메일 비동기 전송 처리 (#40)

* refactor: 필드 주입 대신 생성자 주입으로 변경

* refactor: 개행 및 EOL 추가

* refactor: 서류, 최종 메일 분리 및 비동기 처리

* refactor: 빌더 생성자로 변경

* test: displayName 추가

* fix: 스레드 작업 대기 시간 연장

* feat: 메일 예외 추가

* feat: 메일 병렬처리 추가

* fix: 대기시간 연장

* refactor: 메일 예약, 메일 전송 로직 분리

* fix: 메일 전송 테스트 비활성화

* fix: setter 추가

* feat: 서류 합격 메일 전송

* fix: 템플릿 정구 수

* feat: 메일 전송 비동기, 40개 배치 전송

src/main/java/land/leets/domain/mail/usecase/SendFinalMailImpl.java

@@ -13,7 +13,7 @@
 import land.leets.domain.application.domain.Application;
 import land.leets.domain.application.domain.repository.ApplicationRepository;
 import land.leets.domain.application.type.ApplicationStatus;
-import land.leets.global.mail.MailProvider;
+import land.leets.global.mail.MailManager;
 import land.leets.global.mail.dto.MailDto;
 import lombok.RequiredArgsConstructor;
 
@@ -30,7 +30,7 @@ public class SendFinalMailImpl implements SendMail {
 
 	private final Random RANDOM = new Random();
 	private final ApplicationRepository applicationRepository;
-	private final MailProvider mailProvider;
+	private final MailManager mailManager;
 	private final TemplateEngine templateEngine;
 
 	@Override
@@ -44,7 +44,7 @@ public void execute(ApplicationStatus status) {
 			MailDto mailDto = new MailDto(MAIL_TITLE, new String[] {application.getUser().getEmail()}, message);
 			mailDtos.add(mailDto);
 		}
-		mailProvider.sendEmails(mailDtos);
+		mailManager.sendEmails(mailDtos);
 	}
 
 	private Context makeContext(String name) {

src/main/java/land/leets/domain/mail/usecase/SendPaperMailImpl.java

@@ -26,7 +26,7 @@
 import land.leets.domain.interview.domain.repository.InterviewRepository;
 import land.leets.domain.interview.exception.InterviewNotFoundException;
 import land.leets.domain.interview.type.HasInterview;
-import land.leets.global.mail.MailProvider;
+import land.leets.global.mail.MailManager;
 import land.leets.global.mail.dto.MailDto;
 import lombok.RequiredArgsConstructor;
 import lombok.extern.slf4j.Slf4j;
@@ -48,7 +48,7 @@ public class SendPaperMailImpl implements SendMail {
 	private final InterviewRepository interviewRepository;
 	private final ApplicationRepository applicationRepository;
 	private final TemplateEngine templateEngine;
-	private final MailProvider mailProvider;
+	private final MailManager mailManager;
 
 	@Value("${target.url.dev}")
 	private String LOCAL_TARGET_URL;
@@ -70,7 +70,7 @@ public void execute(ApplicationStatus status) {
 			MailDto mailDto = new MailDto(MAIL_TITLE, new String[] {application.getUser().getEmail()}, message);
 			mailDtos.add(mailDto);
 		}
-		mailProvider.sendEmails(mailDtos);
+		mailManager.sendEmails(mailDtos);
 	}
 
 	private Context makeContext(String name) {

src/main/java/land/leets/global/config/AsyncConfig.java

@@ -0,0 +1,29 @@
+package land.leets.global.config;
+
+import java.util.concurrent.Executor;
+
+import org.springframework.context.annotation.Bean;
+import org.springframework.context.annotation.Configuration;
+import org.springframework.scheduling.annotation.EnableAsync;
+import org.springframework.scheduling.concurrent.ThreadPoolTaskExecutor;
+
+import lombok.extern.slf4j.Slf4j;
+
+@Slf4j
+@EnableAsync
+@Configuration
+public class AsyncConfig {
+
+	@Bean
+	public Executor taskExecutor() {
+		ThreadPoolTaskExecutor executor = new ThreadPoolTaskExecutor();
+		executor.setCorePoolSize(2);
+		executor.setMaxPoolSize(4);
+		executor.setQueueCapacity(200);
+		executor.setThreadNamePrefix("Mailing-");
+		executor.setKeepAliveSeconds(60);
+		executor.setRejectedExecutionHandler(((r, asyncExecutor) -> log.warn("더 이상 요청을 처리할 수 없습니다.")));
+		executor.initialize();
+		return executor;
+	}
+}

src/main/java/land/leets/global/cron/SendMailCron.java

@@ -1,6 +1,5 @@
 package land.leets.global.cron;
 
-import org.springframework.scheduling.annotation.Scheduled;
 import org.springframework.stereotype.Component;
 
 import land.leets.domain.application.type.ApplicationStatus;
@@ -17,7 +16,7 @@ public class SendMailCron {
 	private final SendFinalMailImpl sendFinalMailImpl;
 	private final SendPaperMailImpl sendPaperMailImpl;
 
