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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. It uses a bounded buffer to store logging events.

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 bounded buffer.

Refer to the results in `Logging` for the impact of using this appender.

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

Since:
  0.9.1
Author:
  Ceki Gülcü

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()`

Method Summary
`void` | `addAppender(Appender newAppender)` Add an 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.
`Enumeration` | `getAllAppenders()` Get all previously added appenders as an Enumeration.
`Appender` | `getAppender(String name)` Get an appender by name.
`int` | `getBufferSize()` Returns the current value of the BufferSize option.
`boolean` | `getLocationInfo()` Returns the current value of the LocationInfo option.
`boolean` | `isAttached(Appender appender)` Is the appender passed as parameter attached to this category?
`void` | `removeAllAppenders()` Remove all previously added appenders.
`void` | `removeAppender(Appender appender)` Remove the appender passed as parameter from the list of appenders.
`void` | `removeAppender(String name)` Remove the appender with the name passed as parameter from the list of appenders.
`boolean` | `requiresLayout()` The `AsyncAppender` does not require a layout.
`void` | `setBufferSize(int size)` The BufferSize option takes a non-negative integer value.
`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.

Constructor Detail

### AsyncAppender

    public AsyncAppender()

Method Detail

### addAppender

    public void addAppender(Appender newAppender)

  Description copied from interface: `AppenderAttachable`
  Add an appender.
  Specified by:
    `addAppender` in interface `AppenderAttachable`

### append

    public void append(LoggingEvent event)

  Description copied from class: `AppenderSkeleton`
  Subclasses of `AppenderSkeleton` should implement this method to perform actual logging. See also `AppenderSkeleton.doAppend` method.
  Overrides:
    `append` in class `AppenderSkeleton`

### close

    public void close()

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

### getAllAppenders

    public Enumeration getAllAppenders()

  Description copied from interface: `AppenderAttachable`
  Get all previously added appenders as an Enumeration.
  Specified by:
    `getAllAppenders` in interface `AppenderAttachable`

### getAppender

    public Appender getAppender(String name)

  Description copied from interface: `AppenderAttachable`
  Get an appender by name.
  Specified by:
    `getAppender` in interface `AppenderAttachable`

### getLocationInfo

    public boolean getLocationInfo()

  Returns the current value of the LocationInfo option.

### isAttached

    public boolean isAttached(Appender appender)

  Is the appender passed as parameter attached to this category?
  Specified by:
    `isAttached` in interface `AppenderAttachable`

### requiresLayout

    public boolean requiresLayout()

  The `AsyncAppender` does not require a layout. Hence, this method always returns `false`.

### removeAllAppenders

    public void removeAllAppenders()

  Description copied from interface: `AppenderAttachable`
  Remove all previously added appenders.
  Specified by:
    `removeAllAppenders` in interface `AppenderAttachable`

### removeAppender

    public void removeAppender(Appender appender)

  Description copied from interface: `AppenderAttachable`
  Remove the appender passed as parameter from the list of appenders.
  Specified by:
    `removeAppender` in interface `AppenderAttachable`

### removeAppender

    public void removeAppender(String name)

  Description copied from interface: `AppenderAttachable`
  Remove the appender with the name passed as parameter from the list of appenders.
  Specified by:
    `removeAppender` in interface `AppenderAttachable`

### 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.

### setBufferSize

    public void setBufferSize(int size)

  The BufferSize option takes a non-negative integer value. This integer value determines the maximum size of the bounded buffer. Increasing the size of the buffer is always safe. However, if an existing buffer holds unwritten elements, then decreasing the buffer size will result in event loss. Nevertheless, while script configuring the AsyncAppender, it is safe to set a buffer size smaller than the `default buffer size` because configurators guarantee that an appender cannot be used before being completely configured.

### getBufferSize

    public int getBufferSize()

  Returns the current value of the BufferSize option.

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