Improve mailer performance

Signed-off-by: Bryan Frimin <bryan@getprobo.com>

pkg/coredata/email.go

@@ -28,15 +28,21 @@ import (
 
 type (
 	Email struct {
-		ID             gid.GID    `db:"id"`
-		RecipientEmail string     `db:"recipient_email"`
-		RecipientName  string     `db:"recipient_name"`
-		Subject        string     `db:"subject"`
-		TextBody       string     `db:"text_body"`
-		HtmlBody       *string    `db:"html_body"`
-		CreatedAt      time.Time  `db:"created_at"`
-		UpdatedAt      time.Time  `db:"updated_at"`
-		SentAt         *time.Time `db:"sent_at"`
+		ID                  gid.GID     `db:"id"`
+		RecipientEmail      string      `db:"recipient_email"`
+		RecipientName       string      `db:"recipient_name"`
+		Subject             string      `db:"subject"`
+		TextBody            string      `db:"text_body"`
+		HtmlBody            *string     `db:"html_body"`
+		Status              EmailStatus `db:"status"`
+		ProcessingStartedAt *time.Time  `db:"processing_started_at"`
+		AttemptCount        int         `db:"attempt_count"`
+		MaxAttempts         int         `db:"max_attempts"`
+		LastAttemptedAt     *time.Time  `db:"last_attempted_at"`
+		LastError           *string     `db:"last_error"`
+		CreatedAt           time.Time   `db:"created_at"`
+		UpdatedAt           time.Time   `db:"updated_at"`
+		SentAt              *time.Time  `db:"sent_at"`
 	}
 )
 
@@ -65,6 +71,9 @@ func NewEmail(
 		Subject:        subject,
 		TextBody:       textBody,
 		HtmlBody:       htmlBody,
+		Status:         EmailStatusPending,
+		AttemptCount:   0,
+		MaxAttempts:    10,
 		CreatedAt:      now,
 		UpdatedAt:      now,
 	}
@@ -75,8 +84,14 @@ func (e *Email) Insert(
 	conn pg.Conn,
 ) error {
 	q := `
-INSERT INTO emails (id, recipient_email, recipient_name, subject, text_body, html_body, created_at, updated_at)
-VALUES (@id, @recipient_email, @recipient_name, @subject, @text_body, @html_body, @created_at, @updated_at)
+INSERT INTO emails (
+	id, recipient_email, recipient_name, subject, text_body, html_body,
+	status, attempt_count, max_attempts, created_at, updated_at
+)
+VALUES (
+	@id, @recipient_email, @recipient_name, @subject, @text_body, @html_body,
+	@status, @attempt_count, @max_attempts, @created_at, @updated_at
+)
 	`
 
 	args := pgx.StrictNamedArgs{
@@ -86,6 +101,9 @@ VALUES (@id, @recipient_email, @recipient_name, @subject, @text_body, @html_body
 		"subject":         e.Subject,
 		"text_body":       e.TextBody,
 		"html_body":       e.HtmlBody,
+		"status":          e.Status,
+		"attempt_count":   e.AttemptCount,
+		"max_attempts":    e.MaxAttempts,
 		"created_at":      e.CreatedAt,
 		"updated_at":      e.UpdatedAt,
 	}
@@ -94,17 +112,20 @@ VALUES (@id, @recipient_email, @recipient_name, @subject, @text_body, @html_body
 	return err
 }
 
-func (e *Email) LoadNextUnsentForUpdate(
+func (e *Email) LoadNextPendingForUpdateSkipLocked(
 	ctx context.Context,
 	conn pg.Conn,
 ) error {
 	q := `
-SELECT id, recipient_email, recipient_name, subject, text_body, html_body, created_at, updated_at, sent_at
+SELECT
+	id, recipient_email, recipient_name, subject, text_body, html_body,
+	status, processing_started_at, attempt_count, max_attempts,
+	last_attempted_at, last_error, created_at, updated_at, sent_at
 FROM emails
-WHERE sent_at IS NULL
+WHERE status = 'PENDING' AND attempt_count < max_attempts
 ORDER BY created_at ASC
 LIMIT 1
-FOR UPDATE
+FOR UPDATE SKIP LOCKED
 	`
 
