Shulou(Shulou.com)06/03 Report--

Logging is an important topic in software development, especially if you need to analyze errors and other unexpected events in a production environment. Logging is usually easy to implement. But as you may have experienced, logging is far more complicated than it seems. That's why you can find so many articles about it on blogs.

As an experienced developer, you should understand the different logging frameworks available, common pitfalls and best practices, and of course the log file types used in common deployment scenarios. In this article, I will focus on the latter. I'll tell you about four different types of logs that can be found in almost any development or production environment.

application log

Let's start with the most common type of log: application logs.

Most developers think of this log when they talk about logging. The reason is simple. Their application generates this log which contains various error messages, warnings or other events written by the application. These messages can provide logical high-level information relevant to a particular use case. Typical examples are:

Stack trace of exceptions that occurred in the use case.

Warning message about slow response time of external systems.

Information that the use case was triggered or completed.

Application logging is probably the most important type of logging mentioned in this article because you have complete control over it. This means that you are responsible for writing the message.

Each log message needs to provide useful information to help you understand the behavior of your application. If you want to learn more about application logging, you should check out Eric's article, which describes a set of best practices for application logging.

Web and application server logs

The next interesting and important type is your Web or application server logs.

Most enterprise applications are deployed to Web servers (such as Apache Tomcat) or application servers (such as Wildfly or WebSphere Liberty). Their log files provide you with information about technical issues and the current state of the server.

Each server has different configurations and features, and I won't explain them in detail in this article. However, be sure to check the server documentation and configure it accordingly. Getting the right information from the server can make the difference between identifying potential problems and server outages.

Garbage Collector Log

The garbage collector provides automatic memory management. It keeps track of all objects instantiated in the JVM and deletes objects that are no longer in use. This is a very complex task, and there are several different garbage collector implementations available.

In general, garbage collection in Java is very efficient. It is very efficient, and there are many applications that use the default implementation and its standard configuration. However, if your application has to handle heavy loads or use a lot of complex object structures, the performance of your application may degrade over time. This usually happens when the garbage collector needs to spend more and more time managing the available memory. The garbage collector log provides you with the information necessary to analyze all garbage collector activity.

By default, the garbage collector log is disabled. You need to activate it using a set of command-line properties.

If you are using JDK 8 or earlier, you can do this using the following properties:

XX：+ PrintGCDetails - Xloggc：

Starting with JDK 9, you need to use the following attributes:

class = "prettyprint" - Xlog：gc *：file =

When you start an application using these command-line properties, the garbage collector writes detailed information about all operations. Unfortunately, the content and format of the generated garbage collector log depends on the vendor and version of the JVM and the garbage collection algorithm.

My blog will be synchronized to Tencent Cloud (Cloud)+ community soon. I invite you to join me: cloud.tencent.com/developer/support-plan? invite_code=1loab4y69jfje

system log

All of the logs discussed earlier are written by the JVM or by applications running in the JVM. In addition to these logs, you should be familiar with the logs written by the operating system.

As a Java developer, you probably never write these logs yourself. However, your operating system writes certain events to these logs. Other applications that are part of the deployment can do the same. Therefore, the system log is a good place to get an overview of external events.

If you are running an application on Windows, this is the event log. On Linux, you should know about the syslog service and its successors.

Windows Event Log

Windows Event Log contains important hardware and software events in categories Application, Security, Settings, System and Forward Events.

Application events and system categories are particularly useful for understanding events that occur outside of an application. The Applications category contains events reported by other applications running on the native Windows system. Hardware and driver-related events belong to the system category.

You can learn more about Windows event logs in this article.

Linux System Logging

Linux's syslog service and its successors provide a highly configurable logging system. It writes messages triggered by applications or operating systems to files or sends them to remote systems.

The logging service you use and its configuration depend on your Linux distribution. Check the documentation for more information about specific operating systems.

Ian Shields has written an excellent introduction to Linux system logging. If you're looking for a general introduction, I recommend reading his Learn Linux, 101: System Logging Guide.

conclusion

Recording is an important subject with many different aspects. In this article, I summarized four important logs you should know as a Java developer:

Application logging is the most obvious one. It is written by your application and you are responsible for its content.

If you deploy your application to a Web or application server, you also need to know what logs that server provides.

Garbage collector logs can provide important information if you need to analyze performance problems.

community information

Community nickname

dodott

Column information

Dodott's column

Articles from your original personal site/blog will be migrated to this column, and new articles will be updated regularly in the future.

You can examine the system log for an overview of all external events that may affect your application and cause service events.

My blog will be synchronized to Tencent Cloud (Cloud)+ community soon. I invite you to join me: cloud.tencent.com/developer/support-plan? invite_code=1loab4y69jfje

Welcome to subscribe "Shulou Technology Information " to get latest news, interesting things and hot topics in the IT industry, and controls the hottest and latest Internet news, technology news and IT industry trends.