# Customizing a Node

URL: https://deploy-preview-2977--selenium-dev.netlify.app/ja/documentation/grid/advanced_features/customize_node/

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## How to customize a Node

There are times when we would like a Node to be customized to our needs. 

For e.g., we may like to do some additional setup before a session begins execution and some clean-up after a session runs to completion.

Following steps can be followed for this:

* Create a class that extends `org.openqa.selenium.grid.node.Node`
* Add a static method (this will be our factory method) to the newly created class whose signature looks like this: 

  `public static Node create(Config config)`. Here:

    * `Node` is of type `org.openqa.selenium.grid.node.Node`
    * `Config` is of type `org.openqa.selenium.grid.config.Config`
* Within this factory method, include logic for creating your new Class.
* To wire in this new customized logic into the hub, start the node and pass in the fully qualified class name of the above class to the argument `--node-implementation`

Let's see an example of all this:

### Custom Node as an uber jar

1. Create a sample project using your favourite build tool (**Maven**|**Gradle**).
2. Add the below dependency to your sample project.
    * [org.seleniumhq.selenium/selenium-grid](https://mvnrepository.com/artifact/org.seleniumhq.selenium/selenium-grid)
3. Add your customized Node to the project.
4. Build an [uber jar](https://imagej.net/develop/uber-jars) to be able to start the Node using `java -jar` command.
5. Now start the Node using the command:

```bash
java -jar custom_node-server.jar node \
--node-implementation org.seleniumhq.samples.DecoratedLoggingNode
```

**Note:** If you are using Maven as a build tool, please prefer using [maven-shade-plugin](https://maven.apache.org/plugins/maven-shade-plugin) instead of [maven-assembly-plugin](https://maven.apache.org/plugins/maven-assembly-plugin) because maven-assembly plugin seems to have issues with being able to merge multiple Service Provider Interface files (`META-INF/services`)

### Custom Node as a regular jar

1. Create a sample project using your favourite build tool (**Maven**|**Gradle**).
2. Add the below dependency to your sample project.
    * [org.seleniumhq.selenium/selenium-grid](https://mvnrepository.com/artifact/org.seleniumhq.selenium/selenium-grid)
3. Add your customized Node to the project.
4. Build a jar of your project using your build tool.
5. Now start the Node using the command:

```bash
java -jar selenium-server-4.6.0.jar \
--ext custom_node-1.0-SNAPSHOT.jar node \
--node-implementation org.seleniumhq.samples.DecoratedLoggingNode
```
Below is a sample that just prints some messages on to the console whenever there's an activity of interest (session created, session deleted, a webdriver command executed etc.,) on the Node.

