You don't say how long you'll be travelling in India, or whether your country of residence will change, but you should have your file number before you leave, which is good. You basically have 2 choices -
1) Find someone in Canada you TRUST with your mail, and submit a change of address, using that person's address, at that time.
2) Submit a change of address for your address in India. it won't affect processing times, apart from any delays caused by mail delivery taking longer.
In either case, be sure you include a permanent email address on your application, so that CIC can contact you by email wherever you are in the world.
Here is the information you need to update your address with CIC-Buffalo:
http://www.canadainternational.gc.ca/buffalo/visas/update-how_mettre-comment.aspx?lang=eng&view=d