mining: Refactor policy into its own struct.

This introduces the concept of a mining policy struct which is used to
control block template generation instead of directly accessing the
config struct.  This is a step toward decoupling the mining code from
the internals of btcd.  Ultimately the intent is to create a separate
mining package.

cpuminer.go

@@ -52,6 +52,7 @@ var (
 // system which is typically sufficient.
 type CPUMiner struct {
 	sync.Mutex
+	policy            *miningPolicy
 	server            *server
 	numWorkers        uint32
 	started           bool
@@ -302,7 +303,7 @@ out:
 		// Create a new block template using the available transactions
 		// in the memory pool as a source of transactions to potentially
 		// include in the block.
-		template, err := NewBlockTemplate(m.server, payToAddr)
+		template, err := NewBlockTemplate(m.policy, m.server, payToAddr)
 		m.submitBlockLock.Unlock()
 		if err != nil {
 			errStr := fmt.Sprintf("Failed to create new block "+
@@ -564,7 +565,7 @@ func (m *CPUMiner) GenerateNBlocks(n uint32) ([]*wire.ShaHash, error) {
 		// Create a new block template using the available transactions
 		// in the memory pool as a source of transactions to potentially
 		// include in the block.
-		template, err := NewBlockTemplate(m.server, payToAddr)
+		template, err := NewBlockTemplate(m.policy, m.server, payToAddr)
 		m.submitBlockLock.Unlock()
 		if err != nil {
 			errStr := fmt.Sprintf("Failed to create new block "+
@@ -599,8 +600,9 @@ func (m *CPUMiner) GenerateNBlocks(n uint32) ([]*wire.ShaHash, error) {
 // newCPUMiner returns a new instance of a CPU miner for the provided server.
 // Use Start to begin the mining process.  See the documentation for CPUMiner
 // type for more details.
-func newCPUMiner(s *server) *CPUMiner {
+func newCPUMiner(policy *miningPolicy, s *server) *CPUMiner {
 	return &CPUMiner{
+		policy:            policy,
 		server:            s,
 		numWorkers:        defaultNumWorkers,
 		updateNumWorkers:  make(chan struct{}),

mining.go

@@ -40,6 +40,28 @@ const (
 	coinbaseFlags = "/P2SH/btcd/"
 )
 
