graphvm: resolve genesis as last-accepted block (fix G-Chain init)

The G-Chain VM declared chain.ChainVM but stubbed the block methods: GetBlock/ParseBlock returned errNotImplemented, LastAccepted returned the unset preferredID (ids.Empty), and Block.Status() returned choices.Status (not the uint8 the block.Block interface requires, so *Block never satisfied the interface). At boot the ZAP VM server (vm/rpc/vm_server_zap.go handleInitialize) calls LastAccepted() then GetBlock(lastAccepted); the GetBlock stub produced 'get last accepted block: not implemented', failing G-Chain initialization and the lux-mainnet node health check. The G-Chain is a read-only query/index VM that never advances past genesis, but consensus still requires a resolvable last-accepted block. Build a deterministic genesis block (height 0, content-addressed ID = SHA-256 of its canonical encoding) in Initialize, pin it as lastAccepted, and serve it from GetBlock/ParseBlock/GetBlockIDAtHeight. Fix Status() to return uint8 and add the var _ block.Block compile assertion so this can't regress. Tests reproduce the exact handleInitialize sequence plus byte/ID round-trip and cross-validator determinism.
2026-07-27 03:39:41 +00:00 · 2026-06-26 15:39:05 -07:00
parent 12eb748077
commit 9c00994218
3 changed files with 256 additions and 17 deletions
@@ -5,14 +5,23 @@ package graphvm

 import (
 	"context"
+	"encoding/json"
 	"errors"
 	"time"

 	"github.com/luxfi/consensus/core/choices"
-	"github.com/luxfi/ids"
+	"github.com/luxfi/consensus/engine/chain/block"
 	"github.com/luxfi/crypto/hash"
+	"github.com/luxfi/ids"
 )

+// The consensus engine requires every ChainVM to resolve a real last-accepted
+// block at boot (LastAccepted -> GetBlock). This assertion guarantees *Block
+// satisfies block.Block; it is what catches the Status() signature mismatch
+// (the interface needs a concrete uint8, not the named choices.Status) at
+// compile time so GetBlock can actually return a *Block.
+var _ block.Block = (*Block)(nil)
+
 var (
 	errInvalidBlock = errors.New("invalid block")
 )
@@ -126,6 +135,7 @@ func (b *Block) Accept(context.Context) error {
 	}

 	// Update last accepted
+	b.vm.lastAcceptedID = b.id
 	b.vm.preferredID = b.id

 	return nil
@@ -137,9 +147,12 @@ func (b *Block) Reject(context.Context) error {
 	return nil
 }

-// Status implements the chain.Block interface
-func (b *Block) Status() choices.Status {
-	return b.status
+// Status implements the block.Block interface. The interface requires a
+// concrete uint8; choices.Status is `type Status uint8`, so a method returning
+// the named type would NOT satisfy block.Block — which is why GetBlock could
+// never have returned a *Block before this fix.
+func (b *Block) Status() uint8 {
+	return uint8(b.status)
 }

 // Parent implements the chain.Block interface
@@ -184,10 +197,74 @@ func (b *Block) Verify(ctx context.Context) error {
 	return nil
 }

