Class AbstractFileWatchingService
- All Implemented Interfaces:
Closeable,AutoCloseable,LifecycleComponent,Releasable
- Direct Known Subclasses:
MasterNodeFileWatchingService
A file watching service watches for changes in a particular file on disk. There are three assumptions about the file structure:
- The file itself may or may not exist.
- The file's parent directory may or may not exist.
- 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.
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Field Summary
Fields inherited from class org.elasticsearch.common.component.AbstractLifecycleComponent
lifecycle -
Constructor Summary
Constructors -
Method Summary
Modifier and TypeMethodDescriptionfinal voidaddFileChangedListener(FileChangedListener listener) protected final voiddoClose()Close this component.protected voiddoStart()Start this component.protected voiddoStop()Stop this component.protected abstract booleanfilesExists(Path path) protected abstract booleanfilesIsDirectory(Path path) protected abstract InputStreamfilesNewInputStream(Path path) protected abstract <A extends BasicFileAttributes>
AfilesReadAttributes(Path path, Class<A> clazz) protected abstract PathfilesSetLastModifiedTime(Path path, FileTime time) protected abstract voidAny implementation of this class must implement this method in order to define what happens once the watched file changes.protected voidDefaults to genericprocessFileChanges()behavior.protected abstract voidprotected final voidprotected final voidfinal Pathfinal Pathprotected final voidfinal booleanwatching()Methods inherited from class org.elasticsearch.common.component.AbstractLifecycleComponent
addLifecycleListener, close, lifecycleState, start, stop
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Constructor Details
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AbstractFileWatchingService
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Method Details
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processFileChanges
protected abstract void processFileChanges() throws InterruptedException, ExecutionException, IOExceptionAny 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 itselfExecutionException- if there is an issue while applying the changes from the fileInterruptedException- if the file processing is interrupted by another thread.
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processInitialFileMissing
protected abstract void processInitialFileMissing() throws InterruptedException, ExecutionException, IOException -
processFileOnServiceStart
protected void processFileOnServiceStart() throws IOException, ExecutionException, InterruptedExceptionDefaults to genericprocessFileChanges()behavior. An implementation can override this to define different file handling when the file is processed during initial service start. -
addFileChangedListener
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watchedFileDir
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watchedFile
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doStart
protected void doStart()Description copied from class:AbstractLifecycleComponentStart 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:
doStartin classAbstractLifecycleComponent
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doStop
protected void doStop()Description copied from class:AbstractLifecycleComponentStop this component. Typically that means doing the reverse of whateverAbstractLifecycleComponent.doStart()does.This method is called while synchronized on
AbstractLifecycleComponent.lifecycle. It is only called once in the lifetime of a component, after callingAbstractLifecycleComponent.doStart(), although it will not be called at all if this component did not successfully start.- Specified by:
doStopin classAbstractLifecycleComponent
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doClose
protected final void doClose()Description copied from class:AbstractLifecycleComponentClose 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:
doClosein classAbstractLifecycleComponent
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watching
public final boolean watching() -
startWatcher
protected final void startWatcher() -
watcherThread
protected final void watcherThread() -
stopWatcher
protected final void stopWatcher() -
filesExists
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filesIsDirectory
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filesReadAttributes
protected abstract <A extends BasicFileAttributes> A filesReadAttributes(Path path, Class<A> clazz) throws IOException - Throws:
IOException
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filesList
- Throws:
IOException
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filesSetLastModifiedTime
- Throws:
IOException
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filesNewInputStream
- Throws:
IOException
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