+// miningPolicy houses the policy (configuration parameters) which is used to
+// control the generation of block templates.  See the documentation for
+// NewBlockTemplate for more details on each of these parameters are used.
+type miningPolicy struct {
+	// BlockMinSize is the minimum block size in bytes to be used when
+	// generating a block template.
+	BlockMinSize uint32
+
+	// BlockMaxSize is the maximum block size in bytes to be used when
+	// generating a block template.
+	BlockMaxSize uint32
+
+	// BlockPrioritySize is the size in bytes for high-priority / low-fee
+	// transactions to be used when generating a block template.
+	BlockPrioritySize uint32
+
+	// TxMinFreeFee is the minimum fee in Satoshi/kB that is required for a
+	// transaction to be treated as free for mining purposes (block template
+	// generation).  This value is in Satoshi/1000 bytes.
+	TxMinFreeFee btcutil.Amount
+}
+
 // txPrioItem houses a transaction along with extra information that allows the
 // transaction to be prioritized and track dependencies on other transactions
 // which have not been mined into a block yet.
@@ -320,53 +342,54 @@ func medianAdjustedTime(chainState *chainState, timeSource blockchain.MedianTime
 // amounts, older inputs, and small sizes have the highest priority.  Second, a
 // fee per kilobyte is calculated for each transaction.  Transactions with a
 // higher fee per kilobyte are preferred.  Finally, the block generation related
-// configuration options are all taken into account.
+// policy settings are all taken into account.
 //
 // Transactions which only spend outputs from other transactions already in the
 // block chain are immediately added to a priority queue which either
 // prioritizes based on the priority (then fee per kilobyte) or the fee per
 // kilobyte (then priority) depending on whether or not the BlockPrioritySize
-// configuration option allots space for high-priority transactions.
-// Transactions which spend outputs from other transactions in the memory pool
-// are added to a dependency map so they can be added to the priority queue once
-// the transactions they depend on have been included.
+// policy setting allots space for high-priority transactions.  Transactions
+// which spend outputs from other transactions in the memory pool are added to a
+// dependency map so they can be added to the priority queue once the
+// transactions they depend on have been included.
 //
-// Once the high-priority area (if configured) has been filled with transactions,
-// or the priority falls below what is considered high-priority, the priority
-// queue is updated to prioritize by fees per kilobyte (then priority).
+// Once the high-priority area (if configured) has been filled with
+// transactions, or the priority falls below what is considered high-priority,
+// the priority queue is updated to prioritize by fees per kilobyte (then
+// priority).
 //
-// When the fees per kilobyte drop below the TxMinFreeFee configuration option,
-// the transaction will be skipped unless there is a BlockMinSize set, in which
-// case the block will be filled with the low-fee/free transactions until the
-// block size reaches that minimum size.
+// When the fees per kilobyte drop below the TxMinFreeFee policy setting, the
+// transaction will be skipped unless the BlockMinSize policy setting is
+// nonzero, in which case the block will be filled with the low-fee/free
+// transactions until the block size reaches that minimum size.
 //
 // Any transactions which would cause the block to exceed the BlockMaxSize
-// configuration option, exceed the maximum allowed signature operations per
-// block, or otherwise cause the block to be invalid are skipped.
+// policy setting, exceed the maximum allowed signature operations per block, or
+// otherwise cause the block to be invalid are skipped.
 //
 // Given the above, a block generated by this function is of the following form:
 //
 //   -----------------------------------  --  --
 //  |      Coinbase Transaction         |   |   |
 //  |-----------------------------------|   |   |
-//  |                                   |   |   | ----- cfg.BlockPrioritySize
+//  |                                   |   |   | ----- policy.BlockPrioritySize
 //  |   High-priority Transactions      |   |   |
 //  |                                   |   |   |
 //  |-----------------------------------|   | --
 //  |                                   |   |
 //  |                                   |   |
-//  |                                   |   |--- cfg.BlockMaxSize
+//  |                                   |   |--- policy.BlockMaxSize
 //  |  Transactions prioritized by fee  |   |
-//  |  until <= cfg.TxMinFreeFee        |   |
+//  |  until <= policy.TxMinFreeFee     |   |
 //  |                                   |   |
 //  |                                   |   |
 //  |                                   |   |
 //  |-----------------------------------|   |
 //  |  Low-fee/Non high-priority (free) |   |
 //  |  transactions (while block size   |   |
-//  |  <= cfg.BlockMinSize)             |   |
+//  |  <= policy.BlockMinSize)          |   |
 //   -----------------------------------  --
-func NewBlockTemplate(server *server, payToAddress btcutil.Address) (*BlockTemplate, error) {
+func NewBlockTemplate(policy *miningPolicy, server *server, payToAddress btcutil.Address) (*BlockTemplate, error) {
 	blockManager := server.blockManager
 	timeSource := server.timeSource
 	chainState := &blockManager.chainState
@@ -405,7 +428,7 @@ func NewBlockTemplate(server *server, payToAddress btcutil.Address) (*BlockTempl
 	// whether or not there is an area allocated for high-priority
 	// transactions.
 	mempoolTxns := server.txMemPool.TxDescs()
-	sortedByFee := cfg.BlockPrioritySize == 0
+	sortedByFee := policy.BlockPrioritySize == 0
 	priorityQueue := newTxPriorityQueue(len(mempoolTxns), sortedByFee)
 
 	// Create a slice to hold the transactions to be included in the
@@ -563,7 +586,7 @@ mempoolLoop:
 		// Enforce maximum block size.  Also check for overflow.
 		txSize := uint32(tx.MsgTx().SerializeSize())
 		blockPlusTxSize := blockSize + txSize
-		if blockPlusTxSize < blockSize || blockPlusTxSize >= cfg.BlockMaxSize {
+		if blockPlusTxSize < blockSize || blockPlusTxSize >= policy.BlockMaxSize {
 			minrLog.Tracef("Skipping tx %s because it would exceed "+
 				"the max block size", tx.Sha())
 			logSkippedDeps(tx, deps)
@@ -601,14 +624,14 @@ mempoolLoop:
 		// Skip free transactions once the block is larger than the
 		// minimum block size.
 		if sortedByFee &&
-			prioItem.feePerKB < int64(cfg.minRelayTxFee) &&
-			blockPlusTxSize >= cfg.BlockMinSize {
+			prioItem.feePerKB < int64(policy.TxMinFreeFee) &&
+			blockPlusTxSize >= policy.BlockMinSize {
 