 	rows, err := conn.Query(ctx, q)
@@ -132,16 +153,47 @@ func (e *Email) Update(
 ) error {
 	q := `
 UPDATE emails
-SET sent_at = @sent_at, updated_at = @updated_at
+SET
+	status = @status,
+	processing_started_at = @processing_started_at,
+	attempt_count = @attempt_count,
+	last_attempted_at = @last_attempted_at,
+	last_error = @last_error,
+	sent_at = @sent_at,
+	updated_at = @updated_at
 WHERE id = @id
 	`
 
 	args := pgx.StrictNamedArgs{
-		"id":         e.ID,
-		"sent_at":    e.SentAt,
-		"updated_at": e.UpdatedAt,
+		"id":                    e.ID,
+		"status":                e.Status,
+		"processing_started_at": e.ProcessingStartedAt,
+		"attempt_count":         e.AttemptCount,
+		"last_attempted_at":     e.LastAttemptedAt,
+		"last_error":            e.LastError,
+		"sent_at":               e.SentAt,
+		"updated_at":            e.UpdatedAt,
 	}
 
 	_, err := conn.Exec(ctx, q, args)
 	return err
 }
+
+func ResetStaleProcessingEmails(
+	ctx context.Context,
+	conn pg.Conn,
+	staleAfter time.Duration,
+) error {
+	q := `
+UPDATE emails
+SET status = 'PENDING', processing_started_at = NULL, updated_at = NOW()
+WHERE status = 'PROCESSING'
+	AND processing_started_at < NOW() - $1::interval
+`
+	_, err := conn.Exec(ctx, q, staleAfter)
+	if err != nil {
+		return fmt.Errorf("cannot reset stale processing emails: %w", err)
+	}
+
+	return nil
+}

pkg/coredata/email_status.go

@@ -0,0 +1,71 @@
+// Copyright (c) 2025 Probo Inc <hello@getprobo.com>.
+//
+// Permission to use, copy, modify, and/or distribute this software for any
+// purpose with or without fee is hereby granted, provided that the above
+// copyright notice and this permission notice appear in all copies.
+//
+// THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES WITH
+// REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
+// AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT,
+// INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM
+// LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR
+// OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
+// PERFORMANCE OF THIS SOFTWARE.
+
+package coredata
+
+import (
+	"database/sql/driver"
+	"fmt"
+)
+
+type (
+	EmailStatus string
+)
+
+const (
+	EmailStatusPending    EmailStatus = "PENDING"
+	EmailStatusProcessing EmailStatus = "PROCESSING"
+	EmailStatusSent       EmailStatus = "SENT"
+	EmailStatusFailed     EmailStatus = "FAILED"
+)
+
+func (s EmailStatus) MarshalText() ([]byte, error) {
+	return []byte(s.String()), nil
+}
+
+func (s *EmailStatus) UnmarshalText(data []byte) error {
+	val := string(data)
+
+	switch val {
+	case EmailStatusPending.String():
+		*s = EmailStatusPending
+	case EmailStatusProcessing.String():
+		*s = EmailStatusProcessing
+	case EmailStatusSent.String():
+		*s = EmailStatusSent
+	case EmailStatusFailed.String():
+		*s = EmailStatusFailed
+	default:
+		return fmt.Errorf("invalid EmailStatus value: %q", val)
+	}
+
+	return nil
+}
+
+func (s EmailStatus) String() string {
+	return string(s)
+}
+
+func (s *EmailStatus) Scan(value any) error {
+	val, ok := value.(string)
+	if !ok {
+		return fmt.Errorf("invalid scan source for EmailStatus, expected string got %T", value)
+	}
+
+	return s.UnmarshalText([]byte(val))
+}
+
+func (s EmailStatus) Value() (driver.Value, error) {
+	return s.String(), nil
+}

pkg/coredata/migrations/20260308T120000Z.sql

@@ -0,0 +1,12 @@
+ALTER TABLE emails
+ADD COLUMN status TEXT NOT NULL DEFAULT 'PENDING',
+ADD COLUMN processing_started_at TIMESTAMP WITH TIME ZONE,
+ADD COLUMN attempt_count INTEGER NOT NULL DEFAULT 0,
+ADD COLUMN max_attempts INTEGER NOT NULL DEFAULT 10,
+ADD COLUMN last_attempted_at TIMESTAMP WITH TIME ZONE,
+ADD COLUMN last_error TEXT;
+
+UPDATE emails SET status = 'SENT' WHERE sent_at IS NOT NULL;
+
+CREATE INDEX idx_emails_pending ON emails (status, created_at)
+WHERE status = 'PENDING';

pkg/mailer/mailer.go

@@ -22,6 +22,7 @@ import (
 	"fmt"
 	"net"
 	"net/smtp"
+	"sync"
 	"time"
 
