Added batching support for bulk email service (#11388)

no issue

- The limitation on Mailgun side of API seems to be 1000 emails per message.
- The only place where I could find a hard limit of 1000 emails per
batch was this PHP SDK issue: https://github.com/mailgun/mailgun-php/issues/469
- To store ids of sent messages introduce a mega column on the emails table. They can be synced with stats or other metrics during even pooling in the future
- Removed redundant `join(',')` statement.The SDK accepts an array of emails as well. Less code - better code :)

core/server/data/schema/schema.js

@@ -389,6 +389,7 @@ module.exports = {
             validations: {isIn: [['pending', 'submitting', 'submitted', 'failed']]}
         },
         error: {type: 'string', maxlength: 2000, nullable: true},
+        meta: {type: 'text', maxlength: 65535, nullable: true},
         stats: {type: 'text', maxlength: 65535, nullable: true},
         email_count: {type: 'integer', nullable: false, unsigned: true, defaultTo: 0},
         subject: {type: 'string', maxlength: 300, nullable: true},

core/server/services/bulk-email/index.js

@@ -1,4 +1,5 @@
 const {URL} = require('url');
+const _ = require('lodash');
 const mailgun = require('mailgun-js');
 const configService = require('../../config');
 const common = require('../../lib/common');
@@ -46,22 +47,34 @@ module.exports = {
      * @param {Email} message - The message to send
      * @param {[EmailAddress]} recipients - the recipients to send the email to
      * @param {[object]} recipientData - list of data keyed by email to inject into the email
-     * @returns {Promise<boolean>} A promise representing the success of the email sending
+     * @returns {Promise<Array<object>>} An array of promises representing the success of the batch email sending
      */
     async send(message, recipients, recipientData) {
+        let BATCH_SIZE = 1000;
+
         if (!mailgunInstance) {
             return;
         }
         let fromAddress = message.from;
-        if (/@localhost$/.test(message.from)) {
+        if (/@localhost$/.test(message.from) || /@ghost.local$/.test(message.from)) {
             fromAddress = 'localhost@example.com';
             common.logging.warn(`Rewriting bulk email from address ${message.from} to ${fromAddress}`);
+
+            BATCH_SIZE = 2;
         }
         try {
+            const chunkedRecipients = _.chunk(recipients, BATCH_SIZE);
+
+            return Promise.map(chunkedRecipients, (toAddresses) => {
+                const recipientVariables = {};
+                toAddresses.forEach((email) => {
+                    recipientVariables[email] = recipientData[email];
+                });
+
                 const messageData = Object.assign({}, message, {
-                to: recipients.join(', '),
+                    to: toAddresses,
                     from: fromAddress,
-                'recipient-variables': recipientData
+                    'recipient-variables': recipientVariables
                 });
 
                 if (config.mailgun.tag) {
@@ -70,7 +83,20 @@ module.exports = {
                     });
                 }
 
-            await mailgunInstance.messages().send(messageData);
+                return mailgunInstance.messages().send(messageData);
+            });
+        } catch (err) {
+            common.logging.error({err});
+        }
+    },
+
+    async getStats(messageId) {
+        try {
+            let filter = {
+                'message-id': messageId
+            };
+
+            return await mailgunInstance.events().get(filter);
         } catch (err) {
             common.logging.error({err});
         }

core/server/services/mega/mega.js

@@ -179,10 +179,11 @@ async function listener(emailModel, options) {
         id: emailModel.id
     });
 
-    await sendEmail(post, members);
+    const meta = await sendEmail(post, members);
 
     await models.Email.edit({
-        status: 'submitted'
+        status: 'submitted',
+        meta: JSON.stringify(meta)
     }, {
         id: emailModel.id
     });

core/test/unit/data/schema/integrity_spec.js

@@ -19,7 +19,7 @@ var should = require('should'),
  */
 describe('DB version integrity', function () {
     // Only these variables should need updating
-    const currentSchemaHash = '34f9620db05fc136fa9abb7133e21615';
+    const currentSchemaHash = '1bfb322b4eeb5275cb1baa0df69d3ada';
     const currentFixturesHash = 'b1787330f042f3954d73c43aa8bfa915';
 
     // If this test is failing, then it is likely a change has been made that requires a DB version bump,