 			minrLog.Tracef("Skipping tx %s with feePerKB %.2f "+
-				"< minTxRelayFee %d and block size %d >= "+
+				"< TxMinFreeFee %d and block size %d >= "+
 				"minBlockSize %d", tx.Sha(), prioItem.feePerKB,
-				cfg.minRelayTxFee, blockPlusTxSize,
-				cfg.BlockMinSize)
+				policy.TxMinFreeFee, blockPlusTxSize,
+				policy.BlockMinSize)
 			logSkippedDeps(tx, deps)
 			continue
 		}
@@ -616,13 +639,13 @@ mempoolLoop:
 		// Prioritize by fee per kilobyte once the block is larger than
 		// the priority size or there are no more high-priority
 		// transactions.
-		if !sortedByFee && (blockPlusTxSize >= cfg.BlockPrioritySize ||
+		if !sortedByFee && (blockPlusTxSize >= policy.BlockPrioritySize ||
 			prioItem.priority <= minHighPriority) {
 
 			minrLog.Tracef("Switching to sort by fees per "+
 				"kilobyte blockSize %d >= BlockPrioritySize "+
 				"%d || priority %.2f <= minHighPriority %.2f",
-				blockPlusTxSize, cfg.BlockPrioritySize,
+				blockPlusTxSize, policy.BlockPrioritySize,
 				prioItem.priority, minHighPriority)
 
 			sortedByFee = true
@@ -634,7 +657,7 @@ mempoolLoop:
 			// too low.  Otherwise this transaction will be the
 			// final one in the high-priority section, so just fall
 			// though to the code below so it is added now.
-			if blockPlusTxSize > cfg.BlockPrioritySize ||
+			if blockPlusTxSize > policy.BlockPrioritySize ||
 				prioItem.priority < minHighPriority {
 
 				heap.Push(priorityQueue, prioItem)

rpcserver.go

@@ -1518,7 +1518,7 @@ func (state *gbtWorkState) updateBlockTemplate(s *rpcServer, useCoinbaseValue bo
 		// block template doesn't include the coinbase, so the caller
 		// will ultimately create their own coinbase which pays to the
 		// appropriate address(es).
-		blkTemplate, err := NewBlockTemplate(s.server, payAddr)
+		blkTemplate, err := NewBlockTemplate(s.policy, s.server, payAddr)
 		if err != nil {
 			return internalRPCError("Failed to create new block "+
 				"template: "+err.Error(), "")
@@ -2708,8 +2708,7 @@ func handleGetWorkRequest(s *rpcServer) (interface{}, error) {
 
 		// Choose a payment address at random.
 		payToAddr := cfg.miningAddrs[rand.Intn(len(cfg.miningAddrs))]
-
-		template, err := NewBlockTemplate(s.server, payToAddr)
+		template, err := NewBlockTemplate(s.policy, s.server, payToAddr)
 		if err != nil {
 			context := "Failed to create new block template"
 			return nil, internalRPCError(err.Error(), context)
@@ -3518,6 +3517,7 @@ func handleVerifyMessage(s *rpcServer, cmd interface{}, closeChan <-chan struct{
 type rpcServer struct {
 	started      int32
 	shutdown     int32
+	policy       *miningPolicy
 	server       *server
 	authsha      [fastsha256.Size]byte
 	limitauthsha [fastsha256.Size]byte
@@ -3995,8 +3995,9 @@ func genCertPair(certFile, keyFile string) error {
 }
 
 // newRPCServer returns a new instance of the rpcServer struct.
-func newRPCServer(listenAddrs []string, s *server) (*rpcServer, error) {
+func newRPCServer(listenAddrs []string, policy *miningPolicy, s *server) (*rpcServer, error) {
 	rpc := rpcServer{
+		policy:       policy,
 		server:       s,
 		statusLines:  make(map[int]string),
 		workState:    newWorkState(),

server.go

@@ -2322,7 +2322,15 @@ func newServer(listenAddrs []string, db database.Db, chainParams *chaincfg.Param
 	}
 	s.blockManager = bm
 	s.txMemPool = newTxMemPool(&s)
-	s.cpuMiner = newCPUMiner(&s)
+
+	// Create the mining policy based on the configuration options.
+	policy := miningPolicy{
+		BlockMinSize:      cfg.BlockMinSize,
+		BlockMaxSize:      cfg.BlockMaxSize,
+		BlockPrioritySize: cfg.BlockPrioritySize,
+		TxMinFreeFee:      cfg.minRelayTxFee,
+	}
+	s.cpuMiner = newCPUMiner(&policy, &s)
 
 	if cfg.AddrIndex {
 		ai, err := newAddrIndexer(&s)
@@ -2333,7 +2341,7 @@ func newServer(listenAddrs []string, db database.Db, chainParams *chaincfg.Param
 	}
 
 	if !cfg.DisableRPC {
-		s.rpcServer, err = newRPCServer(cfg.RPCListeners, &s)
+		s.rpcServer, err = newRPCServer(cfg.RPCListeners, &policy, &s)
 		if err != nil {
 			return nil, err
 		}