Develop Reference

How to select Logback appender based on property file or environment variable

I have configured logback xml for a spring boot project.
I want to configure another appender based on the property configured. We want to create an appender either for JSON logs or for text log, this will be decided either by property file or by environment variable.
So I am thinking about the best approach to do this.
Using filters to print logs to 1 of the file (either to JSON or to Txt). But this will create both of the appenders. I want to create only 1 appender.
Use "If else" blocks in logback XML file. To put if else around appenders, loggers seems untidy and error prone. So will try to avoid as much as possible.
So now exploring options where I can add appender at runtime.
So I want to know if it is possible to add appender at runtime. And will it be added before spring boots up or it could be done anytime in the project.
What could be the best approach to include this scenario.

As you're already using Spring, I suggest using Spring Profiles, lot cleaner than trying to do the same programmatically. This approach is also outlined in Spring Boot docs.
You can set an active profile from either property file:
spring.profiles.active=jsonlogs
or from environment value:
spring_profiles_active=jsonlogs
of from startup parameter:
-Dspring.profiles.active=jsonlogs
Then have separate configurations per profile:
<?xml version="1.0" encoding="UTF-8"?>
<configuration>
<appender name="stdout-classic" class="ch.qos.logback.core.ConsoleAppender">
<encoder>
<pattern>%d{dd-MM-yyyy HH:mm:ss.SSS} %magenta([%thread]) %highlight(%-5level) %logger{36}.%M - %msg%n</pattern>
</encoder>
</appender>
<appender name="stdout-json" class="ch.qos.logback.core.ConsoleAppender">
<encoder class="ch.qos.logback.core.encoder.LayoutWrappingEncoder">
<layout class="ch.qos.logback.contrib.json.classic.JsonLayout">
<timestampFormat>yyyy-MM-dd'T'HH:mm:ss.SSSX</timestampFormat>
<timestampFormatTimezoneId>Etc/UTC</timestampFormatTimezoneId>
<jsonFormatter class="ch.qos.logback.contrib.jackson.JacksonJsonFormatter">
<prettyPrint>true</prettyPrint>
</jsonFormatter>
</layout>
</encoder>
</appender>
<!-- begin profile-specific stuff -->
<springProfile name="jsonlogs">
<root level="info">
<appender-ref ref="stdout-json" />
</root>
</springProfile>
<springProfile name="classiclogs">
<root level="info">
<appender-ref ref="stdout-classic" />
</root>
</springProfile>
</configuration>

As the previous answer states, you can set different appenders based on Spring Profiles.
However, if you do not want to rely on that feature, you can use environments variables as described in the Logback manual. I.e.:
<appender name="json" class="ch.qos.logback.core.ConsoleAppender">
<encoder class="ch.qos.logback.core.encoder.LayoutWrappingEncoder">
<layout class="ch.qos.logback.contrib.json.classic.JsonLayout">
<jsonFormatter class="ch.qos.logback.contrib.jackson.JacksonJsonFormatter">
<prettyPrint>true</prettyPrint>
</jsonFormatter>
<appendLineSeparator>true</appendLineSeparator>
</layout>
</encoder>
</appender>
<appender name="console" class="ch.qos.logback.core.ConsoleAppender">
<encoder>
<pattern>
%cyan(%d{HH:mm:ss.SSS}) %gray([%thread]) %highlight(%-5level) %magenta(%logger{36}) - %msg%n
</pattern>
</encoder>
</appender>
<root level="info">
<!--
! Use the content of the LOGBACK_APPENDER environment variable falling back
! to 'json' if it is not defined
-->
<appender-ref ref="${LOGBACK_APPENDER:-json}"/>
</root>

Ways to configure logs other than log4j xml, properties file, and source code (mainly java)?

