les/checkpointoracle: don't lookup checkpoint more than once per minute (#21285)

* les/checkpointoracle: don't lookup checkpoint more than once per second

* les/checkpoint/oracle: change oracle checktime to 1 minute

les/checkpointoracle/oracle.go

@@ -21,7 +21,9 @@ package checkpointoracle
 
 import (
 	"encoding/binary"
+	"sync"
 	"sync/atomic"
+	"time"
 
 	"github.com/ethereum/go-ethereum/accounts/abi/bind"
 	"github.com/ethereum/go-ethereum/common"
@@ -40,6 +42,11 @@ type CheckpointOracle struct {
 
 	running  int32                                 // Flag whether the contract backend is set or not
 	getLocal func(uint64) params.TrustedCheckpoint // Function used to retrieve local checkpoint
+
+	checkMu              sync.Mutex                // Mutex to sync access to the fields below
+	lastCheckTime        time.Time                 // Time we last checked the checkpoint
+	lastCheckPoint       *params.TrustedCheckpoint // The last stable checkpoint
+	lastCheckPointHeight uint64                    // The height of last stable checkpoint
 }
 
 // New creates a checkpoint oracle handler with given configs and callback.
@@ -88,6 +95,12 @@ func (oracle *CheckpointOracle) Contract() *checkpointoracle.CheckpointOracle {
 // StableCheckpoint returns the stable checkpoint which was generated by local
 // indexers and announced by trusted signers.
 func (oracle *CheckpointOracle) StableCheckpoint() (*params.TrustedCheckpoint, uint64) {
+	oracle.checkMu.Lock()
+	defer oracle.checkMu.Unlock()
+	if time.Since(oracle.lastCheckTime) < 1*time.Minute {
+		return oracle.lastCheckPoint, oracle.lastCheckPointHeight
+	}
+	// Look it up properly
 	// Retrieve the latest checkpoint from the contract, abort if empty
 	latest, hash, height, err := oracle.contract.Contract().GetLatestCheckpoint(nil)
 	if err != nil || (latest == 0 && hash == [32]byte{}) {
@@ -103,6 +116,9 @@ func (oracle *CheckpointOracle) StableCheckpoint() (*params.TrustedCheckpoint, u
 	//
 	// In both cases, no stable checkpoint will be returned.
 	if local.HashEqual(hash) {
+		oracle.lastCheckTime = time.Now()
+		oracle.lastCheckPointHeight = height.Uint64()
+		oracle.lastCheckPoint = &local
 		return &local, height.Uint64()
 	}
 	return nil, 0