Send oom email to cloudron admins

Part of #166

src/apphealthmonitor.js

@@ -167,7 +167,7 @@ function processDockerEvents() {
 
                 // do not send mails for dev apps
                 if ((!app || app.appStoreId !== '') && (now - lastOomMailTime > OOM_MAIL_LIMIT)) {
-                    mailer.unexpectedExit(program, context); // app can be null if it's an addon crash
+                    mailer.oomEvent(program, context); // app can be null if it's an addon crash
                     lastOomMailTime = now;
                 }
             });

src/mail_templates/oom_event.ejs

@@ -0,0 +1,19 @@
+<%if (format === 'text') { %>
+
+Dear Cloudron Team,
+
+Unfortunately <%= program %> on <%= fqdn %> exited unexpectedly!
+
+Please see some excerpt of the logs below.
+
+Thank you,
+Your Cloudron
+
+-------------------------------------
+
+<%- context %>
+
+<% } else { %>
+
+<% } %>
+

src/mailer.js

@@ -15,6 +15,7 @@ exports = module.exports = {
     unexpectedExit: unexpectedExit,
 
     appDied: appDied,
+    oomEvent: oomEvent,
 
     outOfDiskSpace: outOfDiskSpace,
     backupFailed: backupFailed,
@@ -499,6 +500,24 @@ function certificateRenewalError(domain, message) {
     });
 }
 
+function oomEvent(program, context) {
+    assert.strictEqual(typeof program, 'string');
+    assert.strictEqual(typeof context, 'string');
+
+    getAdminEmails(function (error, adminEmails) {
+        if (error) return console.log('Error getting admins', error);
+
+        var mailOptions = {
+            from: mailConfig().from,
+            to: config.provider() === 'caas' ? 'support@cloudron.io' : adminEmails.concat('support@cloudron.io').join(', '),
+            subject: util.format('[%s] %s exited unexpectedly', config.fqdn(), program),
+            text: render('oom_event.ejs', { fqdn: config.fqdn(), program: program, context: context, format: 'text' })
+        };
+
+        sendMails([ mailOptions ]);
+    });
+}
+
 // this function bypasses the queue intentionally. it is also expected to work without the mailer module initialized
 // NOTE: crashnotifier should be able to send mail when there is no db
 function unexpectedExit(program, context) {