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Asynchronous programming models including coroutines, async/await, and reactive patterns
Game server communication protocols including gRPC, REST, and custom binary protocols
Efficient data serialization for game networking including Protobuf, FlatBuffers, and custom binary
Game data persistence with player profiles, leaderboards, inventory systems using Redis and PostgreSQL
Game server deployment with Docker, Kubernetes, and global distribution strategies
Game server design patterns including ECS, command pattern, and event sourcing
Server-side game loop implementation with fixed timestep, physics simulation, and tick rate optimization
| name | async-programming |
| description | Asynchronous programming models including coroutines, async/await, and reactive patterns |
| sasmp_version | 1.3.0 |
| version | 2.0.0 |
| bonded_agent | 01-game-server-architect |
| bond_type | SECONDARY_BOND |
| parameters | {"required":["async_model"],"optional":["concurrency_limit","timeout_ms"],"validation":{"async_model":{"type":"string","enum":["async_await","coroutines","goroutines","futures","reactive"]},"concurrency_limit":{"type":"integer","min":1,"max":10000,"default":1000},"timeout_ms":{"type":"integer","min":100,"max":60000,"default":30000}}} |
| retry_config | {"max_attempts":3,"backoff":"exponential","initial_delay_ms":100,"retryable_errors":["TIMEOUT","CONNECTION_RESET"]} |
| observability | {"logging":{"level":"debug","fields":["task_id","async_model","duration_ms"]},"metrics":[{"name":"async_tasks_active","type":"gauge"},{"name":"async_task_duration_seconds","type":"histogram"},{"name":"async_errors_total","type":"counter"},{"name":"event_loop_lag_ms","type":"gauge"}]} |
Implement efficient asynchronous patterns for scalable game server code.
| Model | Language | Overhead | Complexity | Best For |
|---|---|---|---|---|
| async/await | C#, JS, Rust | Low | Low | I/O bound |
| Coroutines | C++20, Kotlin | Very Low | Medium | High performance |
| Goroutines | Go | Very Low | Low | Concurrent services |
| Futures | C++, Java | Medium | Medium | Composable async |
| Reactive | All | Low | High | Stream processing |
public class GameServer
{
private readonly SemaphoreSlim _connectionLimit = new(1000);
private readonly CancellationTokenSource _cts = new();
public async Task HandlePlayerAsync(
Player player,
CancellationToken cancellationToken = default)
{
// Combine with server shutdown token
using var linkedCts = CancellationTokenSource.CreateLinkedTokenSource(
cancellationToken, _cts.Token);
var token = linkedCts.Token;
try
{
await _connectionLimit.WaitAsync(token);
while (player.Connected && !token.IsCancellationRequested)
{
// Non-blocking read with timeout
using var timeoutCts = new CancellationTokenSource(TimeSpan.FromSeconds(30));
using var combinedCts = CancellationTokenSource.CreateLinkedTokenSource(
token, timeoutCts.Token);
var message = await player.ReadMessageAsync(combinedCts.Token);
var result = await ProcessCommandAsync(message, token);
await player.SendAsync(result, token);
}
}
catch (OperationCanceledException) when (token.IsCancellationRequested)
{
// Graceful shutdown
}
finally
{
_connectionLimit.Release();
}
}
private async Task<GameState> ProcessCommandAsync(
Message msg,
CancellationToken token)
{
// Parallel async operations with structured concurrency
var validationTask = ValidateAsync(msg, token);
var playerDataTask = LoadPlayerDataAsync(msg.PlayerId, token);
var permissionsTask = CheckPermissionsAsync(msg.PlayerId, token);
await Task.WhenAll(validationTask, playerDataTask, permissionsTask);
// All tasks completed - apply command
return ApplyCommand(msg,
await validationTask,
await playerDataTask,
