Issue
The Problem:
My application is using Spring Boot and Java 8. I have a schedule task to get some data from three different data sources but now they are running in sequence. I want to speed them up by dividing the three data retrieval actions by using CompletableFuture at the same time concurrently. However, I run the code and found that the CompletableFuture tasks are running in one single thread called 'scheduling-1' rather than running asynchronously.
What I have tried:
I thought I was doing something not great. So, I decided to step back and tried it out by running a small testing project. What I have tried is like I combine the techniques mentioned by the two examples below:
But when I put them together, I find that they are using the same thread when calling the Async method.
The output was:
[ scheduling-1] Looking up PivotalSoftware, thread: scheduling-1
[ scheduling-1] Looking up CloudFoundry, thread: scheduling-1
[ scheduling-1] Looking up Spring-Projects, thread: scheduling-1
My Question:
Whether my code went wrong or there is only one thread available in the scheduler even I use Async for CompletableFuture? What's the underlying reasons behind the result of my experiment result?
My code:
AsyncMethodApplication
@SpringBootApplication
@EnableAsync
@EnableScheduling
@PropertySource("classpath:common.properties")
public class AsyncMethodApplication {
public static void main(String[] args) {
// close the application context to shut down the custom ExecutorService
SpringApplication.run(AsyncMethodApplication.class, args).close();
}
@Bean
public Executor taskExecutor() {
ThreadPoolTaskExecutor executor = new ThreadPoolTaskExecutor();
executor.setCorePoolSize(3);
executor.setMaxPoolSize(3);
executor.setQueueCapacity(500);
executor.setThreadNamePrefix("GithubLookup-");
executor.initialize();
return executor;
}
}
MyService
@Service
public class MyService {
private static final Logger logger = LoggerFactory.getLogger(MyService.class);
@Autowired
private UserLookupService gitHubLookupService;
@Scheduled(cron = "${cron.expression.reloadUserData}")
@PostConstruct
public void loadCurrentDayUsers() throws Exception {
this.loadUsers();
// this.loadOthers();
}
public void loadUsers() throws Exception {
// Start the clock
long start = System.currentTimeMillis();
// Kick of multiple, asynchronous lookups
CompletableFuture<User> page1 = gitHubLookupService.findUser("PivotalSoftware");
CompletableFuture<User> page2 = gitHubLookupService.findUser("CloudFoundry");
CompletableFuture<User> page3 = gitHubLookupService.findUser("Spring-Projects");
// Wait until they are all done
CompletableFuture.allOf(page1,page2,page3).join();
// Print results, including elapsed time
logger.info("Elapsed time: " + (System.currentTimeMillis() - start));
logger.info("--> " + page1.get());
logger.info("--> " + page2.get());
logger.info("--> " + page3.get());
}
}
User
@JsonIgnoreProperties(ignoreUnknown=true)
public class User {
private String name;
private String blog;
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public String getBlog() {
return blog;
}
public void setBlog(String blog) {
this.blog = blog;
}
@Override
public String toString() {
return "User [name=" + name + ", blog=" + blog + "]";
}
}
UserLookupService
@Service
public class UserLookupService {
private static final Logger logger = LoggerFactory.getLogger(UserLookupService.class);
@Async
public CompletableFuture<User> findUser(String user) throws InterruptedException {
logger.info("Looking up " + user + ", thread: " + Thread.currentThread().getName());
// mock result
User results = new User();
results.setName(user);
results.setBlog("Blog - " + user);
// Artificial delay of 1s for demonstration purposes
Thread.sleep(1000L);
return CompletableFuture.completedFuture(results);
}
}
common.properties
cron.expression.reloadUserData=0 0/1 3-23 * * MON-SAT
Solution
Credit to M. Deinum.
remove the @PostConstruct as that might lead to eager init of your UserLookupService leading to no proxy and thus no @Async behavior
Answered By - ADS
Answer Checked By - Mildred Charles (JavaFixing Admin)