I'm looking at the source code of some application. It is using Spring framework, Apache Tiles, JSP, Log4j, java, javascript, jquery, jqplot, Jsch, and etc.
I know where the logs are created. (a/b/logs) However, when I look at source code, I don't know how logs are created under the folder name 'logs'. I looked at log4j.xml, web.xml , property files. I found the code for how the path 'a/b' is created, but not logs. Also that folder has 4 types of logs. And they are name in a pattern like access.20181227001 , errors.20182111. I want to know where I have to look to find how the logs are created in this manner.
Log4J.xml
<!-- Appenders -->
<appender name="console" class="org.apache.log4j.ConsoleAppender">
<layout class="org.apache.log4j.PatternLayout">
<param name="ConversionPattern" value="%d %5p [%c] %m%n" />
</layout>
</appender>
<appender name="console-infolog" class="org.apache.log4j.ConsoleAppender">
<layout class="org.apache.log4j.PatternLayout">
<param name="ConversionPattern" value="%d %5p %m%n" />
</layout>
</appender>
<!-- Application Loggers -->
<logger name="com.dsmentoring.chakan" additivity="false">
<level value="debug" />
<appender-ref ref="console"/>
</logger>
<!-- 3rdparty Loggers -->
<logger name="org.springframework.core">
<level value="error"/>
</logger>
<!-- Bean logger -->
<logger name="org.springframework.beans">
<level value="error"/>
</logger>
<!-- Context logger -->
<logger name="org.springframework.context">
<level value="error"/>
</logger>
<!-- Web logger -->
<logger name="org.springframework.web">
<level value="error"/>
</logger>
<logger name="org.springframework.ldap" additivity="true">
<level value="error"/>
</logger>
<!-- LDAP logger -->
<logger name="com.unboundid.ldap" additivity="true">
<level value="error"/>
</logger>
<!-- Root Logger -->
<root>
<priority value="off" />
<appender-ref ref="console" />
</root>
To sum up :
1) Is there a way to configure where logs are created and how they are created (4 types of logs) Other than log4j.xml, xml files and property files? I looked at all the java, jsp, js code but can't seem to find the configuration for logs. So I want to know if there are other ways to do that or where I should look for those configuration.
2) The 'logs' folder is possibly default for log4j?
ldap.properties
#LDAP Connection Info
ldap.host=192.168.0.17
ldap.port=22389
ldap.userName=cn=directory manager
ldap.password= 9074B18A0DE2D50C068D37B60BE5DFDE
ldap.baseDN=o=sso30root
ldap.defaultLoadSize=1000
ldap.start=start-ds
ldap.stop=stop-ds
ldap.workdir=/home/KB_openDJ // logs are created under this path
// /home/KB_openDJ/logs
In other java class, they use this.
#Value("${ldap.workdir}")
private String WORK_DIR;
// I ommited many lines in between
try{
diskUsage = sigar.getFileSystemUsage(WORK_DIR);
diskIOInfo.setDiskRead((int)(diskUsage.getDiskReadBytes()));
diskIOInfo.setDiskWrite((int)(diskUsage.getDiskWriteBytes()));
}catch(SigarException sigarEx){
log.debug("Disk Usage info load Error : " + sigarEx.getMessage());
}
I used the 'Search' feature in Eclipse many times. ( logs, WORK_DIR, and 4 types of log name, and many others. I am unable to locate the code about logging configuration. :(
My log4j version :
1.2.15

Ok, it seems that there's a solution which might help you. It requires some debugging of static initalization block of org.apache.log4j.LogManager class. This class is responsible for loading logger configuration file. Here's a documention link which thoroughly describes initalization process: link.
Here's an excerpt from a LogManager source file:
String configurationOptionStr = OptionConverter.getSystemProperty(DEFAULT_CONFIGURATION_KEY, null);
String configuratorClassName = OptionConverter.getSystemProperty(CONFIGURATOR_CLASS_KEY, null);
What I'm trying to show you here, is that your logger configuration file might be specified as a JVM option supplied to your application-server. That's why you are not able to determine actual file being used.
Even if this approach fails, I'd recommend you to investigate the appenders list retrieved at run-time. Here's a stackoverflow thread which describes how to do so: link.

