Create disk memory health checker

core/src/main/java/com/linecorp/armeria/server/healthcheck/DiskMemoryHealthChecker.java

@@ -0,0 +1,58 @@
+/*
+ * Copyright 2024 LY Corporation
+ *
+ * LY Corporation licenses this file to you 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 com.linecorp.armeria.server.healthcheck;
+
+import static com.google.common.base.Preconditions.checkArgument;
+import static java.util.Objects.requireNonNull;
+
+import java.io.File;
+
+/**
+ * A {@link HealthChecker} that reports as unhealthy
+ * when the target free disk space exceeds a file disk usable space.
+ * For example:
+ * <pre>{@code
+ * final DiskMemoryHealthChecker diskMemoryHealthChecker = HealthChecker.ofDisk(80, new File("/tmp"));
+ *
+ * // Returns false if a file disk usable memory space is less than 80%,
+ * // or true if a file disk usable memory space is greater than or equal to 80%.
+ * final boolean healthy = diskMemoryHealthChecker.isHealthy();
+ * }</pre>
+ */
+// Forked from <a href="https://github.com/micrometer-metrics/micrometer/blob/8339d57bef8689beb8d7a18b429a166f6595f2af/micrometer-core/src/main/java/io/micrometer/core/instrument/binder/system/DiskSpaceMetrics.java">DiskSpaceMetrics.java</a> in the micrometer core.
+final class DiskMemoryHealthChecker implements HealthChecker {
+
+    private final double targetFreeSpacePercentage;
+
+    private final File path;
+
+    DiskMemoryHealthChecker(double targetFreeSpacePercentage, File path) {
+        checkArgument(targetFreeSpacePercentage >= 0 && targetFreeSpacePercentage <= 1,
+                      "freeDiskSpace: %s (expected < 0 or expected > 1)", targetFreeSpacePercentage);
+        requireNonNull(path);
+        this.targetFreeSpacePercentage = targetFreeSpacePercentage;
+        this.path = path;
+    }
+
+    /**
+     * Returns true if the file usable space is greater or equal than the target space.
+     * @return boolean
+     */
+    @Override
+    public boolean isHealthy() {
+        return targetFreeSpacePercentage * path.getTotalSpace() <= path.getUsableSpace();
+    }
+}

core/src/main/java/com/linecorp/armeria/server/healthcheck/HealthChecker.java

@@ -19,6 +19,7 @@
 import static com.google.common.base.Preconditions.checkArgument;
 import static java.util.Objects.requireNonNull;
 
+import java.io.File;
 import java.time.Duration;
 import java.util.concurrent.CompletionStage;
 import java.util.function.Supplier;
@@ -105,6 +106,19 @@ static HealthChecker ofCpu(double targetSystemCpuUsage, double targetProcessCpuU
         return new CpuHealthChecker(targetSystemCpuUsage, targetProcessCpuUsage);
     }
 
+    /**
+     * Creates a new instance of {@link HealthChecker} which reports health based on free disk space
+     * of the file system the specified path belongs to.
+     * Both free disk space must be (inclusive) lower than the specified threshold in order
+     * for the {@link HealthChecker} to report as healthy.
+     *
+     * @param targetDiskSpacePercentage the target free disk space as a percentage (0 - 1).
+     * @return an instance of {@link HealthChecker} configured with the provided disk memory space targets.
+     */
+    static HealthChecker ofDisk(double targetDiskSpacePercentage, File path) {
+        return new DiskMemoryHealthChecker(targetDiskSpacePercentage, path);
+    }
+
     /**
      * Returns {@code true} if and only if the {@link Server} is healthy.
      */

core/src/test/java/com/linecorp/armeria/server/healthcheck/DiskMemoryCheckerTest.java

@@ -0,0 +1,51 @@
+/*
+ * Copyright 2024 LY Corporation
+ *
+ * LY Corporation licenses this file to you 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 com.linecorp.armeria.server.healthcheck;
+
+import static org.assertj.core.api.Assertions.assertThat;
+import static org.assertj.core.api.Assertions.assertThatThrownBy;
+
+import java.io.File;
+
+import org.junit.jupiter.api.Test;
+
+class DiskMemoryCheckerTest {
+
+    @Test
+    void throwExceptionWhenTargetFreeDiskSpaceLowerThanZero() {
+        final double targetFreeDiskSpace = -1.0;
+        assertThatThrownBy(() -> HealthChecker.ofDisk(targetFreeDiskSpace, new File("/tmp")))
+                .isInstanceOf(IllegalArgumentException.class)
+                .hasMessageContaining("freeDiskSpace: %.1f (expected < 0 or expected > 1)",
+                                      targetFreeDiskSpace);
+    }
+
+    @Test
+    void throwExceptionWhenPathIsNull() {
+        final double targetFreeDiskSpace = 1.0;
+        assertThatThrownBy(() -> HealthChecker.ofDisk(targetFreeDiskSpace, null))
+                .isInstanceOf(NullPointerException.class);
+    }
+
+    @Test
+    void shouldReturnTrueWhenDiskSpaceIsHealthy() {
+        final DiskMemoryHealthChecker diskMemoryHealthChecker =
+                (DiskMemoryHealthChecker) HealthChecker.ofDisk(
+                        0.01, new File(".")
+                );
+        assertThat(diskMemoryHealthChecker.isHealthy()).isTrue();
+    }
+}