Add support for RAFT_METADATA_ONLY_VOTERS setting

Author: antas-marcin

.cicd/test.sh

@@ -231,6 +231,10 @@ function check_creates_template() {
   check_setting_has_value "--set replicas=100" "name: RAFT_JOIN" "value: \"weaviate-0,weaviate-1,weaviate-2,weaviate-3,weaviate-4\""
   check_setting_has_value "--set replicas=100" "name: RAFT_BOOTSTRAP_EXPECT" "value: \"5\""
 
+  check_setting_has_value "--set replicas=9 --set env.RAFT_METADATA_ONLY_VOTERS=true" "name: RAFT_BOOTSTRAP_EXPECT" "value: \"3\""
+  check_setting_has_value "--set replicas=9 --set env.RAFT_METADATA_ONLY_VOTERS=true" "name: RAFT_METADATA_ONLY_VOTERS" "value: \"true\""
+  check_setting_has_value "--set replicas=3 --set env.RAFT_METADATA_ONLY_VOTERS=false" "name: RAFT_BOOTSTRAP_EXPECT" "value: \"3\""
+
   _settingPassageQueryOn="--set modules.text2vec-contextionary.enabled=false --set modules.text2vec-transformers.passageQueryServices.passage.enabled=true --set modules.text2vec-transformers.passageQueryServices.query.enabled=true"
   check_setting_has_value "$_settingPassageQueryOn" "name: TRANSFORMERS_PASSAGE_INFERENCE_API" "value: http://transformers-inference-passage.default.svc.cluster.local.:8080"
   check_setting_has_value "$_settingPassageQueryOn" "name: TRANSFORMERS_QUERY_INFERENCE_API" "value: http://transformers-inference-query.default.svc.cluster.local.:8080"

weaviate/templates/_helpers.tpl

@@ -181,6 +181,10 @@ Raft cluster configuration settings
 {{- define "raft_configuration" -}}
   {{- $replicas := .Values.replicas | int -}}
   {{- $voters := .Values.env.RAFT_BOOTSTRAP_EXPECT | int -}}
+  {{- $metada_only_voters := false -}}
+  {{- if not (empty .Values.env.RAFT_METADATA_ONLY_VOTERS) -}}
+    {{- $metada_only_voters = .Values.env.RAFT_METADATA_ONLY_VOTERS -}}
+  {{- end -}} 
   {{- if empty .Values.env.RAFT_BOOTSTRAP_EXPECT -}}
     {{- if ge $replicas 10 -}}
       {{- $voters = 5 -}}
@@ -216,4 +220,7 @@ Raft cluster configuration settings
           - name: RAFT_BOOTSTRAP_EXPECT
             value: "{{ $voters }}"
   {{- end -}}
+  {{- if and ($metada_only_voters) (le $replicas $voters) -}}
+    {{- fail "env.RAFT_METADATA_ONLY_VOTERS is true then .replicas size must be greater than env.RAFT_BOOTSTRAP_EXPECT" -}}
+  {{- end -}}
 {{- end -}}

weaviate/values.yaml

@@ -275,6 +275,11 @@ env:
   # then RAFT_BOOTSTRAP_EXPECT needs to be equal 2 also.
   # RAFT_JOIN: "weaviate-0"
 
+  # Set to true if voters nodes should handle only schema. With this setting enabled
+  # voter nodes will not accept any data, one needs to resize the cluster using replicas
+  # setting so that replicas > voters.
+  # RAFT_METADATA_ONLY_VOTERS: false
+
   # The aggressiveness of the Go Garbage Collector. 100 is the default value.
   GOGC: 100