-// Bytes implements the chain.Block interface
+// Bytes implements the block.Block interface. It returns the deterministic
+// canonical encoding set at construction; the block ID is the SHA-256 of
+// exactly these bytes, so ParseBlock(b.Bytes()).ID() == b.ID().
 func (b *Block) Bytes() []byte {
-	if b.bytes == nil {
-		b.bytes = hash.ComputeHash256([]byte(b.id.String()))
-	}
 	return b.bytes
 }
+
+// genesisTimestamp is the deterministic timestamp of the G-Chain genesis block.
+// Genesis is the root of trust (accepted by definition), so a fixed,
+// node-independent value is used — never time.Now(), which would make the
+// genesis block ID diverge across validators and break consensus agreement.
+var genesisTimestamp = time.Unix(0, 0).UTC()
+
+// blockWire is the deterministic on-wire encoding of a G-Chain block. The block
+// ID is hash.ComputeHash256 of these bytes, so marshal/parse round-trips a
+// byte-identical ID across nodes and restarts.
+type blockWire struct {
+	ParentID  ids.ID `json:"parentID"`
+	Height    uint64 `json:"height"`
+	Timestamp int64  `json:"timestamp"`
+	Payload   []byte `json:"payload,omitempty"`
+}
+
+// newGenesisBlock builds the G-Chain genesis block (height 0) deterministically
+// from the genesis config bytes. The G-Chain is a read-only query/index chain —
+// it never builds blocks past genesis — so this is its permanent last-accepted
+// block, the one GetBlock(LastAccepted()) must return during Initialize.
+func newGenesisBlock(vm *VM, genesisBytes []byte) (*Block, error) {
+	return newBlock(vm, ids.Empty, 0, genesisTimestamp, genesisBytes)
+}
+
+// newBlock constructs a block, computes its canonical bytes and content-
+// addressed ID, and returns it ready to serve.
+func newBlock(vm *VM, parentID ids.ID, height uint64, timestamp time.Time, payload []byte) (*Block, error) {
+	raw, err := json.Marshal(blockWire{
+		ParentID:  parentID,
+		Height:    height,
+		Timestamp: timestamp.Unix(),
+		Payload:   payload,
+	})
+	if err != nil {
+		return nil, err
+	}
+	return &Block{
+		vm:        vm,
+		id:        ids.ID(hash.ComputeHash256(raw)),
+		parentID:  parentID,
+		height:    height,
+		timestamp: timestamp,
+		status:    choices.Accepted,
+		bytes:     raw,
+	}, nil
+}
+
+// parseBlock decodes the canonical wire bytes produced by newBlock back into a
+// Block whose ID is recomputed from those exact bytes.
+func parseBlock(vm *VM, raw []byte) (*Block, error) {
+	var wire blockWire
+	if err := json.Unmarshal(raw, &wire); err != nil {
+		return nil, err
+	}
+	return &Block{
+		vm:        vm,
+		id:        ids.ID(hash.ComputeHash256(raw)),
+		parentID:  wire.ParentID,
+		height:    wire.Height,
+		timestamp: time.Unix(wire.Timestamp, 0).UTC(),
+		status:    choices.Accepted,
+		bytes:     raw,
+	}, nil
+}
@@ -70,8 +70,13 @@ type VM struct {
 	toEngine  chan<- vmcore.Message
 	appSender warp.Sender

-	// State
-	preferredID ids.ID
+	// State. The G-Chain is read-only and never advances past genesis, so
+	// genesisBlock is permanently the last-accepted block. lastAcceptedID is
+	// what LastAccepted() returns and what the engine resolves via GetBlock at
+	// initialization; preferredID tracks SetPreference separately.
+	genesisBlock   *Block
+	lastAcceptedID ids.ID
+	preferredID    ids.ID

 	// Graph-specific fields
 	schemas       map[string]*GraphSchema
@@ -187,9 +192,25 @@ func (vm *VM) Initialize(
 		}
 	}

+	// Build the deterministic genesis block and pin it as the last-accepted
+	// block. The G-Chain is a read-only query/index VM that never advances
+	// past genesis, but the consensus engine still REQUIRES a resolvable
+	// last-accepted block at boot: the ZAP VM server calls LastAccepted() then
+	// GetBlock(lastAccepted) inside Initialize, and a miss there is the
+	// "get last accepted block: not implemented" failure that fails the node's
+	// G-Chain health check on lux-mainnet.
+	genesisBlock, err := newGenesisBlock(vm, vmInit.Genesis)
+	if err != nil {
+		return fmt.Errorf("failed to build genesis block: %w", err)
+	}
+	vm.genesisBlock = genesisBlock
+	vm.lastAcceptedID = genesisBlock.ID()
+	vm.preferredID = genesisBlock.ID()
+
 	if logger, ok := vm.rt.Log.(log.Logger); ok {
 		logger.Info("initialized Graph VM",
 			log.Reflect("version", Version),
+			log.String("genesisBlockID", vm.lastAcceptedID.String()),
 		)
 	}

