WebSocket endpoint

build.gradle

@@ -21,6 +21,7 @@ sourceCompatibility = 17
 // Set our project variables
 project.ext {
     dropwizardVersion = '4.0.5'
+    jettyVersion = '11.0.19'
 }
 
 repositories {
@@ -62,6 +63,8 @@ dependencies {
             'io.dropwizard:dropwizard-hibernate:' + dropwizardVersion,
             'io.dropwizard:dropwizard-auth:' + dropwizardVersion,
             'io.dropwizard:dropwizard-jdbi3:' + dropwizardVersion,
+            'org.eclipse.jetty.websocket:websocket-jetty-api:' + jettyVersion,
+            'org.eclipse.jetty.websocket:websocket-jetty-server:' + jettyVersion,
     )
     // Database
     implementation('com.h2database:h2:2.2.220')

src/main/java/telraam/App.java

@@ -11,6 +11,7 @@
 import jakarta.servlet.DispatcherType;
 import jakarta.servlet.FilterRegistration;
 import org.eclipse.jetty.servlets.CrossOriginFilter;
+import org.eclipse.jetty.websocket.server.config.JettyWebSocketServletContainerInitializer;
 import org.jdbi.v3.core.Jdbi;
 import telraam.api.*;
 import telraam.database.daos.*;
@@ -21,6 +22,7 @@
 import telraam.logic.robust.RobustLapper;
 import telraam.station.Fetcher;
 import telraam.util.AcceptedLapsUtil;
+import telraam.websocket.WebSocketConnection;
 
 import java.io.IOException;
 import java.util.EnumSet;
@@ -78,6 +80,15 @@ public void run(AppConfiguration configuration, Environment environment) throws
         // Initialize AcceptedLapUtil
         AcceptedLapsUtil.createInstance(this.database);
 
+        // Register websocket endpoint
+        JettyWebSocketServletContainerInitializer.configure(
+            environment.getApplicationContext(),
+            (servletContext, wsContainer) -> {
+                wsContainer.setMaxTextMessageSize(65535);
+                wsContainer.addMapping("/ws", (req, res) -> new WebSocketConnection());
+            }
+        );
+
         // Add api resources
         JerseyEnvironment jersey = environment.jersey();
         jersey.register(new BatonResource(database.onDemand(BatonDAO.class)));
@@ -94,7 +105,6 @@ public void run(AppConfiguration configuration, Environment environment) throws
         jersey.register(new MonitoringResource(database));
         environment.healthChecks().register("template", new TemplateHealthCheck(configuration.getTemplate()));
 
-
         // Enable CORS
         final FilterRegistration.Dynamic cors = environment.servlets().addFilter("CORS", CrossOriginFilter.class);
 

src/main/java/telraam/api/TeamResource.java

@@ -2,14 +2,14 @@
 
 import io.swagger.v3.oas.annotations.Operation;
 import io.swagger.v3.oas.annotations.tags.Tag;
+import jakarta.ws.rs.Path;
 import jakarta.ws.rs.Produces;
+import jakarta.ws.rs.core.MediaType;
 import telraam.database.daos.BatonSwitchoverDAO;
 import telraam.database.daos.TeamDAO;
 import telraam.database.models.BatonSwitchover;
 import telraam.database.models.Team;
 
-import jakarta.ws.rs.Path;
-import jakarta.ws.rs.core.MediaType;
 import java.sql.Timestamp;
 import java.time.Instant;
 import java.util.List;

src/main/java/telraam/websocket/WebSocketConnection.java

@@ -0,0 +1,41 @@
+package telraam.websocket;
+
+import java.io.IOException;
+import java.util.logging.Logger;
+
+import org.eclipse.jetty.websocket.api.Session;
+import org.eclipse.jetty.websocket.api.WebSocketAdapter;
+
+public class WebSocketConnection extends WebSocketAdapter {
+    private static final Logger logger = Logger.getLogger(WebSocketConnection.class.getName());
+
+    @Override
+    public void onWebSocketConnect(Session session) {
+        super.onWebSocketConnect(session);
+        WebSocketMessageSingleton.getInstance().registerConnection(this);
+        logger.info("Instance with remote \"%s\" connected".formatted(getRemote().getRemoteAddress()));
+    }
+
+    @Override
+    public void onWebSocketClose(int statusCode, String reason) {
+        super.onWebSocketClose(statusCode, reason);
+        WebSocketMessageSingleton.getInstance().unregisterConnection(this);
+        logger.info("Instance with remote \"%s\" closed: [%s] %s".formatted(getRemote().getRemoteAddress(), statusCode, reason));
+    }
+
+    @Override
+    public void onWebSocketError(Throwable cause) {
+        super.onWebSocketError(cause);
+        logger.severe("WebSocket error in instance with remote \"%s\": %s".formatted(getRemote().getRemoteAddress(), cause));
+    }
+
+    public void send(String s) {
+        try {
+            getRemote().sendString(s);
+        } catch (IOException e) {
+            logger.severe("Sending \"%s\" through instance with remote \"%s\" failed with %s".formatted(s, getRemote().getRemoteAddress(), e));
+            return;
+        }
+        logger.finest("Sent \"%s\" through instance with remote \"%s\"".formatted(s, getRemote().getRemoteAddress()));
+    }
+}

src/main/java/telraam/websocket/WebSocketMessageSingleton.java

@@ -0,0 +1,37 @@
+package telraam.websocket;
+
+import lombok.Getter;
+
+import java.util.HashSet;
+import java.util.Set;
+import java.util.logging.Logger;
+
+public class WebSocketMessageSingleton {
+    private static final Logger logger = Logger.getLogger(WebSocketMessageSingleton.class.getName());
+
+    @Getter
+    private static final WebSocketMessageSingleton instance = new WebSocketMessageSingleton();
+    private static final Set<WebSocketConnection> registeredConnections = new HashSet<>();
+
+    private WebSocketMessageSingleton() {
+    }
+
+    public void registerConnection(WebSocketConnection conn) {
+        boolean modified = registeredConnections.add(conn);
+        if (modified) {
+            logger.info("Registered WebSocketConnection %s".formatted(conn));
+        }
+    }
+
+    public void unregisterConnection(WebSocketConnection conn) {
+        boolean modified = registeredConnections.remove(conn);
+        if (modified) {
+            logger.info("Unregistered WebSocketConnection %s".formatted(conn));
+        }
+    }
+
+    public void sendToAll(String s) {
+        logger.finest("Sending \"%s\" to all registered WebSocketConnection instances".formatted(s));
+        registeredConnections.forEach(conn -> conn.send(s));
+    }
+}