Retry connection to blockchain rpc on startup

After restart, the blockchain daemons are not immediately ready
to serve requests. Blockbook must wait for them.

bchain/coins/bch/bcashrpc.go

@@ -30,10 +30,10 @@ func NewBCashRPC(config json.RawMessage, pushHandler func(bchain.NotificationTyp
 	return s, nil
 }
 
+// Initialize initializes BCashRPC instance.
 func (b *BCashRPC) Initialize() error {
-	b.Mempool = bchain.NewUTXOMempool(b)
 
-	chainName, err := b.GetBlockChainInfo()
+	chainName, err := b.GetChainInfoAndInitializeMempool()
 	if err != nil {
 		return err
 	}

bchain/coins/btc/bitcoinrpc.go

@@ -19,17 +19,19 @@ import (
 
 // BitcoinRPC is an interface to JSON-RPC bitcoind service.
 type BitcoinRPC struct {
-	client      http.Client
-	rpcURL      string
-	user        string
-	password    string
-	Parser      bchain.BlockChainParser
-	Testnet     bool
-	Network     string
-	Mempool     *bchain.UTXOMempool
-	ParseBlocks bool
-	mq          *bchain.MQ
-	Subversion  string
+	client        http.Client
+	rpcURL        string
+	user          string
+	password      string
+	Parser        bchain.BlockChainParser
+	Testnet       bool
+	Network       string
+	Mempool       *bchain.UTXOMempool
+	ParseBlocks   bool
+	zeroMQBinding string
+	pushHandler   func(bchain.NotificationType)
+	mq            *bchain.MQ
+	Subversion    string
 }
 
 type configuration struct {
@@ -57,28 +59,45 @@ func NewBitcoinRPC(config json.RawMessage, pushHandler func(bchain.NotificationT
 	}
 
 	s := &BitcoinRPC{
-		client:      http.Client{Timeout: time.Duration(c.RPCTimeout) * time.Second, Transport: transport},
-		rpcURL:      c.RPCURL,
-		user:        c.RPCUser,
-		password:    c.RPCPass,
-		ParseBlocks: c.Parse,
-		Subversion:  c.Subversion,
+		client:        http.Client{Timeout: time.Duration(c.RPCTimeout) * time.Second, Transport: transport},
+		rpcURL:        c.RPCURL,
+		user:          c.RPCUser,
+		password:      c.RPCPass,
+		ParseBlocks:   c.Parse,
+		Subversion:    c.Subversion,
+		zeroMQBinding: c.ZeroMQBinding,
+		pushHandler:   pushHandler,
 	}
 
-	mq, err := bchain.NewMQ(c.ZeroMQBinding, pushHandler)
-	if err != nil {
-		glog.Error("mq: ", err)
-		return nil, err
-	}
-	s.mq = mq
-
 	return s, nil
 }
 
-func (b *BitcoinRPC) Initialize() error {
+// GetChainInfoAndInitializeMempool is called by Initialize and reused by other coins
+// it contacts the blockchain rpc interface for the first time
+// and if successful it connects to ZeroMQ and creates mempool handler
+func (b *BitcoinRPC) GetChainInfoAndInitializeMempool() (string, error) {
+	// try to connect to block chain and get some info
+	chainName, err := b.GetBlockChainInfo()
+	if err != nil {
+		return "", err
+	}
+
+	mq, err := bchain.NewMQ(b.zeroMQBinding, b.pushHandler)
+	if err != nil {
+		glog.Error("mq: ", err)
+		return "", err
+	}
+	b.mq = mq
+
 	b.Mempool = bchain.NewUTXOMempool(b)
 
-	chainName, err := b.GetBlockChainInfo()
+	return chainName, nil
+}
+
+// Initialize initializes BitcoinRPC instance.
+func (b *BitcoinRPC) Initialize() error {
+
+	chainName, err := b.GetChainInfoAndInitializeMempool()
 	if err != nil {
 		return err
 	}

bchain/coins/zec/zcashrpc.go

@@ -24,8 +24,13 @@ func NewZCashRPC(config json.RawMessage, pushHandler func(bchain.NotificationTyp
 	return z, nil
 }
 
+// Initialize initializes ZCashRPC instance.
 func (z *ZCashRPC) Initialize() error {
-	z.Mempool = bchain.NewUTXOMempool(z)
+	_, err := z.GetChainInfoAndInitializeMempool()
+	if err != nil {
+		return err
+	}
+
 	z.Parser = &ZCashParser{}
 	z.Testnet = false
 	z.Network = "livenet"

blockbook.go

@@ -86,6 +86,29 @@ func init() {
 	glog.CopyStandardLogTo("INFO")
 }
 
+func getBlockChainWithRetry(coin string, configfile string, pushHandler func(bchain.NotificationType), metrics *common.Metrics, seconds int) (bchain.BlockChain, error) {
+	var chain bchain.BlockChain
+	var err error
+	timer := time.NewTimer(time.Second)
+	for i := 0; ; i++ {
+		if chain, err = coins.NewBlockChain(coin, configfile, pushHandler, metrics); err != nil {
+			if i < seconds {
+				glog.Error("rpc: ", err, " Retrying...")
+				select {
+				case <-chanOsSignal:
+					return nil, errors.New("Interrupted")
+				case <-timer.C:
+					timer.Reset(time.Second)
+					continue
+				}
+			} else {
+				return nil, err
+			}
+		}
+		return chain, nil
+	}
+}
+
 func main() {
 	flag.Parse()
 
@@ -116,7 +139,7 @@ func main() {
 		glog.Fatal("Missing blockchaincfg configuration parameter")
 	}
 
-	if chain, err = coins.NewBlockChain(*coin, *blockchain, pushSynchronizationHandler, metrics); err != nil {
+	if chain, err = getBlockChainWithRetry(*coin, *blockchain, pushSynchronizationHandler, metrics, 60); err != nil {
 		glog.Fatal("rpc: ", err)
 	}