consensus: add three method for consensus interface

consensus/clique/clique.go

@@ -23,6 +23,7 @@ import (
 	"math/big"
 	"math/rand"
 	"sync"
+	"sync/atomic"
 	"time"
 
 	"github.com/ethereum/go-ethereum/accounts"
@@ -194,8 +195,9 @@ func ecrecover(header *types.Header, sigcache *lru.ARCCache) (common.Address, er
 // Clique is the proof-of-authority consensus engine proposed to support the
 // Ethereum testnet following the Ropsten attacks.
 type Clique struct {
-	config *params.CliqueConfig // Consensus engine configuration parameters
+	config  *params.CliqueConfig // Consensus engine configuration parameters
-	db     ethdb.Database       // Database to store and retrieve snapshot checkpoints
+	db      ethdb.Database       // Database to store and retrieve snapshot checkpoints
+	running int32                // Indicator whether clique engine is running or not.
 
 	recents    *lru.ARCCache // Snapshots for recent block to speed up reorgs
 	signatures *lru.ARCCache // Signatures of recent blocks to speed up mining
@@ -601,6 +603,10 @@ func (c *Clique) Seal(chain consensus.ChainReader, block *types.Block, stop <-ch
 	if c.config.Period == 0 && len(block.Transactions()) == 0 {
 		return nil, errWaitTransactions
 	}
+	// Make sure clique engine is started.
+	if !c.IsRunning() {
+		return nil, consensus.ErrEngineNotStart
+	}
 	// Don't hold the signer fields for the entire sealing procedure
 	c.lock.RLock()
 	signer, signFn := c.signer, c.signFn
@@ -672,6 +678,21 @@ func CalcDifficulty(snap *Snapshot, signer common.Address) *big.Int {
 	return new(big.Int).Set(diffNoTurn)
 }
 
+// Start implements consensus.Engine, starting the clique consensus engine.
+func (c *Clique) Start() {
+	atomic.StoreInt32(&c.running, 1)
+}
+
+// Stop implements consensus.Engine, stopping the clique consensus engine.
+func (c *Clique) Stop() {
+	atomic.StoreInt32(&c.running, 0)
+}
+
+// IsRunning implements consensus.Engine, returning an indication if the clique engine is currently mining.
+func (c *Clique) IsRunning() bool {
+	return atomic.LoadInt32(&c.running) > 0
+}
+
 // Close implements consensus.Engine, returning internal error and close the clique.
 func (c *Clique) Close() error {
 	return nil

consensus/consensus.go

@@ -97,6 +97,15 @@ type Engine interface {
 	// APIs returns the RPC APIs this consensus engine provides.
 	APIs(chain ChainReader) []rpc.API
 
+	// Start starts the consensus engine.
+	Start()
+
+	// Stop stops the consensus engine.
+	Stop()
+
+	// IsRunning returns an indication whether consensus engine is running or not.
+	IsRunning() bool
+
 	// Close closes the consensus engine.
 	Close() error
 }

consensus/errors.go

@@ -34,4 +34,7 @@ var (
 	// ErrInvalidNumber is returned if a block's number doesn't equal it's parent's
 	// plus one.
 	ErrInvalidNumber = errors.New("invalid block number")
+
+	// ErrEngineNotStart is returned if the consensus engine is not started.
+	ErrEngineNotStart = errors.New("consensus engine is not started")
 )

consensus/ethash/api.go

@@ -44,6 +44,12 @@ func (api *API) GetWork() ([3]string, error) {
 		err    error
 	)
 
+	// Trigger ethash to start in remote mining mode(local/cpu mining is disabled)
+	// if ethash is not running.
+	if !api.ethash.IsRunning() {
+		api.ethash.StartMining(new(int))
+	}
+
 	select {
 	case api.ethash.fetchWorkCh <- &sealWork{errCh: errCh, resCh: workCh}:
 	case <-api.ethash.exitCh:

consensus/ethash/consensus.go

@@ -22,6 +22,7 @@ import (
 	"fmt"
 	"math/big"
 	"runtime"
+	"sync/atomic"
 	"time"
 
 	mapset "github.com/deckarep/golang-set"
@@ -552,3 +553,18 @@ func accumulateRewards(config *params.ChainConfig, state *state.StateDB, header
 	}
 	state.AddBalance(header.Coinbase, reward)
 }
+
+// Start implements consensus.Engine, starting the ethash engine.
+func (ethash *Ethash) Start() {
+	atomic.StoreInt32(&ethash.running, 1)
+}
+
+// Stop implements consensus.Engine, stopping the ethash engine.
+func (ethash *Ethash) Stop() {
+	atomic.StoreInt32(&ethash.running, 0)
+}
+
+// IsRunning implements consensus.Engine, returning an indication if the ethash engine is currently mining.
+func (ethash *Ethash) IsRunning() bool {
+	return atomic.LoadInt32(&ethash.running) > 0
+}

consensus/ethash/ethash.go

@@ -428,6 +428,7 @@ type Ethash struct {
 	threads  int           // Number of threads to mine on if mining
 	update   chan struct{} // Notification channel to update mining parameters
 	hashrate metrics.Meter // Meter tracking the average hashrate
+	running  int32         // Indicator whether ethash engine is running or not.
 
 	// Remote sealer related fields
 	workCh       chan *types.Block // Notification channel to push new work to remote sealer
@@ -486,6 +487,7 @@ func NewTester() *Ethash {
 		datasets:     newlru("dataset", 1, newDataset),
 		update:       make(chan struct{}),
 		hashrate:     metrics.NewMeter(),
+		running:      1, // enable local mining by default
 		workCh:       make(chan *types.Block),
 		resultCh:     make(chan *types.Block),
 		fetchWorkCh:  make(chan *sealWork),
@@ -680,6 +682,20 @@ func (ethash *Ethash) APIs(chain consensus.ChainReader) []rpc.API {
 	}
 }
 
+// StartMining starts the ethash engine with the given number of threads.
+// If threads is nil the number of workers started is equal to the number of logical CPUs
+// that are usable by this process. If threads is 0, than local/cpu mining will be disabled.
+// If mining is already running, this method adjust the number of threads allowed to use.
+func (ethash *Ethash) StartMining(threads *int) {
+	if threads == nil {
+		threads = new(int)
+	} else if *threads == 0 {
+		*threads = -1 // Disable local/cpu mining.
+	}
+	ethash.Start()
+	ethash.SetThreads(*threads)
+}
+
 // SeedHash is the seed to use for generating a verification cache and the mining
 // dataset.
 func SeedHash(block uint64) []byte {

consensus/ethash/sealer.go

@@ -50,6 +50,10 @@ func (ethash *Ethash) Seal(chain consensus.ChainReader, block *types.Block, stop
 	if ethash.shared != nil {
 		return ethash.shared.Seal(chain, block, stop)
 	}
+	// Make sure ethash engine is started.
+	if !ethash.IsRunning() {
+		return nil, consensus.ErrEngineNotStart
+	}
 	// Create a runner and the multiple search threads it directs
 	abort := make(chan struct{})