^\[(.*?)\](?:\[(.*?)\])?->([a-zA-Z ]+)
>>> for x in re.finditer(r'^\[(.*?)\](?:\[(.*?)\])?->([a-zA-Z ]+)', file, re.M):
print(x.group(1), x.group(2), x.group(3))
2018.07.10 00:30:03:109 TraceID: 8HRWSI105YVO91 IncomingTime
2018.07.10 00:30:03:109 TraceID: 8HRWSI105YVO91 IncomingData
2018.07.10 00:30:03:109 TraceID: 8HRWSI105YVO91 ThreadID
2018.07.10 00:30:03:109 TraceID: 8HRWSI105YVO91 RequestExecuteStart
2018.07.10 00:30:03:109 TraceID: 8HRWSI105YVO91 RequestInfo
2018.07.10 00:30:03:109 TraceID: 8HRWSI105YVO91 CheckUserInfo
2018.07.10 00:30:03:218 None Start RTS
2018.07.10 00:30:03:640 TraceID: 8HRWSI105YVO91 StartExecuteTask
2018.07.10 00:30:03:749 TraceID: 8HRWSI105YVO91 EndExecuteTask
2018.07.10 00:30:03:749 TraceID: 8HRWSI105YVO91 RequestExecuteEnd
2018.07.10 00:30:03:749 TraceID: 8HRWSI105YVO91 OutgoingData
^\[(.*?)\](?:\[TraceID: (.*?)\])?->([a-zA-Z ]+)