[kafka] Expose resolve_canonical_bootstrap_servers_only (#26022)

**Description:** The latest release of IBM/sarama includes the
`resolve_canonical_bootstrap_servers_only` setting for
`client.dns.lookup`. In a GSSAPI context, this enables replacing a list
of brokers with a single name that resolves to all of the underlying
IPs. Previously this would fail with a Kerberos error. This PR exposes
the new option in collector config.

**Testing:** Added new cases to check the option is set correctly.

**Documentation:** Added a description of the parameter to the relevant
READMEs.

.chloggen/kafka-bootstrap.yaml

@@ -0,0 +1,27 @@
+# Use this changelog template to create an entry for release notes.
+
+# One of 'breaking', 'deprecation', 'new_component', 'enhancement', 'bug_fix'
+change_type: enhancement
+
+# The name of the component, or a single word describing the area of concern, (e.g. filelogreceiver)
+component: kafka
+
+# A brief description of the change.  Surround your text with quotes ("") if it needs to start with a backtick (`).
+note: Expose resolve_canonical_bootstrap_servers_only
+
+# Mandatory: One or more tracking issues related to the change. You can use the PR number here if no issue exists.
+issues: [26022]
+
+# (Optional) One or more lines of additional information to render under the primary note.
+# These lines will be padded with 2 spaces and then inserted directly into the document.
+# Use pipe (|) for multiline entries.
+subtext:
+
+# If your change doesn't affect end users or the exported elements of any package,
+# you should instead start your pull request title with [chore] or use the "Skip Changelog" label.
+# Optional: The change log or logs in which this entry should be included.
+# e.g. '[user]' or '[user, api]'
+# Include 'user' if the change is relevant to end users.
+# Include 'api' if there is a change to a library API.
+# Default: '[user]'
+change_logs: []

exporter/kafkaexporter/README.md

@@ -21,10 +21,11 @@ that blocks and does not batch messages, therefore it should be used with batch
 processors for higher throughput and resiliency. Message payload encoding is configurable.
 
 The following settings are required:
-- `protocol_version` (no default): Kafka protocol version e.g. 2.0.0
+- `protocol_version` (no default): Kafka protocol version e.g. `2.0.0`.
 
 The following settings can be optionally configured:
-- `brokers` (default = localhost:9092): The list of kafka brokers
+- `brokers` (default = localhost:9092): The list of kafka brokers.
+- `resolve_canonical_bootstrap_servers_only` (default = false): Whether to resolve then reverse-lookup broker IPs during startup.
 - `topic` (default = otlp_spans for traces, otlp_metrics for metrics, otlp_logs for logs): The name of the kafka topic to export to.
 - `encoding` (default = otlp_proto): The encoding of the traces sent to kafka. All available encodings:
   - `otlp_proto`: payload is Protobuf serialized from `ExportTraceServiceRequest` if set as a traces exporter or `ExportMetricsServiceRequest` for metrics or `ExportLogsServiceRequest` for logs.

exporter/kafkaexporter/config.go

@@ -22,8 +22,16 @@ type Config struct {
 
 	// The list of kafka brokers (default localhost:9092)
 	Brokers []string `mapstructure:"brokers"`
+
+	// ResolveCanonicalBootstrapServersOnly makes Sarama do a DNS lookup for
+	// each of the provided brokers. It will then do a PTR lookup for each
+	// returned IP, and that set of names becomes the broker list. This can be
+	// required in SASL environments.
+	ResolveCanonicalBootstrapServersOnly bool `mapstructure:"resolve_canonical_bootstrap_servers_only"`
+
 	// Kafka protocol version
 	ProtocolVersion string `mapstructure:"protocol_version"`
+
 	// The name of the kafka topic to export to (default otlp_spans for traces, otlp_metrics for metrics)
 	Topic string `mapstructure:"topic"`
 

exporter/kafkaexporter/config_test.go

@@ -135,6 +135,52 @@ func TestLoadConfig(t *testing.T) {
 				},
 			},
 		},
+		{
+			id: component.NewIDWithName(metadata.Type, ""),
+			option: func(conf *Config) {
+				conf.ResolveCanonicalBootstrapServersOnly = true
+			},
+			expected: &Config{
+				TimeoutSettings: exporterhelper.TimeoutSettings{
+					Timeout: 10 * time.Second,
+				},
+				RetrySettings: exporterhelper.RetrySettings{
+					Enabled:             true,
+					InitialInterval:     10 * time.Second,
+					MaxInterval:         1 * time.Minute,
+					MaxElapsedTime:      10 * time.Minute,
+					RandomizationFactor: backoff.DefaultRandomizationFactor,
+					Multiplier:          backoff.DefaultMultiplier,
+				},
+				QueueSettings: exporterhelper.QueueSettings{
+					Enabled:      true,
+					NumConsumers: 2,
+					QueueSize:    10,
+				},
+				Topic:                                "spans",
+				Encoding:                             "otlp_proto",
+				Brokers:                              []string{"foo:123", "bar:456"},
+				ResolveCanonicalBootstrapServersOnly: true,
+				Authentication: kafka.Authentication{
+					PlainText: &kafka.PlainTextConfig{
+						Username: "jdoe",
+						Password: "pass",
+					},
+				},
+				Metadata: Metadata{
+					Full: false,
+					Retry: MetadataRetry{
+						Max:     15,
+						Backoff: defaultMetadataRetryBackoff,
+					},
+				},
+				Producer: Producer{
+					MaxMessageBytes: 10000000,
+					RequiredAcks:    sarama.WaitForAll,
+					Compression:     "none",
+				},
+			},
+		},
 	}
 
 	for _, tt := range tests {

exporter/kafkaexporter/kafka_exporter.go

@@ -134,6 +134,10 @@ func newSaramaProducer(config Config) (sarama.SyncProducer, error) {
 	c.Producer.MaxMessageBytes = config.Producer.MaxMessageBytes
 	c.Producer.Flush.MaxMessages = config.Producer.FlushMaxMessages
 
