Add health indicator for Cassandra that uses the CqlSession

This commit provides a CassandraDriverHealthIndicator and
CassandraDriverReactiveHealthIndicator that do not require Spring Data.
As a result, a health indicator for Cassandra is provided even if the
application does not use Spring Data.

See gh-20887

spring-boot-project/spring-boot-actuator/src/test/java/org/springframework/boot/actuate/cassandra/CassandraDriverHealthIndicatorTests.java

@@ -0,0 +1,74 @@
+/*
+ * Copyright 2012-2020 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.springframework.boot.actuate.cassandra;
+
+import com.datastax.oss.driver.api.core.CqlSession;
+import com.datastax.oss.driver.api.core.DriverTimeoutException;
+import com.datastax.oss.driver.api.core.cql.ResultSet;
+import com.datastax.oss.driver.api.core.cql.Row;
+import com.datastax.oss.driver.api.core.cql.SimpleStatement;
+import org.junit.jupiter.api.Test;
+
+import org.springframework.boot.actuate.health.Health;
+import org.springframework.boot.actuate.health.Status;
+
+import static org.assertj.core.api.Assertions.assertThat;
+import static org.assertj.core.api.Assertions.assertThatIllegalArgumentException;
+import static org.mockito.ArgumentMatchers.any;
+import static org.mockito.BDDMockito.given;
+import static org.mockito.Mockito.mock;
+
+/**
+ * Tests for {@link CassandraDriverHealthIndicator}.
+ *
+ * @author Alexandre Dutra
+ * @since 2.4.0
+ */
+class CassandraDriverHealthIndicatorTests {
+
+	@Test
+	void createWhenCqlSessionIsNullShouldThrowException() {
+		assertThatIllegalArgumentException().isThrownBy(() -> new CassandraDriverHealthIndicator(null));
+	}
+
+	@Test
+	void healthWithCassandraUp() {
+		CqlSession session = mock(CqlSession.class);
+		ResultSet resultSet = mock(ResultSet.class);
+		Row row = mock(Row.class);
+		given(session.execute(any(SimpleStatement.class))).willReturn(resultSet);
+		given(resultSet.one()).willReturn(row);
+		given(row.isNull(0)).willReturn(false);
+		given(row.getString(0)).willReturn("1.0.0");
+		CassandraDriverHealthIndicator healthIndicator = new CassandraDriverHealthIndicator(session);
+		Health health = healthIndicator.health();
+		assertThat(health.getStatus()).isEqualTo(Status.UP);
+		assertThat(health.getDetails().get("version")).isEqualTo("1.0.0");
+	}
+
+	@Test
+	void healthWithCassandraDown() {
+		CqlSession session = mock(CqlSession.class);
+		given(session.execute(any(SimpleStatement.class))).willThrow(new DriverTimeoutException("Test Exception"));
+		CassandraDriverHealthIndicator healthIndicator = new CassandraDriverHealthIndicator(session);
+		Health health = healthIndicator.health();
+		assertThat(health.getStatus()).isEqualTo(Status.DOWN);
+		assertThat(health.getDetails().get("error"))
+				.isEqualTo(DriverTimeoutException.class.getName() + ": Test Exception");
+	}
+
+}

spring-boot-project/spring-boot-actuator/src/test/java/org/springframework/boot/actuate/cassandra/CassandraDriverReactiveHealthIndicatorTests.java

@@ -0,0 +1,108 @@
+/*
+ * Copyright 2012-2020 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.springframework.boot.actuate.cassandra;
+
+import com.datastax.dse.driver.api.core.cql.reactive.ReactiveResultSet;
+import com.datastax.dse.driver.api.core.cql.reactive.ReactiveRow;
+import com.datastax.oss.driver.api.core.CqlSession;
+import com.datastax.oss.driver.api.core.DriverTimeoutException;
+import com.datastax.oss.driver.api.core.cql.SimpleStatement;
+import org.junit.jupiter.api.Test;
+import org.mockito.stubbing.Answer;
+import org.reactivestreams.Subscriber;
+import org.reactivestreams.Subscription;
+import reactor.core.publisher.Mono;
+import reactor.test.StepVerifier;
+
+import org.springframework.boot.actuate.health.Health;
+import org.springframework.boot.actuate.health.Status;
+
+import static org.assertj.core.api.Assertions.assertThat;
+import static org.assertj.core.api.Assertions.assertThatIllegalArgumentException;
+import static org.mockito.ArgumentMatchers.any;
+import static org.mockito.BDDMockito.doAnswer;
+import static org.mockito.BDDMockito.given;
+import static org.mockito.BDDMockito.mock;
+
+/**
+ * Tests for {@link CassandraDriverReactiveHealthIndicator}.
+ *
+ * @author Alexandre Dutra
+ * @since 2.4.0
+ */
+class CassandraDriverReactiveHealthIndicatorTests {
+
+	@Test
+	void createWhenCqlSessionIsNullShouldThrowException() {
+		assertThatIllegalArgumentException().isThrownBy(() -> new CassandraDriverReactiveHealthIndicator(null));
+	}
+
+	@Test
+	void testCassandraIsUp() {
+		CqlSession session = mock(CqlSession.class);
+		ReactiveResultSet results = mock(ReactiveResultSet.class);
+		ReactiveRow row = mock(ReactiveRow.class);
+		given(session.executeReactive(any(SimpleStatement.class))).willReturn(results);
+		doAnswer(mockReactiveResultSetBehavior(row)).when(results).subscribe(any());
+		given(row.getString(0)).willReturn("6.0.0");
+
+		CassandraDriverReactiveHealthIndicator cassandraReactiveHealthIndicator = new CassandraDriverReactiveHealthIndicator(
+				session);
+		Mono<Health> health = cassandraReactiveHealthIndicator.health();
+		StepVerifier.create(health).consumeNextWith((h) -> {
+			assertThat(h.getStatus()).isEqualTo(Status.UP);
+			assertThat(h.getDetails()).containsOnlyKeys("version");
+			assertThat(h.getDetails().get("version")).isEqualTo("6.0.0");
+		}).verifyComplete();
+	}
+
+	@Test
+	void testCassandraIsDown() {
+		CqlSession session = mock(CqlSession.class);
+		given(session.executeReactive(any(SimpleStatement.class)))
+				.willThrow(new DriverTimeoutException("Test Exception"));
+
+		CassandraDriverReactiveHealthIndicator cassandraReactiveHealthIndicator = new CassandraDriverReactiveHealthIndicator(
+				session);
+		Mono<Health> health = cassandraReactiveHealthIndicator.health();
+		StepVerifier.create(health).consumeNextWith((h) -> {
+			assertThat(h.getStatus()).isEqualTo(Status.DOWN);
+			assertThat(h.getDetails()).containsOnlyKeys("error");
+			assertThat(h.getDetails().get("error"))
+					.isEqualTo(DriverTimeoutException.class.getName() + ": Test Exception");
+		}).verifyComplete();
+	}
+
+	private Answer<Void> mockReactiveResultSetBehavior(ReactiveRow row) {
+		return (invocation) -> {
+			Subscriber<ReactiveRow> subscriber = invocation.getArgument(0);
+			Subscription s = new Subscription() {
+				@Override
+				public void request(long n) {
+					subscriber.onNext(row);
+					subscriber.onComplete();
+				}
+
+				@Override
+				public void cancel() {
+				}
+			};
+			subscriber.onSubscribe(s);
+			return null;
+		};
+	}
+
+}