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{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"NullPointerException in NASBackupProvider.syncBackupStorageStats when no KVM host is in \"Up\" state","articleBody":"### problem\n\n`NASBackupProvider.syncBackupStorageStats()` crashes with a `NullPointerException` when `ResourceManager.findOneRandomRunningHostByHypervisor()` returns `null`. This happens when no KVM host in the zone has `status=Up` at the exact moment the `BackupSyncTask` runs (e.g., during management server startup, brief agent disconnections, or host state\n  transitions).\n\n  The NPE kills the entire `BackupSyncTask` background job every sync interval (default 300s), flooding the management server log with stack traces and preventing backup storage stats from being updated.\n\n  ## Stack Trace\n\n  ERROR [o.a.c.b.B.BackupSyncTask] Error trying to run backup-sync background task due to:\n  [Cannot invoke \"com.cloud.host.Host.getId()\" because \"host\" is null].\n  java.lang.NullPointerException: Cannot invoke \"com.cloud.host.Host.getId()\" because \"host\" is null\n      at org.apache.cloudstack.backup.NASBackupProvider.syncBackupStorageStats(NASBackupProvider.java:544)\n      at org.apache.cloudstack.backup.BackupManagerImpl$BackupSyncTask.runInContext(BackupManagerImpl.java:1947)\n\n  ## Affected Code\n\n  File: plugins/backup/nas/src/main/java/org/apache/cloudstack/backup/NASBackupProvider.java`\n\n  java\n  @Override\n  public void syncBackupStorageStats(Long zoneId) {\n      final List\u003cBackupRepository\u003e repositories = backupRepositoryDao.listByZoneAndProvider(zoneId, getName());\n      final Host host = resourceManager.findOneRandomRunningHostByHypervisor(Hypervisor.HypervisorType.KVM, zoneId);\n      // host can be null here, but no null check before using it:\n      for (final BackupRepository repository : repositories) {\n          ...\n          answer = (BackupStorageStatsAnswer) agentManager.send(host.getId(), command); // NPE\n          ...\n      }\n  }\n\n  findOneRandomRunningHostByHypervisor in ResourceManagerImpl returns null when no matching host is found:\n\n  if (CollectionUtils.isEmpty(hosts)) {\n      return null;\n  }\n\n  The same pattern also exists in deleteBackup() (line ~450) where the host can be null when the VM is removed and no running KVM host is available.\n\n  Suggested Fix\n\n  Add a null check after findOneRandomRunningHostByHypervisor, log a warning, and return early:\n\n  @Override\n  public void syncBackupStorageStats(Long zoneId) {\n      final List\u003cBackupRepository\u003e repositories = backupRepositoryDao.listByZoneAndProvider(zoneId, getName());\n      if (repositories.isEmpty()) {\n          return;\n      }\n      final Host host = resourceManager.findOneRandomRunningHostByHypervisor(Hypervisor.HypervisorType.KVM, zoneId);\n      if (host == null) {\n          logger.warn(\"Unable to find a running KVM host in zone {} to sync backup storage stats\", zoneId);\n          return;\n      }\n      for (final BackupRepository repository : repositories) {\n          ...\n      }\n  }\n\n  And similarly for deleteBackup():\n\n  Host host = vm != null ? getVMHypervisorHost(vm) :\n      resourceManager.findOneRandomRunningHostByHypervisor(HypervisorType.KVM, Long.valueOf(backup.getZoneId()));\n  if (host == null) {\n      throw new CloudRuntimeException(\"Unable to find a running KVM host to process backup deletion\");\n  }\n\n  Environment\n\n  - CloudStack version: 4.22.0.0\n  - Hypervisor: KVM\n  - Backup provider: NAS (NFS)\n  - OS: Ubuntu 24.04, Java 21\n\n  How to Reproduce\n\n  1. Configure NAS backup provider with an NFS backup repository\n  2. Assign backup offerings to VMs\n  3. Restart cloudstack-management (or wait for a transient host disconnect)\n  4. Observe management-server.log — the NPE fires every backup.framework.sync.interval seconds\n\n  Impact\n\n  - BackupSyncTask fails completely on every cycle, backup storage capacity stats are never updated\n  - Log spam (one full stack trace every 5 minutes)\n  - No data loss, but backup monitoring/reporting is degraded\n\n\n\n### versions\n\nThe versions of ACS, hypervisors, storage, network etc..\n\n### The steps to reproduce the bug\n\n1.\n2.\n3.\n...\n\n\n### What to do about it?\n\n_No response_","author":{"url":"https://github.com/jmsperu","@type":"Person","name":"jmsperu"},"datePublished":"2026-02-21T19:46:43.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":3},"url":"https://github.com/12679/cloudstack/issues/12679"}