fix: detect abnormal exit via sentinel for filename index

[Johnson-zs]

fix: detect abnormal exit via sentinel for filename index

1. Root cause: when the index service is killed by SIGKILL, crash,
   or OOM while in Clean state with no running tasks, cleanup() is
   never called and the state remains Clean — on restart no recovery
   is triggered, silently losing all file changes during the downtime
2. Fix: create a sentinel file at startup in the index directory and
   remove it during normal cleanup(); if the sentinel persists across
   a restart, the previous exit was abnormal, so mark state Dirty to
   trigger a compensating full Update via the existing recovery path
3. Impact: only FileNameIndexDBus is affected; TextIndex and OcrIndex
   are unchanged per the requirement that only filename index needs
   full completeness guarantees

Influence:

1. Test normal service restart — sentinel file should be removed and
   no false Dirty state on next startup
2. Test SIGKILL during Clean idle state — sentinel persists, restart
   triggers full Update covering all missed file changes
3. Verify no regression on existing Dirty state recovery path

fix: 通过哨兵文件检测文件名索引服务异常退出

1. 根因：索引服务在 Clean 空闲状态下被 SIGKILL、崩溃或 OOM 杀死时，
   cleanup() 未被调用，状态保持 Clean，重启后不触发恢复，退出期间的
   文件变更静默丢失
2. 方案：启动时在索引目录创建哨兵文件，正常退出时删除；若重启时哨兵
   文件仍在，说明上次异常退出，标记 Dirty 状态触发已有恢复路径的
   全量 Update 补偿丢失的文件变更
3. 影响：仅修改 FileNameIndexDBus，TextIndex 和 OcrIndex 不变，符合
   仅文件名索引需要完整性保证的需求

Influence:

1. 测试正常重启场景——哨兵文件应被删除，下次启动不误触发 Dirty
2. 测试 Clean 空闲状态下 SIGKILL——哨兵文件残留，重启触发全量 Update
3. 验证已有 Dirty 状态恢复路径无回归

Summary by Sourcery

Detect abnormal filename-index shutdowns and trigger full recovery while making D-Bus service registration failures explicit and safe.

New Features:

• Add abnormal-exit detection for the filename index using a startup sentinel that triggers recovery after an unclean shutdown.

Bug Fixes:

• Prevent file changes from being missed when the filename index service is killed or crashes while idle and clean.
• Make index service startup fail cleanly when any required D-Bus service cannot be registered.

Enhancements:

• Ensure failed D-Bus registration rolls back previously registered services and improve registration result handling.

Tests:

• Update registration tests to accept either successful registration or the expected failure result without crashing.

[deepin-ci-robot]

[APPROVALNOTIFIER] This PR is NOT APPROVED

This pull-request has been approved by: Johnson-zs

The full list of commands accepted by this bot can be found here.

Details

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• debian/deepin/OWNERS

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[sourcery-ai]

Reviewer's Guide

FileNameIndexDBus now uses a running sentinel file to detect crashes, SIGKILL, or OOM while idle; a leftover sentinel marks the index Dirty and routes startup through the existing full-update recovery path, while normal cleanup removes it. TextIndex and OcrIndex are unchanged.

Sequence diagram for filename index abnormal-exit recovery

sequenceDiagram
    participant Service as FileNameIndexDBus
    participant FS as IndexDirectory
    participant State as StateStore
    participant Recovery as ExistingRecoveryPath

    Service->>FS: QFile::exists(sentinelPath)
    alt Sentinel remains from previous run
        Service->>State: setIndexState(Dirty)
    end
    Service->>FS: QDir::mkpath(indexDir)
    Service->>FS: QFile::open(WriteOnly)
    Service->>State: getIndexState()
    State-->>Service: Dirty
    Service->>Recovery: handleSilentStart()
    Recovery->>Recovery: Update()

    alt Normal cleanup
        Service->>FS: QFile::remove(sentinelPath)
    end

Loading

File-Level Changes

Change	Details	Files
Add a startup/shutdown sentinel to distinguish abnormal termination from normal cleanup and force filename-index recovery after an unclean exit.	Define a sentinel path under the configured index directory. Detect a leftover sentinel at startup and mark the index Dirty before existing recovery checks run. Create or recreate the sentinel for the current process and remove it during normal cleanup. Log failures to create or remove the sentinel without changing the existing recovery mechanism.	src/index/dbus/filenameindexdbus.cpp

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[sourcery-ai]

Hey - I've found 2 issues

Prompt for AI Agents

Please address the comments from this code review:

## Individual Comments

### Comment 1
<location path="src/index/dbus/filenameindexdbus.cpp" line_range="25-28" />
<code_context>
+// when the service starts, the previous run was killed without cleanup.
+inline constexpr char kSentinelFileName[] = ".filename_index_running";
+
+QString sentinelFilePath(const QString &indexDir)
+{
+    return indexDir + QLatin1Char('/') + QLatin1String(kSentinelFileName);
+}
+
 QStringList defaultPathsToProcess()
</code_context>
<issue_to_address>
**issue (bug_risk):** When `indexDir` is empty, `sentinelFilePath()` returns `/.filename_index_running`, which is non-empty. Startup therefore probes the filesystem root for the sentinel and cleanup attempts to remove that root-level path instead of skipping sentinel handling.

**Triggers:** When the filename index directory provider returns an empty path.

**Suggested fix:** Return an empty path from `sentinelFilePath()` when `indexDir` is empty, or guard the existence check with `!indexDir.isEmpty()` as is done for creation.

```suggestion
QString sentinelFilePath(const QString &indexDir)
{
    return indexDir.isEmpty() ? QString() : indexDir + QLatin1Char('/') + QLatin1String(kSentinelFileName);
}
```
</issue_to_address>

### Comment 2
<location path="src/index/dbus/filenameindexdbus.cpp" line_range="69-74" />
<code_context>
+        runtime->stateStore().setIndexState(IndexUtility::IndexState::Dirty);
+    }
+
+    // Create (or recreate) the sentinel file for this run.
+    if (!indexDir.isEmpty()) {
+        QDir().mkpath(indexDir);
+        QFile sentinel(sentinelPath);
+        if (sentinel.open(QIODevice::WriteOnly)) {
+            sentinel.close();
+        } else {
+            qWarning() << "FileNameIndexDBus: Failed to create sentinel file:" << sentinelPath;
</code_context>
<issue_to_address>
**issue (bug_risk):** Two filename-index service instances sharing the same index directory overwrite and remove one another's sentinel: the later startup truncates the shared file, and either instance's normal cleanup removes it while the other is still running. If the remaining instance is then killed, its abnormal exit leaves no sentinel and recovery is skipped.

**Triggers:** When a second service process starts before the first process has exited, including after DBus service registration fails but object construction continues.

**Suggested fix:** Use an ownership-specific/atomic lease sentinel, or refuse to construct the service when DBus name registration fails; cleanup must only remove a sentinel owned by the current process.
</issue_to_address>

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