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】： v3.0.12
- 【问题描述】： 使用了DM，从源头mysql同步数据到tidb，在同步的过程中遇到这样的错误，请问一下如何处理？
query-status task_51saas { “result”: true, “msg”: “”, “workers”: [ { “result”: true, “worker”: “192.168.15.118:8262”, “msg”: “”, “subTaskStatus”: [ { “name”: “task_51saas”, “stage”: “Running”, “unit”: “Sync”, “result”: null, “unresolvedDDLLockID”: “”, “sync”: { “totalEvents”: “0”, “totalTps”: “0”, “recentTps”: “0”, “masterBinlog”: “(mysql-bin.000024, 83076819)”, “masterBinlogGtid”: “”, “syncerBinlog”: “(mysql-bin|000001.000023, 85753875)”, “syncerBinlogGtid”: “”, “blockingDDLs”: [ ], “unresolvedGroups”: [ ], “synced”: false } } ], “relayStatus”: { “masterBinlog”: “(mysql-bin.000024, 83076819)”, “masterBinlogGtid”: “”, “relaySubDir”: “1826f70a-bd8f-11e9-a897-0cc47ac5691a.000001”, “relayBinlog”: “(mysql-bin.000023, 85753875)”, “relayBinlogGtid”: “”, “relayCatchUpMaster”: false, “stage”: “Paused”, “result”: { “isCanceled”: false, “errors”: [ { “Type”: “UnknownError”, “msg”: “[code=30012:class=relay-unit:scope=upstream:level=high] start reader for UUID 1826f70a-bd8f-11e9-a897-0cc47ac5691a.000001: start sync from position (mysql-bin.000023, 85753875): dial tcp 192.168.15.143:3306: connect: connection refused\ngithub.com/pingcap/dm/pkg/terror.(*Error).Delegate\ \t/home/jenkins/agent/workspace/build_dm_master/go/src/github.com/pingcap/dm/pkg/terror/terror.go:267\ngithub.com/pingcap/dm/pkg/binlog/reader.(*TCPReader).StartSyncByPos\ \t/home/jenkins/agent/workspace/build_dm_master/go/src/github.com/pingcap/dm/pkg/binlog/reader/tcp.go:79\ngithub.com/pingcap/dm/relay/reader.(*reader).setUpReaderByPos\ \t/home/jenkins/agent/workspace/build_dm_master/go/src/github.com/pingcap/dm/relay/reader/reader.go:166\ngithub.com/pingcap/dm/relay/reader.(*reader).Start\ \t/home/jenkins/agent/workspace/build_dm_master/go/src/github.com/pingcap/dm/relay/reader/reader.go:111\ngithub.com/pingcap/dm/relay.(*Relay).setUpReader\ \t/home/jenkins/agent/workspace/build_dm_master/go/src/github.com/pingcap/dm/relay/relay.go:610\ngithub.com/pingcap/dm/relay.(*Relay).process\ \t/home/jenkins/agent/workspace/build_dm_master/go/src/github.com/pingcap/dm/relay/relay.go:304\ngithub.com/pingcap/dm/relay.(*Relay).Process\ \t/home/jenkins/agent/workspace/build_dm_master/go/src/github.com/pingcap/dm/relay/relay.go:191\ngithub.com/pingcap/dm/dm/worker.(*realRelayHolder).run\ \t/home/jenkins/agent/workspace/build_dm_master/go/src/github.com/pingcap/dm/dm/worker/relay.go:167\ngithub.com/pingcap/dm/dm/worker.(*realRelayHolder).Start.func1\ \t/home/jenkins/agent/workspace/build_dm_master/go/src/github.com/pingcap/dm/dm/worker/relay.go:143\ runtime.goexit\ \t/usr/local/go/src/runtime/asm_amd64.s:1357”, “error”: null } ], “detail”: null } }, “sourceID”: “mysql-replica-01” } ] } 若提问为性能优化、故障排查类问题，请下载脚本运行。终端输出的打印结果，请务必全选并复制粘贴上传。