 	"github.com/jhillyerd/enmime"
@@ -32,90 +33,333 @@ import (
 )
 
 type (
-	Mailer struct {
-		pg          *pg.Client
-		fileManager *filemanager.Service
-		l           *log.Logger
-		cfg         Config
-		interval    time.Duration
+	SendingWorker struct {
+		pg             *pg.Client
+		fileManager    *filemanager.Service
+		logger         *log.Logger
+		smtp           SMTPConfig
+		senderName     string
+		senderEmail    string
+		interval       time.Duration
+		smtpTimeout    time.Duration
+		staleAfter     time.Duration
+		maxConcurrency int
 	}
 
-	Config struct {
-		SenderName  string
-		SenderEmail string
+	SMTPConfig struct {
 		Addr        string
-		Timeout     time.Duration
 		User        string
 		Password    string
 		TLSRequired bool
-		Interval    time.Duration
 	}
+
+	SendingWorkerOption func(*SendingWorker)
 )
 
-func NewMailer(pg *pg.Client, fileManager *filemanager.Service, l *log.Logger, cfg Config) *Mailer {
-	// Set a default timeout if not provided
-	if cfg.Timeout == 0 {
-		cfg.Timeout = 10 * time.Second
-	}
-
-	// Set a default interval if not provided
-	if cfg.Interval == 0 {
-		cfg.Interval = 60 * time.Second
-	}
-
-	return &Mailer{pg: pg, fileManager: fileManager, l: l, cfg: cfg, interval: cfg.Interval}
+func WithSendingWorkerInterval(d time.Duration) SendingWorkerOption {
+	return func(w *SendingWorker) { w.interval = d }
 }
 
-func (m *Mailer) Run(ctx context.Context) error {
-LOOP:
+func WithSendingWorkerSMTPTimeout(d time.Duration) SendingWorkerOption {
+	return func(w *SendingWorker) { w.smtpTimeout = d }
+}
+
+func WithSendingWorkerStaleAfter(d time.Duration) SendingWorkerOption {
+	return func(w *SendingWorker) { w.staleAfter = d }
+}
+
+func WithSendingWorkerMaxConcurrency(n int) SendingWorkerOption {
+	return func(w *SendingWorker) {
+		if n > 0 {
+			w.maxConcurrency = n
+		}
+	}
+}
+
+func NewSendingWorker(
+	pgClient *pg.Client,
+	fileManager *filemanager.Service,
+	senderName string,
+	senderEmail string,
+	smtpCfg SMTPConfig,
+	logger *log.Logger,
+	opts ...SendingWorkerOption,
+) *SendingWorker {
+	w := &SendingWorker{
+		pg:             pgClient,
+		fileManager:    fileManager,
+		logger:         logger,
+		smtp:           smtpCfg,
+		senderName:     senderName,
+		senderEmail:    senderEmail,
+		interval:       30 * time.Second,
+		smtpTimeout:    25 * time.Second,
+		staleAfter:     5 * time.Minute,
+		maxConcurrency: 20,
+	}
+
+	for _, opt := range opts {
+		opt(w)
+	}
+
+	return w
+}
+
+func (w *SendingWorker) Run(ctx context.Context) error {
+	var (
+		wg  sync.WaitGroup
+		sem = make(chan struct{}, w.maxConcurrency)
+	)
+
+	defer wg.Wait()
+
+	ticker := time.NewTicker(w.interval)
+	defer ticker.Stop()
+
+	for {
+		select {
+		case <-ctx.Done():
+			return ctx.Err()
+		case <-ticker.C:
+			nonCancelableCtx := context.WithoutCancel(ctx)
+			w.recoverStaleRows(nonCancelableCtx)
+
+			for {
+				if err := w.processNext(ctx, sem, &wg); err != nil {
+					if !errors.Is(err, coredata.ErrNoUnsentEmail) {
+						w.logger.ErrorCtx(nonCancelableCtx, "cannot process email", log.Error(err))
+					}
+					break
+				}
+			}
+		}
+	}
+}
+
+func (w *SendingWorker) processNext(ctx context.Context, sem chan struct{}, wg *sync.WaitGroup) error {
 	select {
+	case sem <- struct{}{}:
 	case <-ctx.Done():
 		return ctx.Err()
-	case <-time.After(m.interval):
-		ctx := context.Background()
-		if err := m.batchSendEmails(ctx); err != nil {
-			m.l.ErrorCtx(ctx, "cannot send email", log.Error(err))
-		}
+	}
 
