Clustering and replication in ArangoDB

[Sam Latifi]

Hi since I'm fairly new to ArangoDB I have a couple of question regarding clustering and replications. It seems that the documentation is not really clear on those topics:

1. What is the purpose of having a cluster in ArangoDB since the replication is not enabled but default and thus the failover would not make any sense there. Is the idea to have a shared data store all instances in the cluster should have access to?
2. Since the replication model can be either sync or async what about the replication factor on a collection. So the replication needs to configured on each database individually, and the idea to set the replication factor on the collection level? My understanding is that changing the replication factor on the collection level would make the replication to be sync, but what if the database replication is in a async mode?

I have an additional question about arangosh. Tried to configure an async replication on a database and got this error:

JavaScript exception in file '/usr/share/arangodb3/js/client/modules/@arangodb/replication.js' at 209,7: ArangoError 1470: replication API is not supported on a coordinator

!      throw err;

!      ^

stacktrace: ArangoError: replication API is not supported on a coordinator

    at Object.exports.checkRequestResult (/usr/share/arangodb3/js/client/modules/@arangodb/arangosh.js:96:21)

    at waitForResult (/usr/share/arangodb3/js/client/modules/@arangodb/replication.js:207:16)

    at setup (/usr/share/arangodb3/js/client/modules/@arangodb/replication.js:310:10)

    at Object.setupReplication (/usr/share/arangodb3/js/client/modules/@arangodb/replication.js:313:51)

    at <shell command>:1:34

Any idea what could have caused it? I'm on the latest 3.3.3 version with a cluster up and running on 3 different machines.

Thanks,

Sam