Log error java log4j

Introduction to Java Logging

The Kubernetes ecosystem is huge and quite complex, so it’s easy to forget about costs when trying out all of the exciting tools.

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We rely on other people’s code in our own work. Every day.

It might be the language you’re writing in, the framework you’re building on, or some esoteric piece of software that does one thing so well you never found the need to implement it yourself.

The problem is, of course, when things fall apart in production — debugging the implementation of a 3rd party library you have no intimate knowledge of is, to say the least, tricky.

Lightrun is a new kind of debugger.

It’s one geared specifically towards real-life production environments. Using Lightrun, you can drill down into running applications, including 3rd party dependencies, with real-time logs, snapshots, and metrics.

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Slow MySQL query performance is all too common. Of course it is. A good way to go is, naturally, a dedicated profiler that actually understands the ins and outs of MySQL.

The Jet Profiler was built for MySQL only, so it can do things like real-time query performance, focus on most used tables or most frequent queries, quickly identify performance issues and basically help you optimize your queries.

Critically, it has very minimal impact on your server’s performance, with most of the profiling work done separately — so it needs no server changes, agents or separate services.

Basically, you install the desktop application, connect to your MySQL server, hit the record button, and you’ll have results within minutes:

DbSchema is a super-flexible database designer, which can take you from designing the DB with your team all the way to safely deploying the schema.

The way it does all of that is by using a design model, a database-independent image of the schema, which can be shared in a team using GIT and compared or deployed on to any database.

And, of course, it can be heavily visual, allowing you to interact with the database using diagrams, visually compose queries, explore the data, generate random data, import data or build HTML5 database reports.

The Kubernetes ecosystem is huge and quite complex, so it’s easy to forget about costs when trying out all of the exciting tools.

To avoid overspending on your Kubernetes cluster, definitely have a look at the free K8s cost monitoring tool from the automation platform CAST AI. You can view your costs in real time, allocate them, calculate burn rates for projects, spot anomalies or spikes, and get insightful reports you can share with your team.

Connect your cluster and start monitoring your K8s costs right away:

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1. Overview

Logging is a powerful aid for understanding and debugging program’s run-time behavior. Logs capture and persist the important data and make it available for analysis at any point in time.

This article discusses the most popular java logging framewloorks, Log4j 2 and Logback, along with their predecessor Log4j, and briefly touches upon SLF4J, a logging facade that provides a common interface for different logging frameworks.

2. Enabling Logging

All the logging frameworks discussed in the article share the notion of loggers, appenders and layouts. Enabling logging inside the project follows three common steps:

The upcoming sections discuss the steps for each framework individually.

3. Log4j 2

Log4j 2 is new and improved version of the Log4j logging framework. The most compelling improvement is the possibility of asynchronous logging. Log4j 2 requires the following libraries:

 org.apache.logging.log4j log4j-api 2.6.1  org.apache.logging.log4j log4j-core 2.6.1 

Latest version of log4j-api you can find here and log4j-core – here.

3.1. Configuration

Configuring Log4j 2 is based on the main configuration log4j2.xml file. The first thing to configure is the appender.

These determine where the log message will be routed. Destination can be a console, a file, socket, etc.

Log4j 2 has many appenders for different purposes, you can find more information on the official Log4j 2 site.

Lets take a look at a simple config example:

You can set a name for each appender, for example use name console instead of stdout.

Notice the PatternLayout element – this determines how message should look like. In our example, the pattern is set based on the pattern param, where %d determines date pattern, %p – output of log level, %m – output of logged message and %n – adds new line symbol. More info about pattern you can find on official Log4j 2 page.

Finally – to enable an appender (or multiple) you need to add it to section:

3.2. Logging to File

Sometimes you will need to use logging to a file, so we will add fout logger to our configuration:

The File appender have several parameters that can be configured:

• file – determines file name of the log file
• append – The default value for this param is true, meaning that by default a File appender will append to an existing file and not truncate it.
• PatternLayout that was described in previous example.

In order to enable File appender you need to add it to section:

import org.apache.logging.log4j.Logger; import org.apache.logging.log4j.LogManager; public class Log4jExample < private static Logger logger = LogManager.getLogger(Log4jExample.class); public static void main(String[] args) < logger.debug("Debug log message"); logger.info("Info log message"); logger.error("Error log message"); >>

2016-06-16 17:02:13 INFO Info log message 2016-06-16 17:02:13 ERROR Error log message

2016-06-16 17:02:13 ERROR Error log message

logger.trace("Trace log message");

2016-06-16 17:02:13 TRACE Trace log message 2016-06-16 17:02:13 DEBUG Debug log message 2016-06-16 17:02:13 INFO Info log message 2016-06-16 17:02:13 ERROR Error log message

 ch.qos.logback logback-classic 1.2.6 

 # Console appender %d %-5p %m%n   # File appender baeldung.log false # Pattern of log message for file appender %d %-5p %m%n   # Override log level for specified package     

import org.slf4j.Logger; import org.slf4j.LoggerFactory; public class Log4jExample < private static Logger logger = LoggerFactory.getLogger(Log4jExample.class); public static void main(String[] args) < logger.debug("Debug log message"); logger.info("Info log message"); logger.error("Error log message"); >>

import org.apache.log4j.Logger; public class Log4jExample < private static Logger logger = Logger.getLogger(Log4jExample.class); public static void main(String[] args) < logger.debug("Debug log message"); logger.info("Info log message"); logger.error("Error log message"); >>