Apache Log4cxx: log4cxx::AsyncAppender Class Reference (original) (raw)

The AsyncAppender decouples logging event creation from output by processing log events asynchronously. More...

#include <[asyncappender.h](asyncappender%5F8h%5Fsource.html)>

Public Member Functions
	AsyncAppender ()
	Create new instance.
virtual	~AsyncAppender ()
	Destructor.
void	addAppender (const AppenderPtr newAppender) override
	Ensure newAppender receives any logging event added to this appender.
void	doAppend (const spi::LoggingEventPtr &event, helpers::Pool &pool1) override
	This method performs threshold checks and invokes filters before delegating actual logging to the subclasses specific AppenderSkeleton::append method.
void	append (const spi::LoggingEventPtr &event, helpers::Pool &p) override
	Subclasses of AppenderSkeleton should implement this method to perform actual logging.
void	close () override
	Close this AsyncAppender by interrupting the dispatcher thread which will process all pending events before exiting.
AppenderList	getAllAppenders () const override
	Get iterator over attached appenders.
AppenderPtr	getAppender (const LogString &name) const override
	Get appender by name.
bool	getLocationInfo () const
	The current value of the (unused) LocationInfo option.
bool	isAttached (const AppenderPtr appender) const override
	Determines if specified appender is attached.
bool	requiresLayout () const override
	Configurators call this method to determine if the appender requires a layout.
void	removeAllAppenders () override
	Removes and closes all attached appenders.
void	removeAppender (const AppenderPtr appender) override
	Removes an appender.
void	removeAppender (const LogString &name) override
	Remove appender by name.
bool	replaceAppender (const AppenderPtr &oldAppender, const AppenderPtr &newAppender) LOG4CXX_16_VIRTUAL_SPECIFIER
	Replace oldAppender with newAppender.
void	replaceAppenders (const AppenderList &newList) LOG4CXX_16_VIRTUAL_SPECIFIER
	Replace any previously added appenders with newList.
void	setLocationInfo (bool flag)
	The LocationInfo attribute is provided for compatibility with log4j and has no effect on the log output.
void	setBufferSize (int size)
	The BufferSize option takes a non-negative integer value.
int	getBufferSize () const
	Gets the current buffer size.
void	setBlocking (bool value)
	Sets whether appender should wait if there is no space available in the event buffer or immediately return.
bool	getBlocking () const
	Gets whether appender should block calling thread when buffer is full.
void	setOption (const LogString &option, const LogString &value) override
	Set option to value.
Public Member Functions inherited from log4cxx::spi::AppenderAttachable
virtual void	addAppender (const AppenderPtr newAppender)=0
	Add an appender.
virtual AppenderList	getAllAppenders () const =0
	Get all previously added appenders as an AppenderList.
virtual AppenderPtr	getAppender (const LogString &name) const =0
	Get an appender by name.
virtual bool	isAttached (const AppenderPtr appender) const =0
	Returns true if the specified appender is in list of attached appenders, false otherwise.
virtual void	removeAllAppenders ()=0
	Remove all previously added appenders.
virtual void	removeAppender (const AppenderPtr appender)=0
	Remove the appender passed as parameter from the list of appenders.
virtual void	removeAppender (const LogString &name)=0
	Remove the appender with the name passed as parameter from the list of appenders.
virtual	~AppenderAttachable ()
Public Member Functions inherited from log4cxx::helpers::Object
virtual	~Object ()
virtual const helpers::Class &	getClass () const =0
virtual bool	instanceof (const Class &clazz) const =0
virtual const void *	cast (const Class &clazz) const =0
Public Member Functions inherited from log4cxx::AppenderSkeleton
	AppenderSkeleton ()
	AppenderSkeleton (const LayoutPtr &layout)
virtual	~AppenderSkeleton ()
void	finalize ()
	Finalize this appender by calling the derived class' close method.
void	activateOptions (helpers::Pool &) override
	Activate the options that were previously set with calls to option setters.
void	setOption (const LogString &option, const LogString &value) override
	Set option to value.
void	addFilter (const spi::FilterPtr newFilter) override
	Add a filter to end of the filter list.
void	clearFilters () override
	Clear the filters chain.
const spi::ErrorHandlerPtr	getErrorHandler () const
	Return the currently set spi::ErrorHandler for this Appender.
spi::FilterPtr	getFilter () const override
	Returns the head Filter.
const spi::FilterPtr	getFirstFilter () const
	Return the first filter in the filter chain for this Appender.
LayoutPtr	getLayout () const override
	Returns the layout of this appender.
LogString	getName () const override
	Returns the name of this Appender.
const LevelPtr	getThreshold () const
	Returns this appenders threshold level.
bool	isAsSevereAsThreshold (const LevelPtr &level) const
	Check whether the message level is below the appender's threshold.
void	doAppend (const spi::LoggingEventPtr &event, helpers::Pool &pool) override
	This method performs threshold checks and invokes filters before delegating actual logging to the subclasses specific AppenderSkeleton::append method.
void	setErrorHandler (const spi::ErrorHandlerPtr eh)
	Set the ErrorHandler for this Appender.
void	setLayout (const LayoutPtr layout1) override
	Set the layout for this appender.
void	setName (const LogString &name1) override
	Set the name of this Appender.
void	setThreshold (const LevelPtr &threshold)
	Set the threshold level.
Public Member Functions inherited from log4cxx::Appender
virtual	~Appender ()
virtual void	addFilter (const spi::FilterPtr newFilter)=0
	Add a filter to the end of the filter list.
virtual spi::FilterPtr	getFilter () const =0
	Returns the head Filter.
virtual void	clearFilters ()=0
	Clear the list of filters by removing all the filters in it.
virtual void	close ()=0
	Release any resources allocated within the appender such as file handles, network connections, etc.
virtual void	doAppend (const spi::LoggingEventPtr &event, log4cxx::helpers::Pool &pool)=0
	Log in Appender specific way.
virtual LogString	getName () const =0
	Get the name of this appender.
virtual void	setLayout (const LayoutPtr layout)=0
	Set the Layout for this appender.
virtual LayoutPtr	getLayout () const =0
	Returns this appenders layout.
virtual void	setName (const LogString &name)=0
	Set the name of this appender.
virtual bool	requiresLayout () const =0
	Configurators call this method to determine if the appender requires a layout.
Public Member Functions inherited from log4cxx::spi::OptionHandler
virtual	~OptionHandler ()
virtual void	activateOptions (helpers::Pool &p)=0
	Activate the options that were previously set with calls to option setters.
virtual void	setOption (const LogString &option, const LogString &value)=0
	Set option to value.

