The kamon-servlet module brings traces and metrics to your servlet based applications.

Kamon Servlet is currently available for Scala 2.10, 2.11 and 2.12.

Supported releases and dependencies are shown below.

To get kamon-servlet in your project:

• Maven:

<dependencies>
  <dependency>
    <groupId>io.kamon</groupId>
    <artifactId>kamon-servlet-3_2.12</artifactId>
    <version>2.0.0</version>
  </dependency>
</dependencies>

• Gradle:

dependencies {
  compile 'io.kamon:kamon-servlet-3_2.12:2.0.0'
}

• SBT:

libraryDependencies += "io.kamon" %% "kamon-servlet-3" % "2.0.0"

All you need to do is to add the Kamon Filter on your Web App:

• For Servlet 2.5: kamon.servlet.v25.KamonFilterV25
• For Servlet 3.x.x: kamon.servlet.v3.KamonFilterV3

You should register it in the specific way your framework required. Otherwise, you need to configure it manually. Below there are some example.

You could programmatically register it using a ServletContextListener:

package kamon.servlet.v3.example;

import java.util.EnumSet;
import javax.servlet.DispatcherType;
import javax.servlet.ServletContextEvent;
import javax.servlet.ServletContextListener;
import kamon.Kamon;
import kamon.servlet.v3.KamonFilterV3;

public class KamonContextListener implements ServletContextListener {

  @Override
  public void contextInitialized(ServletContextEvent servletContextEvent) {
    // here you might subscribe all reporters you want. e.g. `Kamon.addReporter(new PrometheusReporter())`
    servletContextEvent
        .getServletContext()
        .addFilter("KamonFilter", new KamonFilterV3())
        .addMappingForUrlPatterns(EnumSet.allOf(DispatcherType.class), true, "/*");
  }

  @Override
  public void contextDestroyed(ServletContextEvent arg0) {
    // in case you have subscribed some reporters: `Kamon.stopAllReporters();`
    System.out.println("KamonContextListener destroyed");
  }
}

For Servlet 2.5 there isn't a programmatic way to achieve it, so you have to define it in web.xml:

<filter>
   <filter-name>kamonFilter</filter-name>
   <filter-class>kamon.servlet.v25.KamonFilterV25</filter-class>
 </filter>
 <filter-mapping>
   <filter-name>kamonFilter</filter-name>
   <url-pattern>/*</url-pattern>
 </filter-mapping>

kamon-servlet uses TypeSafe Config. Default configuration is in resources/reference.conf for each subproject:

• kamon-servlet-25 config
• kamon-servlet-3 config

You can customize/override any property adding an application.conf in the /resources/ of your app or by providing System properties (e.g. -Dpath.of.your.key=value). This is the standard behavior of TypeSafe Config, for more info see its doc.

Execute from your terminal:

sbt
project benchmarks-3 # or benchmarks-25
jmh:run -i 50 -wi 20 -f1 -t1 .*Benchmark.*