Meteor server being flooded

My server is going down again and again. Here are the log from monti apm:

I have an Android App connected to Meteor server.

Meteor version =
Server OS = Ubuntu 16.04

Android is using this DDP library:

Though we never updated that library since 3 years, could that be the issue?

Also my server is going down since 2 months, because I updated Meteor from 1.2 to 1.8, could that also be the reason? Is server itself capable of flooding server?