orchestrator/kafka: alter topic configuration only when needed (config diff) and allow strict policy disabling

console/data/docs/02-configuration.md

@@ -658,6 +658,7 @@ The following keys are accepted for the topic configuration:
 - `num-partitions` for the number of partitions
 - `replication-factor` for the replication factor
 - `config-entries` is a mapping from configuration names to their values
+- `config-entries-strict-sync` for the configuration in-sync policy
 
 For example:
 
@@ -671,6 +672,7 @@ kafka:
       segment.bytes: 1073741824
       retention.ms: 86400000
       cleanup.policy: delete
+    config-entries-strict-sync: true
 ```
 
 Another useful setting is `retention.bytes` to limit the size of a
@@ -678,8 +680,10 @@ partition in bytes too (divide it by the number of partitions to have
 a limit for the topic).
 
 Currently, the orchestrator service won't update the replication
-factor. The configuration entries are kept in sync with the content of
-the configuration file.
+factor. 
+By default, the configuration entries are kept in sync with the content of
+the configuration file, except if you disable the `config-entries-strict-sync`,
+the existing non-listed overrides won't be removed from topic configuration entries.
 
 ### ClickHouse
 

orchestrator/kafka/config.go

@@ -3,7 +3,9 @@
 
 package kafka
 
-import "akvorado/common/kafka"
+import (
+	"akvorado/common/kafka"
+)
 
 // Configuration describes the configuration for the Kafka configurator.
 type Configuration struct {
@@ -18,8 +20,10 @@ type TopicConfiguration struct {
 	NumPartitions int32 `validate:"min=1"`
 	// ReplicationFactor tells the replication factor for the topic.
 	ReplicationFactor int16 `validate:"min=1"`
-	// ConfigEntries is a map to specify the topic overrides. Non-listed overrides will be removed
+	// ConfigEntries is a map to specify the topic overrides. Non-listed overrides will be removed by default.
 	ConfigEntries map[string]*string
+	// ConfigEntriesStrictSync says if non-listed overrides should be removed (strict sync) or not. Default is True.
+	ConfigEntriesStrictSync bool
 }
 
 // DefaultConfiguration represents the default configuration for the Kafka configurator.
@@ -27,8 +31,22 @@ func DefaultConfiguration() Configuration {
 	return Configuration{
 		Configuration: kafka.DefaultConfiguration(),
 		TopicConfiguration: TopicConfiguration{
-			NumPartitions:     1,
-			ReplicationFactor: 1,
+			NumPartitions:           1,
+			ReplicationFactor:       1,
+			ConfigEntriesStrictSync: true,
 		},
 	}
 }
+
+// ShouldAlterConfiguration validates if topic configuration update is needed regarding in-sync policy.
+func ShouldAlterConfiguration(target, source map[string]*string, strict bool) bool {
+	for k, v := range target {
+		if ov, ok := source[k]; !ok || *ov != *v {
+			return true
+		}
+	}
+	if !strict {
+		return false
+	}
+	return len(target) != len(source)
+}

orchestrator/kafka/config_test.go

@@ -14,3 +14,34 @@ func TestDefaultConfiguration(t *testing.T) {
 		t.Fatalf("validate.Struct() error:\n%+v", err)
 	}
 }
+
+func TestShouldAlterConfiguration(t *testing.T) {
+	referenceTestFoo := "foo"
+	referenceTestBar := "bar"
+	referenceTestOtherFoo := "foo"
+	cases := []struct {
+		name         string
+		target       map[string]*string
+		source       map[string]*string
+		strictPolicy bool
+		expected     bool
+	}{
+		{"subset in strict policy", map[string]*string{"a": &referenceTestFoo}, map[string]*string{"a": &referenceTestFoo, "otherconfigentry": &referenceTestBar}, true, true},
