Your greatest source when starting your appender will be this Logback page. Thus, one can take advantage of connection pooling and whatever other goodies the application server provides. When I sat down to write the appender, I encountered some caveats that I wanted to share because I could not find much documentation on writing new appenders at all. ILoggingEvent When you start extending the AppenderBase class, you will notice that the one thing you basically need to do is to handle this: Extracting caller data can be rather expensive. If you don’t specify a cyclicBufferTracker , an instance of CyclicBufferTracker will be automatically created.

SocketAppender properties are listed in the following table. It is worth noting that I have removed the colours that were added to the encoder pattern when saving to file as it will include characters that are not meant to be displayed and will clutter the log file. This option represents the pattern that will be followed by the FixedWindowRollingPolicy when renaming the log files. Thus, each outgoing email generated by SMTPAppender will belong to a unique remote host, greatly facilitating problem diagnosis. AppenderBase calls another generic class so we can integrate more frameworks easily. In contrast, the SocketAppender is designed to log to a remote entity by transmitting serialized ILoggingEvent instances over the wire. One thing sets off a hundred others.

This process will continue if wrtiing maxIndex is not set, but when it is the log file with the specified maximum index is deleted it contains the oldest messages at the point when another archive file should be created. This option is wriging component that will dictate RollingFileAppender ‘s behavior when rollover occurs.

You should set includeCallerData to true if asynchronousSending is enabled and you wish to include caller data in the logs. Here are a few logback. Although reasonable, the default triggering policy whereby every event of level ERROR triggers an outgoing email may result in too many emails, cluttering the targeted user’s mailbox. In conclusion from this tutorial you should have grasped a understanding on how to use Logback with Spring Boot, including how to use property files to alter the loghack settings provided by Spring Boot and how to custmo even further and create your own custom made configurations using Logback via logback.


Once a DataSource is defined in the J2EE server, it can be easily referenced by your logback configuration file, as shown in the next example. We are working on a cloud application and have this as a requirement.

In this and subsequent rollovers, there will be three archive logs and one active log file. Set to true and the appender will just drop the message and will not block your application.

logback.xml Example

They must exist before DBAppender can be used. Here was the answer: This means that if the link to server is slow but still faster than the rate of event production by the client, the client will not be affected by the slow network connection. A logging event that contains MDC or Context properties has a flag number of 1.

writing custom logback appender

It does so based on the keys returned by the discriminator see above. Because the ServerSocketAppender subtypes are designed to be used with receiver components, we will defer presenting illustrative examples to the chapter entitled Receivers. There are two important sub-components that interact with RollingFileAppender. Custoom In Sign Up. The reconnectionDelay option takes a duration string, such “10 seconds” representing the time to wait between each failed connection attempt to the server.

Let us now study an example. Instead of wditing a connection to a remote logging server, ServerSocketAppender passively listens on a TCP socket awaiting incoming connections from remote clients. In prudent mode, FileAppender will safely wrlting to the specified file, even in the presence of other FileAppender instances running in different JVMs, potentially running on different hosts. After setting all the properties of an appender, Joran, logback’s configuration framework, calls the start method to signal the appender to activate its properties.


When handling a logging event, SiftingAppender will select a child appender to delegate to.

writing custom logback appender

Its call could be directed to the very same appender that just called it resulting in an infinite loop and a stack overflow. Indeed, most operating systems do not allow renaming of a file while another process has it opened.

Lessons Learned While Writing Our New Logback Appender

The approach to encoding logging events for transmission on the wire is identical to that used by SocketAppender ; each event is a serialized instance of ILoggingEvent. The includeCallerData option takes a boolean value. One thing sets off a hundred others. If the JVM hosting the SocketAppender exits before the SocketAppender is closed, either explicitly or subsequent to garbage collection, then there might be untransmitted data in the pipe which may be lost.

In the above configuration file, a SiftingAppender nests FileAppender instances. DZone ‘s Guide to. This is not necessarily a bad thing.

Example –

This method does the actual work of appending the custo to the appropriate device. The template for the configuration file illustrates the use of SiftingAppender.

You can easily write your appender by subclassing AppenderBase.