Memory Optimization: Backend Threading/GC + Frontend Monaco Lazy-Loading

backend/build.gradle.kts

@@ -56,8 +56,10 @@ dependencies {
     implementation("org.springframework.boot:spring-boot-starter-data-jpa")
     implementation("org.springframework.boot:spring-boot-starter-liquibase")
     implementation("org.springframework.boot:spring-boot-starter-validation")
-    implementation("org.springframework.boot:spring-boot-starter-webmvc")
-    implementation("org.springframework.boot:spring-boot-starter-webclient")
+    implementation("org.springframework.boot:spring-boot-starter-webmvc"){
+        exclude(group = "org.springframework.boot", module = "spring-boot-starter-tomcat")
+    }
+    implementation("org.springframework.boot:spring-boot-starter-jetty")
     implementation("org.springframework.security:spring-security-crypto")
     implementation("org.mapstruct:mapstruct:${mapStructVersion}")
     implementation("org.springdoc:springdoc-openapi-starter-webmvc-ui:${swaggerOpenAPIVersion}")
@@ -96,6 +98,19 @@ tasks.named<org.springframework.boot.gradle.tasks.run.BootRun>("bootRun") {
     mainClass.set("com.devaulty.backend.BackendApplication")
 }
 
+tasks.withType<JavaExec>().configureEach {
+    jvmArgs(
+        "-Xms64m",
+        "-Xmx256m",
+        "-XX:MetaspaceSize=96m",
+        "-XX:MaxMetaspaceSize=192m",
+        "-XX:ParallelGCThreads=2",
+        "-XX:ConcGCThreads=1",
+        "-XX:+UseG1GC",
+        "-XX:MaxGCPauseMillis=100"
+    )
+}
+
 // task to build frontend (npm run build)
 val buildFrontend by tasks.registering(Exec::class) {
     group = "build"
@@ -146,7 +161,25 @@ runtime {
     jpackage {
         imageName = "devaulty"
         appVersion = jpackageImageVersion
-        imageOptions = listOf("--java-options", "-Dspring.profiles.active=prod")
+        imageOptions = listOf(
+            // 1. Memory do Heap Limits (Obj dynamic RAM)
+            "--java-options", "-Xms64m",
+            "--java-options", "-Xmx256m",
+
+            // 2. Metaspace limits (Spring/Hibernate Class Metadata Memory)
+            "--java-options", "-XX:MetaspaceSize=96m",
+            "--java-options", "-XX:MaxMetaspaceSize=192m",
+
+            // 3. Garbage Collector (GC) Thread Control
+            "--java-options", "-XX:ParallelGCThreads=2",
+            "--java-options", "-XX:ConcGCThreads=1",
+            "--java-options", "-XX:+UseG1GC",
+            "--java-options", "-XX:MaxGCPauseMillis=100",
+
+            // 4. Spring Production Profile
+            "--java-options", "-Dspring.profiles.active=prod"
+        )
+
     }
 }
 

backend/src/main/java/com/devaulty/backend/adapter/in/web/common/BackgroundTaskRunner.java

@@ -0,0 +1,36 @@
+package com.devaulty.backend.adapter.in.web.common;
+
+import jakarta.annotation.PreDestroy;
+import org.springframework.stereotype.Component;
+
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Executors;
+import java.util.concurrent.TimeUnit;
+
+/**
+ * Runs long-lived, blocking background tasks (e.g. file downloads) outside
+ * of the servlet request thread pool, so HTTP worker threads are never held
+ * hostage by slow I/O operations.
+ */
+@Component
+public class BackgroundTaskRunner {
+
+    private final ExecutorService executor = Executors.newSingleThreadExecutor();
+
+    public void run(Runnable task) {
+        executor.execute(task);
+    }
+
+    @PreDestroy
+    public void shutdown() {
+        executor.shutdown();
+        try {
+            if (!executor.awaitTermination(30, TimeUnit.SECONDS)) {
+                executor.shutdownNow();
+            }
+        } catch (InterruptedException e) {
+            executor.shutdownNow();
+            Thread.currentThread().interrupt();
+        }
+    }
+}

backend/src/main/java/com/devaulty/backend/adapter/in/web/util/UriLocationBuilderHelper.java → backend/src/main/java/com/devaulty/backend/adapter/in/web/common/UriLocationBuilderHelper.java

