Replication Redirection #48
Description
Hi,
I'm trying to use reindexer in k8s environment with 1 master and 2 slaves. And I'm using slaves for ha and performance(for select queries). And I'm struggling with some diffuculties.
Sometimes the slave nodes can't replicate some namespaces. I haven't figure out why this happening yet. But this can be happened anytime in the future. So if I query a namespace on a slave that hasn't replicated that namespace yet, it should redirect the query to a node which has the namespace and ready to query on that namespace. In a replication environments like redis or elasticsearch, you send a query to any node, and it can handle the query or redirect request to a valid node.
I can check everytime if the namespace's hash is same as master's hash, and if it isn't same, I can query on another node. And this hash cheking loop continues to all slave nodes until I found a slave node that has namespace with same hash with master. But this leads to performance issues.
I saw replication statuses on #memstats like "idle", "syncing", etc. I can also check this status everytime on every query, but it is same logic as I described above and it can lead to performance issues. Also this requires an extra sql parser to determine the target namespace in the query.