DX-15655: restrict dremio master to a single pod

Change-Id: I5945385b35480a10922c0750902eb5648bcd0194

Author: Nirmalya Sen

charts/dremio/templates/dremio-master.yaml

@@ -4,7 +4,7 @@ metadata:
   name: dremio-master
 spec:
   serviceName: "dremio-cluster-pod"
-  replicas: {{.Values.coordinator.master_count}}
+  replicas: 1
   selector:
     matchLabels:
       app: dremio-coordinator
@@ -64,6 +64,9 @@ spec:
         - containerPort: 45678
           name: server
       initContainers:
+      - name: start-only-one-master
+        image: busybox
+        command: ["sh", "-c", "INDEX=${HOSTNAME##*-}; if [ $INDEX -ne 0 ]; then echo Only one master should be running.; exit 1; fi; "]
       - name: wait-for-zk
         image: busybox
         command:  ["sh", "-c", "until ping -c 1 -W 1 zk-hs > /dev/null; do echo waiting for zookeeper host; sleep 2; done;"]

charts/dremio/values.yaml

@@ -9,19 +9,20 @@ image: dremio/dremio-oss:latest
 coordinator:
   memory: 16384
   cpu: 8
+  # This count is for slave coordinators only.
+  # The chart will always create one master coordinator - you are
+  # not required to have more than one master coordinator.
   count: 0
-  # This value should NOT be set to more than 1.
-  master_count: 1
   web:
     port: 9047
   client:
     port: 31010
-  volumeSize: 20Gi
+  volumeSize: 100Gi
 executor:
   memory: 16384
   cpu: 4
-  count: 1
-  volumeSize: 20Gi
+  count: 3
+  volumeSize: 100Gi
 
 # If your Kubernetes cluster does not support LoadBalancer,
 # comment out the line below for the helm chart to succeed or add