-		goto LOOP
+	var (
+		email            = coredata.Email{}
+		nonCancelableCtx = context.WithoutCancel(ctx)
+	)
+
+	if err := w.pg.WithTx(
+		nonCancelableCtx,
+		func(tx pg.Conn) error {
+			if err := email.LoadNextPendingForUpdateSkipLocked(nonCancelableCtx, tx); err != nil {
+				return err
+			}
+
+			now := time.Now()
+			email.Status = coredata.EmailStatusProcessing
+			email.ProcessingStartedAt = &now
+			email.AttemptCount++
+			email.LastAttemptedAt = &now
+			email.UpdatedAt = now
+
+			if err := email.Update(nonCancelableCtx, tx); err != nil {
+				return fmt.Errorf("cannot update email: %w", err)
+			}
+
+			return nil
+		},
+	); err != nil {
+		<-sem
+		return err
+	}
+
+	wg.Add(1)
+	go func(email coredata.Email) {
+		defer wg.Done()
+		defer func() { <-sem }()
+
+		if sendErr := w.sendAndCommit(nonCancelableCtx, &email); sendErr != nil {
+			if failErr := w.failEmail(nonCancelableCtx, &email, sendErr); failErr != nil {
+				w.logger.ErrorCtx(nonCancelableCtx, "cannot fail email", log.Error(failErr))
+			}
+		}
+	}(email)
+
+	return nil
+}
+
+func (w *SendingWorker) sendAndCommit(
+	ctx context.Context,
+	email *coredata.Email,
+) error {
+	var buf bytes.Buffer
+
+	if err := w.pg.WithConn(
+		ctx,
+		func(conn pg.Conn) error {
+			var attachments coredata.EmailAttachments
+			if err := attachments.LoadByEmailID(ctx, conn, email.ID); err != nil {
+				return fmt.Errorf("cannot load email attachments: %w", err)
+			}
+
+			mail := enmime.Builder().
+				Subject(email.Subject).
+				From(w.senderName, w.senderEmail).
+				To(email.RecipientName, email.RecipientEmail).
+				Text([]byte(email.TextBody))
+
+			if email.HtmlBody != nil {
+				mail = mail.HTML([]byte(*email.HtmlBody))
+			}
+
+			for _, att := range attachments {
+				var file coredata.File
+				if err := file.LoadByID(ctx, conn, coredata.NewNoScope(), att.FileID); err != nil {
+					return fmt.Errorf("cannot load file record for attachment %s: %w", att.Filename, err)
+				}
+
+				data, err := w.fileManager.GetFileBytes(ctx, &file)
+				if err != nil {
+					return fmt.Errorf("cannot download attachment %s: %w", att.Filename, err)
+				}
+
+				mail = mail.AddAttachment(data, file.MimeType, att.Filename)
+			}
+
+			envelope, err := mail.Build()
+			if err != nil {
+				return fmt.Errorf("cannot build email: %w", err)
+			}
+
+			if err := envelope.Encode(&buf); err != nil {
+				return fmt.Errorf("cannot encode email: %w", err)
+			}
+
+			return nil
+		},
+	); err != nil {
+		return err
+	}
+
+	sendCtx, cancel := context.WithTimeout(ctx, w.smtpTimeout)
+	defer cancel()
+
+	if err := w.sendMail(sendCtx, []string{email.RecipientEmail}, buf.Bytes()); err != nil {
+		if errors.Is(err, context.DeadlineExceeded) {
+			return fmt.Errorf("email sending timed out after %s: %w", w.smtpTimeout, err)
+		}
+		return fmt.Errorf("cannot send email: %w", err)
+	}
+
+	if err := w.pg.WithTx(
+		ctx,
+		func(tx pg.Conn) error {
+			now := time.Now()
+			email.Status = coredata.EmailStatusSent
+			email.SentAt = &now
+			email.ProcessingStartedAt = nil
+			email.LastError = nil
+			email.UpdatedAt = now
+
+			if err := email.Update(ctx, tx); err != nil {
+				return fmt.Errorf("cannot update email: %w", err)
+			}
+
+			return nil
+		},
+	); err != nil {
+		w.logger.ErrorCtx(ctx,
+			"email sent but failed to commit status update; will not re-queue to avoid duplicate delivery",
+			log.Error(err),
+			log.String("email_id", email.ID.String()),
+		)
+	}
+
+	return nil
+}
+
+func (w *SendingWorker) failEmail(
+	ctx context.Context,
+	email *coredata.Email,
+	processingError error,
+) error {
+	w.logger.ErrorCtx(ctx, "sending worker failure",
+		log.Error(processingError),
+		log.String("email_id", email.ID.String()),
+	)
+
+	return w.pg.WithTx(
+		ctx,
+		func(tx pg.Conn) error {
+			errStr := processingError.Error()
+			email.LastError = &errStr
+			email.ProcessingStartedAt = nil
+			email.UpdatedAt = time.Now()
+
+			if email.AttemptCount >= email.MaxAttempts {
+				email.Status = coredata.EmailStatusFailed
+			} else {
+				email.Status = coredata.EmailStatusPending
+			}
+
+			if err := email.Update(ctx, tx); err != nil {
+				return fmt.Errorf("cannot update email: %w", err)
+			}
+
+			return nil
+		},
+	)
+}
+
+func (w *SendingWorker) recoverStaleRows(ctx context.Context) {
+	if err := w.pg.WithConn(
+		ctx,
+		func(conn pg.Conn) error {
+			return coredata.ResetStaleProcessingEmails(ctx, conn, w.staleAfter)
+		},
+	); err != nil {
+		w.logger.ErrorCtx(ctx, "cannot recover stale emails", log.Error(err))
 	}
 }
 
