make face load balancer more atomic, not to get spikes when face free (…

…#164)

cmd/eskimo-hut/api/docs.go

@@ -1321,6 +1321,12 @@ const docTemplate = `{
                         "description": "the kyc steps you wish to skip",
                         "name": "skipKYCSteps",
                         "in": "query"
+                    },
+                    {
+                        "type": "integer",
+                        "description": "the kyc step which would be next",
+                        "name": "nextKYCStep",
+                        "in": "query"
                     }
                 ],
                 "responses": {

cmd/eskimo-hut/api/swagger.json

@@ -1314,6 +1314,12 @@
                         "description": "the kyc steps you wish to skip",
                         "name": "skipKYCSteps",
                         "in": "query"
+                    },
+                    {
+                        "type": "integer",
+                        "description": "the kyc step which would be next",
+                        "name": "nextKYCStep",
+                        "in": "query"
                     }
                 ],
                 "responses": {

cmd/eskimo-hut/api/swagger.yaml

@@ -1663,6 +1663,10 @@ paths:
           type: integer
         name: skipKYCSteps
         type: array
+      - description: the kyc step which would be next
+        in: query
+        name: nextKYCStep
+        type: integer
       produces:
       - application/json
       responses:

cmd/eskimo-hut/kyc.go

@@ -245,6 +245,7 @@ func validateVerifySocialKYCStep(req *server.Request[kycsocial.VerificationMetad
 //	@Param			X-Account-Metadata	header		string	false	"Insert your metadata token"	default(<Add metadata token here>)
 //	@Param			userId				path		string	true	"ID of the user"
 //	@Param			skipKYCSteps		query		[]int	false	"the kyc steps you wish to skip"	collectionFormat(multi)
+//	@Param			nextKYCStep			query		int		false	"the kyc step which would be next"
 //	@Success		200					{object}	User
 //	@Failure		400					{object}	server.ErrorResponse	"if validations fail"
 //	@Failure		401					{object}	server.ErrorResponse	"if not authorized"

kyc/face/face.go

@@ -24,7 +24,7 @@ func New(ctx context.Context, usersRep UserRepository) Client {
 		cfg.UnexpectedErrorsAllowed = 5
 	}
 	db := storage.MustConnect(ctx, ddl, applicationYamlKey)
-	cl := &client{client: threedivi.New3Divi(usersRep, &cfg.ThreeDiVi), cfg: cfg, db: db}
+	cl := &client{client: threedivi.New3Divi(ctx, usersRep, &cfg.ThreeDiVi), cfg: cfg, db: db}
 	go cl.clearErrs(ctx)
 
 	return cl
@@ -56,19 +56,16 @@ func (c *client) CheckStatus(ctx context.Context, user *users.User, nextKYCStep
 			}
 		}
 	}
-	//nolint:nestif // .
 	if !hasResult || nextKYCStep == users.LivenessDetectionKYCStep {
-		availabilityErr := c.client.Available(ctx)
+		availabilityErr := c.client.Available(ctx, userWasPreviouslyForwardedToFaceKYC)
 		if availabilityErr == nil {
 			kycFaceAvailable = true
 			if fErr := c.saveUserForwarded(ctx, user.ID); fErr != nil {
 				return false, errors.Wrapf(fErr, "failed ")
 			}
-		} else {
-			if !errors.Is(availabilityErr, internal.ErrNotAvailable) {
-				c.unexpectedErrors.Add(1)
-			}
-			log.Error(errors.Wrapf(err, "[unexpected]face auth is unavailable for userID %v KYCStep %v", user.ID, nextKYCStep))
+		} else if !errors.Is(availabilityErr, internal.ErrNotAvailable) {
+			c.unexpectedErrors.Add(1)
+			log.Error(errors.Wrapf(availabilityErr, "[unexpected]face auth is unavailable for userID %v KYCStep %v", user.ID, nextKYCStep))
 		}
 	}
 

kyc/face/internal/contract.go

@@ -13,7 +13,7 @@ import (
 
 type (
 	Client interface {
-		Available(ctx context.Context) error
+		Available(ctx context.Context, userWasPreviouslyForwardedToFaceKYC bool) error
 		CheckAndUpdateStatus(ctx context.Context, user *users.User) (hasFaceKYCResult bool, err error)
 		Reset(ctx context.Context, user *users.User, fetchState bool) error
 	}

kyc/face/internal/threedivi/contract.go

@@ -3,6 +3,7 @@
 package threedivi
 
 import (
+	"sync/atomic"
 	stdlibtime "time"
 