await permissionsTask);
}
public async Task GracefulShutdownAsync()
{
_cts.Cancel();
// Wait for all connections to drain
await Task.Delay(TimeSpan.FromSeconds(30));
}
}
type Server struct {
listener net.Listener
players sync.Map
wg sync.WaitGroup
quit chan struct{}
semaphore chan struct{} // Connection limiter
}
func NewServer(maxConnections int) *Server {
return &Server{
quit: make(chan struct{}),
semaphore: make(chan struct{}, maxConnections),
}
}
func (s *Server) AcceptLoop() {
for {
conn, err := s.listener.Accept()
if err != nil {
select {
case <-s.quit:
return // Server shutting down
default:
log.Printf("Accept error: %v", err)
continue
}
}
// Rate limit connections
select {
case s.semaphore <- struct{}{}:
s.wg.Add(1)
go s.handlePlayer(conn)
default:
conn.Close() // At capacity
}
}
}
func (s *Server) handlePlayer(conn net.Conn) {
defer func() {
<-s.semaphore
s.wg.Done()
conn.Close()
}()
player := NewPlayer(conn)
s.players.Store(player.ID, player)
defer s.players.Delete(player.ID)
// Separate goroutines for read/write with channels
readChan := make(chan Message, 100)
writeChan := make(chan Message, 100)
errChan := make(chan error, 2)
go func() {
errChan <- player.readLoop(readChan)
}()
go func() {
errChan <- player.writeLoop(writeChan)
}()
for {
select {
case msg := <-readChan:
result := s.processMessage(msg)
writeChan <- result
case err := <-errChan:
if err != nil && !errors.Is(err, io.EOF) {
log.Printf("Player %s error: %v", player.ID, err)
}
return
case <-s.quit:
return
}
}
}
func (s *Server) Shutdown(ctx context.Context) error {
close(s.quit)
s.listener.Close()
done := make(chan struct{})
go func() {
s.wg.Wait()
close(done)
}()
select {
case <-done:
return nil
case <-ctx.Done():
return ctx.Err()
}
}
#include <coroutine>
#include <optional>
// Awaitable task type
template<typename T>
class Task {
public:
struct promise_type {
T value;
std::exception_ptr exception;
Task get_return_object() {
return Task{std::coroutine_handle<promise_type>::from_promise(*this)};
}
std::suspend_never initial_suspend() { return {}; }
std::suspend_always final_suspend() noexcept { return {}; }
void return_value(T v) { value = std::move(v); }
void unhandled_exception() { exception = std::current_exception(); }
};
bool await_ready() { return handle.done(); }
void await_suspend(std::coroutine_handle<> h) { /* ... */ }
T await_resume() {
if (handle.promise().exception)
std::rethrow_exception(handle.promise().exception);
return std::move(handle.promise().value);
}
private:
std::coroutine_handle<promise_type> handle;
};
// Async game server
class AsyncGameServer {
public:
Task<void> handlePlayer(Connection& conn) {
while (conn.isOpen()) {
auto msg = co_await conn.readAsync();
auto result = co_await processAsync(msg);
co_await conn.writeAsync(result);
}
}
Task<GameState> processAsync(const Message& msg) {
// Parallel async operations
auto [validation, playerData] = co_await whenAll(
validateAsync(msg),
loadPlayerAsync(msg.playerId)
);
co_return applyCommand(msg, validation, playerData);
}
};
// Generator for game updates
template<typename T>
class Generator {
public:
struct promise_type {
T current_value;
Generator get_return_object() { /* ... */ }
std::suspend_always yield_value(T value) {
current_value = std::move(value);
return {};
}
};
class iterator { /* ... */ };
iterator begin() { /* ... */ }
iterator end() { /* ... */ }
};
Generator<GameState> gameLoop() {
while (running) {
updatePhysics();
updateAI();
co_yield currentState;
}
}
use tokio::net::{TcpListener, TcpStream};
use tokio::sync::{mpsc, Semaphore};
use std::sync::Arc;
struct GameServer {
max_connections: Arc<Semaphore>,
shutdown: tokio::sync::broadcast::Sender<()>,
}
impl GameServer {
async fn run(&self, listener: TcpListener) -> Result<()> {
