마시멜로

try (var scope = new StructuredTaskScope.ShutdownOnFailure()) {
    Future<String> page1 = scope.fork(() -> fetch("https://a.com"));
    Future<String> page2 = scope.fork(() -> fetch("https://b.com"));

    scope.join();           // 모든 작업 대기
    scope.throwIfFailed();  // 하나라도 실패 시 예외 발생

    return page1.result() + page2.result();
}

ExecutorService executor = Executors.newFixedThreadPool(10);

List<Callable<String>> tasks = IntStream.range(0, 100)
    .mapToObj(i -> (Callable<String>) () -> {
        HttpClient client = HttpClient.newHttpClient();
        HttpRequest request = HttpRequest.newBuilder(URI.create("https://httpbin.org/delay/0.5")).build();
        return client.send(request, HttpResponse.BodyHandlers.ofString()).body();
    }).toList();

long start = System.currentTimeMillis();
List<Future<String>> futures = executor.invokeAll(tasks);
executor.shutdown();
long elapsed = System.currentTimeMillis() - start;

System.out.println("ThreadPool 총 소요시간: " + elapsed + "ms");

ExecutorService executor = Executors.newVirtualThreadPerTaskExecutor();

List<Callable<String>> tasks = IntStream.range(0, 100)
    .mapToObj(i -> (Callable<String>) () -> {
        HttpClient client = HttpClient.newHttpClient();
        HttpRequest request = HttpRequest.newBuilder(URI.create("https://httpbin.org/delay/0.5")).build();
        return client.send(request, HttpResponse.BodyHandlers.ofString()).body();
    }).toList();

long start = System.currentTimeMillis();
List<Future<String>> futures = executor.invokeAll(tasks);
executor.shutdown();
long elapsed = System.currentTimeMillis() - start;

System.out.println("VirtualThread 총 소요시간: " + elapsed + "ms");

@Bean
public TaskExecutor applicationTaskExecutor() {
    return TaskExecutors.virtual();
}

           [Kafka Topic: eai-events]
                    │
               (Consumer)
                    ▼
       ┌──────────────────────────────┐
       │ try { process(msg) }         │
       │ catch → produce to DLQ topic │
       └──────────────────────────────┘
                    │
                    ▼
         [Kafka Topic: eai-events.dlq]

@Component
@RequiredArgsConstructor
public class DlqProducer {

    private final KafkaTemplate<String, String> kafkaTemplate;

    public void sendToDlq(String traceId, String message) {
        kafkaTemplate.send("eai-events.dlq", traceId, message);
    }
}

@KafkaListener(topics = "eai-events", groupId = "eai-group")
public void listen(ConsumerRecord<String, String> record) {
    try {
        processMessage(record.value());
    } catch (Exception ex) {
        log.error("Processing failed, sending to DLQ: {}", record.value(), ex);
        dlqProducer.sendToDlq(record.key(), record.value());
    }
}

int waitMinutes = fibonacci(i); // 예: 1,1,2,3,5,8,13,...

private int fibonacci(int n) {
    if (n <= 1) return 1;
    int a = 1, b = 1;
    for (int i = 2; i <= n; i++) {
        int temp = a + b;
        a = b;
        b = temp;
    }
    return b;
}

int base = (int) Math.min(180, Math.pow(2, i));
int waitMinutes = new Random().nextInt(base + 1); // 0 ~ base 사이 랜덤

int waitMinutes = (int) Math.min(180, Math.log(i + 2) * 5); // log 기반 증가

public class DynamicRoutingDataSource extends AbstractRoutingDataSource {
    @Override
    protected Object determineCurrentLookupKey() {
        return DataSourceContextHolder.getCurrentKey(); // ThreadLocal 기반
    }
}

spring:
  datasource:
    dynamic:
      db1:
        url: jdbc:mysql://db1-url
        username: user1
      db2:
        url: jdbc:oracle:thin:@db2-url
        username: user2

public Connection getConnectionForTarget(TargetDbInfo dbInfo) throws SQLException {
    String url = dbInfo.getJdbcUrl();  // 예: jdbc:oracle:thin:@...
    String user = dbInfo.getUsername();
    String pass = dbInfo.getPassword();

    return DriverManager.getConnection(url, user, pass); // 직접 연결
}

try (Connection conn = getConnectionForTarget(targetInfo);
     PreparedStatement stmt = conn.prepareStatement("INSERT INTO ...")) {
    stmt.setString(1, value);
    stmt.executeUpdate();
}

