engine refactor

internal/config/config.go

@@ -28,6 +28,12 @@ type Config struct {
 // HTTPConfig configures the HTTP server.
 type HTTPConfig struct {
 	Port int `yaml:"port"`
+	// AsyncWorkers caps concurrent prediction executions for the async endpoint.
+	AsyncWorkers int `yaml:"async_workers"`
+	// AsyncQueueSize bounds the async pending queue.
+	AsyncQueueSize int `yaml:"async_queue_size"`
+	// AsyncResultTTL is how long completed async results are retained.
+	AsyncResultTTL time.Duration `yaml:"async_result_ttl"`
 }
 
 // DataConfig configures dataset and elevation storage.
@@ -60,11 +66,16 @@ type LogConfig struct {
 // Defaults returns a Config with reasonable default values.
 func Defaults() Config {
 	return Config{
-		HTTP: HTTPConfig{Port: 8080},
+		HTTP: HTTPConfig{
+			Port:           8080,
+			AsyncWorkers:   4,
+			AsyncQueueSize: 64,
+			AsyncResultTTL: time.Hour,
+		},
 		Data: DataConfig{
 			Dir:           "/tmp/predictor-data",
 			ElevationPath: "/srv/ruaumoko-dataset",
-			Source:        "noaa-gfs-0p50",
+			Source:        "gfs-0p50-3h",
 		},
 		Download: DownloadConfig{
 			Parallel:                8,