Scale db middleware

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

cmd/web-app/handlers/routes.go

@@ -25,6 +25,7 @@ import (
 	"geeks-accelerator/oss/saas-starter-kit/internal/user_account/invite"
 	"geeks-accelerator/oss/saas-starter-kit/internal/user_auth"
 
+	"github.com/aws/aws-sdk-go/aws/session"
 	"github.com/ikeikeikeike/go-sitemap-generator/v2/stm"
 	"github.com/jmoiron/sqlx"
 	"gopkg.in/DataDog/dd-trace-go.v1/contrib/go-redis/redis"
@@ -40,6 +41,7 @@ type AppContext struct {
 	Log               *log.Logger
 	Env               webcontext.Env
 	MasterDB          *sqlx.DB
+	MasterDbHost      string
 	Redis             *redis.Client
 	UserRepo          *user.Repository
 	UserAccountRepo   *user_account.Repository
@@ -57,6 +59,7 @@ type AppContext struct {
 	ProjectRoute      project_route.ProjectRoute
 	PreAppMiddleware  []web.Middleware
 	PostAppMiddleware []web.Middleware
+	AwsSession        *session.Session
 }
 
 // API returns a handler for a set of routes.
@@ -81,6 +84,24 @@ func APP(shutdown chan os.Signal, appCtx *AppContext) http.Handler {
 	// Construct the web.App which holds all routes as well as common Middleware.
 	app := web.NewApp(shutdown, appCtx.Log, appCtx.Env, middlewares...)
 
+	// Register serverless endpoint. This route is not authenticated.
+	serverless := Serverless{
+		MasterDB:     appCtx.MasterDB,
+		MasterDbHost: appCtx.MasterDbHost,
+		AwsSession:   appCtx.AwsSession,
+		Renderer:     appCtx.Renderer,
+	}
+	app.Handle("GET", "/serverless/pending", serverless.Pending)
+
+	// waitDbMid ensures the database is active before allowing the user to access the requested URI.
+	waitDbMid := mid.WaitForDbResumed(mid.WaitForDbResumedConfig{
+		// Database handle to be used to ensure its online.
+		DB: appCtx.MasterDB,
+
+		// WaitHandler defines the handler to render for the user to when the database is being resumed.
+		WaitHandler: serverless.Pending,
+	})
+
 	// Build a sitemap.
 	sm := stm.NewSitemap(1)
 	sm.SetVerbose(false)
@@ -146,7 +167,7 @@ func APP(shutdown chan os.Signal, appCtx *AppContext) http.Handler {
 		Renderer:        appCtx.Renderer,
 	}
 	app.Handle("POST", "/user/login", u.Login)
-	app.Handle("GET", "/user/login", u.Login)
+	app.Handle("GET", "/user/login", u.Login, waitDbMid)
 	app.Handle("GET", "/user/logout", u.Logout)
 	app.Handle("POST", "/user/reset-password/:hash", u.ResetConfirm)
 	app.Handle("GET", "/user/reset-password/:hash", u.ResetConfirm)
@@ -188,7 +209,7 @@ func APP(shutdown chan os.Signal, appCtx *AppContext) http.Handler {
 	}
 	// This route is not authenticated
 	app.Handle("POST", "/signup", s.Step1)
-	app.Handle("GET", "/signup", s.Step1)
+	app.Handle("GET", "/signup", s.Step1, waitDbMid)
 
 	// Register example endpoints.
 	ex := Examples{
@@ -224,6 +245,15 @@ func APP(shutdown chan os.Signal, appCtx *AppContext) http.Handler {
 	app.Handle("GET", "/robots.txt", r.RobotTxt)
 	app.Handle("GET", "/sitemap.xml", r.SitemapXml)
 
