storage: un-embed decodedConfChange

I ate a number of NPEs during development because nullable embedded
fields are tricky; they hide the pointer derefs that often need a nil
check. We'll embed the fields of decodedConfChange instead which works
out better.
This commit also adds the unmarshaling code necessary for ConfChangeV2
needed once we issue atomic replication changes.

Release note: None

pkg/storage/replica_application_cmd.go

@@ -20,6 +20,7 @@ import (
 	"github.com/cockroachdb/cockroach/pkg/util/log"
 	"github.com/cockroachdb/cockroach/pkg/util/protoutil"
 	"github.com/cockroachdb/cockroach/pkg/util/tracing"
+	"github.com/cockroachdb/errors"
 	opentracing "github.com/opentracing/opentracing-go"
 	"go.etcd.io/etcd/raft/raftpb"
 )
@@ -79,15 +80,15 @@ type replicatedCmd struct {
 
 // decodedRaftEntry represents the deserialized content of a raftpb.Entry.
 type decodedRaftEntry struct {
-	idKey              storagebase.CmdIDKey
-	raftCmd            storagepb.RaftCommand
-	*decodedConfChange // only non-nil for config changes
+	idKey      storagebase.CmdIDKey
+	raftCmd    storagepb.RaftCommand
+	confChange *decodedConfChange // only non-nil for config changes
 }
 
 // decodedConfChange represents the fields of a config change raft command.
 type decodedConfChange struct {
-	cc    raftpb.ConfChange
-	ccCtx ConfChangeContext
+	raftpb.ConfChangeI
+	ConfChangeContext
 }
 
 // decode decodes the entry e into the replicatedCmd.
@@ -191,17 +192,32 @@ func (d *decodedRaftEntry) decodeNormalEntry(e *raftpb.Entry) error {
 }
 
 func (d *decodedRaftEntry) decodeConfChangeEntry(e *raftpb.Entry) error {
-	d.decodedConfChange = &decodedConfChange{}
-	if err := protoutil.Unmarshal(e.Data, &d.cc); err != nil {
-		return wrapWithNonDeterministicFailure(err, "while unmarshaling ConfChange")
+	d.confChange = &decodedConfChange{}
+
+	switch e.Type {
+	case raftpb.EntryConfChange:
+		var cc raftpb.ConfChange
+		if err := protoutil.Unmarshal(e.Data, &cc); err != nil {
+			return wrapWithNonDeterministicFailure(err, "while unmarshaling ConfChange")
+		}
+		d.confChange.ConfChangeI = cc
+	case raftpb.EntryConfChangeV2:
+		var cc raftpb.ConfChangeV2
+		if err := protoutil.Unmarshal(e.Data, &cc); err != nil {
+			return wrapWithNonDeterministicFailure(err, "while unmarshaling ConfChangeV2")
+		}
+		d.confChange.ConfChangeI = cc
+	default:
+		err := errors.New("unknown entry type")
+		return wrapWithNonDeterministicFailure(err, err.Error())
 	}
-	if err := protoutil.Unmarshal(d.cc.Context, &d.ccCtx); err != nil {
+	if err := protoutil.Unmarshal(d.confChange.AsV2().Context, &d.confChange.ConfChangeContext); err != nil {
 		return wrapWithNonDeterministicFailure(err, "while unmarshaling ConfChangeContext")
 	}
-	if err := protoutil.Unmarshal(d.ccCtx.Payload, &d.raftCmd); err != nil {
+	if err := protoutil.Unmarshal(d.confChange.Payload, &d.raftCmd); err != nil {
 		return wrapWithNonDeterministicFailure(err, "while unmarshaling RaftCommand")
 	}
-	d.idKey = storagebase.CmdIDKey(d.ccCtx.CommandID)
+	d.idKey = storagebase.CmdIDKey(d.confChange.CommandID)
 	return nil
 }
 

pkg/storage/replica_application_state_machine.go

@@ -1001,10 +1001,10 @@ func (sm *replicaStateMachine) maybeApplyConfChange(ctx context.Context, cmd *re
 	case raftpb.EntryConfChange:
 		if cmd.replicatedResult().ChangeReplicas == nil {
 			// The command was rejected.
-			cmd.cc = raftpb.ConfChange{}
+			cmd.confChange.ConfChangeI = raftpb.ConfChange{}
 		}
 		return sm.r.withRaftGroup(true, func(raftGroup *raft.RawNode) (bool, error) {
-			raftGroup.ApplyConfChange(cmd.cc)
+			raftGroup.ApplyConfChange(cmd.confChange.ConfChangeI)
 			return true, nil
 		})
 	default: