Gossiping in Distributed Systems - Part I

This will be my first write up since I foolishly committed to blogging every single day for an entire year. So if your just following along I usually pick a topic I don’t know anything about and write and try really damn hard to figure it out. Do I know anything about Gossiping in Distributed Systems? No. Do I ever know what the hell I’m doing? No. But I’m here and I’ll give it my best shot ;) That being said if you haven’t closed your browser yet I’m going to break this post up into a few blog entries since I probably can’t become an expert on gossip protocols over night.

Where do we start?

Lets start with explaining Gossip communication and what it means in distributed systems. For example, perhaps a co-worker spreads a nasty rumour about you. Apparently you haven’t been testing your code (shame on you). Your colleagues A and B chit chat over lunch and A mentions your bad habit. Once A and B interact with more people the rumour spreads exponentially faster. Pretty soon the whole office is glaring at you and you become the scape goat for every single problem in the office. Eventually this rumour mutates and your boss hears your purposely unfactoring your code and using pig latin for your method definitions. You end up being fired :(

Similarily, in a distributed system its easy to tell one node a message and have that message quickly propogate out to a few servers, maybe thousands with amazing speed. Wikipedia provides an excellent example of a data center that houses 25,000 servers. A search term is passed to a central point where it is propogated out. Since one of the machines has the item being searched for its able to receive and send a result back within 3 seconds in the worst case scenario.

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