Implement sending email with nodemailer

Author: ben-z

apps/mailer/.gitignore

@@ -0,0 +1 @@
+/*.env

apps/mailer/docker-compose.yml

@@ -19,10 +19,17 @@ services:
       target: send
     environment:
       - PORT=8889
+    env_file:
+      - send.env
     ports:
       - "8889:8889"
     develop:
       watch:
         - action: sync+restart
           path: ./dist
-          target: /deploypkg
+          target: /deploypkg
+  
+  smtp-server:
+    image: rnwood/smtp4dev:3.8.7-ci20250525101@sha256:729d01654329fb80379935bb8b9f1e13146851c163a44577ef380c7e3a939e3e
+    ports:
+      - "8000:80"

apps/mailer/send.env.example

@@ -0,0 +1,4 @@
+SMTP_SERVER=smtp-server
+SMTP_PORT=25
+SMTP_USER=myuser
+SMTP_PASSWORD=mypass

apps/mailer/src/send.ts

@@ -1,6 +1,42 @@
-import nodemailer from "nodemailer";
 import { FissionContext, FissionCallback } from "./utils";
+import { getTransporter } from "./smtp-utils";
 
 module.exports = async function ({request, response}: FissionContext, cb: FissionCallback) {
-    response.status(200).json({});
+    if (request.method !== "POST") {
+        response.status(405).json({
+            error: "Only POST is supported",
+        });
+        return;
+    }
+
+    if (!request.body?.data) {
+        response.status(400).json({
+            error: "Missing request.body.data",
+        });
+        return;
+    }
+
+    const transporter = await getTransporter();
+
+    try {
+        const result = await transporter.sendMail({
+            from: request.body.data.from,
+            to: request.body.data.to,
+            replyTo: request.body.data.reply_to,
+            subject: request.body.data.subject,
+            text: request.body.data.text,
+            html: request.body.data.html,
+        })
+
+        response.status(200).json({
+            "transporter.isIdle": transporter.isIdle(),
+            "result": result,
+        });
+    } catch (e) {
+        console.error(e);
+        response.status(500).json({
+            error: "Failed to send email: " + e,
+        });
+        return;
+    }
 }

apps/mailer/src/smtp-utils.ts

@@ -0,0 +1,44 @@
+import { fissionGetConfig, fissionGetSecret } from "./utils";
+import nodemailer from "nodemailer";
+import SMTPPool from "nodemailer/lib/smtp-pool";
+
+let transporterPromise: Promise<nodemailer.Transporter<SMTPPool.SentMessageInfo, SMTPPool.Options>> | null = null;
+
+export function getTransporter(): Promise<nodemailer.Transporter<SMTPPool.SentMessageInfo, SMTPPool.Options>> {
+    if (transporterPromise) {
+        return transporterPromise;
+    }
+
+    transporterPromise = (async () => {
+        const SMTP_SERVER = await fissionGetConfig("SMTP_SERVER");
+        const SMTP_PORT = await fissionGetConfig("SMTP_PORT");
+        const SMTP_USER = await fissionGetConfig("SMTP_USER");
+        const SMTP_PASSWORD = await fissionGetSecret("SMTP_PASSWORD");
+
+        if (!SMTP_SERVER || !SMTP_PORT || !SMTP_USER || !SMTP_PASSWORD) {
+            throw new Error("SMTP_SERVER, SMTP_PORT, SMTP_USER, and SMTP_PASSWORD are required");
+        }
+
+        /**
+         * One shared transporter for your whole process.
+         * The transporter will automatically open up to `maxConnections`
+         * sockets and keep them warm.
+         */
+        const transporter = nodemailer.createTransport({
+            host: SMTP_SERVER,
+            port: Number(SMTP_PORT),
+            secure: Number(SMTP_PORT) === 465,
+            pool: true, // ♻️  enable connection pooling
+            maxConnections: 5, // optional – defaults to 5
+            maxMessages: 100, // optional – defaults to 100
+            auth: {
+                user: SMTP_USER,
+                pass: SMTP_PASSWORD,
+            },
+        });
+
+        return transporter;
+    })();
+
+    return transporterPromise;
+}

apps/mailer/src/utils.ts

@@ -1,4 +1,8 @@
 import express from "express";
+import fsPromise from "fs/promises"
+
+const FISSION_CONFIGS_BASE_PATH = "/configs/fission-default/mailer-configs"
+const FISSION_SECRETS_BASE_PATH = "/secrets/fission-default/mailer-secrets"
 
 // Context type for Fission serverless functions
 // https://github.com/fission/environments/blob/c679ff68371ec779f87e855987157a52f05ea8dd/nodejs/server.js#L138-L142
@@ -9,4 +13,68 @@ export type FissionContext = {
 
 // Callback type for Fission serverless functions
 // https://github.com/fission/environments/blob/c679ff68371ec779f87e855987157a52f05ea8dd/nodejs/server.js#L144-L152
-export type FissionCallback = (status: number, body: any, headers?: Record<string, string>) => void
+export type FissionCallback = (status: number, body: any, headers?: Record<string, string>) => void
+
+// Cache for storing configuration values
+const configCache = new Map<string, string>();
+
+export async function fissionGetConfig(name: string, useCache: boolean = true): Promise<string | null> {
+    // Check environment variables first (highest priority, always fresh)
+    if (process.env[name]) {
+        return process.env[name]!;
+    }
+
+    // Check cache if enabled
+    if (useCache && configCache.has(name)) {
+        return configCache.get(name)!;
+    }
+
+    // Check if file exists
+    try {
+        await fsPromise.access(`${FISSION_CONFIGS_BASE_PATH}/${name}`);
+    } catch (e) {
+        return null;
+    }
+
+    // Read and cache the file content
+    const content = await fsPromise.readFile(`${FISSION_CONFIGS_BASE_PATH}/${name}`, 'utf8');
+    
+    // Update cache
+    if (useCache) {
+        configCache.set(name, content);
+    }
+    
+    return content;
+}
+
+// Cache for storing secret values
+const secretCache = new Map<string, string>();
+
+export async function fissionGetSecret(name: string, useCache: boolean = true): Promise<string | null> {
+    // Check environment variables first (highest priority, always fresh)
+    if (process.env[name]) {
+        return process.env[name]!;
+    }
+
+    // Check cache if enabled
+    if (useCache && secretCache.has(name)) {
+        return secretCache.get(name)!;
+    }
+
+    // Check if file exists
+    try {
+        await fsPromise.access(`${FISSION_SECRETS_BASE_PATH}/${name}`);
+    } catch (e) {
+        return null;
+    }
+
+    // Read and cache the secret content
+    const content = await fsPromise.readFile(`${FISSION_SECRETS_BASE_PATH}/${name}`, 'utf8');
+    
+    // Update cache
+    if (useCache) {
+        secretCache.set(name, content);
+    }
+    
+    return content;
+}