        ┌────────────┐      ┌──────────────┐
        │     A      │      │       B/C    │
        └────┬───────┘      └────┬─────────┘
             │                       │
             ▼                       ▼
       [EAI Gateway/API Layer]  ◀───────┐
             │                          │
             ▼                          │
    ┌─────────────────────────────┐     │
    │     EAI Core (Router)       │◀────┘
    │  ├─ Transformation Engine   │
    │  ├─ Protocol Adapters       │  ↔ Redis/Kafka
    │  ├─ Routing Rules           │
    └─────────────────────────────┘
             │
             ▼
    ┌─────────────────────────────┐
    │ External APIs / SaaS / DBs │
    └─────────────────────────────┘

@GetMapping(value = "/sse/{id}", produces = MediaType.TEXT_EVENT_STREAM_VALUE)
public Flux<ServerSentEvent<String>> stream(@PathVariable String id) {
    return processor.getStreamFor(id)
        .map(data -> ServerSentEvent.builder(data).id(id).event("result").build());
}

scope: https://www.googleapis.com/auth/calendar.events

@Data
@NoArgsConstructor
@AllArgsConstructor
public class CalendarEvent {
    private String summary;
    private String description;

    @JsonProperty("start")
    private CalendarDateTime start;

    @JsonProperty("end")
    private CalendarDateTime end;

    @Data
    @NoArgsConstructor
    @AllArgsConstructor
    public static class CalendarDateTime {
        private String dateTime; // "2025-06-15T10:00:00+09:00"
        private String timeZone; // "Asia/Seoul"
    }
}

@Service
@RequiredArgsConstructor
public class GoogleCalendarService {

    private final WebClient googleWebClient;

    public Mono<String> addEventToPrimaryCalendar(CalendarEvent event) {
        return googleWebClient
                .post()
                .uri("https://www.googleapis.com/calendar/v3/calendars/primary/events")
                .bodyValue(event)
                .retrieve()
                .bodyToMono(String.class); // 또는 CalendarEventResponse.class
    }
}

@Component
@RequiredArgsConstructor
public class CalendarTestRunner implements CommandLineRunner {

    private final GoogleCalendarService service;

    @Override
    public void run(String... args) {
        CalendarEvent.CalendarDateTime start = new CalendarEvent.CalendarDateTime(
                "2025-06-20T10:00:00+09:00", "Asia/Seoul"
        );
        CalendarEvent.CalendarDateTime end = new CalendarEvent.CalendarDateTime(
                "2025-06-20T11:00:00+09:00", "Asia/Seoul"
        );

        CalendarEvent event = new CalendarEvent("회의 제목", "회의 설명입니다", start, end);

        service.addEventToPrimaryCalendar(event)
               .doOnNext(response -> System.out.println("응답: " + response))
               .subscribe();
    }
}

{
  "id": "abc123def456",
  "summary": "회의 제목",
  "start": {
    "dateTime": "2025-06-20T10:00:00+09:00",
    "timeZone": "Asia/Seoul"
  },
  "end": {
    "dateTime": "2025-06-20T11:00:00+09:00",
    "timeZone": "Asia/Seoul"
  }
}

implementation 'org.springframework.boot:spring-boot-starter-oauth2-client'
implementation 'org.springframework.boot:spring-boot-starter-webflux'

spring:
  security:
    oauth2:
      client:
        registration:
          google:
            client-id: <your-client-id>
            client-secret: <your-client-secret>
            scope: https://www.googleapis.com/auth/calendar.readonly
            redirect-uri: "{baseUrl}/login/oauth2/code/{registrationId}"
            authorization-grant-type: authorization_code
            client-name: Google
        provider:
          google:
            authorization-uri: https://accounts.google.com/o/oauth2/v2/auth
            token-uri: https://oauth2.googleapis.com/token
            user-info-uri: https://www.googleapis.com/oauth2/v3/userinfo

@Configuration
public class WebClientConfig {

    @Bean
    public WebClient googleWebClient(ReactiveOAuth2AuthorizedClientManager manager) {
        ServerOAuth2AuthorizedClientExchangeFilterFunction oauth =
                new ServerOAuth2AuthorizedClientExchangeFilterFunction(manager);
        oauth.setDefaultClientRegistrationId("google");

        return WebClient.builder()
                .apply(oauth.oauth2Configuration())
                .build();
    }
}

@Service
@RequiredArgsConstructor
public class GoogleCalendarService {

    private final WebClient googleWebClient;

    public Mono<String> getCalendarList() {
        return googleWebClient
                .get()
                .uri("https://www.googleapis.com/calendar/v3/users/me/calendarList")
                .retrieve()
                .bodyToMono(String.class);
    }
}