Phase 11.6: Async Email Integration with Thread Pool & SMTP Optimization

Dockerfile

@@ -10,7 +10,7 @@ COPY src ./src
 RUN mvn clean package -DskipTests
 
 # ---------- Stage 2: Runtime ----------
-FROM eclipse-temurin:21-jre-alpine
+FROM eclipse-temurin:21-jre
 
 WORKDIR /app
 

pom.xml

@@ -99,18 +99,6 @@
 			<version>8.9.0</version>
 		</dependency>
 
-		<dependency>
-			<groupId>com.bucket4j</groupId>
-			<artifactId>bucket4j-redis</artifactId>
-			<version>8.9.0</version>
-		</dependency>
-
-		<!-- Spring Redis -->
-		<dependency>
-			<groupId>org.springframework.boot</groupId>
-			<artifactId>spring-boot-starter-data-redis</artifactId>
-		</dependency>
-
 		<dependency>
 			<groupId>org.springframework.boot</groupId>
 			<artifactId>spring-boot-starter-actuator</artifactId>

src/main/java/com/vimaltech/contactapi/ContactApiApplication.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 ContactApiApplication {
 
 	public static void main(String[] args) {

src/main/java/com/vimaltech/contactapi/config/AppProperties.java

@@ -0,0 +1,19 @@
+package com.vimaltech.contactapi.config;
+
+import org.springframework.boot.context.properties.ConfigurationProperties;
+import org.springframework.stereotype.Component;
+
+@ConfigurationProperties(prefix = "app.admin")
+@Component
+public class AppProperties {
+
+    private String email;
+
+    public String getEmail() {
+        return email;
+    }
+
+    public void setEmail(String email) {
+        this.email = email;
+    }
+}

src/main/java/com/vimaltech/contactapi/config/AsyncConfig.java

@@ -0,0 +1,22 @@
+package com.vimaltech.contactapi.config;
+
+import org.springframework.context.annotation.Bean;
+import org.springframework.context.annotation.Configuration;
+import org.springframework.scheduling.concurrent.ThreadPoolTaskExecutor;
+
+import java.util.concurrent.Executor;
+
+@Configuration
+public class AsyncConfig {
+
+    @Bean(name = "emailExecutor")
+    public Executor emailExecutor() {
+        ThreadPoolTaskExecutor executor = new ThreadPoolTaskExecutor();
+        executor.setCorePoolSize(3);       // baseline threads (good for VPS)
+        executor.setMaxPoolSize(8);        // peak load
+        executor.setQueueCapacity(100);    // queue size
+        executor.setThreadNamePrefix("EmailThread-");
+        executor.initialize();
+        return executor;
+    }
+}

src/main/java/com/vimaltech/contactapi/controller/EmailTestController.java

@@ -0,0 +1,35 @@
+package com.vimaltech.contactapi.controller;
+
+import com.vimaltech.contactapi.config.AppProperties;
+import com.vimaltech.contactapi.dto.EmailRequest;
+import com.vimaltech.contactapi.service.EmailService;
+import lombok.RequiredArgsConstructor;
+import org.springframework.context.annotation.Profile;
+import org.springframework.web.bind.annotation.GetMapping;
+import org.springframework.web.bind.annotation.RequestMapping;
+import org.springframework.web.bind.annotation.RestController;
+
+//@Profile({"dev"})
+//@Profile({"dev", "local"})
+@RestController
+@RequestMapping("/test")
+@RequiredArgsConstructor
+public class EmailTestController {
+
+    private final EmailService emailService;
+    private final AppProperties appProperties;
+
+    @GetMapping("/email")
+    public String testEmail() {
+
+        emailService.sendEmail(
+                EmailRequest.builder()
+                        .to(appProperties.getEmail()) // 👈 CHANGE THIS
+                        .subject("Test Email from VimalTech API")
+                        .body("Email service is working successfully 🚀")
+                        .build()
+        );
+
+        return "Email sent successfully";
+    }
+}

src/main/java/com/vimaltech/contactapi/dto/EmailRequest.java

@@ -0,0 +1,14 @@
+package com.vimaltech.contactapi.dto;
+
+import lombok.Builder;
+import lombok.Getter;
+
+@Getter
+@Builder
+public class EmailRequest {
+    private final String to;
+    private final String subject;
+    private final String body;
+
+    private final String replyTo;
+}

src/main/java/com/vimaltech/contactapi/service/ContactService.java

@@ -1,31 +1,91 @@
 package com.vimaltech.contactapi.service;
 