@@ -1,4 +1,4 @@
-package com.devaulty.backend.adapter.in.web.util;
+package com.devaulty.backend.adapter.in.web.common;
 
 import org.springframework.stereotype.Component;
 import org.springframework.web.servlet.support.ServletUriComponentsBuilder;

backend/src/main/java/com/devaulty/backend/adapter/in/web/credential/CredentialController.java

@@ -4,7 +4,7 @@
 import com.devaulty.backend.adapter.in.web.credential.dto.CredentialSummaryResponse;
 import com.devaulty.backend.adapter.in.web.credential.dto.CredentialViewResponse;
 import com.devaulty.backend.adapter.in.web.credential.dto.UpdateCredentialRequest;
-import com.devaulty.backend.adapter.in.web.util.UriLocationBuilderHelper;
+import com.devaulty.backend.adapter.in.web.common.UriLocationBuilderHelper;
 import com.devaulty.backend.application.port.in.credential.*;
 import com.devaulty.backend.application.port.in.tag.item.GetTagsForItemUseCase;
 import com.devaulty.backend.application.port.in.tag.item.GetTagsForItemsUseCase;

backend/src/main/java/com/devaulty/backend/adapter/in/web/link/LinkController.java

@@ -3,7 +3,7 @@
 import com.devaulty.backend.adapter.in.web.link.dto.CreateLinkRequest;
 import com.devaulty.backend.adapter.in.web.link.dto.LinkViewResponse;
 import com.devaulty.backend.adapter.in.web.link.dto.UpdateLinkRequest;
-import com.devaulty.backend.adapter.in.web.util.UriLocationBuilderHelper;
+import com.devaulty.backend.adapter.in.web.common.UriLocationBuilderHelper;
 import com.devaulty.backend.application.port.in.link.*;
 import com.devaulty.backend.domain.model.Link;
 import com.devaulty.backend.application.port.in.tag.item.GetTagsForItemUseCase;

backend/src/main/java/com/devaulty/backend/adapter/in/web/note/NoteController.java

@@ -4,7 +4,7 @@
 import com.devaulty.backend.adapter.in.web.note.dto.NoteSummaryResponse;
 import com.devaulty.backend.adapter.in.web.note.dto.NoteViewResponse;
 import com.devaulty.backend.adapter.in.web.note.dto.UpdateNoteRequest;
-import com.devaulty.backend.adapter.in.web.util.UriLocationBuilderHelper;
+import com.devaulty.backend.adapter.in.web.common.UriLocationBuilderHelper;
 import com.devaulty.backend.application.port.in.note.*;
 import com.devaulty.backend.domain.model.Note;
 import com.devaulty.backend.application.port.in.tag.item.GetTagsForItemUseCase;

backend/src/main/java/com/devaulty/backend/adapter/in/web/problem/ProblemController.java

@@ -1,7 +1,7 @@
 package com.devaulty.backend.adapter.in.web.problem;
 
 import com.devaulty.backend.adapter.in.web.problem.dto.*;
-import com.devaulty.backend.adapter.in.web.util.UriLocationBuilderHelper;
+import com.devaulty.backend.adapter.in.web.common.UriLocationBuilderHelper;
 import com.devaulty.backend.application.port.in.problem.*;
 import com.devaulty.backend.domain.model.Problem;
 import com.devaulty.backend.application.port.in.tag.item.GetTagsForItemUseCase;

backend/src/main/java/com/devaulty/backend/adapter/in/web/project/ProjectController.java

