Added bulkEmail.batchSize option to configure batch size

refs https://github.com/TryGhost/Ghost/issues/15725

This pull request adds a new configuration option for the Mailgun email
provider that allows the user to set the maximum number of recipients
per email batch via a new config option `bulkEmail.batchSize`

ghost/core/core/shared/config/defaults.json

@@ -228,5 +228,8 @@
             "members": [0, 100, 1000, 10000, 25000, 50000, 100000, 250000, 500000, 1000000],
             "minDaysSinceImported": 7,
             "minDaysSinceLastEmail": 14
-        }
+        },
+    "bulkEmail": {
+        "batchSize": 1000
+    }
 }

ghost/core/test/integration/services/email-service/batch-sending.test.js

@@ -6,7 +6,6 @@ const sinon = require('sinon');
 const assert = require('assert/strict');
 const jobManager = require('../../../../core/server/services/jobs/job-service');
 const _ = require('lodash');
-const {MailgunEmailProvider} = require('@tryghost/email-service');
 const escapeRegExp = require('lodash/escapeRegExp');
 const configUtils = require('../../../utils/configUtils');
 const {settingsCache} = require('../../../../core/server/services/settings-helpers');
@@ -259,7 +258,7 @@ describe('Batch sending tests', function () {
     let ghostServer;
 
     beforeEach(function () {
-        MailgunEmailProvider.BATCH_SIZE = 100;
+        configUtils.set('bulkEmail:batchSize', 100);
         stubbedSend = sinon.fake.resolves({
             id: 'stubbed-email-id'
         });
@@ -548,7 +547,7 @@ describe('Batch sending tests', function () {
     });
 
     it('Splits up in batches according to email provider batch size', async function () {
-        MailgunEmailProvider.BATCH_SIZE = 1;
+        configUtils.set('bulkEmail:batchSize', 1);
         await testEmailBatches({
             mobiledoc: mobileDocExample
         }, null, [
@@ -561,7 +560,7 @@ describe('Batch sending tests', function () {
     });
 
     it('Splits up in batches according to email provider batch size with paid and free segments', async function () {
-        MailgunEmailProvider.BATCH_SIZE = 1;
+        configUtils.set('bulkEmail:batchSize', 1);
         await testEmailBatches({
             mobiledoc: mobileDocWithPaidMemberOnly
         }, null, [
@@ -577,7 +576,7 @@ describe('Batch sending tests', function () {
     });
 
     it('One failed batch marks the email as failed and allows for a retry', async function () {
-        MailgunEmailProvider.BATCH_SIZE = 1;
+        configUtils.set('bulkEmail:batchSize', 1);
         let counter = 0;
         stubbedSend = async function () {
             counter += 1;

ghost/email-service/lib/MailgunEmailProvider.js

@@ -30,8 +30,6 @@ class MailgunEmailProvider {
     #mailgunClient;
     #errorHandler;
 
-    static BATCH_SIZE = 1000;
-
     /**
      * @param {object} dependencies
      * @param {import('@tryghost/mailgun-client/lib/MailgunClient')} dependencies.mailgunClient - mailgun client to send emails
@@ -172,7 +170,7 @@ class MailgunEmailProvider {
     }
 
     getMaximumRecipients() {
-        return MailgunEmailProvider.BATCH_SIZE;
+        return this.#mailgunClient.getBatchSize();
     }
 }
 

ghost/email-service/test/mailgun-email-provider.test.js

@@ -225,8 +225,20 @@ describe('Mailgun Email Provider', function () {
     });
 
     describe('getMaximumRecipients', function () {
+        let mailgunClient;
+        let getBatchSizeStub;
+
         it('returns 1000', function () {
-            const provider = new MailgunEmailProvider({});
+            getBatchSizeStub = sinon.stub().returns(1000);
+
+            mailgunClient = {
+                getBatchSize: getBatchSizeStub
+            };
+            
+            const provider = new MailgunEmailProvider({
+                mailgunClient,
+                errorHandler: () => {}
+            });
             assert.equal(provider.getMaximumRecipients(), 1000);
         });
     });

ghost/mailgun-client/lib/MailgunClient.js

@@ -8,7 +8,7 @@ module.exports = class MailgunClient {
     #config;
     #settings;
 
