[Failsafe] Retry with Fallback

Scenario
If we cannot get connection, then we will retry 5 times with 2 seconds delay.
If we fail to retry with 5 times, then we will pause X minutes then retry again.
How to implement it?


How-to
You can make good use of failsafe to fulfill this implement.
In this exampe, it will demonstrate:
1. create a retry policy with 5 max retries and have 2 seconds delay among retries
2. If you got failed execution, it will retry again after 5 seconds.

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package albert.practice.retry; import java.sql.Connection; import java.text.SimpleDateFormat; import java.util.Date; import java.util.concurrent.TimeUnit; import lombok.extern.slf4j.Slf4j; import net.jodah.failsafe.Failsafe; import net.jodah.failsafe.RetryPolicy; @Slf4j public class RetryTest { private int count = 0; public static void main(String[] args) throws ConnectionException { new RetryTest().connectWithRetry(); } public Connection connectWithRetry() { // create a retry policy with 5 max retries and have 2 seconds delay among retries RetryPolicy retryPolicy = new RetryPolicy(); retryPolicy.retryOn(ConnectionException.class).withDelay(2, TimeUnit.SECONDS) .withMaxRetries(5); // Using Fallbacks allow you to provide an alternative result for a failed execution. // In this example, it will retry again after 5 seconds. Connection conn = Failsafe.with(retryPolicy).withFallback(() -> retryIfFail()) .get(() -> connect()); return conn; } public void retryIfFail() throws InterruptedException { log.debug("GG at " + getCurrentTime()); Thread.sleep(5000); log.debug("retry....." + getCurrentTime()); connectWithRetry(); } public Connection connect() throws ConnectionException { log.debug(" time = " + getCurrentTime()); Connection conn = null; if (count < 9) { count++; throw new ConnectionException("connection fail!"); } else { log.debug("get connection successfuly..."); } return conn; } private String getCurrentTime() { SimpleDateFormat dateFormat = new SimpleDateFormat("yyyy/MM/dd HH:mm:ss.SSS"); return dateFormat.format(new Date()); } }

Console log:

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DEBUG albert.practice.retry.RetryTest - time = 2016/11/05 11:42:13.832 DEBUG albert.practice.retry.RetryTest - time = 2016/11/05 11:42:15.837 DEBUG albert.practice.retry.RetryTest - time = 2016/11/05 11:42:17.837 DEBUG albert.practice.retry.RetryTest - time = 2016/11/05 11:42:19.837 DEBUG albert.practice.retry.RetryTest - time = 2016/11/05 11:42:21.838 DEBUG albert.practice.retry.RetryTest - time = 2016/11/05 11:42:23.839 DEBUG albert.practice.retry.RetryTest - GG at 2016/11/05 11:42:23.839 DEBUG albert.practice.retry.RetryTest - retry.....2016/11/05 11:42:28.839 DEBUG albert.practice.retry.RetryTest - time = 2016/11/05 11:42:28.839 DEBUG albert.practice.retry.RetryTest - time = 2016/11/05 11:42:30.839 DEBUG albert.practice.retry.RetryTest - time = 2016/11/05 11:42:32.839 DEBUG albert.practice.retry.RetryTest - time = 2016/11/05 11:42:34.840 DEBUG albert.practice.retry.RetryTest - get connection successfuly...

Reference
[1] https://github.com/jhalterman/failsafe#fallbacks