@@ -3,7 +3,7 @@
 import com.devaulty.backend.adapter.in.web.project.dto.CreateProjectRequest;
 import com.devaulty.backend.adapter.in.web.project.dto.ProjectViewResponse;
 import com.devaulty.backend.adapter.in.web.project.dto.UpdateProjectRequest;
-import com.devaulty.backend.adapter.in.web.util.UriLocationBuilderHelper;
+import com.devaulty.backend.adapter.in.web.common.UriLocationBuilderHelper;
 import com.devaulty.backend.application.port.in.project.*;
 import com.devaulty.backend.domain.model.Project;
 import jakarta.validation.Valid;

backend/src/main/java/com/devaulty/backend/adapter/in/web/release/ReleaseApi.java

@@ -15,7 +15,7 @@
 import org.springframework.web.bind.annotation.GetMapping;
 import org.springframework.web.bind.annotation.PostMapping;
 import org.springframework.web.bind.annotation.RequestMapping;
-import reactor.core.publisher.Flux;
+import org.springframework.web.servlet.mvc.method.annotation.SseEmitter;
 
 @Tag(name = "Releases", description = "Endpoints for checking desktop application updates, streaming asset downloads, and invoking native OS installation")
 @RequestMapping("/api/v1/releases")
@@ -48,32 +48,28 @@ public interface ReleaseApi {
 
     @Operation(
             summary = "Stream update download and trigger native OS installation",
-            description = "Establishes a Server-Sent Events (SSE) HTTP stream (`text/event-stream`) to download the latest installer binary into the local platform temp directory (`~/.config/devaulty/temp` on Linux, `%LOCALAPPDATA%\\devaulty\\temp` on Windows, `~/Library/Caches/devaulty/temp` on macOS). Emits real-time progress events (`DOWNLOADING` status with percentage and byte counts). Once download reaches 100%, transitions to `INSTALLING` status, launches the native OS installer/restart script detached from the current process, and gracefully shuts down the running Devaulty application instance."
+            description = "Establishes a Server-Sent Events (SSE) HTTP stream (`text/event-stream`) to download the latest installer binary into the local platform temp directory (`~/.config/devaulty/temp` on Linux, `%LOCALAPPDATA%\\devaulty\\temp` on Windows, `~/Library/Caches/devaulty/temp` on macOS). Emits real-time progress events (`DOWNLOADING` status with percentage and byte counts). Once download reaches 100%, transitions to `INSTALLING` status, launches the native OS installer/restart script detached from the current process, and gracefully shuts down the running Devaulty application instance. " +
+                    "Backed by a blocking download pipeline (JDK `HttpClient`) executed on a dedicated background thread, decoupled from the servlet request thread pool."
     )
     @ApiResponses(value = {
             @ApiResponse(
                     responseCode = "200",
-                    description = "Server-Sent Events (SSE) stream established successfully. Emits real-time `UpdateDownloadProgressResponse` events.",
+                    description = "Server-Sent Events (SSE) stream established successfully. Emits real-time `UpdateDownloadProgressResponse` events until the stream completes or errors out.",
                     content = @Content(mediaType = MediaType.TEXT_EVENT_STREAM_VALUE, schema = @Schema(implementation = UpdateDownloadProgressResponse.class))
             ),
-            @ApiResponse(
-                    responseCode = "400",
-                    description = "Bad Request. Thrown when no update is available (`updateAvailable == false`) or no compatible installer asset exists for the current host OS.",
-                    content = @Content(mediaType = MediaType.APPLICATION_JSON_VALUE, schema = @Schema(implementation = ApiErrorResponse.class))
-            ),
             @ApiResponse(
                     responseCode = "403",
                     description = "Forbidden. Request missing or containing an invalid `X-Devaulty-Internal-Token` header.",
                     content = @Content(mediaType = MediaType.APPLICATION_JSON_VALUE, schema = @Schema(implementation = ApiErrorResponse.class))
             ),
             @ApiResponse(
                     responseCode = "500",
-                    description = "Internal Server Error. Streaming network failure, file I/O error during installer save, or native process execution failure.",
+                    description = "Internal Server Error. Streaming network failure, file I/O error during installer save, or native process execution failure. Reported as a terminal SSE error event, since HTTP headers are already committed by the time streaming begins.",
                     content = @Content(mediaType = MediaType.APPLICATION_JSON_VALUE, schema = @Schema(implementation = ApiErrorResponse.class))
             )
     })
     @PostMapping(value = "/download-and-install", produces = MediaType.TEXT_EVENT_STREAM_VALUE)
-    ResponseEntity<Flux<UpdateDownloadProgressResponse>> downloadUpdate();
+    SseEmitter downloadUpdate();
 
