how do I change log level in runtime without resta

Question

I have deployed springboot application in PCF . I want to log the message based on the environment variable .What should I do so that the run time log level change will work without restarting the application?

Answer 1

This is an extension of @Michael Simons answer. With this method you will have a UI for doing that:

This method is a bit longer but it solves much much more. We are going to use a tool called Spring Boot Admin Server.

1. First you need to include some dependencies

   <!--Dependency for registering your app as a Spring Boot Admin Server-->
   <dependency>
       <groupId>de.codecentric</groupId>
       <artifactId>spring-boot-admin-server</artifactId>
       <version>1.3.3</version>
   </dependency>
   
   <!--Provide a nice looking ui-->
   <dependency>
       <groupId>de.codecentric</groupId>
       <artifactId>spring-boot-admin-server-ui</artifactId>
       <version>1.3.3</version>
   </dependency>
   
   <!--Dependency for registering your app as a Spring Boot Admin Client-->
   <dependency>
       <groupId>de.codecentric</groupId>
       <artifactId>spring-boot-admin-starter-client</artifactId>
       <version>1.3.0</version>
   </dependency>
   <dependency>
           <groupId>org.jolokia</groupId>
           <artifactId>jolokia-core</artifactId>
   </dependency>
   

2. Enable your app to be a Spring Boot Admin Server using the annotation @EnableAdminServer.

   @SpringBootApplication
   @EnableAdminServer
   public class Application {
      public static void main(String[] args) {
         // ... your code as before ...
      }
   }
   

3. In your application.properties add the following:

   Register your app to the Spring Boot Admin Server which is still your app

   spring.boot.admin.url=http://localhost:8031
   

   Instruct Spring Boot Admin Server where to find the client

   // For versions 2.*.*
   spring.boot.admin.client.url=http://localhost:8031
   // For versions 1.*.*
   spring.boot.admin.client.service-url=http://localhost:8031
   spring.boot.admin.client.management-url=http://localhost:8031
   spring.boot.admin.client.health-url=http://localhost:8031/health
   

4. In your logback.xml just add the following line <jmxConfigurator/>. This allows configuration of logback via JMX. More info here

... and voila you are done. Now you can change the debug level for any logger at runtime.

i. Just visit the url for your Spring Boot Admin Server-in our case here (http:/localhost:8031).

ii. A list of applications (clients) registered will be displayed on the home page.

iii. Click Details against the registered clients which will take you to another page.

iv. Click the Logging tab which will list all loggers registered in your application.

v. You can change the log levels it will change your logging level at runtime. Here is a snippet of what you expect

Answer 2

Since Spring Boot 1.5.x, you can use logger endpoint to POST desired logging level.

Answer 3

Changing the log level in Spring Boot 1.5+ can be done with a http-endpoint

Add

<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-actuator</artifactId>
</dependency>

and than you can use

curl -X "POST" "http://localhost:8080/loggers/de.springbootbuch" \
     -H "Content-Type: application/json; charset=utf-8" \
     -d $'{
  "configuredLevel": "WARN"
}'  

Where everything beyond /loggers/ is the name of the logger.

If you running this in PCF it get's even better: This is directly supported from their backend.

Answer 4

If you are using logback api to configure logging in the project then you can use the AutoScan feature of logback api. As per documentation

logback-classic will scan for changes in its configuration file and automatically reconfigure itself when the configuration file changes. In order to instruct logback-classic to scan for changes in its configuration file and to automatically re-configure itself set the scan attribute of the element to true.

<configuration scan="true"> 
  ... 
</configuration> 

Please go through logback API documentation for more details.

Answer 5

If you use Log4j 2 for logging you can easily configuration it to set the log level to use based on an environment variable or system property. If you do it this way you won't need to modify the file just because the environment changed.

