GH-1168: Fix sendOffsets in local transaction

Fixes #1168

`sendOffsetsToTransaction` assumed the transaction was started by a
`KafkaTransactionManager` and using `executeInTransaction` failed.

Look for a local transactional producer before checking for a thread-bound transaction.

**cherry-pick to all supported branches**

# Conflicts:
#	spring-kafka/src/test/java/org/springframework/kafka/core/KafkaTemplateTransactionTests.java

# Conflicts:
#	spring-kafka/src/test/java/org/springframework/kafka/core/KafkaTemplateTransactionTests.java

spring-kafka/src/main/java/org/springframework/kafka/core/KafkaTemplate.java

@@ -331,13 +331,15 @@ public void sendOffsetsToTransaction(Map<TopicPartition, OffsetAndMetadata> offs
 
 	@Override
 	public void sendOffsetsToTransaction(Map<TopicPartition, OffsetAndMetadata> offsets, String consumerGroupId) {
-		@SuppressWarnings("unchecked")
-		KafkaResourceHolder<K, V> resourceHolder = (KafkaResourceHolder<K, V>) TransactionSynchronizationManager
-				.getResource(this.producerFactory);
-		Assert.isTrue(resourceHolder != null, "No transaction in process");
-		if (resourceHolder.getProducer() != null) {
-			resourceHolder.getProducer().sendOffsetsToTransaction(offsets, consumerGroupId);
+		Producer<K, V> producer = this.producers.get();
+		if (producer == null) {
+			@SuppressWarnings("unchecked")
+			KafkaResourceHolder<K, V> resourceHolder = (KafkaResourceHolder<K, V>) TransactionSynchronizationManager
+					.getResource(this.producerFactory);
+			Assert.isTrue(resourceHolder != null, "No transaction in process");
+			producer = resourceHolder.getProducer();
 		}
+		producer.sendOffsetsToTransaction(offsets, consumerGroupId);
 	}
 
 	protected void closeProducer(Producer<K, V> producer, boolean inLocalTx) {

spring-kafka/src/test/java/org/springframework/kafka/core/KafkaTemplateTransactionTests.java

@@ -38,11 +38,13 @@
 import org.apache.kafka.clients.consumer.ConsumerConfig;
 import org.apache.kafka.clients.consumer.ConsumerRecord;
 import org.apache.kafka.clients.consumer.ConsumerRecords;
+import org.apache.kafka.clients.consumer.OffsetAndMetadata;
 import org.apache.kafka.clients.producer.Callback;
 import org.apache.kafka.clients.producer.MockProducer;
 import org.apache.kafka.clients.producer.Producer;
 import org.apache.kafka.clients.producer.ProducerConfig;
 import org.apache.kafka.clients.producer.ProducerRecord;
+import org.apache.kafka.common.TopicPartition;
 import org.apache.kafka.common.serialization.StringDeserializer;
 import org.apache.kafka.common.serialization.StringSerializer;
 import org.assertj.core.api.Assertions;
@@ -77,10 +79,13 @@ public class KafkaTemplateTransactionTests {
 
 	private static final String STRING_KEY_TOPIC = "stringKeyTopic";
 
+	private static final String LOCAL_TX_IN_TOPIC = "localTxInTopic";
+
 	@ClassRule
-	public static KafkaEmbedded embeddedKafka = new KafkaEmbedded(1, true, STRING_KEY_TOPIC)
-		.brokerProperty(KafkaConfig.TransactionsTopicReplicationFactorProp(), "1")
-		.brokerProperty(KafkaConfig.TransactionsTopicMinISRProp(), "1");
+	public static KafkaEmbedded embeddedKafka = new KafkaEmbedded(1, true, STRING_KEY_TOPIC,
+			LOCAL_TX_IN_TOPIC)
+			.brokerProperty(KafkaConfig.TransactionsTopicReplicationFactorProp(), "1")
+			.brokerProperty(KafkaConfig.TransactionsTopicMinISRProp(), "1");
 
 	@Test
 	public void testLocalTransaction() throws Exception {
@@ -93,13 +98,22 @@ public void testLocalTransaction() throws Exception {
 		template.setDefaultTopic(STRING_KEY_TOPIC);
 		Map<String, Object> consumerProps = KafkaTestUtils.consumerProps("testTxString", "false", embeddedKafka);
 		consumerProps.put(ConsumerConfig.AUTO_OFFSET_RESET_CONFIG, "earliest");
+		consumerProps.put(ConsumerConfig.ISOLATION_LEVEL_CONFIG, "read_committed");
 		DefaultKafkaConsumerFactory<String, String> cf = new DefaultKafkaConsumerFactory<>(consumerProps);
 		cf.setKeyDeserializer(new StringDeserializer());
 		Consumer<String, String> consumer = cf.createConsumer();
-		embeddedKafka.consumeFromAnEmbeddedTopic(consumer, STRING_KEY_TOPIC);
+		embeddedKafka.consumeFromAllEmbeddedTopics(consumer);
+		template.executeInTransaction(kt -> kt.send(LOCAL_TX_IN_TOPIC, "one"));
+		ConsumerRecord<String, String> singleRecord = KafkaTestUtils.getSingleRecord(consumer, LOCAL_TX_IN_TOPIC);
 		template.executeInTransaction(t -> {
 			t.sendDefault("foo", "bar");
 			t.sendDefault("baz", "qux");
+			t.sendOffsetsToTransaction(Collections.singletonMap(
+					new TopicPartition(LOCAL_TX_IN_TOPIC, singleRecord.partition()),
+					new OffsetAndMetadata(singleRecord.offset() + 1L)), "testLocalTx");
+			assertThat(KafkaTestUtils.getPropertyValue(
+					KafkaTestUtils.getPropertyValue(template, "producers", ThreadLocal.class).get(),
+					"delegate.transactionManager.transactionalId")).isEqualTo("my.transaction.0");
 			return null;
 		});
 		ConsumerRecords<String, String> records = KafkaTestUtils.getRecords(consumer);
@@ -112,6 +126,8 @@ public void testLocalTransaction() throws Exception {
 		}
 		record = iterator.next();
 		assertThat(record).has(Assertions.<ConsumerRecord<String, String>>allOf(key("baz"), value("qux")));
+		// 2 log slots, 1 for the record, 1 for the commit
+		assertThat(consumer.position(new TopicPartition(LOCAL_TX_IN_TOPIC, singleRecord.partition()))).isEqualTo(2L);
 		consumer.close();
 		assertThat(KafkaTestUtils.getPropertyValue(pf, "cache", BlockingQueue.class).size()).isEqualTo(1);
 		pf.destroy();
@@ -210,8 +226,8 @@ public void testNoTx() {
 		KafkaTemplate<String, String> template = new KafkaTemplate<>(pf);
 		template.setDefaultTopic(STRING_KEY_TOPIC);
 		assertThatThrownBy(() -> template.send("foo", "bar"))
-			.isInstanceOf(IllegalStateException.class)
-			.hasMessageContaining("No transaction is in process;");
+				.isInstanceOf(IllegalStateException.class)
+				.hasMessageContaining("No transaction is in process;");
 	}
 
 	@Test