+import com.vimaltech.contactapi.config.AppProperties;
 import com.vimaltech.contactapi.dto.ContactRequest;
+import com.vimaltech.contactapi.dto.EmailRequest;
 import com.vimaltech.contactapi.entity.ContactInquiry;
 import com.vimaltech.contactapi.repository.ContactRepository;
-import lombok.RequiredArgsConstructor;
+import lombok.extern.slf4j.Slf4j;
 import org.springframework.stereotype.Service;
 
-import java.time.LocalDateTime;
 import java.util.List;
 
 @Service
-@RequiredArgsConstructor
+@Slf4j
 public class ContactService {
 
     private final ContactRepository contactRepository;
+    private final EmailService emailService;
+    private final AppProperties appProperties;
+
+    public ContactService(ContactRepository repo, EmailService emailService, AppProperties appProperties) {
+        this.contactRepository = repo;
+        this.emailService = emailService;
+        this.appProperties = appProperties;
+    }
 
     public void processContact(ContactRequest request) {
 
+        // ✅ 1. Save to DB (unchanged behavior)
         ContactInquiry inquiry = ContactInquiry.builder()
                 .name(request.name())
                 .email(request.email())
                 .subject(request.subject())
                 .message(request.message())
-                .createdAt(LocalDateTime.now())
                 .build();
 
         contactRepository.save(inquiry);
+
+        log.info("Contact saved | email={}", request.email());
+
+        // ✅ 2. Send emails {(non-blocking for business logic), try-catch removed}
+        // ✅ Fire async emails (NO try-catch)
+        sendEmails(request);
+    }
+
+    // ✅ NEW METHOD (clean separation)
+    private void sendEmails(ContactRequest request) {
+
+        // 📩 Admin Email
+        EmailRequest adminEmail = EmailRequest.builder()
+                .to(appProperties.getEmail())
+                .subject("New Contact Inquiry: " +
+                        (request.subject() != null ? request.subject() : "No Subject"))
+                .body("""
+                New contact inquiry received:
+
+                Name: %s
+                Email: %s
+                Subject: %s
+
+                Message:
+                %s
+                """.formatted(
+                        request.name(),
+                        request.email(),
+                        request.subject(),
+                        request.message()
+                ))
+                .replyTo(request.email())
+                .build();
+
+        emailService.sendEmail(adminEmail);
+
+        // 📩 User Confirmation Email
+        EmailRequest userEmail = EmailRequest.builder()
+                .to(request.email())
+                .subject("Thanks for contacting VimalTech")
+                .body("""
+                Hi %s,
+
+                Thank you for reaching out. We have received your message and will respond shortly.
+
+                Best regards,
+                VimalTech Team
+                """.formatted(request.name()))
+                .build();
+
+        emailService.sendEmail(userEmail);
     }
 
     public List<ContactInquiry> getAllContacts() {

src/main/java/com/vimaltech/contactapi/service/EmailService.java

@@ -0,0 +1,7 @@
+package com.vimaltech.contactapi.service;
+
+import com.vimaltech.contactapi.dto.EmailRequest;
+
+public interface EmailService {
+    void sendEmail(EmailRequest request);
+}

src/main/java/com/vimaltech/contactapi/service/impl/NoOpEmailService.java

@@ -0,0 +1,18 @@
+package com.vimaltech.contactapi.service.impl;
+
+import com.vimaltech.contactapi.dto.EmailRequest;
+import com.vimaltech.contactapi.service.EmailService;
+import lombok.extern.slf4j.Slf4j;
+import org.springframework.context.annotation.Primary;
+import org.springframework.stereotype.Service;
+
+@Service
+@Primary
+@Slf4j
+public class NoOpEmailService implements EmailService {
+
+    @Override
+    public void sendEmail(EmailRequest request) {
+        log.warn("Email disabled (NoOp) | to={}", request.getTo());
+    }
+}