@@ -321,14 +342,26 @@ func (vm *VM) BuildBlock(ctx context.Context) (chain.Block, error) {
 	return nil, errNotImplemented
 }

-// ParseBlock implements the chain.ChainVM interface
+// ParseBlock implements the chain.ChainVM interface. It decodes the canonical
+// block encoding produced by Block.Bytes(), recomputing the content-addressed
+// ID so a re-parsed block is byte- and ID-identical to the original.
 func (vm *VM) ParseBlock(ctx context.Context, blockBytes []byte) (chain.Block, error) {
-	return nil, errNotImplemented
+	blk, err := parseBlock(vm, blockBytes)
+	if err != nil {
+		return nil, err
+	}
+	return blk, nil
 }

-// GetBlock implements the chain.ChainVM interface
+// GetBlock implements the chain.ChainVM interface. The G-Chain has exactly one
+// block — genesis — which is permanently the accepted frontier; any other ID is
+// unknown. Returning database.ErrNotFound (not errNotImplemented) lets the ZAP
+// VM server map a genuine miss to the wire NotFound code.
 func (vm *VM) GetBlock(ctx context.Context, blkID ids.ID) (chain.Block, error) {
-	return nil, errNotImplemented
+	if vm.genesisBlock != nil && blkID == vm.genesisBlock.ID() {
+		return vm.genesisBlock, nil
+	}
+	return nil, database.ErrNotFound
 }

 // SetPreference implements the chain.ChainVM interface
@@ -337,13 +370,17 @@ func (vm *VM) SetPreference(ctx context.Context, blkID ids.ID) error {
 	return nil
 }

-// LastAccepted implements the chain.ChainVM interface
+// LastAccepted implements the chain.ChainVM interface.
 func (vm *VM) LastAccepted(context.Context) (ids.ID, error) {
-	return vm.preferredID, nil
+	return vm.lastAcceptedID, nil
 }

-// GetBlockIDAtHeight implements the chain.ChainVM interface
+// GetBlockIDAtHeight implements the chain.ChainVM interface. Genesis (height 0)
+// is the only block; every other height is absent.
 func (vm *VM) GetBlockIDAtHeight(ctx context.Context, height uint64) (ids.ID, error) {
+	if height == 0 && vm.genesisBlock != nil {
+		return vm.genesisBlock.ID(), nil
+	}
 	return ids.Empty, database.ErrNotFound
 }