let mut shutdown_rx = self.shutdown.subscribe();
loop {
tokio::select! {
result = listener.accept() => {
let (socket, addr) = result?;
// Acquire connection permit
let permit = self.max_connections.clone().acquire_owned().await?;
let shutdown_rx = self.shutdown.subscribe();
tokio::spawn(async move {
let _permit = permit; // Release on drop
if let Err(e) = handle_player(socket, shutdown_rx).await {
eprintln!("Player error: {}", e);
}
});
}
_ = shutdown_rx.recv() => {
println!("Shutting down");
break;
}
}
}
Ok(())
}
}
async fn handle_player(
stream: TcpStream,
mut shutdown: tokio::sync::broadcast::Receiver<()>
) -> Result<()> {
let (reader, writer) = stream.into_split();
let mut reader = BufReader::new(reader);
let mut writer = BufWriter::new(writer);
loop {
tokio::select! {
result = read_message(&mut reader) => {
let msg = result?;
let response = process_command(&msg).await;
write_message(&mut writer, &response).await?;
}
_ = shutdown.recv() => {
// Graceful shutdown
break;
}
}
}
Ok(())
}
// Concurrent task spawning with limits
async fn process_batch(items: Vec<Item>) -> Vec<Result> {
let semaphore = Arc::new(Semaphore::new(100)); // Max 100 concurrent
let tasks: Vec<_> = items.into_iter().map(|item| {
let permit = semaphore.clone();
tokio::spawn(async move {
let _permit = permit.acquire().await.unwrap();
process_item(item).await
})
}).collect();
futures::future::join_all(tasks)
.await
.into_iter()
.map(|r| r.unwrap())
.collect()
}
| Practice | Benefit |
|---|---|
| Avoid blocking in async | Prevents thread starvation |
| Use cancellation tokens | Clean shutdown |
| Limit concurrency | Prevent resource exhaustion |
| Structured concurrency | Proper error handling |
| Backpressure handling | Prevent memory overflow |
| Problem | Root Cause | Solution |
|---|---|---|
| Thread starvation | Blocking in async | Use spawn_blocking |
| Memory leak | Unbounded channels | Bounded channels |
| Deadlock | Sync in async context | Async-aware locks |
| Event loop lag | Long-running tasks | Break into smaller tasks |
# Node.js event loop lag
node --trace-warnings --inspect server.js
# Go goroutine dump
curl http://localhost:6060/debug/pprof/goroutine?debug=1
# Rust tokio console
tokio-console http://localhost:6669
# C# async diagnostics
dotnet counters monitor --process-id <pid> System.Runtime
// Monitor Node.js event loop
const { monitorEventLoopDelay } = require('perf_hooks');
const histogram = monitorEventLoopDelay({ resolution: 20 });
histogram.enable();
setInterval(() => {
console.log(`Event loop lag: p99=${histogram.percentile(99)}ms`);
}, 5000);
[Fact]
public async Task HandlePlayer_ProcessesMessages()
{
var server = new GameServer();
var mockPlayer = new MockPlayer();
mockPlayer.EnqueueMessage(new MoveCommand { Direction = Vector3.Forward });
var cts = new CancellationTokenSource(TimeSpan.FromSeconds(5));
await server.HandlePlayerAsync(mockPlayer, cts.Token);
Assert.Single(mockPlayer.SentMessages);
Assert.IsType<GameState>(mockPlayer.SentMessages[0]);
}
[Fact]
public async Task ProcessCommand_RunsInParallel()
{
var server = new GameServer();
var stopwatch = Stopwatch.StartNew();
// Each operation takes 100ms
var result = await server.ProcessCommandAsync(new Message());
stopwatch.Stop();
// Should complete in ~100ms, not 300ms (3 x 100ms)
Assert.True(stopwatch.ElapsedMilliseconds < 200);
}
[Fact]
public async Task GracefulShutdown_WaitsForConnections()
{
var server = new GameServer();
var longRunningTask = server.HandlePlayerAsync(new SlowPlayer());
var shutdownTask = server.GracefulShutdownAsync();
// Shutdown should wait for connection
await Task.Delay(100);
Assert.False(shutdownTask.IsCompleted);
}
assets/ - Async patternsreferences/ - Concurrency guides