src/main/java/com/vimaltech/contactapi/service/impl/SmtpEmailService.java

@@ -0,0 +1,57 @@
+package com.vimaltech.contactapi.service.impl;
+
+import com.vimaltech.contactapi.dto.EmailRequest;
+import com.vimaltech.contactapi.service.EmailService;
+import lombok.extern.slf4j.Slf4j;
+import org.springframework.beans.factory.annotation.Value;
+import org.springframework.boot.autoconfigure.condition.ConditionalOnProperty;
+import org.springframework.mail.SimpleMailMessage;
+import org.springframework.mail.javamail.JavaMailSender;
+import org.springframework.scheduling.annotation.Async;
+import org.springframework.stereotype.Service;
+
+@Service
+@Slf4j
+@ConditionalOnProperty(name = "spring.mail.host")
+public class SmtpEmailService implements EmailService {
+
+    private final JavaMailSender mailSender;
+    private final String from;
+
+    public SmtpEmailService(
+            JavaMailSender mailSender,
+            @Value("${app.mail.from}") String from
+    ) {
+        this.mailSender = mailSender;
+        this.from = from;
+    }
+
+    @Override
+    @Async("emailExecutor")
+    public void sendEmail(EmailRequest request) {
+        try {
+            log.info("START: Sending email | to={} | thread={}",
+                    request.getTo(), Thread.currentThread().getName());
+
+            SimpleMailMessage message = new SimpleMailMessage();
+
+            message.setFrom(from); // 🔥 CRITICAL FIX
+            message.setTo(request.getTo());
+            message.setSubject(request.getSubject());
+            message.setText(request.getBody());
+
+            // ✅ OPTIONAL but IMPORTANT
+            if (request.getReplyTo() != null && !request.getReplyTo().isBlank()) {
+                message.setReplyTo(request.getReplyTo().trim());
+            }
+
+            mailSender.send(message);
+
+            log.info("SUCCESS: Email sent | to={}", request.getTo());
+
+        } catch (Exception e) {
+            // ❗ DO NOT THROW in async
+            log.error("ERROR: Email failed | to={}", request.getTo(), e);
+        }
+    }
+}

src/main/resources/application-prod.yml

@@ -11,18 +11,11 @@ spring:
     username: ${MAIL_USERNAME}
     password: ${MAIL_PASSWORD}
     properties:
-      mail:
-        smtp:
-          auth: true
-          starttls:
-            enable: true
-
-  data:
-    redis:
-      host: vimaltech-redis
-      port: 6379
-      password: ${SPRING_DATA_REDIS_PASSWORD}
-      timeout: 2000
+      mail.smtp.auth: true
+      mail.smtp.starttls.enable: true
+      mail.smtp.connectiontimeout: 5000
+      mail.smtp.timeout: 5000
+      mail.smtp.writetimeout: 5000
 
   jpa:
     hibernate:
@@ -61,7 +54,7 @@ management:
         enabled: true   # ✅ IMPORTANT
       group:
         readiness:
-          include: db,redis
+          include: db
 
   health:
     mail:
@@ -73,4 +66,6 @@ management:
 
 app:
   mail:
-    from: ${MAIL_FROM}
+    from: ${MAIL_FROM:?MAIL_FROM is required}
+  admin:
+    email: ${APP_ADMIN_EMAIL:?APP_ADMIN_EMAIL is required}

src/main/resources/application-test.yml

@@ -0,0 +1,14 @@
+# application-test.yml
+spring:
+  mail:
+    host: localhost
+    port: 1025
+    username: test
+    password: test
+
+app:
+  mail:
+    from: test@test.com
+    enabled: false
+  admin:
+    email: test@test.com