@@ -0,0 +1,125 @@
+// Copyright (C) 2019-2025, Lux Industries Inc. All rights reserved.
+// See the file LICENSE for licensing terms.
+
+package graphvm
+
+import (
+	"context"
+	"testing"
+
+	"github.com/stretchr/testify/require"
+
+	"github.com/luxfi/database"
+	"github.com/luxfi/database/memdb"
+	"github.com/luxfi/ids"
+	"github.com/luxfi/runtime"
+	vmcore "github.com/luxfi/vm"
+)
+
+// initVM initializes a fresh G-Chain VM the way the node does, with the given
+// genesis bytes, and returns it ready to serve.
+func initVM(t *testing.T, genesis []byte) *VM {
+	t.Helper()
+	vm := &VM{}
+	require.NoError(t, vm.Initialize(context.Background(), vmcore.Init{
+		Runtime: &runtime.Runtime{NetworkID: 1},
+		DB:      memdb.New(),
+		Genesis: genesis,
+	}))
+	return vm
+}
+
+// TestInitializeResolvesLastAcceptedBlock reproduces the exact call sequence the
+// ZAP VM server performs inside handleInitialize (vm/rpc/vm_server_zap.go:262-270):
+// Initialize -> LastAccepted -> GetBlock(lastAccepted). Before the genesis-block
+// fix the GetBlock call returned errNotImplemented, surfacing on lux-mainnet as
+// "G chain ... failed to initialize VM: zap initialize: remote error: get last
+// accepted block: not implemented" and failing the node health check.
+func TestInitializeResolvesLastAcceptedBlock(t *testing.T) {
+	require := require.New(t)
+	ctx := context.Background()
+
+	vm := initVM(t, []byte(`{"defaultSchema":"type Query { hello: String }","schemaVersion":"1"}`))
+
+	// LastAccepted must be a real, non-empty block ID.
+	lastAccepted, err := vm.LastAccepted(ctx)
+	require.NoError(err)
+	require.NotEqual(ids.Empty, lastAccepted)
+
+	// GetBlock(lastAccepted) is the call that returned "not implemented".
+	blk, err := vm.GetBlock(ctx, lastAccepted)
+	require.NoError(err)
+	require.Equal(lastAccepted, blk.ID())
+	require.Equal(uint64(0), blk.Height())
+	require.Equal(ids.Empty, blk.Parent())
+	require.NotEmpty(blk.Bytes())
+
+	// The ZAP server also reads Timestamp() for the InitializeResponse; it must
+	// be deterministic (genesis epoch), never time.Now().
+	require.Equal(genesisTimestamp, blk.Timestamp())
+
+	// GetBlockIDAtHeight(0) resolves to the same genesis block.
+	at0, err := vm.GetBlockIDAtHeight(ctx, 0)
+	require.NoError(err)
+	require.Equal(lastAccepted, at0)
+}
+
+// TestGenesisBlockRoundTrip proves Bytes()/ParseBlock are inverse and content-
+// addressed: re-parsing the genesis block yields a byte- and ID-identical block.
+// The engine relies on this when it re-parses the accepted frontier during
+// bootstrap.
+func TestGenesisBlockRoundTrip(t *testing.T) {
+	require := require.New(t)
+	ctx := context.Background()
+
+	vm := initVM(t, []byte(`{"schemaVersion":"1"}`))
+
+	lastAccepted, err := vm.LastAccepted(ctx)
+	require.NoError(err)
+	orig, err := vm.GetBlock(ctx, lastAccepted)
+	require.NoError(err)
+
+	reparsed, err := vm.ParseBlock(ctx, orig.Bytes())
+	require.NoError(err)
+	require.Equal(orig.ID(), reparsed.ID())
+	require.Equal(orig.Bytes(), reparsed.Bytes())
+	require.Equal(orig.Height(), reparsed.Height())
+	require.Equal(orig.Parent(), reparsed.Parent())
+	require.Equal(orig.Timestamp(), reparsed.Timestamp())
+}
+
+// TestUnknownBlockNotFound proves a non-genesis ID is reported as a genuine miss
+// (database.ErrNotFound), which the ZAP server maps to the wire NotFound code —
+// not the old errNotImplemented that broke initialization.
+func TestUnknownBlockNotFound(t *testing.T) {
+	require := require.New(t)
+	ctx := context.Background()
+
+	vm := initVM(t, []byte(`{"schemaVersion":"1"}`))
+
+	_, err := vm.GetBlock(ctx, ids.GenerateTestID())
+	require.ErrorIs(err, database.ErrNotFound)
+
+	_, err = vm.GetBlockIDAtHeight(ctx, 1)
+	require.ErrorIs(err, database.ErrNotFound)
+}
+
+// TestGenesisDeterministic proves two independent VMs given identical genesis
+// bytes derive the SAME genesis block ID — the cross-validator agreement the
+// chain needs — while different genesis bytes derive different IDs.
+func TestGenesisDeterministic(t *testing.T) {
+	require := require.New(t)
+	ctx := context.Background()
+
+	idFor := func(genesis []byte) ids.ID {
+		id, err := initVM(t, genesis).LastAccepted(ctx)
+		require.NoError(err)
+		return id
+	}
+
+	a := []byte(`{"defaultSchema":"type Query { a: Int }","schemaVersion":"7"}`)
+	b := []byte(`{"defaultSchema":"type Query { b: Int }","schemaVersion":"7"}`)
+
+	require.Equal(idFor(a), idFor(a))
+	require.NotEqual(idFor(a), idFor(b))
+}