Customizing a 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:Nodeis of typeorg.openqa.selenium.grid.node.NodeConfigis of typeorg.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
- Create a sample project using your favourite build tool (Maven|Gradle).
- Add the below dependency to your sample project.
- Add your customized Node to the project.
- Build an uber jar to be able to start the Node using
java -jarcommand. - Now start the Node using the command:
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 instead of 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
- Create a sample project using your favourite build tool (Maven|Gradle).
- Add the below dependency to your sample project.
- Add your customized Node to the project.
- Build a jar of your project using your build tool.
- Now start the Node using the command:
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.
Sample customized node
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, URI uri, Secret registrationSecret) {
super(tracer, new NodeId(UUID.randomUUID()), uri, registrationSecret);
}
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);
// Refer to the foot notes for additional context on this line.
Node node = LocalNodeFactory.create(config);
DecoratedLoggingNode wrapper = new DecoratedLoggingNode(loggingOptions.getTracer(),
uri, secretOptions.getRegistrationSecret());
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()");
}
}
}
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 anode.- It can be created by calling
LocalNodeFactory.create(config);, where:LocalNodeFactorybelongs toorg.openqa.selenium.grid.node.localConfigbelongs toorg.openqa.selenium.grid.config
- It can be created by calling
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.
