feat(notification): bye email if user reached daily email notificatio…

…n threshold

backend/cmd/notification_sender/main.go

@@ -1,13 +1,15 @@
 package notification_sender
 
 import (
+	"context"
 	"flag"
 	"fmt"
 	"net/http"
 	"os"
 	"sync"
 	"time"
 
+	"github.com/go-redis/redis/v8"
 	"github.com/gobitfly/beaconchain/pkg/commons/cache"
 	"github.com/gobitfly/beaconchain/pkg/commons/db"
 	"github.com/gobitfly/beaconchain/pkg/commons/log"
@@ -147,6 +149,21 @@ func Run() {
 		}()
 	}
 
+	// Initialize the persistent redis client
+	wg.Add(1)
+	go func() {
+		defer wg.Done()
+		rdc := redis.NewClient(&redis.Options{
+			Addr:        cfg.RedisSessionStoreEndpoint,
+			ReadTimeout: time.Second * 60,
+		})
+
+		if err := rdc.Ping(context.Background()).Err(); err != nil {
+			log.Fatal(err, "error connecting to persistent redis store", 0)
+		}
+		db.PersistentRedisDbClient = rdc
+	}()
+
 	wg.Wait()
 
 	defer db.ReaderDb.Close()

backend/pkg/commons/db/subscriptions.go

@@ -1,7 +1,7 @@
 package db
 
 import (
-	"database/sql"
+	"context"
 	"encoding/hex"
 
 	"fmt"
@@ -278,22 +278,19 @@ func UpdateSubscriptionLastSent(tx *sqlx.Tx, ts uint64, epoch uint64, subID uint
 	return err
 }
 
-// CountSentMail increases the count of sent mails in the table `mails_sent` for this day.
-func CountSentMail(email string) error {
+// CountSentMail increases the count of sent mails for this day.
+func CountSentMail(email string) (int64, error) {
 	day := time.Now().Truncate(utils.Day).Unix()
-	_, err := FrontendWriterDB.Exec(`
-		INSERT INTO mails_sent (email, ts, cnt) VALUES ($1, TO_TIMESTAMP($2), 1)
-		ON CONFLICT (email, ts) DO UPDATE SET cnt = mails_sent.cnt+1`, email, day)
-	return err
-}
+	key := fmt.Sprintf("n_mails:%s:%d", email, day)
 
-// GetMailsSentCount returns the number of sent mails for the day of the passed time.
-func GetMailsSentCount(email string, t time.Time) (int, error) {
-	day := t.Truncate(utils.Day).Unix()
-	count := 0
-	err := FrontendWriterDB.Get(&count, "SELECT cnt FROM mails_sent WHERE email = $1 AND ts = TO_TIMESTAMP($2)", email, day)
-	if err == sql.ErrNoRows {
-		return 0, nil
+	pipe := PersistentRedisDbClient.TxPipeline()
+	incr := pipe.Incr(context.Background(), key)
+	pipe.Expire(context.Background(), key, utils.Day)
+	_, err := pipe.Exec(context.Background())
+
+	if incr.Err() != nil {
+		return 0, incr.Err()
 	}
-	return count, err
+
+	return incr.Val(), err
 }

backend/pkg/commons/mail/mail.go

@@ -3,6 +3,7 @@ package mail
 import (
 	"bytes"
 	"context"
+	"html/template"
 
 	"fmt"
 	"net/smtp"
@@ -74,23 +75,30 @@ func createTextMessage(msg types.Email) string {
 func SendMailRateLimited(to, subject string, msg types.Email, attachment []types.EmailAttachment) error {
 	if utils.Config.Frontend.MaxMailsPerEmailPerDay > 0 {
 		now := time.Now()
-		count, err := db.GetMailsSentCount(to, now)
+		count, err := db.CountSentMail(to)
 		if err != nil {
 			return err
 		}
-		if count >= utils.Config.Frontend.MaxMailsPerEmailPerDay {
+		if count > int64(utils.Config.Frontend.MaxMailsPerEmailPerDay) {
 			timeLeft := now.Add(utils.Day).Truncate(utils.Day).Sub(now)
 			return &types.RateLimitError{TimeLeft: timeLeft}
+		} else if count == int64(utils.Config.Frontend.MaxMailsPerEmailPerDay) {
+			// send an email if this was the last email for today
+			err := SendHTMLMail(to,
+				"beaconcha.in - Email notification threshold limit reached",
+				types.Email{
+					Title: "Email notification threshold limit reached",
+					//nolint: gosec
+					Body: template.HTML(fmt.Sprintf("You have reached the email notification threshold limit of %d emails per day. Further notification emails will be suppressed until tomorrow.", utils.Config.Frontend.MaxMailsPerEmailPerDay)),
+				},
+				[]types.EmailAttachment{})
+			if err != nil {
+				return err
+			}
 		}
 	}
 
-	err := db.CountSentMail(to)
-	if err != nil {
-		// only log if counting did not work
-		return fmt.Errorf("error counting sent email: %v", err)
-	}
-
-	err = SendHTMLMail(to, subject, msg, attachment)
+	err := SendHTMLMail(to, subject, msg, attachment)
 	if err != nil {
 		return err
 	}