-	@Scheduled(cron = "0 0 23 8 9 ?")
+	// @Scheduled(cron = "0 0 23 8 9 ?")
 	public void sendPaperMail() {
 		for (ApplicationStatus status : ApplicationStatus.papers()) {
 			sendPaperMailImpl.execute(status);
@@ -26,14 +25,14 @@ public void sendPaperMail() {
 		log.info("Send paper result mail successfully.");
 	}
 
-	@Scheduled(cron = "0 30 23 8 9 ?")
+	// @Scheduled(cron = "0 30 23 8 9 ?")
 	public void sendPassPaperMail() {
 		sendPaperMailImpl.execute(ApplicationStatus.PASS_PAPER);
 
 		log.info("Send paper result mail successfully.");
 	}
 
-	@Scheduled(cron = "0 0 20 11 9 ?")
+	// @Scheduled(cron = "0 0 20 11 9 ?")
 	public void sendFinalMail() {
 		for (ApplicationStatus status : ApplicationStatus.finals()) {
 			sendFinalMailImpl.execute(status);

src/main/java/land/leets/global/mail/MailFactory.java

@@ -0,0 +1,75 @@
+package land.leets.global.mail;
+
+import java.util.List;
+import java.util.Objects;
+
+import org.springframework.mail.MailSendException;
+import org.springframework.mail.javamail.JavaMailSender;
+import org.springframework.mail.javamail.MimeMessageHelper;
+import org.springframework.scheduling.annotation.Async;
+import org.springframework.stereotype.Component;
+import org.springframework.util.function.ThrowingSupplier;
+
+import jakarta.mail.Address;
+import jakarta.mail.MessagingException;
+import jakarta.mail.internet.MimeMessage;
+import land.leets.global.mail.dto.MailDto;
+import land.leets.global.mail.exception.MailException;
+import lombok.RequiredArgsConstructor;
+import lombok.extern.slf4j.Slf4j;
+
+@Slf4j
+@Component
+@RequiredArgsConstructor
+public class MailFactory {
+
+	private final JavaMailSender javaMailSender;
+
+	public MimeMessage createMail(MailDto mailDto) {
+		try {
+			MimeMessage mimeMessage = javaMailSender.createMimeMessage();
+			MimeMessageHelper mimeMessageHelper = new MimeMessageHelper(mimeMessage, false, "UTF-8");
+			mimeMessageHelper.setTo(mailDto.to());
+			mimeMessageHelper.setSubject(mailDto.title());
+			mimeMessageHelper.setText(mailDto.body(), true);
+			return mimeMessage;
+		} catch (MessagingException e) {
+			throw new MailException();
+		}
+	}
+
+	@Async
+	public void sendMails(List<MimeMessage> batch) {
+		try {
+			javaMailSender.send(batch.toArray(new MimeMessage[0]));
+		} catch (MailSendException e) {
+			MimeMessage[] failedMessages = e.getFailedMessages().keySet()
+				.stream()
+				.map(object -> (MimeMessage)object)
+				.toArray(MimeMessage[]::new);
+			retry(failedMessages);
+		}
+	}
+
+	private void retry(MimeMessage[] failedMessages) {
+		try {
+			javaMailSender.send(failedMessages);
+		} catch (MailSendException e) {
+			e.getFailedMessages().keySet()
+				.stream()
+				.map(failure -> (MimeMessage)failure)
+				.map(mimeMessage -> apply(mimeMessage::getAllRecipients))
+				.filter(Objects::nonNull)
+				.forEach(address -> log.error("fail to send mail. address = {}", address));
+		}
+	}
+
+	private Address apply(ThrowingSupplier<Address[]> function) {
+		try {
+			return function.get()[0];
+		} catch (Exception e) {
+			log.error("fail to load failed address");
+			return null;
+		}
+	}
+}

src/main/java/land/leets/global/mail/MailManager.java

@@ -0,0 +1,39 @@
+package land.leets.global.mail;
+
+import java.util.List;
+import java.util.stream.IntStream;
+
+import org.springframework.stereotype.Component;
+
+import jakarta.mail.internet.MimeMessage;
+import land.leets.global.mail.dto.MailDto;
+import lombok.RequiredArgsConstructor;
+
+@Component
+@RequiredArgsConstructor
+public class MailManager {
+
+	private static final int BATCH_SIZE = 40;
+
+	private final MailFactory mailFactory;
+
+	public void sendEmails(List<MailDto> mailDtos) {
+		List<List<MimeMessage>> batchedMails = createChunkedMails(mailDtos);
+
+		batchedMails.parallelStream()
+			.forEach(mailFactory::sendMails);
+	}
+
+	private List<List<MimeMessage>> createChunkedMails(List<MailDto> mailDtos) {
+		List<MimeMessage> messages = mailDtos.parallelStream()
+			.map(mailFactory::createMail)
+			.toList();
+		return partitionMessages(messages);
+	}
+
+	private List<List<MimeMessage>> partitionMessages(List<MimeMessage> messages) {
+		return IntStream.range(0, (messages.size() + BATCH_SIZE - 1) / BATCH_SIZE)
+			.mapToObj(i -> messages.subList(i * BATCH_SIZE, Math.min((i + 1) * BATCH_SIZE, messages.size())))
+			.toList();
+	}
+}