Add check for disk space usage in git directory Introduce a new check (`gitspace`) that monitors available disk space on the volume where Git repositories are stored. The check fails if the usable space falls below a configurable threshold, which defaults to 10%. This addition helps detect low-disk-space conditions early, avoiding potential service instability due to lack of storage. The threshold can be overridden in the healthcheck configuration using the `minDiskFreePercent` parameter. Bug: Issue 428666920 Change-Id: Ic4d56f8ac55f6320dd3a7d2ee9dcadb980e14829

diff --git a/src/main/java/com/googlesource/gerrit/plugins/healthcheck/HealthCheckConfig.java b/src/main/java/com/googlesource/gerrit/plugins/healthcheck/HealthCheckConfig.java
index d866586..c6b5b43 100644
--- a/src/main/java/com/googlesource/gerrit/plugins/healthcheck/HealthCheckConfig.java
+++ b/src/main/java/com/googlesource/gerrit/plugins/healthcheck/HealthCheckConfig.java

@@ -46,6 +46,7 @@
   private static final String QUERY_DEFAULT = "status:open";
   private static final int LIMIT_DEFAULT = 10;
   private static final int ACTIVE_WORKERS_THRESHOLD_DEFAULT = 80;
+  private static final int GIT_SPACE_MIN_DISK_FREE_PCT_DEFAULT = 10;
   private static final String USERNAME_DEFAULT = "healthcheck";
   private static final String PASSWORD_DEFAULT = "";
   private static final String FAIL_FILE_FLAG_DEFAULT = "data/healthcheck/fail";
@@ -128,6 +129,11 @@
     return repos;
   }
 
+  public int getMinFreeDiskPercent(String healthCheckName) {
+    return config.getInt(
+        HEALTHCHECK, healthCheckName, "minFreeDiskPercent", GIT_SPACE_MIN_DISK_FREE_PCT_DEFAULT);
+  }
+
   public String getUsername(String healthCheckName) {
     return getStringWithFallback("username", healthCheckName, USERNAME_DEFAULT);
   }

diff --git a/src/main/java/com/googlesource/gerrit/plugins/healthcheck/HealthCheckSubsystemsModule.java b/src/main/java/com/googlesource/gerrit/plugins/healthcheck/HealthCheckSubsystemsModule.java
index 5d106af..9178537 100644
--- a/src/main/java/com/googlesource/gerrit/plugins/healthcheck/HealthCheckSubsystemsModule.java
+++ b/src/main/java/com/googlesource/gerrit/plugins/healthcheck/HealthCheckSubsystemsModule.java

@@ -22,6 +22,7 @@
 import com.googlesource.gerrit.plugins.healthcheck.check.BlockedThreadsCheck;
 import com.googlesource.gerrit.plugins.healthcheck.check.ChangesIndexHealthCheck;
 import com.googlesource.gerrit.plugins.healthcheck.check.DeadlockCheck;
+import com.googlesource.gerrit.plugins.healthcheck.check.GitSpaceCheck;
 import com.googlesource.gerrit.plugins.healthcheck.check.HealthCheck;
 import com.googlesource.gerrit.plugins.healthcheck.check.HttpActiveWorkersCheck;
 import com.googlesource.gerrit.plugins.healthcheck.check.JGitHealthCheck;
@@ -41,6 +42,7 @@
     bindChecker(DeadlockCheck.class);
     bindChecker(BlockedThreadsCheck.class);
     bindChecker(ChangesIndexHealthCheck.class);
+    bindChecker(GitSpaceCheck.class);
 
     DynamicSet.bind(binder(), OnlineUpgradeListener.class).to(ChangesIndexHealthCheck.class);
 

diff --git a/src/main/java/com/googlesource/gerrit/plugins/healthcheck/check/GitSpaceCheck.java b/src/main/java/com/googlesource/gerrit/plugins/healthcheck/check/GitSpaceCheck.java
new file mode 100644
index 0000000..d8d4b59
--- /dev/null
+++ b/src/main/java/com/googlesource/gerrit/plugins/healthcheck/check/GitSpaceCheck.java

