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Colour-coded Console Logging With Log4J

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I am tracking down some concurrency issues and it would be very helpful to have the output lines from each thread in a different color when logging to a console. I am on OS X. Could this be done using a conversion pattern to output some control codes or would it need a custom appender? Anyone know how?


Just to add, maybe you could also achieve this by setting in the MDC a variable "randColor" with a random ANSI color code, for instance, in a Filter, and using it in the conversionPattern of a standard org.apache.log4j.PatternLayout in your log4j's console appender configuration:



Colour-coded Console Logging with Log4J

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Spring Boot uses Commons Logging for all internal logging but leaves the underlying log implementation open.Default configurations are provided for Java Util Logging, Log4J2, and Logback.In each case, loggers are pre-configured to use console output with optional file output also available.


By default, Spring Boot logs only to the console and does not write log files.If you want to write log files in addition to the console output, you need to set a logging.file or logging.path property (for example, in your application.properties).


Log files rotate when they reach 10 MB and, as with console output, ERROR-level, WARN-level, and INFO-level messages are logged by default.Size limits can be changed using the logging.file.max-size property.Previously rotated files are archived indefinitely unless the logging.file.max-history property has been set.


You can add MDC and other ad-hoc content to log lines by overriding only the LOG_LEVEL_PATTERN (or logging.pattern.level with Logback).For example, if you use logging.pattern.level=user:%Xuser %5p, then the default log format contains an MDC entry for "user", if it exists, as shown in the following example.


The root class for layouts that use a Charset is org.apache.logging.log4j.core.layout.AbstractStringLayout where the default is UTF-8. Each layout that extends AbstractStringLayout can provide its own default. See each layout below.


Outputs the name of the logger that published the logging event. The logger conversion specifier can be optionally followed by precision specifier, which consists of a decimal integer, or a pattern starting with a decimal integer.


Outputs the Thread Context Map (also known as the Mapped Diagnostic Context or MDC) associated with the thread that generated the logging event. The X conversion character can be followed by one or more keys for the map placed between braces, as in %XclientNumber where clientNumber is the key. The value in the MDC corresponding to the key will be output.






ANSI escape sequences are supported natively on many platforms but are not by default on Windows. To enable ANSI support add the Jansi jar to your application and set property log4j.skipJansi to false. This allows Log4j to use Jansi to add ANSI escape codes when writing to the console.


If you configure complete="true", the appender outputs a well-formed XML document where the default namespace is the Log4j namespace " ". By default, with complete="false", you should include the output as an external entity in a separate file to form a well-formed XML document, in which case the appender uses namespacePrefix with a default of "log4j".


However, asynchronous loggers need to make this decision before passing the log message to another thread; the location information will be lost after that point. The performance impact of taking a stack trace snapshot is even higher for asynchronous loggers: logging with location is 30-100 times slower than without location. For this reason, asynchronous loggers and asynchronous appenders do not include location information by default.


Quarkus uses the JBoss Log Manager logging backend for publishing application and framework logs.Quarkus supports the JBoss Logging API and multiple other logging APIs, seamlessly integrated with JBoss Log Manager.You can use any of the following APIs:


By default, the presence of this extension replaces the output format configuration from the console configuration, and the format string and the color settings (if any) are ignored.The other console configuration items, including those controlling asynchronous logging and the log level, will continue to be applied.


A log handler is a logging component responsible for the emission of log events to a recipient.Quarkus includes several different log handlers: console, file, and syslog.


The console output is as per the logging pattern and color defined in the logback-spring.xml file. A new log file by the name application-logback.log is created in the/logs folder present in the current path which gets archived through a rolling policy. The log file output is as follows:


The console output is as per the logging pattern and color defined in the logback-Log4j2.xml file. A new log file by the name application-Log4j2.log is created in the/logs folder present in the current path which gets archived through a rolling policy. The log file output is as follows:


If we would like to use the properties file instead of the XML one we could just create a log4j2.properties file and include it in the classpath or just use the log4j.configuration property and point it to the properties file of our choice. To achieve similar results as we got with the XML-based configuration we would use the following properties:


With the 2.6 version of the framework, two properties are used to control the garbage-free logging capabilities of Log4j 2. The log4j2.enableThreadlocals which is by default set to true for non-web applications and the log4j2.enableDirectEncoders which is also set to true by default are the ones that enable optimizations in Log4j 2.


If at this point you still think about turning on asynchronous logging you need to be aware that additional runtime dependencies are needed. Log4j 2 uses the Disruptor library and requires it as the runtime dependency. You also need to set the log4j2.contextSelector system property to org.apache.logging.log4j.core.async.AsyncLoggerContextSelector.


Now that we know how to use and configure logging with Log4j 2 in our Java application you may be overwhelmed by how many logs your applications will produce. This is especially true for large, distributed applications.


You may get away with logging to a file and only using them when troubleshooting is needed, but working with huge amounts of data quickly becomes unmanageable and you should end up using a log management solution to centralize and monitor your logs. You can either go for an in-house solution based on the open-source software or use one of the products available on the market like Sematext Logs.


Logging is invaluable when troubleshooting Java applications. In fact, logging is invaluable in troubleshooting in general, no matter if that is a Java application or a hardware switch or firewall. Both the software and hardware give us a look into how they are working in the form of parametrized logs enriched with contextual information.


When a message is logged via a Logger it is logged with a certain log level. In the application.yml file, you can define log levels of Spring Boot loggers, application loggers, Hibernate loggers, Thymeleaf loggers, and more. To set the logging level for any logger, add keys starting with logging.level.


Colored logging lets you see different colors for different log levels in your local development console. An ERROR log may be displayed using red text. A WARN log may be displayed using yellow text, while an INFO log may be displayed using green text. This is useful if you are monitoring the logs while using the SAP Commerce application at the same time. You can see the errors quickly.


Modifying the configuration properties allows you to easily redirect logs to various locations including databases, files, log management systems, console, Syslog, or other network destinations, all without requiring changes to the application code.


In case you encounter issues with a specific appender, or face difficulties while working with it. Enabling the internal debugging can help you troubleshoot and resolve these problems by providing additional logging providing insights into its internal operations. To enable internal debugging, set the log4j2.debug system property in the configuration file or add -Dlog4j2.debug to the JVM system variables as below:


The above configuration defines a root logger with a database appender, specifying the JDBC URL, database driver, credentials, SQL statement for insertion, and a pattern layout for logging data into an Oracle database


You can use filters that can be configured to suppress specific log messages. The following are the configuration details for log4j.properties to set up filters in order to suppress certain logging statements.


The above configuration defines two appenders, R and ERROR, with specific settings for logging INFO level messages to a rolling file using a pattern layout and filters, and logging ERROR level messages to another rolling file with matching filters and layouts.


You can specify in your log4j properties which log4j logging levels you want to log. You can use this to send all logs to a file on disk, but perhaps only fatal problems to a database or other appender.


Obviously this is flexible enough that you can use it with any process, not just tailing logfiles. I usually just whip up a new regex on the fly any time I want to colorize something. For this reason, I prefer colout to any custom logfile-coloring tool, because I only need to learn one tool, regardless of what I'm coloring: logging, test output, syntax highlighting snippets of code in the terminal, etc.


We had recently a big debate about logging in applications at my company. Inspired by my colleague, I decided to check how coloring will work on my Windows 8 64-bit machine. The idea is to have the logs colored in the console. Maybe a small detail, but while going through huge amounts of logs - can be handy. So I gave it a try.

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Colour-coded Console Logging With Log4J Cherie Biscoe <biscoecherie@gmail.com> - 2023-12-26 00:27 -0800

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