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## org.apache.log4j
Class AsyncAppender

    java.lang.Object
      org.apache.log4j.AppenderSkeleton
          org.apache.log4j.AsyncAppender

All Implemented Interfaces:
  Appender, AppenderAttachable, OptionHandler

    public class AsyncAppender

extends AppenderSkeleton
implements AppenderAttachable

The AsyncAppender lets users log events asynchronously.

The AsyncAppender will collect the events sent to it and then dispatch them to all the appenders that are attached to it. You can attach multiple appenders to an AsyncAppender.

The AsyncAppender uses a separate thread to serve the events in its buffer.

Important note: The `AsyncAppender` can only be script configured using the `DOMConfigurator`.

Since:
  0.9.1
Author:
  Ceki Gülcü, Curt Arnold

Field Summary
`static int` | `DEFAULT_BUFFER_SIZE` The default buffer size is set to 128 events.

Fields inherited from class org.apache.log4j.AppenderSkeleton
`closed, errorHandler, headFilter, layout, name, tailFilter, threshold`

Constructor Summary
`AsyncAppender()` Create new instance.

Method Summary
`void` | `addAppender(Appender newAppender)` Add appender.
`void` | `append(LoggingEvent event)` Subclasses of `AppenderSkeleton` should implement this method to perform actual logging.
`void` | `close()` Close this `AsyncAppender` by interrupting the dispatcher thread which will process all pending events before exiting.
`java.util.Enumeration` | `getAllAppenders()` Get iterator over attached appenders.
`Appender` | `getAppender(java.lang.String name)` Get appender by name.
`boolean` | `getBlocking()` Gets whether appender should block calling thread when buffer is full.
`int` | `getBufferSize()` Gets the current buffer size.
`boolean` | `getLocationInfo()` Gets whether the location of the logging request call should be captured.
`boolean` | `isAttached(Appender appender)` Determines if specified appender is attached.
`void` | `removeAllAppenders()` Removes and closes all attached appenders.
`void` | `removeAppender(Appender appender)` Removes an appender.
`void` | `removeAppender(java.lang.String name)` Remove appender by name.
`boolean` | `requiresLayout()` Configurators call this method to determine if the appender requires a layout.
`void` | `setBlocking(boolean value)` Sets whether appender should wait if there is no space available in the event buffer or immediately return.
`void` | `setBufferSize(int size)` Sets the number of messages allowed in the event buffer before the calling thread is blocked (if blocking is true) or until messages are summarized and discarded.
`void` | `setLocationInfo(boolean flag)` The LocationInfo option takes a boolean value.

Methods inherited from class org.apache.log4j.AppenderSkeleton
`activateOptions, addFilter, clearFilters, doAppend, finalize, getErrorHandler, getFilter, getFirstFilter, getLayout, getName, getThreshold, isAsSevereAsThreshold, setErrorHandler, setLayout, setName, setThreshold`

Methods inherited from class java.lang.Object
`clone, equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait`

Field Detail

### DEFAULT_BUFFER_SIZE

    public static final int DEFAULT_BUFFER_SIZE

  The default buffer size is set to 128 events.

  See Also:
    Constant Field Values

Constructor Detail

### AsyncAppender

    public AsyncAppender()

  Create new instance.

Method Detail

### addAppender

    public void addAppender(Appender newAppender)

  Add appender.

  Specified by:
    `addAppender` in interface `AppenderAttachable`
  Parameters:
    `newAppender` - appender to add, may not be null.

### append

    public void append(LoggingEvent event)

  Subclasses of `AppenderSkeleton` should implement this method to perform actual logging. See also `AppenderSkeleton.doAppend` method.

  Specified by:
    `append` in class `AppenderSkeleton`

### close

    public void close()

  Close this `AsyncAppender` by interrupting the dispatcher thread which will process all pending events before exiting.

  Specified by:
    `close` in interface `Appender`

### getAllAppenders

    public java.util.Enumeration getAllAppenders()

  Get iterator over attached appenders.

  Specified by:
    `getAllAppenders` in interface `AppenderAttachable`
  Returns:
    iterator or null if no attached appenders.

### getAppender

    public Appender getAppender(java.lang.String name)

  Get appender by name.

  Specified by:
    `getAppender` in interface `AppenderAttachable`
  Parameters:
    `name` - name, may not be null.
  Returns:
    matching appender or null.

### getLocationInfo

    public boolean getLocationInfo()

  Gets whether the location of the logging request call should be captured.

  Returns:
    the current value of the LocationInfo option.

### isAttached

    public boolean isAttached(Appender appender)

  Determines if specified appender is attached.

  Specified by:
    `isAttached` in interface `AppenderAttachable`
  Parameters:
    `appender` - appender.
  Returns:
    true if attached.

### requiresLayout

    public boolean requiresLayout()

  Configurators call this method to determine if the appender requires a layout. If this method returns `true`, meaning that layout is required, then the configurator will configure an layout using the configuration information at its disposal. If this method returns `false`, meaning that a layout is not required, then layout configuration will be skipped even if there is available layout configuration information at the disposal of the configurator..

  In the rather exceptional case, where the appender implementation admits a layout but can also work without it, then the appender should return `true`.

  Specified by:
    `requiresLayout` in interface `Appender`

### removeAllAppenders

    public void removeAllAppenders()

  Removes and closes all attached appenders.

  Specified by:
    `removeAllAppenders` in interface `AppenderAttachable`

### removeAppender

    public void removeAppender(Appender appender)

  Removes an appender.

  Specified by:
    `removeAppender` in interface `AppenderAttachable`
  Parameters:
    `appender` - appender to remove.

### removeAppender

    public void removeAppender(java.lang.String name)

  Remove appender by name.

  Specified by:
    `removeAppender` in interface `AppenderAttachable`
  Parameters:
    `name` - name.

### setLocationInfo

    public void setLocationInfo(boolean flag)

  The LocationInfo option takes a boolean value. By default, it is set to false which means there will be no effort to extract the location information related to the event. As a result, the event that will be ultimately logged will likely to contain the wrong location information (if present in the log format).

  Location information extraction is comparatively very slow and should be avoided unless performance is not a concern.

  Parameters:
    `flag` - true if location information should be extracted.

### setBufferSize

    public void setBufferSize(int size)

  Sets the number of messages allowed in the event buffer before the calling thread is blocked (if blocking is true) or until messages are summarized and discarded. Changing the size will not affect messages already in the buffer.

  Parameters:
    `size` - buffer size, must be positive.

### getBufferSize

    public int getBufferSize()

  Gets the current buffer size.

  Returns:
    the current value of the BufferSize option.

### setBlocking

    public void setBlocking(boolean value)

  Sets whether appender should wait if there is no space available in the event buffer or immediately return.

  Parameters:
    `value` - true if appender should wait until available space in buffer.

### getBlocking

    public boolean getBlocking()

  Gets whether appender should block calling thread when buffer is full. If false, messages will be counted by logger and a summary message appended after the contents of the buffer have been appended.

  Returns:
    true if calling thread will be blocked when buffer is full.

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