Start Snowman++ after Avalanche is Linearized (ava-labs#2478)

chains/linearizable_vm.go

@@ -0,0 +1,80 @@
+// Copyright (C) 2019-2022, Ava Labs, Inc. All rights reserved.
+// See the file LICENSE for licensing terms.
+
+package chains
+
+import (
+	"context"
+
+	"github.com/ava-labs/avalanchego/api/metrics"
+	"github.com/ava-labs/avalanchego/ids"
+	"github.com/ava-labs/avalanchego/snow"
+	"github.com/ava-labs/avalanchego/snow/engine/avalanche/vertex"
+	"github.com/ava-labs/avalanchego/snow/engine/common"
+	"github.com/ava-labs/avalanchego/snow/engine/snowman/block"
+
+	dbManager "github.com/ava-labs/avalanchego/database/manager"
+)
+
+var (
+	_ vertex.LinearizableVM = (*initializeOnLinearizeVM)(nil)
+	_ block.ChainVM         = (*linearizeOnInitializeVM)(nil)
+)
+
+// initializeOnLinearizeVM transforms the consensus engine's call to Linearize
+// into a call to Initialize. This enables the proposervm to be initialized by
+// the call to Linearize. This also provides the stopVertexID to the
+// linearizeOnInitializeVM.
+type initializeOnLinearizeVM struct {
+	vertex.DAGVM
+	vmToInitialize common.VM
+	vmToLinearize  *linearizeOnInitializeVM
+
+	registerer   metrics.OptionalGatherer
+	ctx          *snow.Context
+	dbManager    dbManager.Manager
+	genesisBytes []byte
+	upgradeBytes []byte
+	configBytes  []byte
+	toEngine     chan<- common.Message
+	fxs          []*common.Fx
+	appSender    common.AppSender
+}
+
+func (vm *initializeOnLinearizeVM) Linearize(ctx context.Context, stopVertexID ids.ID) error {
+	vm.vmToLinearize.stopVertexID = stopVertexID
+	vm.ctx.Metrics = vm.registerer
+	return vm.vmToInitialize.Initialize(
+		ctx,
+		vm.ctx,
+		vm.dbManager,
+		vm.genesisBytes,
+		vm.upgradeBytes,
+		vm.configBytes,
+		vm.toEngine,
+		vm.fxs,
+		vm.appSender,
+	)
+}
+
+// linearizeOnInitializeVM transforms the proposervm's call to Initialize into a
+// call to Linearize. This enables the proposervm to provide its toEngine
+// channel to the VM that is being linearized.
+type linearizeOnInitializeVM struct {
+	vertex.LinearizableVMWithEngine
+	stopVertexID ids.ID
+}
+
+func (vm *linearizeOnInitializeVM) Initialize(
+	ctx context.Context,
+	_ *snow.Context,
+	_ dbManager.Manager,
+	_ []byte,
+	_ []byte,
+	_ []byte,
+	toEngine chan<- common.Message,
+	_ []*common.Fx,
+	_ common.AppSender,
+) error {
+	return vm.Linearize(ctx, vm.stopVertexID, toEngine)
+}