Improved resilience of registry communication.

server-registry/src/main/java/nl/andrewlalis/aos_server_registry/servlet/ServerInfoServlet.java

@@ -7,7 +7,6 @@ import nl.andrewlalis.aos_server_registry.servlet.dto.ServerStatusUpdate;
 import nl.andrewlalis.aos_server_registry.util.Requests;
 import nl.andrewlalis.aos_server_registry.util.Responses;
 
-import javax.servlet.ServletException;
 import javax.servlet.http.HttpServlet;
 import javax.servlet.http.HttpServletRequest;
 import javax.servlet.http.HttpServletResponse;
@@ -22,7 +21,7 @@ import java.util.Map;
 
 public class ServerInfoServlet extends HttpServlet {
 	@Override
-	protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
+	protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws IOException {
 		int page = Requests.getIntParam(req, "page", 0, i -> i >= 0);
 		int size = Requests.getIntParam(req, "size", 20, i -> i >= 5 && i <= 50);
 		String searchQuery = Requests.getStringParam(req, "q", null, s -> !s.isBlank());
@@ -44,7 +43,7 @@ public class ServerInfoServlet extends HttpServlet {
 	}
 
 	@Override
-	protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
+	protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws IOException {
 		var info = Requests.getBody(req, ServerInfoUpdate.class);
 		try {
 			this.saveNewServer(info);
@@ -56,15 +55,9 @@ public class ServerInfoServlet extends HttpServlet {
 	}
 
 	@Override
-	protected void doPut(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
+	protected void doPut(HttpServletRequest req, HttpServletResponse resp) throws IOException {
 		var status = Requests.getBody(req, ServerStatusUpdate.class);
-		try {
+		this.updateServerStatus(status, resp);
-			this.updateServerStatus(status);
-			Responses.ok(resp, Map.of("message", "Server status updated."));
-		} catch (SQLException e) {
-			e.printStackTrace();
-			Responses.internalServerError(resp, "Database error.");
-		}
 	}
 
 	private List<ServerInfoResponse> getData(int size, int page, String searchQuery, String order, String orderDir) throws SQLException {
@@ -146,7 +139,8 @@ public class ServerInfoServlet extends HttpServlet {
 		}
 	}
 
-	private void updateServerStatus(ServerStatusUpdate status) throws SQLException {
+	private void updateServerStatus(ServerStatusUpdate status, HttpServletResponse resp) throws IOException {
+		try {
 			var con = DataManager.getInstance().getConnection();
 			PreparedStatement stmt = con.prepareStatement("""
 			UPDATE servers SET current_players = ?
@@ -157,7 +151,14 @@ public class ServerInfoServlet extends HttpServlet {
 			stmt.setString(3, status.address());
 			int rowCount = stmt.executeUpdate();
 			stmt.close();
-		if (rowCount != 1) throw new SQLException("Could not update server status.");
+			if (rowCount != 1) {
-		System.out.println("Updated server status for " + status.name() + " @ " + status.address());
+				Responses.notFound(resp);
+			} else {
+				Responses.ok(resp);
+			}
+		} catch (SQLException e) {
+			e.printStackTrace();
+			Responses.internalServerError(resp, "Database error.");
+		}
 	}
 }

server-registry/src/main/java/nl/andrewlalis/aos_server_registry/util/Responses.java

@@ -11,6 +11,10 @@ import static nl.andrewlalis.aos_server_registry.ServerRegistry.mapper;
  * JSON responses.
  */
 public class Responses {
+	public static void ok(HttpServletResponse resp) {
+		resp.setStatus(HttpServletResponse.SC_OK);
+	}
+
 	public static void ok(HttpServletResponse resp, Object body) throws IOException {
 		resp.setStatus(HttpServletResponse.SC_OK);
 		resp.setContentType("application/json");

server/src/main/java/module-info.java

@@ -2,6 +2,7 @@ module aos_server {
 	requires java.logging;
 	requires aos_core;
 	requires java.desktop;
+	requires java.net.http;
 	requires com.fasterxml.jackson.databind;
 	requires com.fasterxml.jackson.dataformat.yaml;
 