     @Operation(
             summary = "Get current running application version",
@@ -93,4 +89,4 @@ public interface ReleaseApi {
     })
     @GetMapping("/current-app-version")
     ResponseEntity<CurrentVersionResponse> getAppInfo();
-}
+}

backend/src/main/java/com/devaulty/backend/adapter/in/web/release/ReleaseController.java

@@ -1,33 +1,44 @@
 package com.devaulty.backend.adapter.in.web.release;
 
-import com.devaulty.backend.adapter.in.web.release.dto.CurrentVersionResponse;
+import com.devaulty.backend.adapter.in.web.common.BackgroundTaskRunner;
 import com.devaulty.backend.adapter.in.web.release.dto.AppUpdateInfoResponse;
-import com.devaulty.backend.adapter.in.web.release.dto.UpdateDownloadProgressResponse;
+import com.devaulty.backend.adapter.in.web.release.dto.CurrentVersionResponse;
 import com.devaulty.backend.application.port.in.release.CheckForUpdatesUseCase;
 import com.devaulty.backend.application.port.in.release.DownloadUpdateUseCase;
 import com.devaulty.backend.application.port.in.release.GetCurrentVersionUseCase;
-import org.springframework.http.MediaType;
+import com.devaulty.backend.application.port.in.release.UpdateProgressInfo;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
 import org.springframework.http.ResponseEntity;
 import org.springframework.web.bind.annotation.GetMapping;
 import org.springframework.web.bind.annotation.PostMapping;
 import org.springframework.web.bind.annotation.RequestMapping;
 import org.springframework.web.bind.annotation.RestController;
-import reactor.core.publisher.Flux;
+import org.springframework.web.servlet.mvc.method.annotation.SseEmitter;
+
+import java.io.IOException;
+import java.util.concurrent.atomic.AtomicBoolean;
 
 @RestController
 @RequestMapping("/api/v1/releases")
 public class ReleaseController implements ReleaseApi {
 
+    private static final Logger logger = LoggerFactory.getLogger(ReleaseController.class);
+
     private final CheckForUpdatesUseCase checkForUpdatesUseCase;
     private final DownloadUpdateUseCase downloadUpdateUseCase;
     private final GetCurrentVersionUseCase getCurrentVersionUseCase;
     private final ReleaseWebMapper releaseWebMapper;
+    private final BackgroundTaskRunner backgroundTaskRunner;
+
+    private static final long SSE_TIMEOUT_MS = 20 * 60 * 1000L;
 
-    public ReleaseController(CheckForUpdatesUseCase checkForUpdatesUseCase, DownloadUpdateUseCase downloadUpdateUseCase, GetCurrentVersionUseCase getCurrentVersionUseCase, ReleaseWebMapper releaseWebMapper) {
+    public ReleaseController(CheckForUpdatesUseCase checkForUpdatesUseCase, DownloadUpdateUseCase downloadUpdateUseCase, GetCurrentVersionUseCase getCurrentVersionUseCase, ReleaseWebMapper releaseWebMapper, BackgroundTaskRunner backgroundTaskRunner) {
         this.checkForUpdatesUseCase = checkForUpdatesUseCase;
         this.downloadUpdateUseCase = downloadUpdateUseCase;
         this.getCurrentVersionUseCase = getCurrentVersionUseCase;
         this.releaseWebMapper = releaseWebMapper;
+        this.backgroundTaskRunner = backgroundTaskRunner;
     }
 
