What was Stalin and Hitler's relationship like?

Both Stalin and Hilter hated each other during the interbellum period leading up toward WWII. Nazi fascisim and communism do not get along. Yet they signed a non-agression act and split Poland between them. This is speculated to be caused by Germany's need to stay out of a 2 front war (also their plan in WWI with the Schlieffen Plan, which did not happen and they ended up fighting 4 years on both fronts) and Russia feeling cut out of discussions about European affairs- mainly the Munich Agreement; where the Sudetenland was given to Germany. The non-agression pact was not a treaty where they help each other and become allies, but an agreement not to invade each other's country, territorys, and area's of intrest. The rest of Europe for Germany, and the Balkans for Russia. It must also be remembered that Russia at that time was undergoing economic difficulties and felt that it would be best for their economy to stay out of the war. Hitler entered the agreement with Stalin with every intention of betraying the agreement to take over Russia. It was written in his book, Mein Kampf, that Hitler desired to exterminate the Russian people leaving only a thousand or so to be used as slaves and to use Russian land as a place for more Germans. It was well known on both sides that this is what Hitler had intended.