etcdserver: Implement running defrag if freeable space will exceed privided threshold

server/embed/config.go

@@ -314,6 +314,9 @@ type Config struct {
 	// ExperimentalWarningApplyDuration is the time duration after which a warning is generated if applying request
 	// takes more time than this value.
 	ExperimentalWarningApplyDuration time.Duration `json:"experimental-warning-apply-duration"`
+	// ExperimentalBootstrapDefragThresholdMegabytes is the minimum number of megabytes needed to be freed for etcd server to
+	// consider running defrag during bootstrap. Needs to be set to non-zero value to take effect.
+	ExperimentalBootstrapDefragThresholdMegabytes uint `json:"experimental-bootstrap-defrag-threshold-megabytes"`
 
 	// ForceNewCluster starts a new cluster even if previously started; unsafe.
 	ForceNewCluster bool `json:"force-new-cluster"`

server/embed/etcd.go

@@ -225,6 +225,7 @@ func StartEtcd(inCfg *Config) (e *Etcd, err error) {
 		WarningApplyDuration:                     cfg.ExperimentalWarningApplyDuration,
 		ExperimentalMemoryMlock:                  cfg.ExperimentalMemoryMlock,
 		ExperimentalTxnModeWriteWithSharedBuffer: cfg.ExperimentalTxnModeWriteWithSharedBuffer,
+		ExperimentalBootstrapDefragThresholdMegabytes: cfg.ExperimentalBootstrapDefragThresholdMegabytes,
 	}
 
 	if srvcfg.ExperimentalEnableDistributedTracing {