     @Override
@@ -37,19 +48,47 @@ public ResponseEntity<AppUpdateInfoResponse> checkUpdates() {
     }
 
     @Override
-    @PostMapping(value = "/download-and-install", produces = MediaType.TEXT_EVENT_STREAM_VALUE)
-    public ResponseEntity<Flux<UpdateDownloadProgressResponse>> downloadUpdate() {
-        Flux<UpdateDownloadProgressResponse> stream = downloadUpdateUseCase.execute()
-                .map(releaseWebMapper::toProgressResponse);
-
-        return ResponseEntity.ok()
-                .contentType(MediaType.TEXT_EVENT_STREAM)
-                .body(stream);
+    @PostMapping("/download-and-install")
+    public SseEmitter downloadUpdate() {
+        SseEmitter emitter = new SseEmitter(SSE_TIMEOUT_MS);
+        AtomicBoolean isCancelled = new AtomicBoolean(false);
+
+        emitter.onCompletion(() -> isCancelled.set(true));
+        emitter.onTimeout(() -> isCancelled.set(true));
+        emitter.onError(ex -> isCancelled.set(true));
+
+        backgroundTaskRunner.run(() -> runDownload(emitter, isCancelled));
+        return emitter;
     }
 
     @Override
     @GetMapping("/current-app-version")
     public ResponseEntity<CurrentVersionResponse> getAppInfo() {
         return ResponseEntity.ok(new CurrentVersionResponse(getCurrentVersionUseCase.execute()));
     }
+
+    private void runDownload(SseEmitter emitter, AtomicBoolean isCancelled) {
+        try {
+            downloadUpdateUseCase.execute(progress -> sendProgress(emitter, progress, isCancelled));
+            if (!isCancelled.get()) {
+                emitter.complete();
+            }
+        } catch (Exception ex) {
+            if (!isCancelled.get()) {
+                emitter.completeWithError(ex);
+            }
+        }
+    }
+
+    private void sendProgress(SseEmitter emitter, UpdateProgressInfo progress, AtomicBoolean isCancelled) {
+        if (isCancelled.get()) {
+            throw new IllegalStateException("Client disconnected or SSE stream cancelled.");
+        }
+        try {
+            emitter.send(releaseWebMapper.toProgressResponse(progress));
+        } catch (IOException | IllegalStateException e) {
+            isCancelled.set(true);
+            logger.debug("Failed to send SSE progress, client likely disconnected: {}", e.getMessage());
+        }
+    }
 }

backend/src/main/java/com/devaulty/backend/adapter/in/web/snippet/SnippetController.java

@@ -4,7 +4,7 @@
 import com.devaulty.backend.adapter.in.web.snippet.dto.SnippetSummaryResponse;
 import com.devaulty.backend.adapter.in.web.snippet.dto.SnippetViewResponse;
 import com.devaulty.backend.adapter.in.web.snippet.dto.UpdateSnippetRequest;
-import com.devaulty.backend.adapter.in.web.util.UriLocationBuilderHelper;
+import com.devaulty.backend.adapter.in.web.common.UriLocationBuilderHelper;
 import com.devaulty.backend.application.port.in.snippet.*;
 import com.devaulty.backend.application.port.in.tag.item.GetTagsForItemUseCase;
 import com.devaulty.backend.application.port.in.tag.item.GetTagsForItemsUseCase;

backend/src/main/java/com/devaulty/backend/adapter/in/web/tag/TagController.java

@@ -3,7 +3,7 @@
 import com.devaulty.backend.adapter.in.web.tag.dto.CreateTagRequest;
 import com.devaulty.backend.adapter.in.web.tag.dto.TagViewResponse;
 import com.devaulty.backend.adapter.in.web.tag.dto.UpdateTagRequest;
-import com.devaulty.backend.adapter.in.web.util.UriLocationBuilderHelper;
+import com.devaulty.backend.adapter.in.web.common.UriLocationBuilderHelper;
 import com.devaulty.backend.application.port.in.tag.*;
 import jakarta.validation.Valid;
 import org.springframework.http.ResponseEntity;