+		{"subset in non-strict policy", map[string]*string{"a": &referenceTestFoo}, map[string]*string{"a": &referenceTestFoo, "otherconfigentry": &referenceTestBar}, false, false},
+		{"subset with different references in non strict policy", map[string]*string{"a": &referenceTestFoo}, map[string]*string{"a": &referenceTestOtherFoo, "otherconfigentry": &referenceTestBar}, false, false},
+		{"missing config entry in strict policy", map[string]*string{"a": &referenceTestFoo}, map[string]*string{"otherconfigentry": &referenceTestBar}, true, true},
+		{"missing config entry in non-strict policy", map[string]*string{"a": &referenceTestFoo}, map[string]*string{"otherconfigentry": &referenceTestBar}, false, true},
+		{"same config in strict policy", map[string]*string{"a": &referenceTestFoo}, map[string]*string{"a": &referenceTestOtherFoo}, true, false},
+		{"same config in non-strict policy", map[string]*string{"a": &referenceTestFoo}, map[string]*string{"a": &referenceTestOtherFoo}, false, false},
+	}
+	for _, tc := range cases {
+		t.Run(tc.name, func(t *testing.T) {
+			got := ShouldAlterConfiguration(tc.target, tc.source, tc.strictPolicy)
+			if got && !tc.expected {
+				t.Errorf("Configuration should not update inplace config.")
+			} else if !got && tc.expected {
+				t.Errorf("Configuration should update inplace config.")
+			}
+		})
+	}
+}

orchestrator/kafka/functional_test.go

@@ -45,6 +45,13 @@ func TestTopicCreation(t *testing.T) {
 				"segment.bytes":  &segmentBytes2,
 				"cleanup.policy": &cleanupPolicy,
 			},
+		}, {
+			Name: "Do not alter equivalent config",
+			ConfigEntries: map[string]*string{
+				"retention.ms":   &retentionMs,
+				"segment.bytes":  &segmentBytes2,
+				"cleanup.policy": &cleanupPolicy,
+			},
 		}, {
 			Name: "Remove item",
 			ConfigEntries: map[string]*string{
@@ -59,9 +66,10 @@ func TestTopicCreation(t *testing.T) {
 			configuration := DefaultConfiguration()
 			configuration.Topic = topicName
 			configuration.TopicConfiguration = TopicConfiguration{
-				NumPartitions:     1,
-				ReplicationFactor: 1,
-				ConfigEntries:     tc.ConfigEntries,
+				NumPartitions:           1,
+				ReplicationFactor:       1,
+				ConfigEntries:           tc.ConfigEntries,
+				ConfigEntriesStrictSync: true,
 			}
 			configuration.Brokers = brokers
 			configuration.Version = kafka.Version(sarama.V2_8_1_0)

orchestrator/kafka/root.go

@@ -105,12 +105,14 @@ func (c *Component) Start() error {
 			l.Warn().Msgf("mismatch for replication factor: got %d, want %d",
 				topic.ReplicationFactor, c.config.TopicConfiguration.ReplicationFactor)
 		}
-		if err := admin.AlterConfig(sarama.TopicResource, c.kafkaTopic, c.config.TopicConfiguration.ConfigEntries, false); err != nil {
-			l.Err(err).Msg("unable to set topic configuration")
-			return fmt.Errorf("unable to set topic configuration for %q: %w",
-				c.kafkaTopic, err)
+		if ShouldAlterConfiguration(c.config.TopicConfiguration.ConfigEntries, topic.ConfigEntries, c.config.TopicConfiguration.ConfigEntriesStrictSync) {
+			if err := admin.AlterConfig(sarama.TopicResource, c.kafkaTopic, c.config.TopicConfiguration.ConfigEntries, false); err != nil {
+				l.Err(err).Msg("unable to set topic configuration")
+				return fmt.Errorf("unable to set topic configuration for %q: %w",
+					c.kafkaTopic, err)
+			}
+			l.Info().Msg("topic updated")
 		}
-		l.Info().Msg("topic updated")
 	}
 	return nil
 }