Can i run my log asynchronously using log4j 1.x with log4j.properties file?

I am currently working on performance of "log4j 1.x" vs "logback" i.e. (slf4j).
I can append async to my logback, but i am not able to find any link which can async my log4j.
Async is only introduced in log4j 2.x? or is there any way to make my log4j 1.x work async.
Please assist me.
Thank you.

Asynchronous logging is one of Log4j 2's strong points. Instead of the AsyncAppender, use Async Loggers: the performance is much better.
The Log4j 2 performance page compares Log4j-1.x, Logback and Log4j 2. Take a look and then decide what logging framework to use.
By the way, Log4j 2 has an adapter called log4j-1.2-api-2.6.jar which lets your application use the old log4j-1.2 API, but uses the new log4j 2 implementation.
(Log4j-1.x also has an AsyncAppender. Just like the Log4j 2 AsyncAppender and the Logback AsyncAppender, it uses a BlockingQueue. Log4j 2's Async Loggers use a non-blocking data structure which is much faster.)

log4j.properties does not handle the advanced configuration features
supported by the DOMConfigurator such as support custom ErrorHandlers,
nested appenders such as the AsyncAppender, etc.
Refer log4j API Documentation
There are two ways to configure AsyncAppender in log4j 1.x
Using log4j.xml
Configure AsyncAppender as below
<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE log4j:configuration SYSTEM "log4j.dtd">
<log4j:configuration xmlns:log4j="http://jakarta.apache.org/log4j/">
<appender name="console1" class="org.apache.log4j.ConsoleAppender">
<param name="target" value="System.out" />
<layout class="org.apache.log4j.PatternLayout">
<param name="ConversionPattern" value="%d{ABSOLUTE} %-5p [%c{1}] %m%n" />
</layout>
</appender>
<!--wrap ASYNC around other appender if you want -->
<appender name="ASYNC" class="org.apache.log4j.AsyncAppender">
<param name="BufferSize" value="500" />
<!-- LocationInfo is Optional, use only if location info is required. (Default value : false)-->
<!-- <param name="LocationInfo" value="true" /> -->
<appender-ref ref="console1" />
<root>
<priority value="debug" />
<appender-ref ref="ASYNC" />
</root>
</log4j:configuration>
Programmatically
You can configure AsyncAppender programmatically as below
static {
enableAsyncAuditLog(Logger.getRootLogger());
}
private static void enableAsyncAuditLog(Logger targetLogger) {
Enumeration<Appender> appenders = targetLogger.getAllAppenders();
AsyncAppender asyncAppender = new AsyncAppender();
asyncAppender.setBufferSize(500);
asyncAppender.setLocationInfo(true); // Otherwise Class and Line info will not be available to logger
while (appenders.hasMoreElements()) {
Appender appender = appenders.nextElement();
if (!(appender instanceof AsyncAppender)) {
targetLogger.removeAppender(appender);
asyncAppender.addAppender(appender);
}
}
appenders = asyncAppender.getAllAppenders();
if (appenders != null && appenders.hasMoreElements()) {
targetLogger.addAppender(asyncAppender);
}
}
You can refer this project for reference

How to make isInfoEnabled disabled in Log4J XML configuration

I have various log files (debug, error) and different configurations (e.g. dev, prod). In dev I'd like to have everything logged into my debug.log and errors written to error.log. However in production I'd like to switch the debug logging off. Right now I'm using this config:
<appender name="FileAppender" class="org.apache.log4j.DailyRollingFileAppender">
<param name="File" value="/logs/debug.log" />
<param name="Append" value="true" />
<param name="Threshold" value="OFF" />
...
So it will decide whether to write or not itself. But I'd like to check in the code sometimes, if the logger writes to log:
if(logger.isInfoEnabled()) {};
Even the threshold is set to 'OFF' it does says, that info is enabled.
What I'm trying to do is to configure the XML, so it would not only skip writing to the debug.log in the production, but also it would set the infoEnabled value to false, so I could use it in my code. Is there are any possibilities to do that?
Thanks in advance!

