Attempt to prevent node explosions with parallel node creation #7004
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Forgind
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rainersigwald
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I don't think this will solve any current problems but it's conservative so 👍🏻
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Context
A long time ago, I was struggling with a bug in which we created thousands of MSBuild nodes.
Looking at our code for creating nodes, we fail early in NodeProviderOutOfProc if (_nodeContexts.Count == ComponentHost.BuildParameters.MaxNodeCount). We have an equivalent check in NodeProviderOutOfProcTaskHost. We don't in NodeProviderInProc, presumably because we shouldn't ever have > 1 in proc node.Actually, I don't think this is true because _nodeContexts aren't shared between providers. That said, rainersigwald pointed out this is still helpful if we parallelize this.
I'm wondering if the explosion might be avertable by changing the == to >=. If we haven't used the in-proc node for whatever reason and we use MaxNodeCount nodes, and then we create an in-proc node, we'd have MaxNodeCount + 1 nodes, and we could spiral out of control because the
==checks would no longer be valid.Changes Made
Switched equality to >= or <= as appropriate.
Testing
None. I'm not exactly sure how to set up a situation in which the in-proc node isn't there until MaxNodeCount has been exhausted, then decides to be used. Could happen also if the in-proc node dies for some reason, but I think that would kill the build.
Notes
Maybe not useful; not sure, but it seemed like an easy and possibly impactful change. Computer deaths can be really frustrating.