Module org.elasticsearch.server

Package org.elasticsearch.common.file

Class AbstractFileWatchingService

java.lang.Object

org.elasticsearch.common.component.AbstractLifecycleComponent

org.elasticsearch.common.file.AbstractFileWatchingService

All Implemented Interfaces:

Closeable, AutoCloseable, LifecycleComponent, Releasable

Direct Known Subclasses:

MasterNodeFileWatchingService

public abstract class AbstractFileWatchingService
extends AbstractLifecycleComponent

A skeleton service for watching and reacting to a single file changing on disk

A file watching service watches for changes in a particular file on disk. There are three assumptions about the file structure:

1. The file itself may or may not exist.
2. The file's parent directory may or may not exist.
3. The directory above the file's parent directory must always exist.

For example, if the watched file is under /usr/elastic/elasticsearch/conf/special/settings.yml, then /usr/elastic/elasticsearch/conf/ must exist, but special/ and special/settings.yml may be created, updated, or deleted during runtime.

What this class does not do is define what should happen after the file changes. An implementation class should override processFileChanges() to define the correct behavior.

Field Summary

Fields inherited from class org.elasticsearch.common.component.AbstractLifecycleComponent

lifecycle

Constructor Summary

Constructors

Constructor	Description
AbstractFileWatchingService(Path watchedFile)

Method Summary

Modifier and Type	Method	Description
final void	addFileChangedListener(FileChangedListener listener)
protected final void	doClose()	Close this component.
protected void	doStart()	Start this component.
protected void	doStop()	Stop this component.
protected abstract boolean	filesExists(Path path)
protected abstract boolean	filesIsDirectory(Path path)
protected abstract Stream<Path>	filesList(Path dir)
protected abstract InputStream	filesNewInputStream(Path path)
protected abstract <A extends BasicFileAttributes> A	filesReadAttributes(Path path, Class<A> clazz)
protected abstract Path	filesSetLastModifiedTime(Path path, FileTime time)
protected void	onProcessFileChangesException(Exception e)	Called for checked exceptions only.
protected abstract void	processFileChanges()	Any implementation of this class must implement this method in order to define what happens once the watched file changes.
protected void	processFileOnServiceStart()	Defaults to generic processFileChanges() behavior.
protected abstract void	processInitialFileMissing()
protected final void	startWatcher()
protected final void	stopWatcher()
final Path	watchedFile()
final Path	watchedFileDir()
protected final void	watcherThread()
final boolean	watching()

Methods inherited from class org.elasticsearch.common.component.AbstractLifecycleComponent

addLifecycleListener, close, lifecycleState, start, stop

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Details

AbstractFileWatchingService

public AbstractFileWatchingService(Path watchedFile)

Method Details

processFileChanges

protected abstract void processFileChanges()
                                    throws InterruptedException,
ExecutionException,
IOException

Any implementation of this class must implement this method in order to define what happens once the watched file changes.

Throws:

IOException - if there is an error reading the file itself

ExecutionException - if there is an issue while applying the changes from the file

InterruptedException - if the file processing is interrupted by another thread.

processInitialFileMissing

protected abstract void processInitialFileMissing()
                                           throws InterruptedException,
ExecutionException,
IOException

Throws:

InterruptedException

ExecutionException

IOException

processFileOnServiceStart

protected void processFileOnServiceStart()
                                  throws IOException,
ExecutionException,
InterruptedException

Defaults to generic processFileChanges() behavior. An implementation can override this to define different file handling when the file is processed during initial service start.

Throws:

IOException

ExecutionException

InterruptedException

addFileChangedListener

public final void addFileChangedListener(FileChangedListener listener)

watchedFileDir

public final Path watchedFileDir()

watchedFile

public final Path watchedFile()

doStart

protected void doStart()

Description copied from class: AbstractLifecycleComponent

Start this component. Typically that means doing things like launching background processes and registering listeners on other components. Other components have been initialized by this point, but may not yet be started.

If this method throws an exception then the startup process will fail, but this component will not be stopped before it is closed.

This method is called while synchronized on AbstractLifecycleComponent.lifecycle. It is only called once in the lifetime of a component, although it may not be called at all if the startup process encountered some kind of fatal error, such as the failure of some other component to initialize or start.

Specified by:

doStart in class AbstractLifecycleComponent

doStop

protected void doStop()

Description copied from class: AbstractLifecycleComponent

Stop this component. Typically that means doing the reverse of whatever AbstractLifecycleComponent.doStart() does.

This method is called while synchronized on AbstractLifecycleComponent.lifecycle. It is only called once in the lifetime of a component, after calling AbstractLifecycleComponent.doStart(), although it will not be called at all if this component did not successfully start.

Specified by:

doStop in class AbstractLifecycleComponent

doClose

protected final void doClose()

Description copied from class: AbstractLifecycleComponent

Close this component. Typically that means doing the reverse of whatever happened during initialization, such as releasing resources acquired there.

This method is called while synchronized on AbstractLifecycleComponent.lifecycle. It is called once in the lifetime of a component. If the component was started then it will be stopped before it is closed, and once it is closed it will not be started or stopped.

Specified by:

doClose in class AbstractLifecycleComponent

watching

public final boolean watching()

startWatcher

protected final void startWatcher()

watcherThread

protected final void watcherThread()

stopWatcher

protected final void stopWatcher()

onProcessFileChangesException

protected void onProcessFileChangesException(Exception e)

Called for checked exceptions only.

filesExists

protected abstract boolean filesExists(Path path)

filesIsDirectory

protected abstract boolean filesIsDirectory(Path path)

filesReadAttributes

protected abstract <A extends BasicFileAttributes>
A filesReadAttributes(Path path,
 Class<A> clazz)
               throws IOException

Throws:

IOException

filesList

protected abstract Stream<Path> filesList(Path dir)
                                   throws IOException

Throws:

IOException

filesSetLastModifiedTime

protected abstract Path filesSetLastModifiedTime(Path path,
 FileTime time)
                                          throws IOException

Throws:

IOException

filesNewInputStream

protected abstract InputStream filesNewInputStream(Path path)
                                            throws IOException

Throws:

IOException