feat(language-web): add health check endpoint

subprojects/language-web/src/main/java/tools/refinery/language/web/CacheControlFilter.java

@@ -19,8 +19,8 @@ public class CacheControlFilter implements Filter {
 	private static final Pattern CACHE_URI_PATTERN = Pattern.compile(".*\\.(css|gif|js|map|png|svg|woff2?)");
 
 	private static final Set<String> CACHE_URI_DENYLIST = Set.of("apple-touch-icon.png", "config.json", "favicon.png",
-			"favicon.svg", "favicon-96x96.png", "icon-any.svg", "icon-192x192.png", "icon-512x512.png", "mask-icon.svg",
-			"sw.js");
+			"favicon.svg", "favicon-96x96.png", "health", "icon-any.svg", "icon-192x192.png", "icon-512x512.png",
+			"mask-icon.svg", "sw.js");
 
 	private static final Duration EXPIRY = Duration.ofDays(365);
 

subprojects/language-web/src/main/java/tools/refinery/language/web/HealthCheckServlet.java

@@ -0,0 +1,37 @@
+package tools.refinery.language.web;/*
+ * SPDX-FileCopyrightText: 2024 The Refinery Authors <https://refinery.tools/>
+ *
+ * SPDX-License-Identifier: EPL-2.0
+ */
+
+import jakarta.servlet.http.HttpServlet;
+import jakarta.servlet.http.HttpServletRequest;
+import jakarta.servlet.http.HttpServletResponse;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import java.io.IOException;
+import java.io.Serial;
+
+public class HealthCheckServlet extends HttpServlet {
+	@Serial
+	private static final long serialVersionUID = 5512947261931111041L;
+
+	private final transient Logger log = LoggerFactory.getLogger(getClass());
+
+	@Override
+	protected void doGet(HttpServletRequest req, HttpServletResponse resp) {
+		resp.setStatus(HttpServletResponse.SC_OK);
+		resp.setContentType("application/json");
+		try (var writer = resp.getWriter()) {
+			writer.println("{\"status\": \"up\"}");
+			writer.flush();
+		} catch (IOException e) {
+			log.error("Failed to write response", e);
+			if (!resp.isCommitted()) {
+				resp.reset();
+				resp.setStatus(HttpServletResponse.SC_INTERNAL_SERVER_ERROR);
+			}
+		}
+	}
+}

subprojects/language-web/src/main/java/tools/refinery/language/web/ServerLauncher.java

@@ -10,11 +10,9 @@
 package tools.refinery.language.web;
 
 import jakarta.servlet.DispatcherType;
-import jakarta.servlet.SessionTrackingMode;
 import org.eclipse.jetty.ee10.servlet.DefaultServlet;
 import org.eclipse.jetty.ee10.servlet.ServletContextHandler;
 import org.eclipse.jetty.ee10.servlet.ServletHolder;
-import org.eclipse.jetty.ee10.servlet.SessionHandler;
 import org.eclipse.jetty.ee10.websocket.server.config.JettyWebSocketServletContainerInitializer;
 import org.eclipse.jetty.server.Server;
 import org.eclipse.jetty.util.resource.Resource;
@@ -30,7 +28,6 @@
 import java.net.URI;
 import java.net.URISyntaxException;
 import java.util.EnumSet;
-import java.util.Set;
 
 public class ServerLauncher {
 	public static final String DEFAULT_LISTEN_HOST = "localhost";
@@ -53,9 +50,9 @@ public ServerLauncher(InetSocketAddress bindAddress, String[] allowedOrigins, St
 		server = new Server(bindAddress);
 		((QueuedThreadPool) server.getThreadPool()).setName("jetty");
 		var handler = new ServletContextHandler();
-		addSessionHandler(handler);
 		addProblemServlet(handler, allowedOrigins);
 		addBackendConfigServlet(handler, webSocketUrl);
+		addHealthCheckServlet(handler);
 		var baseResource = getBaseResource();
 		if (baseResource != null) {
 			handler.setBaseResource(baseResource);
@@ -67,12 +64,6 @@ public ServerLauncher(InetSocketAddress bindAddress, String[] allowedOrigins, St
 		server.setHandler(handler);
 	}
 
-	private void addSessionHandler(ServletContextHandler handler) {
-		var sessionHandler = new SessionHandler();
-		sessionHandler.setSessionTrackingModes(Set.of(SessionTrackingMode.COOKIE));
-		handler.setSessionHandler(sessionHandler);
-	}
-
 	private void addProblemServlet(ServletContextHandler handler, String[] allowedOrigins) {
 		var problemServletHolder = new ServletHolder(ProblemWebSocketServlet.class);
 		if (allowedOrigins == null) {
@@ -93,6 +84,11 @@ private void addBackendConfigServlet(ServletContextHandler handler, String webSo
 		handler.addServlet(backendConfigServletHolder, "/config.json");
 	}
 
+	private void addHealthCheckServlet(ServletContextHandler handler) {
+		var healthCheckServletHolder = new ServletHolder(HealthCheckServlet.class);
+		handler.addServlet(healthCheckServletHolder, "/health");
+	}
+
 	private void addDefaultServlet(ServletContextHandler handler) {
 		var defaultServletHolder = new ServletHolder(DefaultServlet.class);
 		var isWindows = System.getProperty("os.name").toLowerCase().contains("win");

subprojects/language-web/src/main/java/tools/refinery/language/web/config/BackendConfigServlet.java

@@ -38,8 +38,7 @@ public void init(ServletConfig config) throws ServletException {
 	protected void doGet(HttpServletRequest req, HttpServletResponse resp) {
 		resp.setStatus(HttpStatus.OK_200);
 		resp.setContentType("application/json");
-		try {
-			var writer = resp.getWriter();
+		try (var writer = resp.getWriter()) {
 			writer.write(serializedConfig);
 			writer.flush();
 		} catch (IOException e) {