add email queue to handle email sending failures

app/components/user/request-delete-user.tsx

@@ -23,7 +23,7 @@ import { TrashIcon } from "../icons/library";
 
 const Schema = z.object({
   email: z.string().email(),
-  reason: z.string().min(10, "Reason is a required field"),
+  reason: z.string().min(3, "Reason is a required field"),
 });
 
 export const RequestDeleteUser = () => {

app/emails/email.worker.server.ts

@@ -0,0 +1,63 @@
+import { transporter } from "~/emails/transporter.server";
+import { QueueNames, scheduler } from "~/utils/scheduler.server";
+import type { EmailPayloadType } from "./types";
+import { SMTP_FROM } from "../utils/env";
+import { ShelfError } from "../utils/error";
+
+// every node will execute 5 jobs(teamSize) every 3 minutes(newJobCheckIntervalSeconds),
+// increase teamSize if you need better concurrency
+// but keep email provider rate limiting and a potential n/w throughput load on postgress in mind
+// teamSize of 20-25 is a good limit if we need to scale email throughput in the future
+export const registerEmailWorkers = async () => {
+  await scheduler.work<EmailPayloadType>(
+    QueueNames.emailQueue,
+    { newJobCheckIntervalSeconds: 60 * 3, teamSize: 5 },
+    async (job) => {
+      await triggerEmail(job.data);
+    }
+  );
+};
+
+export const triggerEmail = async ({
+  to,
+  subject,
+  text,
+  html,
+  from,
+  replyTo,
+}: EmailPayloadType) => {
+  try {
+    // send mail with defined transport object
+    await transporter.sendMail({
+      from: from || SMTP_FROM || `"Shelf" <[email protected]>`, // sender address
+      replyTo: replyTo || "[email protected]", // reply to
+      to, // list of receivers
+      subject, // Subject line
+      text, // plain text body
+      html: html || "", // html body
+    });
+  } catch (cause) {
+    throw new ShelfError({
+      cause,
+      message: "Unable to send email",
+      additionalData: { to, subject, from },
+      label: "Email",
+    });
+  }
+
+  // verify connection configuration
+  // transporter.verify(function (error) {
+  //   if (error) {
+  //     // eslint-disable-next-line no-console
+  //     console.log(error);
+  //   } else {
+  //     // eslint-disable-next-line no-console
+  //     console.log("Server is ready to take our messages");
+  //   }
+  // });
+
+  // Message sent: <[email protected]>
+
+  // Preview only available when sending through an Ethereal account
+  // console.log("Preview URL: %s", nodemailer.getTestMessageUrl(info));
+};

app/emails/mail.server.ts

@@ -1,104 +1,39 @@
-import type { Attachment } from "nodemailer/lib/mailer";
-import { transporter } from "~/emails/transporter.server";
-import { SMTP_FROM } from "../utils/env";
-import { ShelfError } from "../utils/error";
-
-export const sendEmail = async ({
-  to,
-  subject,
-  text,
-  html,
-  attachments,
-  from,
-  replyTo,
-}: {
-  /** Email address of recipient */
-  to: string;
-
-  /** Subject of email */
-  subject: string;
-
-  /** Text content of email */
-  text: string;
-
-  /** HTML content of email */
-  html?: string;
-
-  attachments?: Attachment[];
-
-  /** Override the default sender */
-  from?: string;
+import { Logger } from "~/utils/logger";
+import { QueueNames, scheduler } from "~/utils/scheduler.server";
+import { triggerEmail } from "./email.worker.server";
+import type { EmailPayloadType } from "./types";
+
+export const sendEmail = (payload: EmailPayloadType) => {
+  // attempt to send email, push to the queue if it fails
+  triggerEmail(payload).catch((err) => {
+    Logger.warn({
+      err,
+      details: {
+        to: payload.to,
+        subject: payload.subject,
+        from: payload.from,
+      },
+      message: "email sending failed, pushing to the queue",
+    });
+    void addToQueue(payload);
+  });
+};
 
-  /** Override the default reply to email address */
-  replyTo?: string;
-}) => {
+const addToQueue = async (payload: EmailPayloadType) => {
   try {
-    // send mail with defined transport object
-    await transporter.sendMail({
-      from: from || SMTP_FROM || `"Shelf" <[email protected]>`, // sender address
-      replyTo: replyTo || "[email protected]", // reply to
-      to, // list of receivers
-      subject, // Subject line
-      text, // plain text body
-      html: html || "", // html body
-      attachments: [...(attachments || [])],
+    await scheduler.send(QueueNames.emailQueue, payload, {
+      retryLimit: 5,
+      retryDelay: 5,
     });
-  } catch (cause) {
-    throw new ShelfError({
-      cause,
-      message: "Unable to send email",
-      additionalData: { to, subject, from },
-      label: "Email",
+  } catch (err) {
+    Logger.warn({
+      err,
+      details: {
+        to: payload.to,
+        subject: payload.subject,
+        from: payload.from,
+      },
+      message: "Failed to push email payload to queue",
     });
   }
-
-  // verify connection configuration
-  // transporter.verify(function (error) {
-  //   if (error) {
-  //     // eslint-disable-next-line no-console
-  //     console.log(error);
-  //   } else {
-  //     // eslint-disable-next-line no-console
-  //     console.log("Server is ready to take our messages");
-  //   }
-  // });
-
-  // Message sent: <[email protected]>
-
-  // Preview only available when sending through an Ethereal account
-  // console.log("Preview URL: %s", nodemailer.getTestMessageUrl(info));
 };
-
-/** Utility function to add delay between operations */
-async function delay(ms: number): Promise<void> {
-  return new Promise((resolve) => setTimeout(resolve, ms));
-}
-
-/** Process emails in batches with rate limiting
- * @param emails - Array of email configurations to send
- * @param batchSize - Number of emails to process per batch (default: 2)
- * @param delayMs - Milliseconds to wait between batches (default: 1000ms)
- */
-export async function sendEmailsWithRateLimit(
-  emails: Array<{
-    to: string;
-    subject: string;
-    text: string;
-    html: string;
-  }>,
-  batchSize = 2,
-  delayMs = 1100
-): Promise<void> {
-  for (let i = 0; i < emails.length; i += batchSize) {
-    // Process emails in batches of specified size
-    const batch = emails.slice(i, i + batchSize);
-
-    // Send emails in current batch concurrently
-    await Promise.all(batch.map((email) => sendEmail(email)));
-
-    // If there are more emails to process, add delay before next batch
-    if (i + batchSize < emails.length) {
-      await delay(delayMs);
-    }
-  }
-}

