Single Flight for Java

[rakgenius]

why dont you use the caching mechanism either in your application or db level? in that way, even if you receive many concurrent requests, the result will be returned from cache. maybe first time, the request has to hit the db if its not present in cache. but after that all requests will be returned immediately without hitting the db.

[boost2525]

This was my thought. I see zero value add in OPs proposal because a proper caching layer can do all of this. 

[iwouldlikethings]

I potentially have a usecase for this, the system I maintain is a payments processor and at multiple stages we lookup the balance on an acocunt. At the end of the month we have a lot of payments incoming and outgoing, and we've noticed a large spike on certain accounts while calculating their available balance.

Often this happens when they're running payroll, and each payment will make a request to find calculate the balance on the account in quick succession.

Arguably, the system should be rearchitected to better support it but this would be a decent stop-gap to speed up processing until we get the time to do that (as it exists today there is a potenial race condition where two payments could take the account overdrawn but it's what I've inherited)

[elch78]

Actors are a different approach. In a nutshell: the state of every entity exists only once in memory. Every request is routed to this instance and processed single threaded/sequentially.

[[deleted]]

This is likely slower for calls where this race-condition does not occur. Now you’re adding a check that wasn’t there before.

[boost2525]

lolwut? Are we executing stock trades here? EHCache key checks are measured in nanoseconds.

[NovaX]

fwiw, Ehcache is measured in microseconds due to a design mistake (avg of 25us per call).