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Comment by ineptech | Hacker News Reader

It's the difference between one customer asking a hundred cooks for a waffle and a hundred customers asking one cook for a waffle. The former is the thundering herd (a bunch of processes trying to do something that only needs to be done once, causing resource contention) and this is akin to the latter (with the "customers" being parallel requests from the frontend).

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The thundering herd problem is more like, there's a hundred cooks, one griddle, and only one of them can make an acceptable waffle for the customer.

This specific problem we're discussing, of concurrent client retries effectively launching a self-imposed DDOS attack, isn't exactly the thundering herd problem. It's clients and servers instead of threads, for one thing. But it's a good enough analogy to another type of cascading failure in concurrent computing, IMO.

Hmm, I was thinking it still applies in the sense that the many many duplicate retries are hitting many of Twitter's servers causing unnecessary duplicated load when a single successful response would satisfy the client and reduce the traffic.

In my mind, it is much closer to needlessly asking every server for the same information because the requests are most likely load balanced, but I guess it's true that I don't know the load balancing strategy. Even still, is it not more likely than not that those retries are hitting multiple servers?

Sure, maybe? We (or at least I) know little about the actual problem here, and metaphors only go so far. But to my mind, "too many things trying to handle a request" gets a cool name because it is a fairly narrow and unusual problem, whereas "too many requests" goes by many names (DoS, hammering, flood, etc) because it's depressingly common.

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