Working with Scheduled Tasks

1. Enabling Scheduling (@EnableScheduling)

Example: Enable task scheduling

@SpringBootApplication
@EnableScheduling
public class App {}

2. Creating Scheduled Methods (@Scheduled)

Attribute	Format
`fixedRate`	ms between starts
`fixedDelay`	ms between end and next start
`fixedRateString`	Property placeholder support
`initialDelay`	Delay before first run
`cron`	Cron expression
`zone`	Timezone for cron

3. Using Fixed Rate Execution

Example: Fixed-rate scheduled task

@Scheduled(fixedRate = 60_000)
public void every60s() { /* every 60s regardless of duration */ }

4. Using Fixed Delay Execution

Example: Fixed-delay with initial delay

@Scheduled(fixedDelay = 5000, initialDelay = 10_000)
public void backoff() { /* 5s after previous completion */ }

5. Using Cron Expressions

Field	Range
second	0–59
minute	0–59
hour	0–23
day-of-month	1–31
month	1–12 / JAN-DEC
day-of-week	0–7 / MON-SUN

Example: Cron expressions with timezone

@Scheduled(cron = "0 0 2 * * *", zone = "UTC")  // every day 02:00 UTC
@Scheduled(cron = "0 */5 * * * MON-FRI")        // every 5 min on weekdays
@Scheduled(cron = "${app.cron.cleanup:0 0 * * * *}")

6. Configuring Initial Delay

Attribute	Notes
`initialDelay`	Wait period before first run (ms)
`initialDelayString`	Property placeholder

7. Using Dynamic Scheduling (SchedulingConfigurer)

Example: Dynamic cron from configuration

@Configuration
@EnableScheduling
public class DynamicSchedule implements SchedulingConfigurer {
  @Override public void configureTasks(ScheduledTaskRegistrar registrar) {
    registrar.addTriggerTask(
      () -> doWork(),
      ctx -> new CronTrigger(props.getCron()).nextExecution(ctx)
    );
  }
}

8. Configuring Task Scheduler Pool Size

Example: Scheduler pool size configuration

spring:
  task:
    scheduling:
      pool:
        size: 4
      thread-name-prefix: scheduler-

Warning: Default pool size = 1 → long-running task blocks all others. Increase for concurrent schedules.

9. Handling Scheduled Task Exceptions

Example: Safe scheduled task with error logging

@Scheduled(fixedRate = 60_000)
public void safeRun() {
  try { work(); }
  catch (Exception ex) { log.error("scheduled failure", ex); }
}

Note: Uncaught exceptions don't stop schedule but are silently logged at WARN — handle explicitly.

10. Using Time Zones in Cron Expressions

Setting	Effect
`zone="UTC"`	Cron evaluated in UTC
`zone="America/New_York"`	Local DST aware
Default	JVM default time zone

11. Testing Scheduled Tasks

Strategy	How
Disable in tests	`@MockBean` the scheduled bean OR set `spring.task.scheduling.enabled=false`
Manual invoke	Call the method directly in unit test
Awaitility	Wait for side effects

Related Cheat Sheets

High Level Design