为提高效率，提问时请提供以下信息，问题描述清晰可优先响应。
- 【TiDB 版本】：v4.0.0-rc
- 【问题描述】：备份失败
I0610 04:13:45.140346 1 backup.go:92] [2020/06/10 04:13:45.140 +00:00] [INFO] [client.go:394] [“backup range finished”] [take=22m33.881456578s] I0610 04:13:45.140365 1 backup.go:92] [2020/06/10 04:13:45.140 +00:00] [INFO] [client.go:329] [“Backup Ranges”] [take=22m43.228012075s] I0610 04:13:45.141084 1 backup.go:92] [2020/06/10 04:13:45.140 +00:00] [INFO] [client_batch.go:351] [“batchRecvLoop fails when receiving, needs to reconnect”] [target=tidb-gid-gejb-102-tikv-2.tidb-gid-gejb-102-tikv-peer.tidb-gid-gejb-102.svc:20160] [error=“rpc error: code = Unavailable desc = transport is closing”] I0610 04:13:45.141208 1 backup.go:92] [2020/06/10 04:13:45.141 +00:00] [INFO] [client_batch.go:351] [“batchRecvLoop fails when receiving, needs to reconnect”] [target=tidb-gid-gejb-102-tikv-2.tidb-gid-gejb-102-tikv-peer.tidb-gid-gejb-102.svc:20160] [error=“rpc error: code = Unavailable desc = transport is closing”] I0610 04:13:45.141309 1 backup.go:92] [2020/06/10 04:13:45.141 +00:00] [INFO] [client_batch.go:351] [“batchRecvLoop fails when receiving, needs to reconnect”] [target=tidb-gid-gejb-102-tikv-2.tidb-gid-gejb-102-tikv-peer.tidb-gid-gejb-102.svc:20160] [error=“rpc error: code = Unavailable desc = transport is closing”] I0610 04:13:45.141323 1 backup.go:92] [2020/06/10 04:13:45.141 +00:00] [INFO] [client_batch.go:351] [“batchRecvLoop fails when receiving, needs to reconnect”] [target=tidb-gid-gejb-102-tikv-2.tidb-gid-gejb-102-tikv-peer.tidb-gid-gejb-102.svc:20160] [error=“rpc error: code = Unavailable desc = transport is closing”] I0610 04:13:45.160145 1 backup.go:92] [2020/06/10 04:13:45.160 +00:00] [INFO] [domain.go:607] [“domain closed”] [“take time”=19.704649ms] I0610 04:13:45.160509 1 backup.go:92] [2020/06/10 04:13:45.160 +00:00] [INFO] [progress.go:102] [“Full backup”] progress=100.00%! I0610 04:13:45.167316 1 backup.go:92] [2020/06/10 04:13:45.167 +00:00] [INFO] [collector.go:180] [“Full backup Failed summary : total backup ranges: 2, total success: 1, total failed: 1”] [“backup total regions”=4] [unitName=“range start:7480000000000000475f720000000000000000 end:7480000000000000475f72ffffffffffffffff00”] [error=“rpc error: code = Unavailable desc = transport is closing”] [errorVerbose=“rpc error: code = Unavailable desc = transport is closing\ngithub.com/pingcap/errors.AddStack\ \t/go/pkg/mod/github.com/pingcap/errors@v0.11.5-0.20190809092503-95897b64e011/errors.go:174\ github.com/pingcap/errors.Trace\ \t/go/pkg/mod/github.com/pingcap/errors@v0.11.5-0.20190809092503-95897b64e011/juju_adaptor.go:15\ github.com/pingcap/br/pkg/backup.SendBackup\ \t/home/jenkins/agent/workspace/build_br_multi_branch_v4.0.0-rc/go/src/github.com/pingcap/br/pkg/backup/client.go:737\ github.com/pingcap/br/pkg/backup.(*Client).handleFineGrained\ \t/home/jenkins/agent/workspace/build_br_multi_branch_v4.0.0-rc/go/src/github.com/pingcap/br/pkg/backup/client.go:689\ngithub.com/pingcap/br/pkg/backup.(*Client).fineGrainedBackup.func1\ \t/home/jenkins/agent/workspace/build_br_multi_branch_v4.0.0-rc/go/src/github.com/pingcap/br/pkg/backup/client.go:528\ runtime.goexit\ \t/usr/local/go/src/runtime/asm_amd64.s:1357”] I0610 04:13:45.170027 1 backup.go:92] I0610 04:13:45.170057 1 backup.go:99] Error: rpc error: code = Unavailable desc = transport is closing I0610 04:13:55.838918 1 manager.go:207] reset cluster tidb-gid-gejb-102/tidb-gid-gejb-102-manaul-backup-1591761010 tikv_gc_life_time to 10m0s success