Scale db middleware

Ensure the database is active and has not been auto paused by RDS.
Resume database for signup and login pages.

internal/mid/serverless.go

@@ -0,0 +1,79 @@
+package mid
+
+import (
+	"context"
+	"net/http"
+	"time"
+
+	"geeks-accelerator/oss/saas-starter-kit/internal/platform/web"
+	"github.com/jmoiron/sqlx"
+	"gopkg.in/DataDog/dd-trace-go.v1/ddtrace/tracer"
+)
+
+// ctxServerlessKey represents the type of value for the context key.
+type ctxServerlessKey int
+
+// Key is used to store/retrieve a Serverless value from a context.Context.
+const ServerlessKey ctxServerlessKey = 1
+
+type (
+	// WaitForDbResumedConfig defines the config for WaitForDbResumed middleware.
+	WaitForDbResumedConfig struct {
+		RedirectConfig
+
+		// Database handle to be used to ensure its online.
+		DB *sqlx.DB
+
+		// WaitHandler defines the handler to render for the user to when the database is being resumed.
+		WaitHandler web.Handler
+	}
+)
+
+// WaitForDbResumed returns an middleware with for ensuring an serverless database is resumed.
+func WaitForDbResumed(config WaitForDbResumedConfig) web.Middleware {
+
+	if config.Skipper == nil {
+		config.Skipper = DefaultSkipper
+	}
+	if config.Code == 0 {
+		config.Code = DefaultRedirectConfig.Code
+	}
+
+	verifyDb := func() error {
+		// When the database is paused, Postgres will return the error, "Canceling statement due to user request"
+
+		ctx, cancel := context.WithTimeout(context.Background(), time.Second*1)
+		defer cancel()
+
+		_, err := config.DB.ExecContext(ctx, "SELECT NULL")
+		if err != nil {
+			return err
+		}
+
+		return nil
+	}
+
+	// This is the actual middleware function to be executed.
+	f := func(after web.Handler) web.Handler {
+
+		h := func(ctx context.Context, w http.ResponseWriter, r *http.Request, params map[string]string) error {
+			span, ctx := tracer.StartSpanFromContext(ctx, "internal.mid.serverless")
+			defer span.Finish()
+
+			if config.Skipper(ctx, w, r, params) {
+				return after(ctx, w, r, params)
+			}
+
+			if err := verifyDb(); err != nil {
+				ctx = context.WithValue(ctx, ServerlessKey, err)
+				return config.WaitHandler(ctx, w, r, params)
+			}
+
+			return after(ctx, w, r, params)
+		}
+
+		return h
+	}
+
+	return f
+}