<details>
<summary>Sample customized node</summary>

```java
package org.seleniumhq.samples;

import java.net.URI;
import java.util.UUID;
import org.openqa.selenium.Capabilities;
import org.openqa.selenium.NoSuchSessionException;
import org.openqa.selenium.WebDriverException;
import org.openqa.selenium.grid.config.Config;
import org.openqa.selenium.grid.data.CreateSessionRequest;
import org.openqa.selenium.grid.data.CreateSessionResponse;
import org.openqa.selenium.grid.data.NodeId;
import org.openqa.selenium.grid.data.NodeStatus;
import org.openqa.selenium.grid.data.Session;
import org.openqa.selenium.grid.log.LoggingOptions;
import org.openqa.selenium.grid.node.HealthCheck;
import org.openqa.selenium.grid.node.Node;
import org.openqa.selenium.grid.node.local.LocalNodeFactory;
import org.openqa.selenium.grid.security.Secret;
import org.openqa.selenium.grid.security.SecretOptions;
import org.openqa.selenium.grid.server.BaseServerOptions;
import org.openqa.selenium.internal.Either;
import org.openqa.selenium.remote.SessionId;
import org.openqa.selenium.remote.http.HttpRequest;
import org.openqa.selenium.remote.http.HttpResponse;
import org.openqa.selenium.remote.tracing.Tracer;

public class DecoratedLoggingNode extends Node {

  private Node node;

  protected DecoratedLoggingNode(Tracer tracer, NodeId nodeId, URI uri, Secret registrationSecret, Duration sessionTimeout) {
    super(tracer, nodeId, uri, registrationSecret, sessionTimeout);
  }

  public static Node create(Config config) {
    LoggingOptions loggingOptions = new LoggingOptions(config);
    BaseServerOptions serverOptions = new BaseServerOptions(config);
    URI uri = serverOptions.getExternalUri();
    SecretOptions secretOptions = new SecretOptions(config);
    NodeOptions nodeOptions = new NodeOptions(config);
    Duration sessionTimeout = nodeOptions.getSessionTimeout();

    // Refer to the foot notes for additional context on this line.
    Node node = LocalNodeFactory.create(config);

    DecoratedLoggingNode wrapper = new DecoratedLoggingNode(loggingOptions.getTracer(),
        node.getId(),
        uri,
        secretOptions.getRegistrationSecret(),
        sessionTimeout);
    wrapper.node = node;
    return wrapper;
  }

  @Override
  public Either<WebDriverException, CreateSessionResponse> newSession(
      CreateSessionRequest sessionRequest) {
    System.out.println("Before newSession()");
    try {
      return this.node.newSession(sessionRequest);
    } finally {
      System.out.println("After newSession()");
    }
  }

  @Override
  public HttpResponse executeWebDriverCommand(HttpRequest req) {
    try {
      System.out.println("Before executeWebDriverCommand(): " + req.getUri());
      return node.executeWebDriverCommand(req);
    } finally {
      System.out.println("After executeWebDriverCommand()");
    }
  }

  @Override
  public Session getSession(SessionId id) throws NoSuchSessionException {
    try {
      System.out.println("Before getSession()");
      return node.getSession(id);
    } finally {
      System.out.println("After getSession()");
    }
  }

  @Override
  public HttpResponse uploadFile(HttpRequest req, SessionId id) {
    try {
      System.out.println("Before uploadFile()");
      return node.uploadFile(req, id);
    } finally {
      System.out.println("After uploadFile()");
    }
  }

  @Override
  public void stop(SessionId id) throws NoSuchSessionException {
    try {
      System.out.println("Before stop()");
      node.stop(id);
    } finally {
      System.out.println("After stop()");
    }
  }

  @Override
  public boolean isSessionOwner(SessionId id) {
    try {
      System.out.println("Before isSessionOwner()");
      return node.isSessionOwner(id);
    } finally {
      System.out.println("After isSessionOwner()");
    }
  }

  @Override
  public boolean isSupporting(Capabilities capabilities) {
    try {
      System.out.println("Before isSupporting");
      return node.isSupporting(capabilities);
    } finally {
      System.out.println("After isSupporting()");
    }
  }

  @Override
  public NodeStatus getStatus() {
    try {
      System.out.println("Before getStatus()");
      return node.getStatus();
    } finally {
      System.out.println("After getStatus()");
    }
  }

  @Override
  public HealthCheck getHealthCheck() {
    try {
      System.out.println("Before getHealthCheck()");
      return node.getHealthCheck();
    } finally {
      System.out.println("After getHealthCheck()");
    }
  }

  @Override
  public void drain() {
    try {
      System.out.println("Before drain()");
      node.drain();
    } finally {
      System.out.println("After drain()");
    }

  }

  @Override
  public boolean isReady() {
    try {
      System.out.println("Before isReady()");
      return node.isReady();
    } finally {
      System.out.println("After isReady()");
    }
  }
}
```
</details>

**_Foot Notes:_**

In the above example, the line `Node node = LocalNodeFactory.create(config);` explicitly creates a `LocalNode`.

There are basically 2 types of *user facing implementations* of `org.openqa.selenium.grid.node.Node` available. 

These classes are good starting points to learn how to build a custom Node and also to learn the internals of a Node.

* `org.openqa.selenium.grid.node.local.LocalNode` - Used to represent a long running Node and is the default implementation that gets wired in when you start a `node`. 
    * It can be created by calling `LocalNodeFactory.create(config);`, where:
      * `LocalNodeFactory` belongs to `org.openqa.selenium.grid.node.local`
      * `Config` belongs to `org.openqa.selenium.grid.config`
* `org.openqa.selenium.grid.node.k8s.OneShotNode` - This is a special reference implementation wherein the Node gracefully shuts itself down after servicing one test session. This class is currently not available as part of any pre-built maven artifact.
  *  You can refer to the source code [here](https://github.com/SeleniumHQ/selenium/blob/trunk/java/src/org/openqa/selenium/grid/node/k8s/OneShotNode.java) to understand its internals. 
  *  To build it locally refer [here](https://github.com/SeleniumHQ/selenium/blob/trunk/deploys/k8s/README.md). 
  *  It can be created by calling `OneShotNode.create(config)`, where:
      * `OneShotNode` belongs to `org.openqa.selenium.grid.node.k8s`
      * `Config` belongs to `org.openqa.selenium.grid.config`