From bbcb2a1096d86b989e5d82dc45289daec38ba4a6 Mon Sep 17 00:00:00 2001
From: Robin Jarry <robin@jarry.cc>
Date: Sat, 14 Dec 2024 23:53:54 +0100
Subject: [PATCH] email: keep smtp client connection alive

Instead of connecting and disconnecting each and every time we need to
send an email, keep the SMTP connection alive attached to a context
variable.

Before sending an email, check if the connection is still valid and
reconnect if it is not.

Signed-off-by: Robin Jarry <robin@jarry.cc>
---
 email/send.go   | 23 ++++++++++++++++++-----
 email/worker.go | 15 +++++++++++----
 2 files changed, 29 insertions(+), 9 deletions(-)

diff --git a/email/send.go b/email/send.go
index 2c75dac82f2a0ca032ec9145248d7fed6e152eb3..27fe52ca2824c7c916712c9fb6686b711ec739eb 100644
--- a/email/send.go
+++ b/email/send.go
@@ -4,10 +4,10 @@ import (
 	"context"
 	"fmt"
 	"io"
-	"net/mail"
 	"strconv"
 
 	_ "github.com/emersion/go-message/charset"
+	"github.com/emersion/go-message/mail"
 	"github.com/emersion/go-sasl"
 	"github.com/emersion/go-smtp"
 
@@ -111,10 +111,23 @@ func mailSetup(ctx context.Context) (*smtp.Client, *mail.Address, error) {
 
 // Sends an email. Blocks until it's sent or an error occurs.
 func Send(ctx context.Context, msg io.Reader, rcpts []string) error {
-	c, sender, err := mailSetup(ctx)
+	worker := ForContext(ctx)
+
+	if worker.client == nil || worker.client.Noop() != nil {
+		worker.client = nil
+
+		c, sender, err := mailSetup(ctx)
+		if err != nil {
+			return err
+		}
+		worker.client = c
+		worker.sender = sender
+	}
+
+	err := worker.client.SendMail(worker.sender.Address, rcpts, msg)
 	if err != nil {
-		return err
+		worker.client.Close()
+		worker.client = nil
 	}
-	defer c.Close()
-	return c.SendMail(sender.Address, rcpts, msg)
+	return err
 }
diff --git a/email/worker.go b/email/worker.go
index 7c75478bc4cc7e747ae7b8467a00746e2081c954..1c6cda2445c0a846ba1c802224f25b1c473f3af2 100644
--- a/email/worker.go
+++ b/email/worker.go
@@ -18,6 +18,7 @@ import (
 	_ "github.com/emersion/go-message/charset"
 	"github.com/emersion/go-message/mail"
 	"github.com/emersion/go-pgpmail"
+	"github.com/emersion/go-smtp"
 	"github.com/vaughan0/go-ini"
 )
 
@@ -27,6 +28,12 @@ type contextKey struct {
 	name string
 }
 
+type workerContext struct {
+	client *smtp.Client
+	sender *mail.Address
+	queue  *Queue
+}
+
 // Returns a task which will send this email for the work queue. If the caller
 // does not need to customize the task parameters, the Enqueue function may be
 // more desirable.
@@ -81,7 +88,7 @@ func prepareSigned(header mail.Header, buf *bytes.Buffer,
 func EnqueueStd(ctx context.Context, header mail.Header,
 	bodyReader io.Reader, rcptKey *string) error {
 
-	queue := ForContext(ctx)
+	queue := ForContext(ctx).queue
 
 	to, err := header.AddressList("To")
 	if err != nil {
@@ -246,8 +253,8 @@ func NewQueue(conf ini.File) *Queue {
 }
 
 // Returns the email worker for this context.
-func ForContext(ctx context.Context) *Queue {
-	q, ok := ctx.Value(emailCtxKey).(*Queue)
+func ForContext(ctx context.Context) *workerContext {
+	q, ok := ctx.Value(emailCtxKey).(*workerContext)
 	if !ok {
 		panic(errors.New("No email worker for this context"))
 	}
@@ -256,7 +263,7 @@ func ForContext(ctx context.Context) *Queue {
 
 // Returns a context which includes the given mail worker.
 func Context(ctx context.Context, queue *Queue) context.Context {
-	return context.WithValue(ctx, emailCtxKey, queue)
+	return context.WithValue(ctx, emailCtxKey, &workerContext{queue: queue})
 }
 
 // Adds HTTP middleware to provide an email work queue to this context.