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Retry Mechanism for Java

The following Java project presents a method to identify problems when trying to allocate a device or web vm from Perfecto CQ Lab and retry the request. Common problems in allocating a device include:

  • The device is busy,
  • Connection failure,
  • No available license

Quick start:

  • Clone the project and import to Intellij (Recommended) / Eclipse IDE.

  • Add your Perfecto Lab credentials at Constants.java :

public class Constants {

    //User pass
    static final String PERFECTO_HOST       = "MyHost";
    static final String PERFECTO_USER       = "MyUser";
    static final String PERFECTO_PASSWORD   = "MyPassword";
    ...

Configure AspectJ for your IDE

Hooking driver creation RemoteWebDriverAspect.java :

We use @Aspect annotations to control the RemoteWebDriver instance creation:

  • By using Before, After, Around annotations we are able to wrap the RemoteWebDriver constructor and add some control operations.
    For example, in the following code: 
@Before("call(org.openqa.selenium.remote.RemoteWebDriver+.new(..))")
@SuppressWarnings("PMD.AvoidCatchingThrowable")
public void remoteWebDriverBeforeAspect(JoinPoint joinPoint) throws Throwable {
    System.out.println("Before Creating driver...");
}

The remoteWebDriverBeforeAspect method will be executed before calling the constructor of every RemoteWebDriver instance.
The @Around annotation enables us to control what happens both before and after the method we wrap with the annotation: 

@Around("call(org.openqa.selenium.remote.RemoteWebDriver+.new(..))")
@SuppressWarnings("PMD.AvoidCatchingThrowable")
public Object remoteWebDriverAspect(ProceedingJoinPoint point) throws Throwable {
    ... //Code before method 

    try{
        proceed = point.proceed();
    } catch (Throwable throwable) {
    ... // Code on failure 
    }
    
    ... // Code to call after the method 
}

Advanced Options (Retry count, delay ....)

We use Constants to determine the retry mechanism settings such as: Maximum times to retry and delay between each retry.
For example in Constants file:

    // Java code ...
    //General constants
    static final int ImplicitlyWait     = 25;
    static final int PageLoadTimeout    = 25;
    static final int WebDriverWait      = 10;
    static final int MaxTimesToRetry    = 10;
    static final long WaitOnRetry       = 10000L;
     
    // Java code

The following code snippet includes the variables:
MaxTimesToRetry - Maximum number of retries to create WebDriver instance.
WaitOnRetry - How long (milliseconds) to wait between each retry.

RemoteWebDriverAspect overview

In this project we wrap the RemoteWebDriver constructor in an @Around annotation and execute the try-catch clause within a while loop. If the constructor throws an exception, the catch clause increments the count of retries and then lets the while loop retry the constructor.