+	// Register health check endpoint. This route is not authenticated.
+	check := Check{
+		MasterDB: appCtx.MasterDB,
+		Redis:    appCtx.Redis,
+	}
+
+	app.Handle("GET", "/v1/health", check.Health)
+	app.Handle("GET", "/ping", check.Ping)
+
 	// Add sitemap entries for Root.
 	smLocAddModified(stm.URL{{"loc", "/"}, {"changefreq", "weekly"}, {"mobile", true}, {"priority", 0.9}}, "site-index.gohtml")
 	smLocAddModified(stm.URL{{"loc", "/pricing"}, {"changefreq", "monthly"}, {"mobile", true}, {"priority", 0.8}}, "site-pricing.gohtml")
@@ -232,14 +262,6 @@ func APP(shutdown chan os.Signal, appCtx *AppContext) http.Handler {
 	smLocAddModified(stm.URL{{"loc", "/legal/privacy"}, {"changefreq", "monthly"}, {"mobile", true}, {"priority", 0.5}}, "legal-privacy.gohtml")
 	smLocAddModified(stm.URL{{"loc", "/legal/terms"}, {"changefreq", "monthly"}, {"mobile", true}, {"priority", 0.5}}, "legal-terms.gohtml")
 
-	// Register health check endpoint. This route is not authenticated.
-	check := Check{
-		MasterDB: appCtx.MasterDB,
-		Redis:    appCtx.Redis,
-	}
-	app.Handle("GET", "/v1/health", check.Health)
-	app.Handle("GET", "/ping", check.Ping)
-
 	// Handle static files/pages. Render a custom 404 page when file not found.
 	static := func(ctx context.Context, w http.ResponseWriter, r *http.Request, params map[string]string) error {
 		err := web.StaticHandler(ctx, w, r, params, appCtx.StaticDir, "")

cmd/web-app/handlers/serverless.go

@@ -0,0 +1,104 @@
+package handlers
+
+import (
+	"context"
+	"net/http"
+	"net/url"
+
+	"geeks-accelerator/oss/saas-starter-kit/internal/mid"
+	"geeks-accelerator/oss/saas-starter-kit/internal/platform/web"
+	"github.com/aws/aws-sdk-go/aws"
+	"github.com/aws/aws-sdk-go/aws/session"
+	"github.com/aws/aws-sdk-go/service/rds"
+	"github.com/jmoiron/sqlx"
+	"github.com/pkg/errors"
+)
+
+// Serverless provides support for ensuring serverless resources are available for the user. .
+type Serverless struct {
+	Renderer     web.Renderer
+	MasterDB     *sqlx.DB
+	MasterDbHost string
+	AwsSession   *session.Session
+}
+
+// WaitDb validates the the database is resumed and ready to accept requests.
+func (h *Serverless) Pending(ctx context.Context, w http.ResponseWriter, r *http.Request, params map[string]string) error {
+
+	var redirectUri string
+	if v, ok := ctx.Value(mid.ServerlessKey).(error); ok && v != nil {
+		redirectUri = r.RequestURI
+	} else {
+		redirectUri = r.URL.Query().Get("redirect")
+	}
+
+	if redirectUri == "" {
+		redirectUri = "/"
+	}
+
+	f := func() (bool, error) {
+		svc := rds.New(h.AwsSession)
+
+		res, err := svc.DescribeDBClusters(&rds.DescribeDBClustersInput{})
+		if err != nil {
+			return false, errors.WithMessage(err, "Failed to list AWS db clusters.")
+		}
+
+		var targetCluster *rds.DBCluster
+		for _, c := range res.DBClusters {
+			if c.Endpoint == nil || *c.Endpoint != h.MasterDbHost {
+				continue
+			}
+
+			targetCluster = c
+		}
+
+		if targetCluster == nil {
+			return false, errors.New("Failed to find database cluster.")
+		} else if targetCluster.ScalingConfigurationInfo == nil || targetCluster.ScalingConfigurationInfo.MinCapacity == nil {
+			return false, errors.New("Database cluster has now scaling configuration.")
+		}
+
+		if targetCluster.Capacity != nil && *targetCluster.Capacity > 0 {
+			return true, nil
+		}
+
+		_, err = svc.ModifyCurrentDBClusterCapacity(&rds.ModifyCurrentDBClusterCapacityInput{
+			DBClusterIdentifier:  targetCluster.DBClusterIdentifier,
+			Capacity:             targetCluster.ScalingConfigurationInfo.MinCapacity,
+			SecondsBeforeTimeout: aws.Int64(10),
+			TimeoutAction:        aws.String("ForceApplyCapacityChange"),
+		})
+		if err != nil {
+			return false, err
+		}
+
+		return false, nil
+	}
+
+	end, err := f()
+	if err != nil {
+		return web.RenderError(ctx, w, r, err, h.Renderer, TmplLayoutBase, TmplContentErrorGeneric, web.MIMETextHTMLCharsetUTF8)
+	}
+
+	if web.RequestIsJson(r) {
+		data := map[string]interface{}{
+			"redirectUri": redirectUri,
+			"statusCode":  http.StatusServiceUnavailable,
+		}
+		if end {
+			data["statusCode"] = http.StatusOK
+		}
+		return web.RespondJson(ctx, w, data, http.StatusOK)
+	}
+
+	if end {
+		// Redirect the user to their requested page.
+		return web.Redirect(ctx, w, r, redirectUri, http.StatusFound)
+	}
+
+	data := map[string]interface{}{
+		"statusUrl": "/serverless/pending?redirect=" + url.QueryEscape(redirectUri),
+	}
+	return h.Renderer.Render(ctx, w, r, TmplLayoutBase, "serverless-db.gohtml", web.MIMETextHTMLCharsetUTF8, http.StatusOK, data)
+}