Additional Inherited Members
Protected Member Functions inherited from log4cxx::AppenderSkeleton
	AppenderSkeleton (LOG4CXX_PRIVATE_PTR(AppenderSkeletonPrivate) priv)
virtual void	append (const spi::LoggingEventPtr &event, log4cxx::helpers::Pool &p)=0
	Subclasses of AppenderSkeleton should implement this method to perform actual logging.
void	doAppendImpl (const spi::LoggingEventPtr &event, log4cxx::helpers::Pool &pool)

The AsyncAppender decouples logging event creation from output by processing log events asynchronously.

The AsyncAppender stores the logging event in a bounded buffer and then returns control to the application. A separate thread forwards events to the attached appender(s).

Important notes:

• Your application must call LogManager::shutdown when it exits to prevent undefined behaviour when using this appender.
• Runtime configuration requires an XML configuration file (see the example below).

This appender is useful when outputting to a slow event sink, for example, a remote SMTP server or a database. Attaching a FileAppender to AsyncAppender to reduce logging overhead is not recommended as the inter-thread communication overhead can exceed the time to write directly to a file.

You can attach multiple appenders to an AsyncAppender by:

• calling AsyncAppender::addAppender repeatedly when progammatically configuring Log4cxx.
• adding multiple appender-ref elements to the appender class="AsyncAppender" element when using runtime configuration.

Here is a sample configuration file:

<log4j:configuration xmlns:log4j="" title="undefined" rel="noopener noreferrer">http://jakarta.apache.org/log4j/"\>

<appender name="A1" class="RollingFileAppender">

<layout class="PatternLayout">

</layout>

</appender>

<appender name="SENDMAIL" class="SMTPAppender">

<layout class="PatternLayout">

</layout>

</appender>

<appender name="ASYNC" class="AsyncAppender">

<appender-ref ref="SENDMAIL"/>

</appender>

<root>

<priority value ="INFO" />

<appender-ref ref="A1" />

<appender-ref ref="ASYNC" />

</root>

</log4j:configuration>

Configurable properties

When the application produces logging events faster than the background thread is able to process, the bounded buffer can become full. In this situation AsyncAppender will either block until the bounded buffer has a free slot or discard the event. The Blocking property controls which behaviour is used. When events are discarded, the logged output will indicate this with a log message prefixed with Discarded. The output may contain one Discarded message per logger name, the logging event of the highest level for each logger whose events have been discarded.

To determine whether the application produces logging events faster than the background thread is able to process, enable Log4cxx internal debugging. The AsyncAppender will output a histogram of queue length frequencies when closed.

See AsyncAppender::setOption for details.

Create new instance.

◆ ~AsyncAppender()

Destructor.

◆ addAppender()

Ensure newAppender receives any logging event added to this appender.

Parameters

Implements log4cxx::spi::AppenderAttachable.

◆ append()

◆ close()

◆ doAppend()

◆ getAllAppenders()

◆ getAppender()

◆ 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.

◆ getBufferSize()

Gets the current buffer size.

Returns

the current value of the BufferSize option.

◆ getLocationInfo()

The current value of the (unused) LocationInfo option.

◆ isAttached()

◆ removeAllAppenders()

◆ removeAppender() [1/2]

◆ removeAppender() [2/2]

◆ replaceAppender()

Replace oldAppender with newAppender.

Returns

true if oldAppender was replaced with newAppender.

◆ replaceAppenders()

Replace any previously added appenders with newList.

◆ 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.

Implements log4cxx::Appender.

◆ setBlocking()

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

Parameters

◆ setBufferSize()

The BufferSize option takes a non-negative integer value.

This integer value determines the maximum size of the bounded buffer.

◆ setLocationInfo()

The LocationInfo attribute is provided for compatibility with log4j and has no effect on the log output.

Parameters

◆ setOption()

The documentation for this class was generated from the following file:

• asyncappender.h