roachtest: perform spec validation on existing clusters

This change adds in a new validation step when running tests with the
`--cluster` flag to verify that the cluster matches the test spec. This
is particularly important for benchmarks, which can produce vastly
different results depending on the machine type they run on.

Release note: None

pkg/cmd/roachtest/cluster.go

@@ -20,6 +20,7 @@ import (
 	"bytes"
 	"context"
 	gosql "database/sql"
+	"encoding/json"
 	"fmt"
 	"io"
 	"math/rand"
@@ -345,7 +346,7 @@ type nodeSpec struct {
 func (s *nodeSpec) args() []string {
 	var args []string
 	if s.MachineType != "" {
-		args = append(args, s.MachineType)
+		args = append(args, "--gce-machine-type="+s.MachineType)
 	}
 	if s.Geo {
 		args = append(args, "--geo")
@@ -370,9 +371,9 @@ func (o nodeCPUOption) apply(spec *nodeSpec) {
 		// configurations, but the rules for the amount of RAM per CPU need to be
 		// determined (you can't request any arbitrary amount of RAM).
 		if spec.CPUs < 16 {
-			spec.MachineType = fmt.Sprintf("--gce-machine-type=n1-standard-%d", spec.CPUs)
+			spec.MachineType = fmt.Sprintf("n1-standard-%d", spec.CPUs)
 		} else {
-			spec.MachineType = fmt.Sprintf("--gce-machine-type=n1-highcpu-%d", spec.CPUs)
+			spec.MachineType = fmt.Sprintf("n1-highcpu-%d", spec.CPUs)
 		}
 	}
 }
@@ -487,9 +488,52 @@ func newCluster(ctx context.Context, t testI, nodes []nodeSpec) *cluster {
 			return nil
 		}
 	} else {
-		// NB: if the existing cluster is not as large as the desired cluster, the
-		// test will fail when trying to perform various operations such as putting
-		// binaries or starting the cockroach nodes.
+		// Perform validation on the existing cluster.
+		c.status("checking that existing cluster matches spec")
+		sargs := []string{roachprod, "list", c.name, "--json"}
+		out, err := execCmdWithBuffer(ctx, l, sargs...)
+		if err != nil {
+			t.Fatal(err)
+			return nil
+		}
+
+		// jsonOutput matches the structure of the output from `roachprod list`
+		// when in json mode.
+		//
+		// TODO DURING REIVIEW: we could use the roachprod.Cloud struct directly
+		// for this if we were ok establishing the dependency.
+		type jsonOutput struct {
+			Clusters map[string]struct {
+				Vms []struct {
+					MachineType string `json:"machine_type"`
+				} `json:"vms"`
+			} `json:"clusters"`
+		}
+		var details jsonOutput
+		if err := json.Unmarshal(out, &details); err != nil {
+			t.Fatal(err)
+			return nil
+		}
+
+		cDetails, ok := details.Clusters[c.name]
+		if !ok {
+			t.Fatalf("cluster %q not found", c.name)
+			return nil
+		}
+		if len(cDetails.Vms) < c.nodes {
+			t.Fatalf("cluster has %d nodes, test requires at least %d", len(cDetails.Vms), c.nodes)
+			return nil
+		}
+		if typ := nodes[0].MachineType; typ != "" {
+			for i, vm := range cDetails.Vms {
+				if vm.MachineType != typ {
+					t.Fatalf("node %d has machine type %s, test requires %s", i, vm.MachineType, typ)
+					return nil
+				}
+			}
+			// TODO DURING REVIEW: should we assert correct zones?
+		}
+
 		c.status("stopping cluster")
 		c.Stop(ctx, c.All())
 		if clusterWipe {