Fixed async error

.gitignore

@@ -14,3 +14,4 @@ AGENTS.md
 
 # Build-tool binaries — provided via the build's dependency management, never committed
 lombok-*.jar
+services/py-genai-helper/.idea/

services/spring-letter/src/main/java/tum/devoops/letterservice/LetterServiceApplication.java

@@ -2,8 +2,10 @@
 
 import org.springframework.boot.SpringApplication;
 import org.springframework.boot.autoconfigure.SpringBootApplication;
+import org.springframework.scheduling.annotation.EnableAsync;
 
 @SpringBootApplication
+@EnableAsync
 public class LetterServiceApplication {
 
     public static void main(String[] args) {

services/spring-letter/src/main/java/tum/devoops/letterservice/config/AsyncConfig.java

@@ -0,0 +1,24 @@
+package tum.devoops.letterservice.config;
+
+import java.util.concurrent.Executor;
+
+import org.springframework.context.annotation.Bean;
+import org.springframework.context.annotation.Configuration;
+import org.springframework.scheduling.annotation.AsyncConfigurer;
+import org.springframework.scheduling.concurrent.ThreadPoolTaskExecutor;
+
+@Configuration
+public class AsyncConfig implements AsyncConfigurer {
+
+    @Override
+    @Bean(name = "taskExecutor")
+    public Executor getAsyncExecutor() {
+        ThreadPoolTaskExecutor executor = new ThreadPoolTaskExecutor();
+        executor.setCorePoolSize(2);
+        executor.setMaxPoolSize(10);
+        executor.setQueueCapacity(500);
+        executor.setThreadNamePrefix("mail-dispatch-");
+        executor.initialize();
+        return executor;
+    }
+}

services/spring-letter/src/main/java/tum/devoops/letterservice/service/LetterService.java

@@ -2,22 +2,16 @@
 
 import com.openhtmltopdf.pdfboxout.PdfRendererBuilder;
 import io.micrometer.core.instrument.MeterRegistry;
-import jakarta.mail.MessagingException;
-import jakarta.mail.internet.MimeMessage;
 import org.jsoup.Jsoup;
 import org.jsoup.nodes.Document;
 import org.jsoup.nodes.Entities;
-import org.springframework.beans.factory.annotation.Value;
 import org.springframework.core.io.ByteArrayResource;
 import org.springframework.core.io.Resource;
-import org.springframework.mail.javamail.JavaMailSender;
-import org.springframework.mail.javamail.MimeMessageHelper;
 import org.springframework.stereotype.Service;
 
 import tum.devoops.letterservice.entity.MemberEntity;
 import tum.devoops.letterservice.entity.TeamEntity;
 import tum.devoops.letterservice.exception.ForbiddenException;
-import tum.devoops.letterservice.exception.MailDeliveryException;
 import tum.devoops.letterservice.exception.PdfGenerationException;
 import tum.devoops.letterservice.model.MailRequest;
 import tum.devoops.letterservice.model.PdfRequest;
@@ -47,8 +41,7 @@ public class LetterService {
     // Tokens are {{snake_case}} per the API description; anything else is left as literal text.
     private static final Pattern TAG_PATTERN = Pattern.compile("\\{\\{([a-z0-9_]+)\\}\\}");
 
-    private final JavaMailSender mailSender;
-    private final String from;
+    private final MailDispatcher mailDispatcher;
     private final MemberRepository memberRepository;
     private final SportRepository sportRepository;
     private final TeamRepository teamRepository;
@@ -58,8 +51,7 @@ public class LetterService {
     private final TransactionRepository transactionRepository;
     private final MeterRegistry meterRegistry;
 
-    public LetterService(JavaMailSender mailSender,
-                          @Value("${spring.mail.username}") String from,
+    public LetterService(MailDispatcher mailDispatcher,
                           MemberRepository memberRepository,
                           SportRepository sportRepository,
                           TeamRepository teamRepository,
@@ -68,8 +60,7 @@ public LetterService(JavaMailSender mailSender,
                           TraineeRepository traineeRepository,
                           TransactionRepository transactionRepository,
                           MeterRegistry meterRegistry) {
-        this.mailSender = mailSender;
-        this.from = from;
+        this.mailDispatcher = mailDispatcher;
         this.memberRepository = memberRepository;
         this.sportRepository = sportRepository;
         this.teamRepository = teamRepository;
@@ -88,13 +79,7 @@ public void sendMail(MailRequest mailRequest, UUID requesterId, boolean isAdmin)
             Map<String, String> tokens = tokensFor(receiver);
             String personalizedSubject = replaceTags(subject, tokens);
             String html = replaceTags(template, tokens);
-            try {
-                sendHtml(receiver.getEmail(), personalizedSubject, html);
-                meterRegistry.counter("letters_sent_total", "status", "success").increment();
-            } catch (MessagingException e) {
-                meterRegistry.counter("letters_sent_total", "status", "failure").increment();
-                throw new MailDeliveryException("Failed to send mail to " + receiver.getEmail(), e);
-            }
+            mailDispatcher.sendAsync(receiver.getEmail(), personalizedSubject, html);
         }
     }
 
@@ -157,16 +142,6 @@ private static String escapeHtml(String value) {
         return value.replace("&", "&amp;").replace("<", "&lt;").replace(">", "&gt;");
     }
 
