Hello guys. I have a GCP cluster in a "Rapid Release Channel" with the latest version

Master version	
1.17.9-gke.1503

The nature of the "Rapid Channel" is that it auto-upgrades the master version, and then a simple change in pulumi config works fine. Problems arise when you try to upgrade the node versions

panic: fatal: An assertion has failed: Expected diff to not require deletion or replacement during Update of urn:pulumi:smth-integration-1::smth-integration-1::gcp:container/cluster:Cluster::mixed-cluster-1
    goroutine 144 [running]:
    <http://github.com/pulumi/pulumi/sdk/v2/go/common/util/contract.failfast(...)|github.com/pulumi/pulumi/sdk/v2/go/common/util/contract.failfast(...)>
        /home/runner/go/pkg/mod/github.com/pulumi/pulumi/sdk/v2@v2.9.1-0.20200825190708-910aa96016cd/go/common/util/contract/failfast.go:23
    <http://github.com/pulumi/pulumi/sdk/v2/go/common/util/contract.Assertf(0xc000724300|github.com/pulumi/pulumi/sdk/v2/go/common/util/contract.Assertf(0xc000724300>, 0x3b887dd, 0x48, 0xc0012357a8, 0x1, 0x1)
        /home/runner/go/pkg/mod/github.com/pulumi/pulumi/sdk/v2@v2.9.1-0.20200825190708-910aa96016cd/go/common/util/contract/assert.go:33 +0x197
    <http://github.com/pulumi/pulumi-terraform-bridge/v2/pkg/tfbridge.(*Provider).Update(0xc0001ea000|github.com/pulumi/pulumi-terraform-bridge/v2/pkg/tfbridge.(*Provider).Update(0xc0001ea000>, 0x41492a0, 0xc001001dd0, 0xc000fd0d20, 0xc0001ea000, 0x3620a01, 0xc00101d500)
        /home/runner/go/pkg/mod/github.com/pulumi/pulumi-terraform-bridge/v2@v2.7.3/pkg/tfbridge/provider.go:971 +0x81d
    <http://github.com/pulumi/pulumi/sdk/v2/proto/go._ResourceProvider_Update_Handler.func1(0x41492a0|github.com/pulumi/pulumi/sdk/v2/proto/go._ResourceProvider_Update_Handler.func1(0x41492a0>, 0xc001001dd0, 0x39f4e40, 0xc000fd0d20, 0x39f3540, 0x580a850, 0x41492a0, 0xc001001dd0)
        /home/runner/go/pkg/mod/github.com/pulumi/pulumi/sdk/v2@v2.9.1-0.20200825190708-910aa96016cd/proto/go/provider.pb.go:1920 +0x89
    <http://github.com/grpc-ecosystem/grpc-opentracing/go/otgrpc.OpenTracingServerInterceptor.func1(0x41492a0|github.com/grpc-ecosystem/grpc-opentracing/go/otgrpc.OpenTracingServerInterceptor.func1(0x41492a0>, 0xc001000210, 0x39f4e40, 0xc000fd0d20, 0xc000ffe640, 0xc000ffe660, 0x0, 0x0, 0x410c160, 0xc000210aa0)
        /home/runner/go/pkg/mod/github.com/grpc-ecosystem/grpc-opentracing@v0.0.0-20180507213350-8e809c8a8645/go/otgrpc/server.go:57 +0x2eb
    <http://github.com/pulumi/pulumi/sdk/v2/proto/go._ResourceProvider_Update_Handler(0x3a67500|github.com/pulumi/pulumi/sdk/v2/proto/go._ResourceProvider_Update_Handler(0x3a67500>, 0xc0001ea000, 0x41492a0, 0xc001000210, 0xc000f5f7a0, 0xc000b594a0, 0x41492a0, 0xc001000210, 0xc0006e7800, 0x3613)
        /home/runner/go/pkg/mod/github.com/pulumi/pulumi/sdk/v2@v2.9.1-0.20200825190708-910aa96016cd/proto/go/provider.pb.go:1922 +0x14b
    <http://google.golang.org/grpc.(*Server).processUnaryRPC(0xc0000e3dc0|google.golang.org/grpc.(*Server).processUnaryRPC(0xc0000e3dc0>, 0x4184520, 0xc000702c00, 0xc0013fcd00, 0xc000af1050, 0x57ca978, 0x0, 0x0, 0x0)
        /home/runner/go/pkg/mod/google.golang.org/grpc@v1.30.0/server.go:1171 +0x50a
    <http://google.golang.org/grpc.(*Server).handleStream(0xc0000e3dc0|google.golang.org/grpc.(*Server).handleStream(0xc0000e3dc0>, 0x4184520, 0xc000702c00, 0xc0013fcd00, 0x0)
        /home/runner/go/pkg/mod/google.golang.org/grpc@v1.30.0/server.go:1494 +0xccd
    <http://google.golang.org/grpc.(*Server).serveStreams.func1.2(0xc000adbba0|google.golang.org/grpc.(*Server).serveStreams.func1.2(0xc000adbba0>, 0xc0000e3dc0, 0x4184520, 0xc000702c00, 0xc0013fcd00)
        /home/runner/go/pkg/mod/google.golang.org/grpc@v1.30.0/server.go:834 +0xa1
    created by <http://google.golang.org/grpc.(*Server).serveStreams.func1|google.golang.org/grpc.(*Server).serveStreams.func1>
        /home/runner/go/pkg/mod/google.golang.org/grpc@v1.30.0/server.go:832 +0x204

I use:

pulumi version ==> v2.9.2

Python Modules:
pulumi==2.9.2
pulumi-gcp==3.21.1
pulumi-kubernetes==2.5.0
pulumi-postgresql==2.3.0
pulumi-random==2.3.1

Can you open an issue at https://github.com/pulumi/pulumi-gcp/issues with the steps and code to reproduce?

ok, sure