Indicate DOWN even if the threshold is zero

Author: Phoosha

spring-boot-project/spring-boot-actuator/src/main/java/org/springframework/boot/actuate/system/DiskSpaceHealthIndicator.java

@@ -59,7 +59,9 @@ public DiskSpaceHealthIndicator(File path, DataSize threshold) {
 	@Override
 	protected void doHealthCheck(Health.Builder builder) throws Exception {
 		long diskFreeInBytes = this.path.getUsableSpace();
-		if (diskFreeInBytes >= this.threshold.toBytes()) {
+		// return value of 0L means "the abstract pathname does not name a
+		// partition" which for our purposes means it's not usable i.e DOWN
+		if (diskFreeInBytes >= this.threshold.toBytes() && diskFreeInBytes != 0L) {
 			builder.up();
 		}
 		else {

spring-boot-project/spring-boot-actuator/src/test/java/org/springframework/boot/actuate/system/DiskSpaceHealthIndicatorPathTests.java

@@ -40,6 +40,8 @@ class DiskSpaceHealthIndicatorPathTests {
 
 	private static final DataSize THRESHOLD = DataSize.ofKilobytes(1);
 
+	private static final DataSize ZERO_THRESHOLD = DataSize.ofBytes(0);
+
 	private static final DataSize TOTAL_SPACE = DataSize.ofKilobytes(10);
 
 	@Mock
@@ -70,6 +72,20 @@ void diskSpaceIsDown() {
 		assertThat(health.getDetails().get("canExecute")).isEqualTo(false);
 	}
 
+	@Test
+	void diskSpaceIsDownWhenThresholdIsZero() {
+		this.healthIndicator = new DiskSpaceHealthIndicator(this.fileMock, ZERO_THRESHOLD);
+		Health health = this.healthIndicator.health();
+		assertThat(health.getStatus()).isEqualTo(Status.DOWN);
+		assertThat(health.getDetails().get("threshold")).isEqualTo(ZERO_THRESHOLD.toBytes());
+		assertThat(health.getDetails().get("free")).isEqualTo(0L);
+		assertThat(health.getDetails().get("total")).isEqualTo(0L);
+		assertThat(health.getDetails().get("exists")).isEqualTo(false);
+		assertThat(health.getDetails().get("canRead")).isEqualTo(false);
+		assertThat(health.getDetails().get("canWrite")).isEqualTo(false);
+		assertThat(health.getDetails().get("canExecute")).isEqualTo(false);
+	}
+
 	@Test
 	void diskSpaceIsUpWhenPathOnlyExists() {
 		long freeSpace = THRESHOLD.toBytes() + 10;