If I were interested in probing each member of the cluster for its state of readiness, what would be the best approach? At the moment I'm thinking of probing zookeeper with netcat to see if the server command gives back a result:

echo srvr | nc localhost 2181
Zookeeper version: 3.5.8-f439ca583e70862c3068a1f2a7d4d068eec33315, built on 05/04/2020 15:53 GMT
Latency min/avg/max: 0/0/20
Received: 5590
Sent: 5751
Connections: 7
Outstanding: 0
Zxid: 0x176
Mode: standalone
Node count: 80

And from there using the following command to ensure the correct number of brokers controllers and servers exist

docker exec -it <container> bin/pinot-admin.sh ShowClusterInfo -clusterName PinotCluster -zkAddress localhost:2181
_brokerInfoList:
- _name: Broker_172.28.0.5_8099
  _state: ONLINE
  _tags: [DefaultTenant_BROKER]
_clusterName: PinotCluster
_controllerInfo: {_leaderName: 172.28.0.3_9000}
_serverInfoList:
- _name: Server_172.28.0.4_8098
  _state: ONLINE
  _tags: [DefaultTenant_OFFLINE, DefaultTenant_REALTIME]
_tableInfoList:
- _segmentInfoList:
  - _name: cases_OFFLINE_20150105_20150106_0
    _segmentStateMap: {Server_172.28.0.4_8098: ONLINE}
  _tableName: cases_OFFLINE
  _tag: cases_OFFLINE

Still, I don't know if this command will produce instances before they are fully ready. I was hoping there was a more direct way to probe each instance individually. Any suggestions would be greatly welcomed.

can you use the

/health

endpoint on each component

I'll give that a go. Thanks so much!