-    private void sendHtml(String to, String subject, String html) throws MessagingException {
-        MimeMessage message = mailSender.createMimeMessage();
-        MimeMessageHelper helper = new MimeMessageHelper(message, true, "UTF-8");
-        helper.setFrom(from);
-        helper.setTo(to);
-        helper.setSubject(subject);
-        helper.setText(html, true);
-        mailSender.send(message);
-    }
-
     // Director/trainer/trainee aren't Spring Security roles here (see LetterController); membership
     // is looked up directly against the organization-schema rows, same pattern as
     // TransactionService.isDirectorOfMember/isTrainerOfMember and FeedbackService.assertTrainerOfMember.

services/spring-letter/src/main/java/tum/devoops/letterservice/service/MailDispatcher.java

@@ -0,0 +1,47 @@
+package tum.devoops.letterservice.service;
+
+import io.micrometer.core.instrument.MeterRegistry;
+import jakarta.mail.MessagingException;
+import jakarta.mail.internet.MimeMessage;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+import org.springframework.beans.factory.annotation.Value;
+import org.springframework.mail.javamail.JavaMailSender;
+import org.springframework.mail.javamail.MimeMessageHelper;
+import org.springframework.scheduling.annotation.Async;
+import org.springframework.stereotype.Component;
+
+@Component
+public class MailDispatcher {
+
+    private static final Logger LOG = LoggerFactory.getLogger(MailDispatcher.class);
+
+    private final JavaMailSender mailSender;
+    private final String from;
+    private final MeterRegistry meterRegistry;
+
+    public MailDispatcher(JavaMailSender mailSender,
+                           @Value("${spring.mail.username}") String from,
+                           MeterRegistry meterRegistry) {
+        this.mailSender = mailSender;
+        this.from = from;
+        this.meterRegistry = meterRegistry;
+    }
+
+    @Async
+    public void sendAsync(String to, String subject, String html) {
+        try {
+            MimeMessage message = mailSender.createMimeMessage();
+            MimeMessageHelper helper = new MimeMessageHelper(message, true, "UTF-8");
+            helper.setFrom(from);
+            helper.setTo(to);
+            helper.setSubject(subject);
+            helper.setText(html, true);
+            mailSender.send(message);
+            meterRegistry.counter("letters_sent_total", "status", "success").increment();
+        } catch (MessagingException e) {
+            meterRegistry.counter("letters_sent_total", "status", "failure").increment();
+            LOG.error("Failed to send mail to {}", to, e);
+        }
+    }
+}

services/spring-letter/src/test/java/tum/devoops/letterservice/service/LetterServiceTest.java

@@ -1,6 +1,7 @@
 package tum.devoops.letterservice.service;
 
 import static org.assertj.core.api.Assertions.assertThat;
+import static org.assertj.core.api.Assertions.assertThatCode;
 import static org.assertj.core.api.Assertions.assertThatThrownBy;
 import static org.mockito.ArgumentMatchers.any;
 import static org.mockito.Mockito.times;
@@ -35,7 +36,6 @@
 import tum.devoops.letterservice.entity.TeamEntity;
 import tum.devoops.letterservice.entity.TransactionEntity;
 import tum.devoops.letterservice.exception.ForbiddenException;
-import tum.devoops.letterservice.exception.MailDeliveryException;
 import tum.devoops.letterservice.model.MailRequest;
 import tum.devoops.letterservice.model.PdfRequest;
 import tum.devoops.letterservice.repository.DirectorRepository;
@@ -74,7 +74,8 @@ class LetterServiceTest {
 
     @BeforeEach
     void setUp() {
-        letterService = new LetterService(mailSender, FROM, memberRepository, sportRepository,
+        MailDispatcher mailDispatcher = new MailDispatcher(mailSender, FROM, meterRegistry);
+        letterService = new LetterService(mailDispatcher, memberRepository, sportRepository,
                 teamRepository, directorRepository, trainerRepository, traineeRepository, transactionRepository,
                 meterRegistry);
     }
@@ -259,20 +260,19 @@ void sendMailWithDirectorWithoutTeamShowsSportNameFromDirectorRole() throws Exce
     // --- sendMail: error handling ---
 
     @Test
-    void sendMailWrapsMessagingExceptionInMailDeliveryException() {
-        LetterService brokenFromService = new LetterService(mailSender, "not a valid from address",
+    void sendMailCountsFailureAndDoesNotPropagateWhenSendingThrows() {
+        MailDispatcher brokenDispatcher = new MailDispatcher(mailSender, "not a valid from address", meterRegistry);
+        LetterService brokenFromService = new LetterService(brokenDispatcher,
                 memberRepository, sportRepository, teamRepository, directorRepository,
                 trainerRepository, traineeRepository, transactionRepository, meterRegistry);
 
         MemberEntity frank = member("Frank", "Foster", "frank@example.com");
         when(memberRepository.findAll()).thenReturn(List.of(frank));
         stubMimeMessages();
 
-        assertThatThrownBy(() -> brokenFromService.sendMail(new MailRequest("Subject", "Body"),
+        assertThatCode(() -> brokenFromService.sendMail(new MailRequest("Subject", "Body"),
                 UUID.randomUUID(), true))
-                .isInstanceOf(MailDeliveryException.class)
-                .hasMessageContaining("frank@example.com")
-                .hasCauseInstanceOf(jakarta.mail.MessagingException.class);
+                .doesNotThrowAnyException();
         assertThat(meterRegistry.counter("letters_sent_total", "status", "failure").count()).isEqualTo(1.0);
     }