-    static BATCH_SIZE = 1000;
+    static DEFAULT_BATCH_SIZE = 1000;
 
     constructor({config, settings}) {
         this.#config = config;
@@ -38,9 +38,10 @@ module.exports = class MailgunClient {
             return null;
         }
 
-        if (Object.keys(recipientData).length > MailgunClient.BATCH_SIZE) {
+        const batchSize = this.getBatchSize();
+        if (Object.keys(recipientData).length > batchSize) {
             throw new errors.IncorrectUsageError({
-                message: `Mailgun only supports sending to ${MailgunClient.BATCH_SIZE} recipients at a time`
+                message: `Mailgun only supports sending to ${batchSize} recipients at a time`
             });
         }
 
@@ -305,4 +306,13 @@ module.exports = class MailgunClient {
         const instance = this.getInstance();
         return !!instance;
     }
+
+    /**
+     * Returns configured batch size
+     *
+     * @returns {number}
+     */ 
+    getBatchSize() {
+        return this.#config.get('bulkEmail')?.batchSize ?? this.DEFAULT_BATCH_SIZE;
+    }
 };

ghost/mailgun-client/test/mailgun-client.test.js

@@ -43,8 +43,19 @@ describe('MailgunClient', function () {
         sinon.restore();
     });
 
-    it('exports a number for BATCH_SIZE', function () {
-        assert(typeof MailgunClient.BATCH_SIZE === 'number');
+    it('exports a number for configurable batch size', function () {
+        const configStub = sinon.stub(config, 'get');
+        configStub.withArgs('bulkEmail').returns({
+            mailgun: {
+                apiKey: 'apiKey',
+                domain: 'domain.com',
+                baseUrl: 'https://api.mailgun.net/v3'
+            },
+            batchSize: 1000
+        });
+
+        const mailgunClient = new MailgunClient({config, settings});
+        assert(typeof mailgunClient.getBatchSize() === 'number');
     });
 
     it('can connect via config', function () {
@@ -54,7 +65,8 @@ describe('MailgunClient', function () {
                 apiKey: 'apiKey',
                 domain: 'domain.com',
                 baseUrl: 'https://api.mailgun.net/v3'
-            }
+            },
+            batchSize: 1000
         });
 
         const mailgunClient = new MailgunClient({config, settings});
@@ -116,7 +128,8 @@ describe('MailgunClient', function () {
                 apiKey: 'apiKey',
                 domain: 'configdomain.com',
                 baseUrl: 'https://api.mailgun.net'
-            }
+            },
+            batchSize: 1000
         });
 
         const settingsStub = sinon.stub(settings, 'get');
@@ -170,7 +183,8 @@ describe('MailgunClient', function () {
                     apiKey: 'apiKey',
                     domain: 'domain.com',
                     baseUrl: 'https://api.mailgun.net/v3'
-                }
+                },
+                batchSize: 1000
             });
 
             const firstPageMock = nock('https://api.mailgun.net')
@@ -214,7 +228,8 @@ describe('MailgunClient', function () {
                     apiKey: 'apiKey',
                     domain: 'domain.com',
                     baseUrl: 'https://api.mailgun.net/v3'
-                }
+                },
+                batchSize: 1000
             });
 
             const firstPageMock = nock('https://api.mailgun.net')
@@ -259,7 +274,8 @@ describe('MailgunClient', function () {
                     apiKey: 'apiKey',
                     domain: 'domain.com',
                     baseUrl: 'https://api.mailgun.net/v3'
-                }
+                },
+                batchSize: 1000
             });
 
             const firstPageMock = nock('https://api.mailgun.net')
@@ -304,7 +320,8 @@ describe('MailgunClient', function () {
                     apiKey: 'apiKey',
                     domain: 'domain.com',
                     baseUrl: 'https://api.mailgun.net/v3'
-                }
+                },
+                batchSize: 1000
             });
 
             const firstPageMock = nock('https://api.mailgun.net')
@@ -349,7 +366,8 @@ describe('MailgunClient', function () {
                     apiKey: 'apiKey',
                     domain: 'domain.com',
                     baseUrl: 'https://api.eu.mailgun.net/v3'
-                }
+                },
+                batchSize: 1000
             });
 
             const firstPageMock = nock('https://api.eu.mailgun.net')