Understanding Flink Restart Strategies: Configuration and Code Examples

Overview : Flink supports multiple restart strategies that determine how a job is restarted after a failure. A default strategy is defined in flink-conf.yaml and is used when no specific strategy is set for a job.

Restart Strategy Types :

Fixed‑delay: restarts a job a fixed number of times with a constant delay between attempts.

Failure‑rate: restarts a job up to a maximum number of failures within a time interval; if the failure rate exceeds the limit, the job is considered failed.

No‑restart: disables automatic restarts.

If checkpointing is disabled, Flink uses the no‑restart strategy; if checkpointing is enabled but no strategy is configured, the fixed‑delay strategy is applied.

Configuration via flink-conf.yaml :

restart-strategy: fixed-delay
restart-strategy.fixed-delay.attempts: 3
restart-strategy.fixed-delay.delay: 10 s

or for failure‑rate:

restart-strategy: failure-rate
restart-strategy.failure-rate.max-failures-per-interval: 3
restart-strategy.failure-rate.failure-rate-interval: 5 min
restart-strategy.failure-rate.delay: 10 s

or to disable restarts: restart-strategy: none Programmatic Configuration (Java) :

env.setRestartStrategy(RestartStrategies.fixedDelayRestart(3, Time.seconds(10)));

env.setRestartStrategy(RestartStrategies.failureRateRestart(
    3, Time.of(5, TimeUnit.MINUTES), Time.of(10, TimeUnit.SECONDS)));

env.setRestartStrategy(RestartStrategies.noRestart());

Full Example :

public class RestartTest {
    public static void main(String[] args) {
        StreamExecutionEnvironment env = StreamExecutionEnvironment.getExecutionEnvironment();
        // Enable checkpointing every 1000 ms
        env.enableCheckpointing(1000);
        // Fixed‑delay: 3 attempts, 10‑second interval
        env.setRestartStrategy(RestartStrategies.fixedDelayRestart(3, Time.seconds(10)));
        // Failure‑rate: max 3 failures in 5 minutes, 10‑second interval
        env.setRestartStrategy(RestartStrategies.failureRateRestart(
            3, Time.of(5, TimeUnit.MINUTES), Time.of(10, TimeUnit.SECONDS)));
        // No restart
        env.setRestartStrategy(RestartStrategies.noRestart());
    }
}

The article also provides links to a series of Flink tutorials and points readers to the original GitHub repository for the full source.