-func (m *Mailer) sendMailWithTimeout(ctx context.Context, to []string, msg []byte) error {
-	host, _, err := net.SplitHostPort(m.cfg.Addr)
+func (w *SendingWorker) sendMail(ctx context.Context, to []string, msg []byte) error {
+	host, _, err := net.SplitHostPort(w.smtp.Addr)
 	if err != nil {
 		return fmt.Errorf("invalid address: %w", err)
 	}
 
 	var d net.Dialer
-	d.Timeout = 5 * time.Second
 
-	conn, err := d.DialContext(ctx, "tcp", m.cfg.Addr)
+	conn, err := d.DialContext(ctx, "tcp", w.smtp.Addr)
 	if err != nil {
 		return fmt.Errorf("connection error: %w", err)
 	}
-	defer func() { _ = conn.Close() }()
+
+	if deadline, ok := ctx.Deadline(); ok {
+		conn.SetDeadline(deadline)
+	}
 
 	c, err := smtp.NewClient(conn, host)
 	if err != nil {
+		_ = conn.Close()
 		return fmt.Errorf("SMTP client creation error: %w", err)
 	}
 	defer func() { _ = c.Quit() }()
 
-	if m.cfg.TLSRequired {
+	if w.smtp.TLSRequired {
 		if err := c.StartTLS(&tls.Config{ServerName: host}); err != nil {
 			return fmt.Errorf("TLS negotiation error: %w", err)
 		}
 	}
 
-	if m.cfg.User != "" && m.cfg.Password != "" {
-		auth := smtp.PlainAuth("", m.cfg.User, m.cfg.Password, host)
+	if w.smtp.User != "" && w.smtp.Password != "" {
+		auth := smtp.PlainAuth("", w.smtp.User, w.smtp.Password, host)
 		if err = c.Auth(auth); err != nil {
 			return fmt.Errorf("SMTP authentication error: %w", err)
 		}
 	}
 
-	if err = c.Mail(m.cfg.SenderEmail); err != nil {
+	if err = c.Mail(w.senderEmail); err != nil {
 		return fmt.Errorf("MAIL FROM error: %w", err)
 	}
 
@@ -125,103 +369,19 @@ func (m *Mailer) sendMailWithTimeout(ctx context.Context, to []string, msg []byt
 		}
 	}
 
-	w, err := c.Data()
+	wr, err := c.Data()
 	if err != nil {
 		return fmt.Errorf("DATA command error: %w", err)
 	}
 
-	_, err = w.Write(msg)
+	_, err = wr.Write(msg)
 	if err != nil {
 		return fmt.Errorf("message write error: %w", err)
 	}
 
-	if err = w.Close(); err != nil {
+	if err = wr.Close(); err != nil {
 		return fmt.Errorf("message close error: %w", err)
 	}
 
