A retry mechanism in java with ScheduledExecutorService

Question

I am trying to write a retry mechanism in java, that reties a function after 3 minutes in case of failure, and retries up to maximum 3 times. I do not want to use Thread.Sleep, and instead I was thinking about using ScheduledExecutorService. I am trying to figure out what would be a good implementation for it. It seems executor.schedule() does not the runnable inside the runnable.

I was thinking something like this:

ScheduledExecutorService executor = Executors.newScheduledThreadPool(1);
final int count = 1;
final int MAX_RETRY = 3;
Runnable runnable = () -> {
   try {
     //This function can fail and throw FunctionException
     callMyFunction();
   }
   catch (FunctionException e) {
     if (++count <= MAX_RETRY) {
        executor.schedule(runnable, 30*60*1000);
     }
   }
};

executor.execute(runnable);

Answer 1

I would suggest you use the spring-retry library instead of writing your own implementation.

Create a RetryTemplate instance. Sample code here - https://github.com/innovationchef/batchpay/blob/master/src/main/java/com/innovationchef/service/PayApiRetryTemplate.java

Then call you method like this -

retryTemplate.execute(arg -> callMyFunction());

Answer 2

This code seems to work, and resolves the issue I had. I could not use lambda to implement my Runnable function, as in lambda there is no way to have "this" reference the instance created by a lambda expression in this line:

scheduler.schedule(this, 1, TimeUnit.SECONDS);

Any idea how to fix that?

Here is the entire code:

ScheduledExecutorService scheduler = Executors.newScheduledThreadPool(1);
AtomicInteger counter = new AtomicInteger(1);
final int MAX_RETRY = 3;
scheduler.execute(new Runnable() {
   @Override
   public void run () {
   try {
     System.out.println("Attempt number: " + counter.get());
     functionCall();
     scheduler.shutdown();
   }
   catch (Exception e) {
      if (counter.get() < MAX_RETRY) {
            System.out.println("Attempt number: " + counter.getAndIncrement() + " failed.");
            scheduler.schedule(this, 1, TimeUnit.SECONDS);
      }
      else {
         System.out.println("Error message: " + e.getMessage());
         scheduler.shutdown();
      }
   }
 }
 });
 }
    
 public static void functionCall() {
     throw new RuntimeException("Does not work");
 }

Thanks @Turing85 for the help and useful comments.