 	"github.com/pkg/errors"
@@ -12,8 +13,9 @@ import (
 
 type (
 	threeDivi struct {
-		users internal.UserRepository
-		cfg   *Config
+		users                  internal.UserRepository
+		cfg                    *Config
+		loadBalancedUsersCount atomic.Uint64
 	}
 	Config struct {
 		ThreeDiVi struct {

kyc/face/internal/threedivi/threedivi.go

@@ -28,7 +28,7 @@ func init() { //nolint:gochecknoinits // It's the only way to tweak the client.
 	req.DefaultClient().GetClient().Timeout = requestDeadline
 }
 
-func New3Divi(usersRepository internal.UserRepository, cfg *Config) internal.Client {
+func New3Divi(ctx context.Context, usersRepository internal.UserRepository, cfg *Config) internal.Client {
 	if cfg.ThreeDiVi.BAFHost == "" {
 		log.Panic(errors.Errorf("no baf-host for 3divi integration"))
 	}
@@ -40,13 +40,16 @@ func New3Divi(usersRepository internal.UserRepository, cfg *Config) internal.Cli
 	}
 	cfg.ThreeDiVi.BAFHost, _ = strings.CutSuffix(cfg.ThreeDiVi.BAFHost, "/")
 
-	return &threeDivi{
+	tdv := &threeDivi{
 		users: usersRepository,
 		cfg:   cfg,
 	}
+	go tdv.clearUsers(ctx)
+
+	return tdv
 }
 
-func (t *threeDivi) Available(ctx context.Context) error {
+func (t *threeDivi) Available(ctx context.Context, userWasPreviouslyForwardedToFaceKYC bool) error {
 	if t.cfg.ThreeDiVi.AvailabilityURL == "" {
 		return nil
 	}
@@ -74,20 +77,39 @@ func (t *threeDivi) Available(ctx context.Context) error {
 	} else if data, err2 := resp.ToBytes(); err2 != nil {
 		return errors.Wrapf(err2, "failed to read body of availability of face auth")
 	} else { //nolint:revive // .
-		return t.isAvailable(data)
+		return t.isAvailable(data, userWasPreviouslyForwardedToFaceKYC)
 	}
 }
 
-func (t *threeDivi) isAvailable(data []byte) error {
+//nolint:revive // .
+func (t *threeDivi) isAvailable(data []byte, userWasPreviouslyForwardedToFaceKYC bool) error {
 	activeUsers, cErr := t.activeUsers(data)
 	if cErr != nil {
 		return errors.Wrapf(cErr, "failed to parse metrics of availability of face auth")
 	}
-	if activeUsers+1 > t.cfg.ThreeDiVi.ConcurrentUsers {
-		return internal.ErrNotAvailable
+	if int64(t.cfg.ThreeDiVi.ConcurrentUsers)-(int64(activeUsers)+int64(t.loadBalancedUsersCount.Load())) >= 1 {
+		if !userWasPreviouslyForwardedToFaceKYC {
+			t.loadBalancedUsersCount.Add(1)
+		}
+
+		return nil
 	}
 
-	return nil
+	return internal.ErrNotAvailable
+}
+
+func (t *threeDivi) clearUsers(ctx context.Context) {
+	ticker := stdlibtime.NewTicker(1 * stdlibtime.Minute)
+	defer ticker.Stop()
+
+	for {
+		select {
+		case <-ticker.C:
+			t.loadBalancedUsersCount.Store(0)
+		case <-ctx.Done():
+			return
+		}
+	}
 }
 
 func (*threeDivi) activeUsers(data []byte) (int, error) {