Merge pull request #485 from nspcc-dev/close-blockchain

core: add Close() to blockchainer, implement it to properly close chain

cli/server/server.go

@@ -154,14 +154,11 @@ func dumpDB(ctx *cli.Context) error {
 	defer outStream.Close()
 	writer := io.NewBinWriterFromIO(outStream)
 
-	grace, cancel := context.WithCancel(newGraceContext())
-	defer cancel()
-
 	chain, err := initBlockChain(cfg)
 	if err != nil {
 		return cli.NewExitError(err, 1)
 	}
-	go chain.Run(grace)
+	go chain.Run()
 
 	chainHeight := chain.BlockHeight()
 	if skip+count > chainHeight {
@@ -182,6 +179,7 @@ func dumpDB(ctx *cli.Context) error {
 			return cli.NewExitError(err, 1)
 		}
 	}
+	chain.Close()
 	return nil
 }
 func restoreDB(ctx *cli.Context) error {
@@ -204,14 +202,11 @@ func restoreDB(ctx *cli.Context) error {
 	defer inStream.Close()
 	reader := io.NewBinReaderFromIO(inStream)
 
-	grace, cancel := context.WithCancel(newGraceContext())
-	defer cancel()
-
 	chain, err := initBlockChain(cfg)
 	if err != nil {
 		return err
 	}
-	go chain.Run(grace)
+	go chain.Run()
 
 	var allBlocks uint32
 	reader.ReadLE(&allBlocks)
@@ -243,6 +238,7 @@ func restoreDB(ctx *cli.Context) error {
 			return cli.NewExitError(fmt.Errorf("failed to add block %d: %s", i, err), 1)
 		}
 	}
+	chain.Close()
 
 	return nil
 }
@@ -272,7 +268,7 @@ func startServer(ctx *cli.Context) error {
 	errChan := make(chan error)
 	monitoring := metrics.NewMetricsService(cfg.ApplicationConfiguration.Monitoring)
 
-	go chain.Run(grace)
+	go chain.Run()
 	go server.Start(errChan)
 	go rpcServer.Start(errChan)
 	go monitoring.Start()
@@ -295,6 +291,7 @@ Main:
 				shutdownErr = errors.Wrap(serverErr, "Error encountered whilst shutting down server")
 			}
 			monitoring.ShutDown()
+			chain.Close()
 			break Main
 		}
 	}

pkg/core/blockchain.go

@@ -2,7 +2,6 @@ package core
 
 import (
 	"bytes"
-	"context"
 	"fmt"
 	"math"
 	"sort"
@@ -65,6 +64,10 @@ type Blockchain struct {
 	headersOp     chan headersOpFunc
 	headersOpDone chan struct{}
 
+	// Stop synchronization mechanisms.
+	stopCh      chan struct{}
+	runToExitCh chan struct{}
+
 	memPool MemPool
 }
 
@@ -78,6 +81,8 @@ func NewBlockchain(s storage.Store, cfg config.ProtocolConfiguration) (*Blockcha
 		store:         storage.NewMemCachedStore(s),
 		headersOp:     make(chan headersOpFunc),
 		headersOpDone: make(chan struct{}),
+		stopCh:        make(chan struct{}),
+		runToExitCh:   make(chan struct{}),
 		memPool:       NewMemPool(50000),
 	}
 
@@ -178,7 +183,7 @@ func (bc *Blockchain) init() error {
 }
 
 // Run runs chain loop.
-func (bc *Blockchain) Run(ctx context.Context) {
+func (bc *Blockchain) Run() {
 	persistTimer := time.NewTimer(persistInterval)
 	defer func() {
 		persistTimer.Stop()
@@ -188,10 +193,11 @@ func (bc *Blockchain) Run(ctx context.Context) {
 		if err := bc.store.Close(); err != nil {
 			log.Warnf("failed to close db: %s", err)
 		}
+		close(bc.runToExitCh)
 	}()
 	for {
 		select {
-		case <-ctx.Done():
+		case <-bc.stopCh:
 			return
 		case op := <-bc.headersOp:
 			op(bc.headerList)
@@ -208,6 +214,13 @@ func (bc *Blockchain) Run(ctx context.Context) {
 	}
 }
 