+	if config.ResolveCanonicalBootstrapServersOnly {
+		c.Net.ResolveCanonicalBootstrapServers = true
+	}
+
 	if config.ProtocolVersion != "" {
 		version, err := sarama.ParseKafkaVersion(config.ProtocolVersion)
 		if err != nil {

receiver/kafkametricsreceiver/README.md

@@ -32,6 +32,7 @@ Metrics collected by the associated scraper are listed [here](metadata.yaml)
 Optional Settings (with defaults):
 
 - `brokers` (default = localhost:9092): the list of brokers to read from.
+- `resolve_canonical_bootstrap_servers_only` (default = false): whether to resolve then reverse-lookup broker IPs during startup.
 - `topic_match` (default = ^[^_].*$): regex pattern of topics to filter on metrics collection. The default filter excludes internal topics (starting with `_`).
 - `group_match` (default = .*): regex pattern of consumer groups to filter on for metrics.
 - `client_id` (default = otel-metrics-receiver): consumer client id

receiver/kafkametricsreceiver/config.go

@@ -17,6 +17,12 @@ type Config struct {
 	// The list of kafka brokers (default localhost:9092)
 	Brokers []string `mapstructure:"brokers"`
 
+	// ResolveCanonicalBootstrapServersOnly makes Sarama do a DNS lookup for
+	// each of the provided brokers. It will then do a PTR lookup for each
+	// returned IP, and that set of names becomes the broker list. This can be
+	// required in SASL environments.
+	ResolveCanonicalBootstrapServersOnly bool `mapstructure:"resolve_canonical_bootstrap_servers_only"`
+
 	// ProtocolVersion Kafka protocol version
 	ProtocolVersion string `mapstructure:"protocol_version"`
 

receiver/kafkametricsreceiver/receiver.go

@@ -39,6 +39,9 @@ var newMetricsReceiver = func(
 ) (receiver.Metrics, error) {
 	sc := sarama.NewConfig()
 	sc.ClientID = config.ClientID
+	if config.ResolveCanonicalBootstrapServersOnly {
+		sc.Net.ResolveCanonicalBootstrapServers = true
+	}
 	if config.ProtocolVersion != "" {
 		version, err := sarama.ParseKafkaVersion(config.ProtocolVersion)
 		if err != nil {

receiver/kafkareceiver/README.md

@@ -30,6 +30,7 @@ The following settings are required:
 The following settings can be optionally configured:
 
 - `brokers` (default = localhost:9092): The list of kafka brokers
+- `resolve_canonical_bootstrap_servers_only` (default = false): Whether to resolve then reverse-lookup broker IPs during startup
 - `topic` (default = otlp_spans): The name of the kafka topic to read from
 - `encoding` (default = otlp_proto): The encoding of the payload received from kafka. Available encodings:
   - `otlp_proto`: the payload is deserialized to `ExportTraceServiceRequest`, `ExportLogsServiceRequest` or `ExportMetricsServiceRequest` respectively.

receiver/kafkareceiver/config.go

@@ -41,6 +41,11 @@ type HeaderExtraction struct {
 type Config struct {
 	// The list of kafka brokers (default localhost:9092)
 	Brokers []string `mapstructure:"brokers"`
+	// ResolveCanonicalBootstrapServersOnly makes Sarama do a DNS lookup for
+	// each of the provided brokers. It will then do a PTR lookup for each
+	// returned IP, and that set of names becomes the broker list. This can be
+	// required in SASL environments.
+	ResolveCanonicalBootstrapServersOnly bool `mapstructure:"resolve_canonical_bootstrap_servers_only"`
 	// Kafka protocol version
 	ProtocolVersion string `mapstructure:"protocol_version"`
 	// The name of the kafka topic to consume from (default "otlp_spans")

receiver/kafkareceiver/config_test.go

@@ -33,12 +33,13 @@ func TestLoadConfig(t *testing.T) {
 		{
 			id: component.NewIDWithName(metadata.Type, ""),
 			expected: &Config{
-				Topic:         "spans",
-				Encoding:      "otlp_proto",
-				Brokers:       []string{"foo:123", "bar:456"},
-				ClientID:      "otel-collector",
-				GroupID:       "otel-collector",
-				InitialOffset: "latest",
+				Topic:                                "spans",
+				Encoding:                             "otlp_proto",
+				Brokers:                              []string{"foo:123", "bar:456"},
+				ResolveCanonicalBootstrapServersOnly: true,
+				ClientID:                             "otel-collector",
+				GroupID:                              "otel-collector",
+				InitialOffset:                        "latest",
 				Authentication: kafka.Authentication{
 					TLS: &configtls.TLSClientSetting{
 						TLSSetting: configtls.TLSSetting{

receiver/kafkareceiver/kafka_receiver.go

@@ -98,6 +98,9 @@ func newTracesReceiver(config Config, set receiver.CreateSettings, unmarshalers
 	} else {
 		return nil, err
 	}
+	if config.ResolveCanonicalBootstrapServersOnly {
+		c.Net.ResolveCanonicalBootstrapServers = true
+	}
 	if config.ProtocolVersion != "" {
 		version, err := sarama.ParseKafkaVersion(config.ProtocolVersion)
 		if err != nil {

receiver/kafkareceiver/testdata/config.yaml

@@ -3,6 +3,7 @@ kafka:
   brokers:
     - "foo:123"
     - "bar:456"
+  resolve_canonical_bootstrap_servers_only: true
   client_id: otel-collector
   group_id: otel-collector
   auth: