通常一个SnapshotRepository仓库对象对应一个DocumentSnapshotRepositoryMonitor监视器对象,同时也对应一个快照存储器对象,它们的关联是通过监视器管理对象DocumentSnapshotRepositoryMonitorManagerImpl实现的

DocumentSnapshotRepositoryMonitorManagerImpl类要实现那些行为,先查看其实现接口DocumentSnapshotRepositoryMonitorManager定义的方法规范

/**
* Management interface to {@link DocumentSnapshotRepositoryMonitor} threads.
*
* @since 2.8
*/
public interface DocumentSnapshotRepositoryMonitorManager {
/**
* Ensures all monitor threads are running.
*
* @param checkpoint for the last completed document or null if none have
* been completed.
* @throws RepositoryException
*/
void start(String checkpoint) throws RepositoryException; /**
* Stops all the configured {@link DocumentSnapshotRepositoryMonitor} threads.
*/
void stop(); /**
* Removes persisted state for {@link DocumentSnapshotRepositoryMonitor}
* threads. After calling this {@link DocumentSnapshotRepositoryMonitor}
* threads will no longer be able to resume from where they left off last
* time.
*/
void clean(); /**
* Returns the number of {@link DocumentSnapshotRepositoryMonitor} threads
* that are alive. This method is for testing purposes.
*/
int getThreadCount(); /**
* Returns the {@link CheckpointAndChangeQueue} for this
* {@link DocumentSnapshotRepositoryMonitorManager}
*/
CheckpointAndChangeQueue getCheckpointAndChangeQueue(); /** Returns whether we are after a start() call and before a stop(). */
boolean isRunning(); /**
* Receives information specifying what is guaranteed to be delivered to GSA.
* Every entry in passed in Map is a monitor name and MonitorCheckpoint.
* The monitor of that name can expect that all documents before and including
* document related with MonitorCheckpoint will be delivered to GSA.
* This information is for the convenience and efficiency of the Monitor so
* that it knows how many changes it has to resend. It's valid for a monitor
* to ignore these updates if it feels like it for some good reason.
* FileConnectorSystemMonitor instances use this information to trim their
* file system snapshots.
*/
void acceptGuarantees(Map<String, MonitorCheckpoint> guarantees); /**
* Receives {@link TraversalSchedule} from TraversalManager which is
* {@link TraversalScheduleAware}.
*/
void setTraversalSchedule(TraversalSchedule traversalSchedule);
}

然后再来看DocumentSnapshotRepositoryMonitorManagerImpl类怎么实现上述接口中定义的行为

先来了解相关属性及如何初始化它们的

private volatile TraversalSchedule traversalSchedule;

//监控器线程
private final List<Thread> threads =
Collections.synchronizedList(new ArrayList<Thread>());
//监控器映射容器
private final Map<String, DocumentSnapshotRepositoryMonitor> fileSystemMonitorsByName =
Collections.synchronizedMap(new HashMap<String, DocumentSnapshotRepositoryMonitor>());
private boolean isRunning = false; // Monitor threads start in off state.
private final List<? extends SnapshotRepository<? extends DocumentSnapshot>>
repositories; private final File snapshotDir;
private final ChecksumGenerator checksumGenerator;
//CheckpointAndChange对象容器(List)
private final CheckpointAndChangeQueue checkpointAndChangeQueue;
//Change对象容器(阻塞队列)
private final ChangeQueue changeQueue; private final DocumentSnapshotFactory documentSnapshotFactory; /**
* Constructs {@link DocumentSnapshotRepositoryMonitorManagerImpl}
* for the {@link DiffingConnector}.
*
* @param repositories a {@code List} of {@link SnapshotRepository
* SnapshotRepositorys}
* @param documentSnapshotFactory a {@link DocumentSnapshotFactory}
* @param snapshotDir directory to store {@link SnapshotRepository}
* @param checksumGenerator a {@link ChecksumGenerator} used to
* detect changes in a document's content
* @param changeQueue a {@link ChangeQueue}
* @param checkpointAndChangeQueue a
* {@link CheckpointAndChangeQueue}
*/
public DocumentSnapshotRepositoryMonitorManagerImpl(
List<? extends SnapshotRepository<
? extends DocumentSnapshot>> repositories,
DocumentSnapshotFactory documentSnapshotFactory,
File snapshotDir, ChecksumGenerator checksumGenerator,
ChangeQueue changeQueue,
CheckpointAndChangeQueue checkpointAndChangeQueue) {
this.repositories = repositories;
this.documentSnapshotFactory = documentSnapshotFactory;
this.snapshotDir = snapshotDir;
this.checksumGenerator = checksumGenerator;
this.changeQueue = changeQueue;
this.checkpointAndChangeQueue = checkpointAndChangeQueue;
}

下面我们再来看它的start方法,在该方法中,主要动作为分别为调用checkpointAndChangeQueue对象的start方法,初始化各个仓库对象相关联的快照存储对象SnapshotStore,最后是启动各个仓库对象的监控器实例

/**
* 启动方法
*/
/** Go from "cold" to "warm" including CheckpointAndChangeQueue. */
public void start(String connectorManagerCheckpoint)
throws RepositoryException { try {
//启动 获取Change(主要动作:从json格式队列文件加载monitorPoints和checkpointAndChangeList队列)
checkpointAndChangeQueue.start(connectorManagerCheckpoint);
} catch (IOException e) {
throw new RepositoryException("Failed starting CheckpointAndChangeQueue.",
e);
}
//MonitorCheckpoint容器
Map<String, MonitorCheckpoint> monitorPoints
= checkpointAndChangeQueue.getMonitorRestartPoints(); Map<String, SnapshotStore> snapshotStores = null; //加载monitorName与SnapshotStore映射容器
try {
snapshotStores =
recoverSnapshotStores(connectorManagerCheckpoint, monitorPoints); } catch (SnapshotStoreException e) {
throw new RepositoryException("Snapshot recovery failed.", e);
} catch (IOException e) {
throw new RepositoryException("Snapshot recovery failed.", e);
} catch (InterruptedException e) {
throw new RepositoryException("Snapshot recovery interrupted.", e);
} //启动监控线程
startMonitorThreads(snapshotStores, monitorPoints); isRunning = true;
}

在初始化每个仓库对象的快照存储对象SnapshotStore时,同时传入相关联的MonitorCheckPoint对象实例,必要时修复快照文件

 /* For each start path gets its monitor recovery files in state were monitor
* can be started. */
/**
* 加载monitorName与SnapshotStore映射容器
* @param connectorManagerCheckpoint
* @param monitorPoints
* @return
* @throws IOException
* @throws SnapshotStoreException
* @throws InterruptedException
*/
private Map<String, SnapshotStore> recoverSnapshotStores(
String connectorManagerCheckpoint, Map<String,
MonitorCheckpoint> monitorPoints)
throws IOException, SnapshotStoreException, InterruptedException {
Map<String, SnapshotStore> snapshotStores =
new HashMap<String, SnapshotStore>();
for (SnapshotRepository<? extends DocumentSnapshot> repository
: repositories) {
String monitorName = makeMonitorNameFromStartPath(repository.getName());
File dir = new File(snapshotDir, monitorName); boolean startEmpty = (connectorManagerCheckpoint == null)
|| (!monitorPoints.containsKey(monitorName));
if (startEmpty) {
LOG.info("Deleting " + repository.getName()
+ " global checkpoint=" + connectorManagerCheckpoint
+ " monitor checkpoint=" + monitorPoints.get(monitorName));
//删除该快照目录
delete(dir);
} else {
//修复该快照目录
SnapshotStore.stitch(dir, monitorPoints.get(monitorName),
documentSnapshotFactory);
} SnapshotStore snapshotStore = new SnapshotStore(dir,
documentSnapshotFactory); snapshotStores.put(monitorName, snapshotStore);
}
return snapshotStores;
}

下面继续跟踪启动监控器线程的方法

 /**
* 启动监控线程(貌似MonitorCheckpoint与SnapshotStore与monitor有映射关系)
* Creates a {@link DocumentSnapshotRepositoryMonitor} thread for each
* startPath.
*
* @throws RepositoryDocumentException if any of the threads cannot be
* started.
*/
private void startMonitorThreads(Map<String, SnapshotStore> snapshotStores,
Map<String, MonitorCheckpoint> monitorPoints)
throws RepositoryDocumentException { for (SnapshotRepository<? extends DocumentSnapshot> repository
: repositories) {
String monitorName = makeMonitorNameFromStartPath(repository.getName());
//monitorName snapshotStores映射
//快照存储器(读写器)
SnapshotStore snapshotStore = snapshotStores.get(monitorName);
//创建监控线程
Thread monitorThread = newMonitorThread(repository, snapshotStore,
monitorPoints.get(monitorName));
threads.add(monitorThread); LOG.info("starting monitor for <" + repository.getName() + ">");
monitorThread.setName(repository.getName());
monitorThread.setDaemon(true);
monitorThread.start();
}
}

监控器对象的创建在下面的方法

/**
* 创建监控线程
* Creates a {@link DocumentSnapshotRepositoryMonitor} thread for the provided
* folder.
*
* @throws RepositoryDocumentException if {@code startPath} is not readable,
* or if there is any problem reading or writing snapshots.
*/
private Thread newMonitorThread(
SnapshotRepository<? extends DocumentSnapshot> repository,
SnapshotStore snapshotStore, MonitorCheckpoint startCp)
throws RepositoryDocumentException {
//注意monitorName
String monitorName = makeMonitorNameFromStartPath(repository.getName());
//document在监控线程里面处理
DocumentSnapshotRepositoryMonitor monitor =
new DocumentSnapshotRepositoryMonitor(monitorName, repository,
snapshotStore, changeQueue.newCallback(), DOCUMENT_SINK, startCp,
documentSnapshotFactory);
monitor.setTraversalSchedule(traversalSchedule);
LOG.fine("Adding a new monitor for " + monitorName + ": " + monitor);
fileSystemMonitorsByName.put(monitorName, monitor);
return new Thread(monitor);
}

stop方法实现监控器线程的停止

/**
* 停止监控器
*/
private void flagAllMonitorsToStop() {
for (SnapshotRepository<? extends DocumentSnapshot> repository
: repositories) {
String monitorName = makeMonitorNameFromStartPath(repository.getName());
DocumentSnapshotRepositoryMonitor
monitor = fileSystemMonitorsByName.get(monitorName);
if (null != monitor) {
monitor.shutdown();
}
else {
LOG.fine("Unable to stop non existent monitor thread for "
+ monitorName);
}
}
}
/**
* 停止监控器线程
*/
/* @Override */
public synchronized void stop() {
for (Thread thread : threads) {
thread.interrupt();
}
for (Thread thread : threads) {
try {
thread.join(MAX_SHUTDOWN_MS);
if (thread.isAlive()) {
LOG.warning("failed to stop background thread: " + thread.getName());
}
} catch (InterruptedException e) {
// Mark this thread as interrupted so it can be dealt with later.
Thread.currentThread().interrupt();
}
}
threads.clear(); /* in case thread.interrupt doesn't stop monitors */
flagAllMonitorsToStop(); fileSystemMonitorsByName.clear();
changeQueue.clear();
this.isRunning = false;
}

在flagAllMonitorsToStop()方法中调用监控器对象的monitor.shutdown()方法,设置监控器对象 的标识属性

 /* The monitor should exit voluntarily if set to false */
private volatile boolean isRunning = true;

---------------------------------------------------------------------------

本系列企业搜索引擎开发之连接器connector系本人原创

转载请注明出处 博客园 刺猬的温驯

本人邮箱: chenying998179@163#com (#改为.)

本文链接 http://www.cnblogs.com/chenying99/p/3789613.html

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