server/src/main/java/nl/andrewlalis/aos_server/RegistryManager.java

@@ -0,0 +1,97 @@
+package nl.andrewlalis.aos_server;
+
+import com.fasterxml.jackson.databind.ObjectMapper;
+
+import java.net.URI;
+import java.net.http.HttpClient;
+import java.net.http.HttpRequest;
+import java.net.http.HttpResponse;
+import java.time.Duration;
+import java.util.HashMap;
+import java.util.Map;
+import java.util.concurrent.Executors;
+import java.util.concurrent.ScheduledExecutorService;
+import java.util.concurrent.TimeUnit;
+
+/**
+ * The registry manager is responsible for keeping the server registry up to
+ * date with this server's information, by sending periodic update HTTP messages.
+ */
+public class RegistryManager {
+	private final ScheduledExecutorService executorService;
+	private final Server server;
+
+	private final ObjectMapper mapper;
+	private final HttpClient httpClient;
+
+	public RegistryManager(Server server) {
+		this.server = server;
+		this.mapper = new ObjectMapper();
+		this.executorService = Executors.newScheduledThreadPool(3);
+		this.httpClient = HttpClient.newBuilder()
+			.executor(this.executorService)
+			.connectTimeout(Duration.ofSeconds(3))
+			.build();
+		this.executorService.submit(this::sendInfo);
+		this.executorService.scheduleAtFixedRate(
+			this::sendUpdate,
+			server.getSettings().getRegistrySettings().getUpdateInterval(),
+			server.getSettings().getRegistrySettings().getUpdateInterval(),
+			TimeUnit.SECONDS
+		);
+	}
+
+	public void sendInfo() {
+		try {
+			Map<String, Object> data = new HashMap<>();
+			data.put("name", this.server.getSettings().getRegistrySettings().getName());
+			data.put("address", this.server.getSettings().getRegistrySettings().getAddress());
+			data.put("description", this.server.getSettings().getRegistrySettings().getDescription());
+			data.put("location", this.server.getSettings().getRegistrySettings().getLocation());
+			data.put("maxPlayers", this.server.getSettings().getMaxPlayers());
+			data.put("currentPlayers", 0);
+			HttpRequest request = HttpRequest.newBuilder()
+				.uri(new URI(this.server.getSettings().getRegistrySettings().getRegistryUri() + "/serverInfo"))
+				.POST(HttpRequest.BodyPublishers.ofByteArray(this.mapper.writeValueAsBytes(data)))
+				.header("Content-Type", "application/json")
+				.build();
+			this.httpClient.sendAsync(request, HttpResponse.BodyHandlers.discarding());
+		} catch (Exception e) {
+			e.printStackTrace();
+		}
+	}
+
+	private void sendUpdate() {
+		try {
+			Map<String, Object> data = new HashMap<>();
+			data.put("name", this.server.getSettings().getRegistrySettings().getName());
+			data.put("address", this.server.getSettings().getRegistrySettings().getAddress());
+			data.put("currentPlayers", server.getPlayerCount());
+			HttpRequest request = HttpRequest.newBuilder()
+				.uri(new URI(this.server.getSettings().getRegistrySettings().getRegistryUri() + "/serverInfo"))
+				.PUT(HttpRequest.BodyPublishers.ofByteArray(this.mapper.writeValueAsBytes(data)))
+				.header("Content-Type", "application/json")
+				.build();
+			this.httpClient.sendAsync(request, responseInfo -> {
+				if (responseInfo.statusCode() == 404) {
+					System.out.println("Received 404 when sending registry update. Re-sending registry info...");
+					this.sendInfo();
+				}
+				return null;
+			});
+		} catch (Exception e) {
+			e.printStackTrace();
+		}
+	}
+
+	public void shutdown() {
+		this.executorService.shutdown();
+		try {
+			while (!this.executorService.awaitTermination(3, TimeUnit.SECONDS)) {
+				System.out.println("Waiting for scheduler to terminate.");
+			}
+		} catch (InterruptedException e) {
+			e.printStackTrace();
+		}
+	}
+}

server/src/main/java/nl/andrewlalis/aos_server/Server.java

@@ -25,7 +25,9 @@ import java.net.Socket;
 import java.net.SocketException;
 import java.util.List;
 import java.util.concurrent.CopyOnWriteArrayList;
+import java.util.concurrent.Executors;
 import java.util.concurrent.ThreadLocalRandom;
+import java.util.concurrent.TimeUnit;
 
 public class Server {
 	private final ServerSettings settings;
@@ -37,6 +39,7 @@ public class Server {
 	private final WorldUpdater worldUpdater;
 	private final ServerCli cli;
 	private final ChatManager chatManager;
+	private RegistryManager registryManager;
 
 	private volatile boolean running;
 
@@ -50,6 +53,9 @@ public class Server {
 		this.initWorld();
 		this.worldUpdater = new WorldUpdater(this, this.world);
 		this.chatManager = new ChatManager(this);
+		if (settings.getRegistrySettings().isDiscoverable()) {
+			this.registryManager = new RegistryManager(this);
+		}
 	}
 
 	public ServerSettings getSettings() {
@@ -230,7 +236,7 @@ public class Server {
 				handler.send(new Message(Type.SERVER_SHUTDOWN));
 				handler.shutdown();
 			}
-		} catch (IOException e) {
+		} catch (Exception e) {
 			System.err.println("Could not close server socket on shutdown: " + e.getMessage());
 		}
 	}
@@ -252,6 +258,10 @@ public class Server {
 		System.out.println("Stopped CLI interface.");
 		this.dataTransceiver.shutdown();
 		System.out.println("Stopped data transceiver.");
+		if (this.registryManager != null) {
+			this.registryManager.shutdown();
+			System.out.println("Stopped registry communications.");
+		}
 	}
 
 

server/src/main/java/nl/andrewlalis/aos_server/settings/RegistrySettings.java

@@ -3,6 +3,7 @@ package nl.andrewlalis.aos_server.settings;
 public class RegistrySettings {
 	private boolean discoverable;
 	private String registryUri;
+	private long updateInterval;
 	private String name;
 	private String address;
 	private String description;
@@ -16,6 +17,10 @@ public class RegistrySettings {
 		return registryUri;
 	}
 
+	public long getUpdateInterval() {
+		return updateInterval;
+	}
+
 	public String getName() {
 		return name;
 	}

server/src/main/java/nl/andrewlalis/aos_server/settings/ServerSettings.java

@@ -24,6 +24,10 @@ public class ServerSettings {
 		return ticksPerSecond;
 	}
 
+	public RegistrySettings getRegistrySettings() {
+		return registrySettings;
+	}
+
 	public PlayerSettings getPlayerSettings() {
 		return playerSettings;
 	}

server/src/main/resources/default_settings.yaml

@@ -3,9 +3,10 @@ max-players: 32
 ticks-per-second: 120
 
 # Information for the public server registry.
-registry-data:
+registry-settings:
   discoverable: true
   registry-uri: "http://localhost:8567"
+  update-interval: 10
   name: "Testing Server"
   address: "localhost:8035"
   description: "A simple testing server for development."