@@ -0,0 +1,68 @@
+// Copyright (C) 2025 The Android Open Source Project
+//
+// 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
+//
+// http://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.googlesource.gerrit.plugins.healthcheck.check;
+
+import static com.googlesource.gerrit.plugins.healthcheck.check.HealthCheckNames.GITSPACE;
+
+import com.google.common.flogger.FluentLogger;
+import com.google.common.util.concurrent.ListeningExecutorService;
+import com.google.gerrit.metrics.MetricMaker;
+import com.google.gerrit.server.config.GerritServerConfig;
+import com.google.gerrit.server.config.SitePaths;
+import com.google.inject.Inject;
+import com.google.inject.Singleton;
+import com.googlesource.gerrit.plugins.healthcheck.HealthCheckConfig;
+import java.io.File;
+import java.nio.file.Path;
+import org.eclipse.jgit.lib.Config;
+
+@Singleton
+public class GitSpaceCheck extends AbstractHealthCheck {
+  private static final FluentLogger logger = FluentLogger.forEnclosingClass();
+  private final Path gitPath;
+
+  @Inject
+  public GitSpaceCheck(
+      @GerritServerConfig Config gerritConfig,
+      SitePaths site,
+      ListeningExecutorService executor,
+      HealthCheckConfig config,
+      MetricMaker metricMaker) {
+    super(executor, config, GITSPACE, metricMaker);
+
+    this.gitPath = site.resolve(gerritConfig.getString("gerrit", null, "basePath"));
+  }
+
+  protected File getGitDirectory() {
+    return gitPath.toFile();
+  }
+
+  @Override
+  protected Result doCheck() throws Exception {
+    int minFreeDiskPercent = config.getMinFreeDiskPercent(GITSPACE);
+    long total = getGitDirectory().getTotalSpace();
+
+    if (total <= 0) {
+      logger.atWarning().log(
+          "Cannot determine total disk space for Git directory: %s", getGitDirectory());
+      return Result.FAILED;
+    }
+
+    long usable = getGitDirectory().getUsableSpace();
+    int freePercent = (int) ((usable * 100.0) / total);
+
+    return freePercent < minFreeDiskPercent ? Result.FAILED : Result.PASSED;
+  }
+}

diff --git a/src/main/java/com/googlesource/gerrit/plugins/healthcheck/check/HealthCheckNames.java b/src/main/java/com/googlesource/gerrit/plugins/healthcheck/check/HealthCheckNames.java
index d8f1621..26ce70e 100644
--- a/src/main/java/com/googlesource/gerrit/plugins/healthcheck/check/HealthCheckNames.java
+++ b/src/main/java/com/googlesource/gerrit/plugins/healthcheck/check/HealthCheckNames.java

@@ -16,6 +16,7 @@
 
 public interface HealthCheckNames {
   String JGIT = "jgit";
+  String GITSPACE = "gitspace";
   String PROJECTSLIST = "projectslist";
   String QUERYCHANGES = "querychanges";
   String AUTH = "auth";

diff --git a/src/main/resources/Documentation/config.md b/src/main/resources/Documentation/config.md
index 1883724..c2c7dd3 100644
--- a/src/main/resources/Documentation/config.md
+++ b/src/main/resources/Documentation/config.md

@@ -51,6 +51,7 @@
 
 - `querychanges`: check the ability to query changes
 - `jgit` : check connectivity to the filesystem and ability to open a JGit ref and object
+- `gitspace`: Checks that sufficient disk space is available on the volume where Git repositories are stored
 - `projectslist` : check the ability to list projects with their descriptions
 - `auth`: check the ability to authenticate with username and password
 - `activeworkers`: check the number of active worker threads and the ability to create a new one
@@ -87,6 +88,11 @@
 
   Default: All-Projects, All-Users
 
+- `healthcheck.gitspace.minFreeDiskPercent` : Minimum acceptable percentage of free disk space
+   before the check fails.
+
+   Default: 10
+
  - `healthcheck.auth.username` : Username to use for authentication
 
    Default: healthcheck

diff --git a/src/test/java/com/googlesource/gerrit/plugins/healthcheck/GitSpaceCheckTest.java b/src/test/java/com/googlesource/gerrit/plugins/healthcheck/GitSpaceCheckTest.java
new file mode 100644
index 0000000..ff21a6a
--- /dev/null
+++ b/src/test/java/com/googlesource/gerrit/plugins/healthcheck/GitSpaceCheckTest.java