cmd/web-app/main.go

@@ -456,6 +456,7 @@ func main() {
 		Log:             log,
 		Env:             cfg.Env,
 		MasterDB:        masterDb,
+		MasterDbHost:    cfg.DB.Host,
 		Redis:           redisClient,
 		TemplateDir:     cfg.Service.TemplateDir,
 		StaticDir:       cfg.Service.StaticFiles.Dir,
@@ -470,6 +471,7 @@ func main() {
 		InviteRepo:      inviteRepo,
 		ProjectRepo:     prjRepo,
 		Authenticator:   authenticator,
+		AwsSession:      awsSession,
 	}
 
 	// =========================================================================

cmd/web-app/templates/content/serverless-db.gohtml

@@ -0,0 +1,51 @@
+{{define "title"}}Service Scaling{{end}}
+{{define "description"}}Service is scaling.{{end}}
+{{define "style"}}
+
+{{end}}
+{{ define "partials/app-wrapper" }}
+    <div class="container" id="page-content">
+        <div class="row justify-content-center">
+            <div class="col-xl-10 col-lg-12 col-md-9">
+                <div class="card o-hidden border-0 shadow-lg my-5">
+                    <div class="card-body p-0">
+                        <!-- Nested Row within Card Body -->
+                        <div class="row">
+                            <div class="col-lg-6 d-none d-lg-block bg-login-image"></div>
+                            <div class="col-lg-6">
+                                <div class="p-5">
+                                    {{ template "app-flashes" . }}
+
+                                    <div class="text-center" style="margin-bottom: 250px; ">
+                                        <h1 class="h4 text-gray-900 mb-4">The service is scaling up!</h1>
+                                        <p>Please wait a moment, you will be redirected to your request page when operation complete.</p>
+                                        <div class="spinner-border" role="status">
+                                            <span class="sr-only">Scaling...</span>
+                                        </div>
+                                    </div>
+                                </div>
+                            </div>
+                        </div>
+                    </div>
+                </div>
+            </div>
+        </div>
+    </div>
+{{end}}
+{{define "js"}}
+    <script>
+        $(document).ready(function() {
+            $(document).find('body').addClass('bg-gradient-primary');
+
+            $.ajax({
+                contentType: "application/json",
+                url: '{{ $.statusUrl }}',
+                dataType: "json"
+            }).done(function(data) {
+                if (data.statusCode == 200) {
+                    window.location = data.redirectUri;
+                }
+            });
+        });
+    </script>
+{{end}}

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
+}