<?xml version="1.0" encoding="UTF-8"?>
<Configuration status="ERROR" monitorInterval="300">
<properties>
  <property name="LOG_DIR">${sys:user.dir}/logs/</property>
  <property name="log_env">${sys:env:-lab}</property>
  <property name="flow_lab">${sys:flow_match:-ACCEPT}</property>
  <property name="flow_prod">NEUTRAL</property>
  <property name="level_lab">DEBUG</property>
  <property name="level_prod">INFO</property>
</properties>
<MarkerFilter marker="FLOW" onMatch="${flow_${log_env}}" onMismatch="NEUTRAL"/>
<Appenders>
    <Console name="Console" target="SYSTEM_OUT">
        <PatternLayout pattern="%d{ABSOLUTE} %-5level # %class.%method %m%n" />
    </Console>

    <RollingFile name="log4j" fileName="${LOG_DIR}/log4j.txt" filePattern="${LOG_DIR}/archive/log4j.txt.%d{yyyyMMdd_HHmmss}-%i">
        <PatternLayout>
            <MarkerPatternSelector defaultPattern="%d [%t] %-5p %X{requestId, sessionId, loginId, userId, ipAddress, corpAcctNumber} %C{1.}.%M:%L - %m%n">
                <PatternMatch key="FLOW" pattern="%d [%t] %-5p %X{requestId, sessionId, loginId, userId, ipAddress, corpAcctNumber} -------- %C{1.}.%M:%L %msg --------%n"/>
            </MarkerPatternSelector>
        </PatternLayout>
        <Policies>
            <SizeBasedTriggeringPolicy size="30 MB"/>
        </Policies>
        <!-- A max of 20 will allow 20 files per second with the date pattern specified on the RollingFile declaration.
             Hopefully that is a ridiculous value -->
        <DefaultRolloverStrategy min="1" max="20">
            <Delete basePath="${LOG_DIR}/archive">
                <!-- Nested conditions: the inner condition is only evaluated on files for which the outer conditions are true. -->
                <IfFileName glob="log4j.txt.*">
                    <!-- Only allow 1 GB of files to accumulate -->
                    <IfAccumulatedFileSize exceeds="1 GB"/>
                </IfFileName>
            </Delete>
        </DefaultRolloverStrategy>
    </RollingFile>
</Appenders>
<Loggers>
    <Logger name="com.mycorp.package1" level="${level_${log_env}}" additivity="false">
        <AppenderRef ref="log4j"/>
    </Logger>
    <Logger name="com.mycorp.package2" level="info" additivity="false">
        <AppenderRef ref="log4j"/>
    </Logger>
    <Root level="${level_${log_env}}">
        <AppenderRef ref="log4j" />
    </Root>
</Loggers>

Answer 6

You can also add a settings page in the web service to update the log level. This can then be done using ajax. The following example includes login and csrf token:

First, add some form to specify the new log level. Can be improved for example by using a select element.

<form>
    <input type="text" id="logClassName" name="logClassName"/>
    <input type="text" id="logLevel" name="logLevel" />
    <button onclick="submitLogLevelChange(); return false;">Submit</button>
</form>

Then, the request is sent:

function submitLogLevelChange() {
    var className = document.getElementById('logClassName').value;
    var logLevel = document.getElementById("logLevel").value;
    $.ajax({
        // Set up security, see below.
        beforeSend: setHeader,
        type: 'POST',
        // specify the logger to be modified
        url: "/loggers/" + className,
        // specify the new log level
        data: '{"configuredLevel":"' + logLevel + '"}',
        contentType: 'application/json',
        processData: false,
        }).done(function(data, textStatus, jqXHR) {
            if (jqXHR.status === 200) {
                // Happy
            } else if (jqXHR.status === 401) {
                // Logged out or not enough user rights
            } else {
                //Some other problem
            }
        })
        .fail(function(jqXHR, textStatus ) {
            if (jqXHR.status === 200) {
                // Actually was successful, FireFox has some issues...
            } else {
                // Failure
            }
        });
    }

The following function injects the csrf token to the POST request:

function setHeader(xhr) {
  var token = $("meta[name='_csrf']").attr("content");
  var header = $("meta[name='_csrf_header']").attr("content");
  xhr.setRequestHeader(header, token);
}