add StopMon to only stop MonAddr but keeps updating blk num (#57)

eth/mon2/monitor.go

@@ -44,6 +44,10 @@ func (m *Monitor) MonAddr(cfg PerAddrCfg, cbfn EventCallback) {
 
 	for {
 		select {
+		case <-m.stopMon:
+			log.Infoln("MonAddr:", key, "stopped")
+			return
+
 		case <-m.quit:
 			log.Infoln("MonAddr:", key, "quit")
 			return

eth/mon2/types.go

@@ -61,6 +61,8 @@ type Monitor struct {
 
 	lock sync.RWMutex // protect blkNum, can be also used to protect ec when later we support replace failed ec
 	quit chan bool    // this ch will close in m.Close so all loops know to exit
+	// support keep loopUpdateBlkNum running but stop all getLogs, needed for use case that monAddr when first start, then later knows no need, stop to save queries
+	stopMon chan bool
 }
 
 // cfg is not pointer to ensure value copy and avoid unexpected change by other code
@@ -80,15 +82,22 @@ func NewMonitor(ec EthClient, dal DAL, cfg PerChainCfg) (*Monitor, error) {
 		chainId: chid.Uint64(),
 		blkNum:  blkNum,
 		quit:    make(chan bool),
+		stopMon: make(chan bool),
 	}
 	go m.loopUpdateBlkNum()
 	return m, nil
 }
 
+// Stops all MonAddr and updating blk num to release all resources. No longer usable after this call
 func (m *Monitor) Close() {
 	close(m.quit)
 }
 
+// StopMon will quit all MonAddr loops, but keep updating blk num.
+func (m *Monitor) StopMon() {
+	close(m.stopMon)
+}
+
 // return cached block number from last BlockNumber call, no rpc, return in memory value directly
 func (m *Monitor) GetBlkNum() uint64 {
 	m.lock.RLock()