@@ -0,0 +1,121 @@
+// Copyright (C) 2025 The Android Open Source Project
+//
+// 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
+//
+// http://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.googlesource.gerrit.plugins.healthcheck;
+
+import static com.google.common.truth.Truth.assertThat;
+import static org.mockito.Mockito.*;
+
+import com.google.common.util.concurrent.MoreExecutors;
+import com.google.gerrit.metrics.DisabledMetricMaker;
+import com.google.gerrit.server.config.SitePaths;
+import com.googlesource.gerrit.plugins.healthcheck.check.AbstractHealthCheck;
+import com.googlesource.gerrit.plugins.healthcheck.check.GitSpaceCheck;
+import java.io.File;
+import java.io.IOException;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import org.eclipse.jgit.lib.Config;
+import org.junit.After;
+import org.junit.Before;
+import org.junit.Test;
+
+public class GitSpaceCheckTest {
+  private File mockFile;
+  private Path tempSitePath;
+
+  private static Path createTempSitePath() throws IOException {
+    Path tmp = Files.createTempFile("gerrit_", "_site");
+    Files.deleteIfExists(tmp);
+    return tmp;
+  }
+
+  @Before
+  public void setUp() throws IOException {
+    mockFile = mock(File.class);
+    tempSitePath = createTempSitePath();
+  }
+
+  @After
+  public void tearDown() throws IOException {
+    if (tempSitePath != null && Files.exists(tempSitePath)) {
+      Files.delete(tempSitePath);
+    }
+  }
+
+  private GitSpaceCheck createGitSpaceCheck(String configContent) throws IOException {
+    HealthCheckConfig config = new HealthCheckConfig(configContent);
+    SitePaths sitePaths = new SitePaths(tempSitePath);
+    return new GitSpaceCheck(
+        new Config(),
+        sitePaths,
+        MoreExecutors.newDirectExecutorService(),
+        config,
+        new DisabledMetricMaker()) {
+      @Override
+      protected File getGitDirectory() {
+        return mockFile;
+      }
+    };
+  }
+
+  private GitSpaceCheck createGitSpaceCheck() throws IOException {
+    Config config = new Config();
+    config.setBoolean("healthcheck", "gitspace", "enabled", true);
+    return createGitSpaceCheck(config.toText());
+  }
+
+  @Test
+  public void shouldPassWhenUsableDiskAboveThreshold() throws Exception {
+    GitSpaceCheck gitSpaceCheck = createGitSpaceCheck();
+    when(mockFile.getTotalSpace()).thenReturn(100L);
+    when(mockFile.getUsableSpace()).thenReturn(20L);
+
+    assertThat(gitSpaceCheck.run().result()).isEqualTo(AbstractHealthCheck.Result.PASSED);
+  }
+
+  @Test
+  public void shouldFailWhenUsableDiskBelowThreshold() throws Exception {
+    GitSpaceCheck gitSpaceCheck = createGitSpaceCheck();
+    when(mockFile.getTotalSpace()).thenReturn(100L);
+    when(mockFile.getUsableSpace()).thenReturn(5L);
+
+    assertThat(gitSpaceCheck.run().result()).isEqualTo(AbstractHealthCheck.Result.FAILED);
+  }
+
+  @Test
+  public void shouldComplyWithNonDefaultThreshold() throws Exception {
+    Config config = new Config();
+    config.setBoolean("healthcheck", "gitspace", "enabled", true);
+    config.setInt("healthcheck", "gitspace", "minFreeDiskPercent", 50);
+    config.toText();
+
+    GitSpaceCheck gitSpaceCheck = createGitSpaceCheck(config.toText());
+
+    when(mockFile.getTotalSpace()).thenReturn(100L);
+    when(mockFile.getUsableSpace()).thenReturn(5L);
+    assertThat(gitSpaceCheck.run().result()).isEqualTo(AbstractHealthCheck.Result.FAILED);
+
+    when(mockFile.getUsableSpace()).thenReturn(60L);
+    assertThat(gitSpaceCheck.run().result()).isEqualTo(AbstractHealthCheck.Result.PASSED);
+  }
+
+  @Test
+  public void shouldFailWhenTotalSpaceIsZero() throws Exception {
+    GitSpaceCheck gitSpaceCheck = createGitSpaceCheck();
+    when(mockFile.getTotalSpace()).thenReturn(0L);
+
+    assertThat(gitSpaceCheck.run().result()).isEqualTo(AbstractHealthCheck.Result.FAILED);
+  }
+}