[MNG-7235] Speed improvements when calculating the sorted project graph

[gnodet]

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[michael-o]

Stupid question: Is this threadsafe?

[gnodet]

Stupid question: Is this threadsafe?

Yes, the access to the SessionData is completely safe. The cache itself is a ConcurrentHashMap, so it should be fine too.

There's no atomicity guarantee, i.e. if two threads request the exact same version simultaneously, there's no guarantee that only a single remote request will be done, but the assumption is that those two requests should return the same result anyway. If we imagine this is not the case, we fallback to the previous behavior (for the first 2 concurrent requests), i.e. 2 remote requests will be performed and the results will be returned. Subsequent requests will return the cached result.

So the data structures are thread safe (no exception will occur). The returned data is more stable than in the current behavior (i.e. two consecutive requests will return the same cached result). The only ap is the one mentioned above, which I don't think we need to care about.