fix: concurrent map write panic

[sl1pm4t]

@justinsb this is the fix for the concurrent map write panic that we discussed.

It only occurs when kops is invoked by Terraform, which is parallelising updates to multiple instance groups at the same time.

The stack trace looked liked:

fatal error: concurrent map writes
fatal error: concurrent map writes

goroutine 102 [running]:
k8s.io/kops/upup/pkg/fi/cloudup/gce.CacheGCECloudInstance(...)
	/Users/matt/git/kops/upup/pkg/fi/cloudup/gce/gce_cloud.go:182
k8s.io/kops/upup/pkg/fi/cloudup/gce.NewGCECloud({0x14001c8a010, 0xb}, {0x14001ff1f96, 0xa}, 0x140007be720)
	/Users/matt/git/kops/upup/pkg/fi/cloudup/gce/gce_cloud.go:165 +0x4d0
k8s.io/kops/upup/pkg/fi/cloudup.BuildCloud(0x140006cd400)
	/Users/matt/git/kops/upup/pkg/fi/cloudup/utils.go:63 +0xd20
github.com/eddycharly/terraform-provider-kops/pkg/api/resources.UpdateInstanceGroup({_, _}, {_, _}, _, _, {{0x14001f063d0, 0xa}, {0x14001f06430, 0xc}, ...}, ...)
	/Users/matt/git/terraform-provider-kops/pkg/api/resources/InstanceGroup.go:104 +0x168
github.com/eddycharly/terraform-provider-kops/pkg/resources.InstanceGroupUpdate({0x105bda908, 0x140019c4e00}, 0x0?, {0x104aadf00?, 0x14000f59120?})
	/Users/matt/git/terraform-provider-kops/pkg/resources/InstanceGroup.go:44 +0xe0
...

[k8s-ci-robot]

Hi @sl1pm4t. Thanks for your PR.

I'm waiting for a kubernetes member to verify that this patch is reasonable to test. If it is, they should reply with /ok-to-test on its own line. Until that is done, I will not automatically test new commits in this PR, but the usual testing commands by org members will still work. Regular contributors should join the org to skip this step.

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[hakman]

/ok-to-test

[hakman]

Shouldn't you also RLock and RUnlock the read(s)?

kops/upup/pkg/fi/cloudup/gce/gce_cloud.go

Line 122 in f44ee89

i := gceCloudInstances[region+"::"+project]

[sl1pm4t]

Yes, good call. I've pushed another commit with the RLock().

[sl1pm4t]

/test pull-kops-e2e-k8s-gce-ipalias

[hakman]

Thanks @sl1pm4t! 👍

[k8s-ci-robot]

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