perf: make digests a little bit faster

and use batch.processArray
dont load data for users who have no email or have not confirmed their emails

src/emailer.js

@@ -216,22 +216,22 @@ Emailer.send = async (template, uid, params) => {
 		throw Error('[emailer] App not ready!');
 	}
 
-	const [userData, userSettings] = await Promise.all([
-		User.getUserFields(uid, ['email', 'username', 'email:confirmed']),
-		User.getSettings(uid),
-	]);
-
+	const userData = await User.getUserFields(uid, ['email', 'username', 'email:confirmed']);
 	if (!userData || !userData.email) {
+		if (process.env.NODE_ENV === 'development') {
 			winston.warn(`uid : ${uid} has no email, not sending "${template}" email.`);
+		}
 		return;
 	}
 
 	const allowedTpls = ['verify_email', 'welcome', 'registration_accepted'];
 	if (meta.config.requireEmailConfirmation && !userData['email:confirmed'] && !allowedTpls.includes(template)) {
+		if (process.env.NODE_ENV === 'development') {
 			winston.warn(`uid : ${uid} (${userData.email}) has not confirmed email, not sending "${template}" email.`);
+		}
 		return;
 	}
-
+	const userSettings = await User.getSettings(uid);
 	// Combined passed-in payload with default values
 	params = { ...Emailer._defaultPayload, ...params };
 	params.uid = uid;

src/user/digest.js

@@ -1,6 +1,5 @@
 'use strict';
 
-const async = require('async');
 const winston = require('winston');
 const nconf = require('nconf');
 
@@ -29,7 +28,7 @@ Digest.execute = async function (payload) {
 		return;
 	}
 	try {
-		winston.info(`[user/jobs] Digest (${payload.interval}) scheduling completed. Sending emails; this may take some time...`);
+		winston.info(`[user/jobs] Digest (${payload.interval}) scheduling completed (${subscribers.length} subscribers). Sending emails; this may take some time...`);
 		await Digest.send({
 			interval: payload.interval,
 			subscribers: subscribers,
@@ -100,8 +99,13 @@ Digest.send = async function (data) {
 		return emailsSent;
 	}
 
-	await async.eachLimit(data.subscribers, 100, async (uid) => {
-		const userObj = await user.getUserFields(uid, ['uid', 'username', 'userslug', 'lastonline']);
+	await batch.processArray(data.subscribers, async (uids) => {
+		let userData = await user.getUsersFields(uids, ['uid', 'email', 'email:confirmed', 'username', 'userslug', 'lastonline']);
+		userData = userData.filter(u => u && u.email && (!meta.config.requireEmailConfirmation || userData['email:confirmed']));
+		if (!userData.length) {
+			return;
+		}
+		await Promise.all(userData.map(async (userObj) => {
 			const [notifications, topTopics, popularTopics, recentTopics] = await Promise.all([
 				user.notifications.getUnreadInterval(userObj.uid, data.interval),
 				getTermTopics(data.interval, userObj.uid, 0, 9, 'votes'),
@@ -140,6 +144,10 @@ Digest.send = async function (data) {
 			if (data.interval !== 'alltime') {
 				await db.sortedSetAdd('digest:delivery', now.getTime(), userObj.uid);
 			}
+		}));
+	}, {
+		interval: 1000,
+		batch: 100,
 	});
 	winston.info(`[user/jobs] Digest (${data.interval}) sending completed. ${emailsSent} emails sent.`);
 };