+// Close stops Blockchain's internal loop, syncs changes to persistent storage
+// and closes it. The Blockchain is no longer functional after the call to Close.
+func (bc *Blockchain) Close() {
+	close(bc.stopCh)
+	<-bc.runToExitCh
+}
+
 // AddBlock accepts successive block for the Blockchain, verifies it and
 // stores internally. Eventually it will be persisted to the backing storage.
 func (bc *Blockchain) AddBlock(block *Block) error {

pkg/core/blockchain_test.go

@@ -155,3 +155,23 @@ func TestGetTransaction(t *testing.T) {
 		assert.NoError(t, bc.persist())
 	}
 }
+
+func TestClose(t *testing.T) {
+	defer func() {
+		r := recover()
+		assert.NotNil(t, r)
+	}()
+	bc := newTestChain(t)
+	blocks := makeBlocks(10)
+	for i := 0; i < len(blocks); i++ {
+		require.NoError(t, bc.AddBlock(blocks[i]))
+	}
+	bc.Close()
+	// It's a hack, but we use internal knowledge of MemoryStore
+	// implementation which makes it completely unusable (up to panicing)
+	// after Close().
+	_ = bc.store.Put([]byte{0}, []byte{1})
+
+	// This should never be executed.
+	assert.Nil(t, t)
+}

pkg/core/blockchainer.go

@@ -15,6 +15,7 @@ type Blockchainer interface {
 	AddHeaders(...*Header) error
 	AddBlock(*Block) error
 	BlockHeight() uint32
+	Close()
 	HeaderHeight() uint32
 	GetBlock(hash util.Uint256) (*Block, error)
 	GetContractState(hash util.Uint160) *ContractState

pkg/core/helper_test.go

@@ -1,7 +1,6 @@
 package core
 
 import (
-	"context"
 	"encoding/hex"
 	"encoding/json"
 	"fmt"
@@ -41,7 +40,7 @@ func newTestChain(t *testing.T) *Blockchain {
 	if err != nil {
 		t.Fatal(err)
 	}
-	go chain.Run(context.Background())
+	go chain.Run()
 	zeroHash, err := chain.GetHeader(chain.GetHeaderHash(0))
 	require.Nil(t, err)
 	newBlockPrevHash = zeroHash.Hash()

pkg/network/helper_test.go

@@ -52,6 +52,9 @@ func (chain *testChain) AddBlock(block *core.Block) error {
 func (chain *testChain) BlockHeight() uint32 {
 	return atomic.LoadUint32(&chain.blockheight)
 }
+func (chain *testChain) Close() {
+	panic("TODO")
+}
 func (chain testChain) HeaderHeight() uint32 {
 	return 0
 }

pkg/rpc/server_helper_test.go

@@ -1,7 +1,6 @@
 package rpc
 
 import (
-	"context"
 	"net/http"
 	"os"
 	"testing"
@@ -139,7 +138,7 @@ type GetAccountStateResponse struct {
 	ID int `json:"id"`
 }
 
-func initServerWithInMemoryChain(ctx context.Context, t *testing.T) (*core.Blockchain, http.HandlerFunc) {
+func initServerWithInMemoryChain(t *testing.T) (*core.Blockchain, http.HandlerFunc) {
 	var nBlocks uint32
 
 	net := config.ModeUnitTestNet
@@ -151,7 +150,7 @@ func initServerWithInMemoryChain(ctx context.Context, t *testing.T) (*core.Block
 	chain, err := core.NewBlockchain(memoryStore, cfg.ProtocolConfiguration)
 	require.NoError(t, err, "could not create chain")
 
-	go chain.Run(ctx)
+	go chain.Run()
 
 	f, err := os.Open("testdata/50testblocks.acc")
 	require.Nil(t, err)

pkg/rpc/server_test.go

@@ -2,7 +2,6 @@ package rpc
 
 import (
 	"bytes"
-	"context"
 	"encoding/json"
 	"fmt"
 	"io/ioutil"
@@ -10,16 +9,12 @@ import (
 	"net/http/httptest"
 	"strings"
 	"testing"
-	"time"
 
 	"github.com/stretchr/testify/assert"
 )
 
 func TestRPC(t *testing.T) {
-	ctx, cancel := context.WithTimeout(context.Background(), time.Second*30)
+	chain, handler := initServerWithInMemoryChain(t)
-	defer cancel()
-
-	chain, handler := initServerWithInMemoryChain(ctx, t)
 
 	t.Run("getbestblockhash", func(t *testing.T) {
 		rpc := `{"jsonrpc": "2.0", "id": 1, "method": "getbestblockhash", "params": []}`