ClickHouse with multiple replicas and shards

[vittoriocanilli]

Hello, I am setting up Plausible on a Kubernetes cluster, where PostgreSQL is hosted on an Azure instance and ClickHouse is hosted on the same Kubernetes cluster, having multiple replicas and shards:

• 2 Plausible replicas
• 3 ClickHouse replicas with 2 shards, corresponding to 6 pods, each with a 8GBi PVC
• 3 ZooKeeper replicas, each with a 8GBi PVC

I am using the BitNami ClickHouse chart and I have set the headless service's endpoint http://plausible_user:plausible_password@plausible-analytics-clickhouse-headless.<namespace>:8123/plausible_events_db as CLICKHOUSE_DATABASE_URL and everything seems to work.

When I try to delete one of the ClickHouse pods to simulate what would happen during a rescheduling through the Kubernetes cluster's nodes, the pod gets recreated correctly, but the data on the sites on my Plausible dashboard is no more consistent as before, when I refresh the page: sometimes the graphs have data, sometimes they are empty, sometimes they are not rendered because of a HTTP 500 error.

I have found a discussion that highlights that Plausible does not support clusters. I am quite new with ClickHouse: does that actually mean that Plausible can only run with ClickHouse if it has one shard and one replica?

Just to understand if it is a limitation of Plausible or if I am doing something wrong with my setup. Thanks in advance.