external ldap: run syncer every 4 hours

hardcoded for now but we should make this configurable

src/cron.js

@@ -15,6 +15,7 @@ exports = module.exports = {
     handleTimeZoneChanged,
     handleAutoupdatePatternChanged,
     handleDynamicDnsChanged,
+    handleExternalLdapChanged,
 
     DEFAULT_AUTOUPDATE_PATTERN,
 };
@@ -29,6 +30,7 @@ const appHealthMonitor = require('./apphealthmonitor.js'),
     CronJob = require('cron').CronJob,
     debug = require('debug')('box:cron'),
     dyndns = require('./dyndns.js'),
+    externalLdap = require('./externalldap.js'),
     eventlog = require('./eventlog.js'),
     janitor = require('./janitor.js'),
     mail = require('./mail.js'),
@@ -57,7 +59,8 @@ const gJobs = {
     dynamicDns: null,
     schedulerSync: null,
     appHealthMonitor: null,
-    diskUsage: null
+    diskUsage: null,
+    externalLdapSyncer: null
 };
 
 // cron format
@@ -173,6 +176,7 @@ async function startJobs() {
     await handleBackupPolicyChanged(await backups.getPolicy());
     await handleAutoupdatePatternChanged(await updater.getAutoupdatePattern());
     await handleDynamicDnsChanged(await network.getDynamicDns());
+    await handleExternalLdapChanged(await externalLdap.getConfig());
 }
 
 async function handleBackupPolicyChanged(value) {
@@ -257,6 +261,21 @@ function handleDynamicDnsChanged(enabled) {
     }
 }
 
+async function handleExternalLdapChanged(config) {
+    assert.strictEqual(typeof config, 'object');
+
+    if (config.provider !== 'noop') {
+        gJobs.externalLdapSyncer = new CronJob({
+            cronTime: '00 00 */4 * * *', // every 4 hours
+            onTick: async () => await safe(externalLdap.startSyncer(AuditSource.CRON), { debug }),
+            start: true
+        });
+    } else {
+        if (gJobs.externalLdapSyncer) gJobs.externalLdapSyncer.stop();
+        gJobs.externalLdapSyncer = null;
+    }
+}
+
 async function stopJobs() {
     for (const job in gJobs) {
         if (!gJobs[job]) continue;