app/emails/types.ts

@@ -16,3 +16,23 @@ export type BookingForEmail = Prisma.BookingGetPayload<{
     };
   };
 }>;
+
+export type EmailPayloadType = {
+  /** Email address of recipient */
+  to: string;
+
+  /** Subject of email */
+  subject: string;
+
+  /** Text content of email */
+  text: string;
+
+  /** HTML content of email */
+  html?: string;
+
+  /** Override the default sender */
+  from?: string;
+
+  /** Override the default reply to email address */
+  replyTo?: string;
+};

app/entry.server.tsx

@@ -7,6 +7,7 @@ import { RemixServer } from "@remix-run/react";
 import * as Sentry from "@sentry/remix";
 import { isbot } from "isbot";
 import { renderToPipeableStream } from "react-dom/server";
+import { registerEmailWorkers } from "./emails/email.worker.server";
 import { registerBookingWorkers } from "./modules/booking/worker.server";
 import { ShelfError } from "./utils/error";
 import { Logger } from "./utils/logger";
@@ -26,6 +27,15 @@ schedulerService
         })
       );
     });
+    await registerEmailWorkers().catch((cause) => {
+      Logger.error(
+        new ShelfError({
+          cause,
+          message: "Something went wrong while registering email workers.",
+          label: "Scheduler",
+        })
+      );
+    });
   })
   .finally(() => {
     // eslint-disable-next-line no-console

app/modules/booking/constants.ts

@@ -1,6 +1,3 @@
-export const schedulerKeys = {
-  bookingQueue: "booking-queue",
-};
 export enum bookingSchedulerEventsEnum {
   checkoutReminder = `booking-checkout-reminder`,
   checkinReminder = `booking-checkin-reminder`,

app/modules/booking/email-helpers.ts

@@ -4,7 +4,6 @@ import type { BookingForEmail } from "~/emails/types";
 import { getDateTimeFormatFromHints } from "~/utils/client-hints";
 import { getTimeRemainingMessage } from "~/utils/date-fns";
 import { SERVER_URL } from "~/utils/env";
-import { ShelfError } from "~/utils/error";
 import type { ClientHint } from "./types";
 
 /**
@@ -156,44 +155,35 @@ export const checkinReminderEmailContent = ({
     )}.`,
   });
 
-export async function sendCheckinReminder(
+export function sendCheckinReminder(
   booking: BookingForEmail,
   assetCount: number,
   hints: ClientHint
 ) {
-  try {
-    await sendEmail({
-      to: booking.custodianUser!.email,
-      subject: `Checkin reminder (${booking.name}) - shelf.nu`,
-      text: checkinReminderEmailContent({
-        hints,
-        bookingName: booking.name,
-        assetsCount: assetCount,
-        custodian:
-          `${booking.custodianUser!.firstName} ${booking.custodianUser
-            ?.lastName}` || (booking.custodianTeamMember?.name as string),
-        from: booking.from!,
-        to: booking.to!,
-        bookingId: booking.id,
-      }),
-      html: bookingUpdatesTemplateString({
-        booking,
-        heading: `Your booking is due for checkin in ${getTimeRemainingMessage(
-          new Date(booking.to!),
-          new Date()
-        )}.`,
-        assetCount,
-        hints,
-      }),
-    });
-  } catch (cause) {
-    throw new ShelfError({
-      cause,
-      message: "Something went wrong while sending the checkin reminder email",
-      additionalData: { booking },
-      label: "Booking",
-    });
-  }
+  sendEmail({
+    to: booking.custodianUser!.email,
+    subject: `🔔 Checkin reminder (${booking.name}) - shelf.nu`,
+    text: checkinReminderEmailContent({
+      hints,
+      bookingName: booking.name,
+      assetsCount: assetCount,
+      custodian:
+        `${booking.custodianUser!.firstName} ${booking.custodianUser
+          ?.lastName}` || (booking.custodianTeamMember?.name as string),
+      from: booking.from!,
+      to: booking.to!,
+      bookingId: booking.id,
+    }),
+    html: bookingUpdatesTemplateString({
+      booking,
+      heading: `Your booking is due for checkin in ${getTimeRemainingMessage(
+        new Date(booking.to!),
+        new Date()
+      )}.`,
+      assetCount,
+      hints,
+    }),
+  });
 }
 
 /**