-	return c.Quit()
-}
-
-func (m *Mailer) batchSendEmails(ctx context.Context) error {
-	for {
-		err := m.pg.WithTx(
-			ctx,
-			func(tx pg.Conn) error {
-				email := &coredata.Email{}
-				err := email.LoadNextUnsentForUpdate(ctx, tx)
-				if err != nil {
-					return err
-				}
-
-				var attachments coredata.EmailAttachments
-				if err := attachments.LoadByEmailID(ctx, tx, email.ID); err != nil {
-					return fmt.Errorf("cannot load email attachments: %w", err)
-				}
-
-				mail := enmime.Builder().
-					Subject(email.Subject).
-					From(m.cfg.SenderName, m.cfg.SenderEmail).
-					To(email.RecipientName, email.RecipientEmail).
-					Text([]byte(email.TextBody))
-
-				if email.HtmlBody != nil {
-					mail = mail.HTML([]byte(*email.HtmlBody))
-				}
-
-				for _, att := range attachments {
-					var file coredata.File
-					if err := file.LoadByID(ctx, tx, coredata.NewNoScope(), att.FileID); err != nil {
-						return fmt.Errorf("cannot load file record for attachment %s: %w", att.Filename, err)
-					}
-
-					// TODO use reader
-					data, err := m.fileManager.GetFileBytes(ctx, &file)
-					if err != nil {
-						return fmt.Errorf("cannot download attachment %s: %w", att.Filename, err)
-					}
-
-					//	TODO [esign] maybe use AddAttachmentWithReader instead?
-					mail = mail.AddAttachment(data, file.MimeType, att.Filename)
-				}
-
-				envelope, err := mail.Build()
-				if err != nil {
-					return fmt.Errorf("cannot build email: %w", err)
-				}
-
-				var buf bytes.Buffer
-				if err := envelope.Encode(&buf); err != nil {
-					return fmt.Errorf("cannot encode email: %w", err)
-				}
-
-				sendCtx, cancel := context.WithTimeout(ctx, m.cfg.Timeout)
-				defer cancel()
-
-				if err := m.sendMailWithTimeout(sendCtx, []string{email.RecipientEmail}, buf.Bytes()); err != nil {
-					if errors.Is(err, context.DeadlineExceeded) {
-						return fmt.Errorf("email sending timed out after %s: %w", m.cfg.Timeout, err)
-					}
-					return fmt.Errorf("cannot send email: %w", err)
-				}
-
-				now := time.Now()
-				email.SentAt = &now
-				email.UpdatedAt = now
-
-				if err := email.Update(ctx, tx); err != nil {
-					return fmt.Errorf("cannot update email: %w", err)
-				}
-
-				return nil
-			},
-		)
-
-		if errors.Is(err, coredata.ErrNoUnsentEmail) {
-			return nil
-		}
-
-		if err != nil {
-			return err
-		}
-	}
+	return nil
 }

pkg/probod/probod.go

@@ -514,25 +514,25 @@ func (impl *Implm) Run(
 	)
 
 	mailerCtx, stopMailer := context.WithCancel(context.Background())
-	mailer := mailer.NewMailer(
+	sendingWorker := mailer.NewSendingWorker(
 		pgClient,
 		fileManagerService,
-		l,
-		mailer.Config{
-			SenderEmail: impl.cfg.Notifications.Mailer.SenderEmail,
-			SenderName:  impl.cfg.Notifications.Mailer.SenderName,
+		impl.cfg.Notifications.Mailer.SenderName,
+		impl.cfg.Notifications.Mailer.SenderEmail,
+		mailer.SMTPConfig{
 			Addr:        impl.cfg.Notifications.Mailer.SMTP.Addr,
 			User:        impl.cfg.Notifications.Mailer.SMTP.User,
 			Password:    impl.cfg.Notifications.Mailer.SMTP.Password,
 			TLSRequired: impl.cfg.Notifications.Mailer.SMTP.TLSRequired,
-			Timeout:     time.Second * 10,
-			Interval:    time.Duration(impl.cfg.Notifications.Mailer.MailerInterval) * time.Second,
 		},
+		l.Named("sending-worker"),
+		mailer.WithSendingWorkerSMTPTimeout(time.Second*10),
+		mailer.WithSendingWorkerInterval(time.Duration(impl.cfg.Notifications.Mailer.MailerInterval)*time.Second),
 	)
 	wg.Go(
 		func() {
-			if err := mailer.Run(mailerCtx); err != nil {
-				cancel(fmt.Errorf("mailer crashed: %w", err))
+			if err := sendingWorker.Run(mailerCtx); err != nil {
+				cancel(fmt.Errorf("sending worker crashed: %w", err))
 			}
 		},
 	)