you will endup with 3 groups. That’s the default behavior. Sharding all along.

@micky_mics

How it creates a HA, because if we don’t mention replica settings of Dgraph RAFT group while deploying zero, then ideally every alpha creates it’s own group.

In your copy paste commands you shown --replicas 3, so I assumed you are doing replication.

@micky_mics

How is that possible? Is it something I am missing or not understanding

I mentioned above. The statefulset replication just replicates the pods. The “magic” relies in the replica flag. Dgraph does all the election based on the RAFT Algorithm.