Optional fields in grok pattern are not working

Elastic Stack Logstash
1

Following are my log lines:

Timestamp: 27-05-2016 13:25:17
Title:Customer.GetCustomer()
Message: Searched Customers for number : 123
InnerException: An error has occurred
StackTrace: An error has occurred
Machine: PQR

Timestamp: 27-05-2016 13:25:17
Title:Customer.GetCustomer()
Message: Searching Customers for number : 123
Machine: PQR

Timestamp: 27-05-2016 13:25:17
Title:Customer.GetCustomer()
Message: Searching Customers for number : 123
StackTrace: An error has occurred
Some exception has taken place
Machine: PQR

Fields like 'InnerException' and 'StackTrace' are optional in my log.
Following is the grok pattern which I have constructed, but its not working.
'InnerException' and 'Trace' are becoming part of 'Message' field, they are not getting created as separate fields, if present in log.

(?m)%{DATESTAMP:Timestamp}\s+%{TITLE:ServiceTitle}\s+%{MESSAGE:ServiceMessage}(\s+%{IEXCEPTION:InnerException})?(\s+%{TRACE:Trace})?\s+%{MACHINE:ServiceMachine}

The extra patterns used are:
TITLE ^\sTitle:.+
MESSAGE ^\sMessage:.+
IEXCEPTION ^\sInnerException:.+
TRACE ^\sStackTrace:.+
MACHINE ^\s*Machine:.\S+

The multi-line filter applied is:
^\Timestamp

Negate the multi-line regex:
True

Can you please tell me, what is wrong in my grok pattern? And how 'InnerException' and 'Trace' will get created as separate fields, if present in log lines.

2

The problem is that .+ is greedy. If it can gobble up your optional InnerException and Trace captures it will. Perhaps you can try to match everything up to a newline character instead? I'm not sure \n works here, but if it does I'd expect

(?m)Timestamp: %{DATESTAMP:Timestamp}\nTitle: %{TITLE:ServiceTitle}\nMessage: %{MESSAGE:ServiceMessage}\n(InnerException: %{IEXCEPTION:InnerException}\n)?(StackTrace: %{TRACE:Trace}\n)?Machine: %{MACHINE:ServiceMachine}

to work.