Configure your ROOT logger to 'WARN' level. In Log4J 1.x:
<root>
<level value="WARN" />
</root>
In Log4J 2.x:
<root level="WARN">
</root>

Run Logback in Debug

I've recently switched from log4j to logback and am wondering if there is an easy way to run logback in debug mode, similar to log4j's log4j.debug property. I need to see where it is picking up my logback.xml from.
The docs mention using a StatusPrinter to print out logback's internal status, but that would require code changes.

[EDIT]
This has been fixed in Logback 1.0.4. You can now use -Dlogback.debug=true to enable debugging of the logback setup.
-- Old Answer --
Unfortunately, there is no way to enable debugging via a System property. You have to use <configuration debug="true"> in the logback.xml. Please submit a feature request.

This is how I do it. I set a system property called 'log.level', then I reference it in logback.xml.
Edit: The downside is that you MUST have 'log.level' always set. The way I deal with this is to check in my main method and set it to INFO if not already set, be sure to do this before you first logging calls. Then I can override on the command line, and have a sensible default.
Here is how it looks in my logback.xml:
<configuration>
<logger name="com.mycompany.project" level="${log.level}" />
<logger name="httpclient" level="WARN" />
<logger name="org.apache" level="WARN" />
<logger name="org.hibernate" level="WARN" />
<logger name="org.hibernate.cfg.AnnotationBinder" level="WARN" />
<logger name="org.hibernate.cfg.annotations" level="WARN" />
<logger name="org.quartz" level="WARN" />
<logger name="org.springframework" level="WARN" />
<appender name="STDOUT" class="ch.qos.logback.core.ConsoleAppender">
<encoder>
<pattern>%d{yyyy-MM-dd HH:mm:ss.SSS} [%-16thread] %-5level %-35.35logger{30} - %msg%n</pattern>
</encoder>
</appender>
<root level="${log.level:-INFO}">
<appender-ref ref="STDOUT" />
</root>
</configuration>

You can set the status listener class via system property:
java -Dlogback.statusListenerClass=ch.qos.logback.core.status.OnConsoleStatusListener ...
See: Logback manual

I could not make it work using the chosen answer. However, the following worked:
java -Dlogback.configurationFile=/path/to/config-debug.xml com.domain.Main
Just add a file (config-debug.xml in this example) somewhere on your server and leave it there when you need to debug. Like the following.
<configuration>
<appender name="STDOUT" class="ch.qos.logback.core.ConsoleAppender">
<!-- encoders are assigned the type
ch.qos.logback.classic.encoder.PatternLayoutEncoder by default -->
<encoder>
<pattern>%d{dd-MMM-yyyy HH:mm:ss.SSS} %-5level [%thread] %logger{36} - %msg%n</pattern>
</encoder>
</appender>
<root level="debug">
<appender-ref ref="STDOUT" />
</root>
</configuration>
Run your application using the afore mentioned -D parameter.
When things are back to normal, remove the -D parameter and restart your application.
Source: Chapter 3: Logback configuration

Well, It's pretty easy. Either you can use
log.level = debug
inside the application.properties of Spring boot.
or you can also set this in the configuration file of logback.xml
<root level="${log.level}">
<appender-ref ref="ANY_APPENDER" />
</root>

In eclipse you can have multiple run configurations. Open your main class. Go to Debug dropdown on eclipse toolbar and select Debug configurations. Click the New launch configuration icon at the top left. Give your launch configuration a better name. Click the Arguments tab under the name and enter -Dlog.level=debug or whatever you want. Click Close or Debug
You can do this again and specify -Dlog.level=warn for example.