Make the datapoint storage cache safe for concurrent use #417
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@jsuereth you had mentioned wanting to review this at standup. |
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Fixes #405
This adds one RW lock for each cache. For GetFoo() functions, it takes a RLock, and for SetFoo() functions, it takes a write Lock. However, since the "used" bool is set in GetFoo() functions (it indicates if the item has been touched since the last GC), this still produced a data race. I could have switched to a full write-lock for Get functions, but thought it would be more performant to use a concurrency-safe bool. That also simplifies the implementation of GC using Compare and swap.
I added tests for concurrency to verify that there are no data races.