.

.idea/gradle.xml

@@ -12,6 +12,7 @@
             <option value="$PROJECT_DIR$/core-bukkit-api" />
             <option value="$PROJECT_DIR$/core-bukkit-impl" />
             <option value="$PROJECT_DIR$/core-lib" />
+            <option value="$PROJECT_DIR$/core-velocity" />
           </set>
         </option>
       </GradleProjectSettings>

README.md

@@ -1,5 +1,8 @@
 TODO
 - timeout/error handling with reactive
+- unregister server on shutdown
+- infrastructure scripts/glue code w/ daemontools
+- djb's multilogd for logging
 
 environment
 -----------

core-lib/src/main/java/de/kentoj/scrowlib/servermanager/CrownServerManager.java

@@ -10,6 +10,8 @@ import org.jetbrains.annotations.NotNull;
 import reactor.core.publisher.Flux;
 import reactor.core.publisher.Mono;
 
+import javax.print.Doc;
+
 public class CrownServerManager implements ServerManager {
 
     private final NatsRepository natsRepo;
@@ -60,6 +62,14 @@ public class CrownServerManager implements ServerManager {
                 .map(doc -> doc.getString("state"));
     }
 
+    @Override
+    public Mono<@NotNull Integer> getPort(String handle) {
+        var payload = DocumentRepository.toBytes(new Document("handle", handle));
+        return natsRepo.request("crown.get-port", payload)
+                .map(DocumentRepository::fromMessage)
+                .map(doc -> doc.getInteger("port"));
+    }
+
     @Override
     public Mono<@NotNull Void> setState(String handle, String state) {
         Preconditions.checkArgument(!state.contains(" "), "state may not contain spaces");

core-lib/src/main/java/de/kentoj/scrowlib/servermanager/ServerManager.java

@@ -23,5 +23,7 @@ public interface ServerManager {
 
     Mono<@NotNull String> getState(String handle);
 
+    Mono<@NotNull Integer> getPort(String handle);
+
     Mono<@NotNull Void> setState(String handle, String state);
 }

core-velocity/src/main/java/de/kentoj/scrow/corevelocity/CoreVelocity.java

@@ -0,0 +1,49 @@
+package de.kentoj.scrow.corevelocity;
+
+import com.google.inject.Inject;
+import com.velocitypowered.api.event.Subscribe;
+import com.velocitypowered.api.event.proxy.ProxyInitializeEvent;
+import com.velocitypowered.api.plugin.Plugin;
+import com.velocitypowered.api.proxy.ProxyServer;
+import de.kentoj.scrowlib.servermanager.CrownServerManager;
+import de.kentoj.scrowlib.servermanager.ServerManager;
+import io.nats.client.Connection;
+import io.nats.client.Nats;
+import io.nats.client.Options;
+import lombok.extern.java.Log;
+
+import java.io.IOException;
+
+@Plugin(
+        id = "corevelocity",
+        name = "CoreVelocity",
+        version = "0.1"
+)
+@Log
+public class CoreVelocity {
+
+    private final ProxyServer server;
+    private final Connection nats;
+    private final ServerManager serverManager;
+    private final ServerRegisterWatchdog registerWatchdog;
+
+    @Inject
+    public CoreVelocity(ProxyServer server) {
+        this.server = server;
+
+        try {
+            var natsHost = System.getenv("HOST_NATS");
+            nats = Nats.connect(Options.builder()
+                    .pedantic()
+                    .server(natsHost)
+                    .build());
+            serverManager = new CrownServerManager(nats);
+            registerWatchdog = new ServerRegisterWatchdog(nats, serverManager, server);
+
+            log.info("listening on " + natsHost + " for server registrations");
+            registerWatchdog.listen();
+        } catch (IOException | InterruptedException e) {
+            throw new RuntimeException(e);
+        }
+    }
+}

core-velocity/src/main/java/de/kentoj/scrow/corevelocity/ServerRegisterWatchdog.java

@@ -0,0 +1,43 @@
+package de.kentoj.scrow.corevelocity;
+
+import com.velocitypowered.api.proxy.ProxyServer;
+import com.velocitypowered.api.proxy.server.ServerInfo;
+import de.kentoj.scrowlib.messaging.DocumentRepository;
+import de.kentoj.scrowlib.messaging.NatsRepository;
+import de.kentoj.scrowlib.servermanager.ServerManager;
+import io.nats.client.Connection;
+import lombok.extern.java.Log;
+import reactor.core.publisher.Mono;
+
+import java.net.InetSocketAddress;
+
+@Log
+public class ServerRegisterWatchdog {
+
+    private final NatsRepository natsRepo;
+    private final ServerManager serverManager;
+    private final ProxyServer server;
+
+    public ServerRegisterWatchdog(Connection nats, ServerManager serverManager, ProxyServer server) {
+        this.natsRepo = new NatsRepository(nats);
+        this.serverManager = serverManager;
+        this.server = server;
+    }
+
+    public void listen() {
+        natsRepo.subscribe("crown.set-state")
+                .map(DocumentRepository::fromMessage)
+                .flatMap(doc -> {
+                    var state = doc.getString("state");
+                    if (!"UP".equals(state)) return Mono.empty();
+
+                    var handle = doc.getString("handle");
+                    return serverManager.getPort(handle)
+                            .map(port -> {
+                                log.info("registering " + handle);
+                                return server.registerServer(new ServerInfo(handle, new InetSocketAddress(port)));
+                            });
+                })
+                .subscribe();
+    }
+}

settings.gradle.kts

@@ -9,4 +9,5 @@ plugins {
 rootProject.name = "core"
 include("core-bukkit-api")
 include("core-bukkit-impl")
-include("core-lib")
+include("core-lib")
+include("core-velocity")