func (cfg *config) ShutdownServer(i int) {
	cfg.mu.Lock()
	defer cfg.mu.Unlock()
	cfg.disconnectUnlocked(i, cfg.All())
	cfg.net.DeleteServer(i)
	if cfg.saved[i] != nil {
		cfg.saved[i] = cfg.saved[i].Copy()
	}
	kv := cfg.kvservers[i]
	if kv != nil {
		cfg.mu.Unlock()
		kv.Kill()
		cfg.mu.Lock()
		cfg.kvservers[i] = nil
	}
}
Shutdown a server by isolating it
package raftkv
import "labrpc"
import "testing"
import "os"
import crand "crypto/rand"
import "math/big"
import "math/rand"
import "encoding/base64"
import "sync"
import "runtime"
import "raft"
import "fmt"
import "time"
import "sync/atomic"
func randstring(n int) string {
	b := make([]byte, 2*n)
	crand.Read(b)
	s := base64.URLEncoding.EncodeToString(b)
	return s[0:n]
}
func makeSeed() int64 {
	max := big.NewInt(int64(1) << 62)
	bigx, _ := crand.Int(crand.Reader, max)
	x := bigx.Int64()
	return x
}
func random_handles(kvh []*labrpc.ClientEnd) []*labrpc.ClientEnd {
	sa := make([]*labrpc.ClientEnd, len(kvh))
	copy(sa, kvh)
	for i := range sa {
		j := rand.Intn(i + 1)
		sa[i], sa[j] = sa[j], sa[i]
	}
	return sa
}
type config struct {
	mu           sync.Mutex
	t            *testing.T
	net          *labrpc.Network
	n            int
	kvservers    []*KVServer
	saved        []*raft.Persister
	endnames     [][]string  
	clerks       map[*Clerk][]string
	nextClientId int
	maxraftstate int
	start        time.Time  
	t0    time.Time  
	rpcs0 int        
	ops   int32      
}
func (cfg *config) checkTimeout() {
	if !cfg.t.Failed() && time.Since(cfg.start) > 120*time.Second {
		cfg.t.Fatal("test took longer than 120 seconds")
	}
}
func (cfg *config) cleanup() {
	cfg.mu.Lock()
	defer cfg.mu.Unlock()
	for i := 0; i < len(cfg.kvservers); i++ {
		if cfg.kvservers[i] != nil {
			cfg.kvservers[i].Kill()
		}
	}
	cfg.net.Cleanup()
	cfg.checkTimeout()
}
func (cfg *config) LogSize() int {
	logsize := 0
	for i := 0; i < cfg.n; i++ {
		n := cfg.saved[i].RaftStateSize()
		if n > logsize {
			logsize = n
		}
	}
	return logsize
}
func (cfg *config) SnapshotSize() int {
	snapshotsize := 0
	for i := 0; i < cfg.n; i++ {
		n := cfg.saved[i].SnapshotSize()
		if n > snapshotsize {
			snapshotsize = n
		}
	}
	return snapshotsize
}
func (cfg *config) connectUnlocked(i int, to []int) {
	for j := 0; j < len(to); j++ {
		endname := cfg.endnames[i][to[j]]
		cfg.net.Enable(endname, true)
	}
	for j := 0; j < len(to); j++ {
		endname := cfg.endnames[to[j]][i]
		cfg.net.Enable(endname, true)
	}
}
func (cfg *config) connect(i int, to []int) {
	cfg.mu.Lock()
	defer cfg.mu.Unlock()
	cfg.connectUnlocked(i, to)
}
func (cfg *config) disconnectUnlocked(i int, from []int) {
	for j := 0; j < len(from); j++ {
		if cfg.endnames[i] != nil {
			endname := cfg.endnames[i][from[j]]
			cfg.net.Enable(endname, false)
		}
	}
	for j := 0; j < len(from); j++ {
		if cfg.endnames[j] != nil {
			endname := cfg.endnames[from[j]][i]
			cfg.net.Enable(endname, false)
		}
	}
}
func (cfg *config) disconnect(i int, from []int) {
	cfg.mu.Lock()
	defer cfg.mu.Unlock()
	cfg.disconnectUnlocked(i, from)
}
func (cfg *config) All() []int {
	all := make([]int, cfg.n)
	for i := 0; i < cfg.n; i++ {
		all[i] = i
	}
	return all
}
func (cfg *config) ConnectAll() {
	cfg.mu.Lock()
	defer cfg.mu.Unlock()
	for i := 0; i < cfg.n; i++ {
		cfg.connectUnlocked(i, cfg.All())
	}
}
func (cfg *config) partition(p1 []int, p2 []int) {
	cfg.mu.Lock()
	defer cfg.mu.Unlock()
	for i := 0; i < len(p1); i++ {
		cfg.disconnectUnlocked(p1[i], p2)
		cfg.connectUnlocked(p1[i], p1)
	}
	for i := 0; i < len(p2); i++ {
		cfg.disconnectUnlocked(p2[i], p1)
		cfg.connectUnlocked(p2[i], p2)
	}
}
func (cfg *config) makeClient(to []int) *Clerk {
	cfg.mu.Lock()
	defer cfg.mu.Unlock()
	ends := make([]*labrpc.ClientEnd, cfg.n)
	endnames := make([]string, cfg.n)
	for j := 0; j < cfg.n; j++ {
		endnames[j] = randstring(20)
		ends[j] = cfg.net.MakeEnd(endnames[j])
		cfg.net.Connect(endnames[j], j)
	}
	ck := MakeClerk(random_handles(ends))
	cfg.clerks[ck] = endnames
	cfg.nextClientId++
	cfg.ConnectClientUnlocked(ck, to)
	return ck
}
func (cfg *config) deleteClient(ck *Clerk) {
	cfg.mu.Lock()
	defer cfg.mu.Unlock()
	v := cfg.clerks[ck]
	for i := 0; i < len(v); i++ {
		os.Remove(v[i])
	}
	delete(cfg.clerks, ck)
}
func (cfg *config) ConnectClientUnlocked(ck *Clerk, to []int) {
	endnames := cfg.clerks[ck]
	for j := 0; j < len(to); j++ {
		s := endnames[to[j]]
		cfg.net.Enable(s, true)
	}
}
func (cfg *config) ConnectClient(ck *Clerk, to []int) {
	cfg.mu.Lock()
	defer cfg.mu.Unlock()
	cfg.ConnectClientUnlocked(ck, to)
}
func (cfg *config) DisconnectClientUnlocked(ck *Clerk, from []int) {
	endnames := cfg.clerks[ck]
	for j := 0; j < len(from); j++ {
		s := endnames[from[j]]
		cfg.net.Enable(s, false)
	}
}
func (cfg *config) DisconnectClient(ck *Clerk, from []int) {
	cfg.mu.Lock()
	defer cfg.mu.Unlock()
	cfg.DisconnectClientUnlocked(ck, from)
}