nxlog service stopped

i configured my nxlog that forwards sharepoint uls log to log server. my nxlog.conf is like below

 ## This is a sample configuration file. See the nxlog reference manual about the
## configuration options. It should be installed locally and is also available
## online at http://nxlog.org/docs/

## Please set the ROOT to the folder your nxlog was installed into,
## otherwise it will not start.

#define ROOT C:\Program Files\nxlog
define ROOT C:\Program Files (x86)\nxlog
define SHAREPOINT_LOGS D:\SHAREPOINTLOGS

Moduledir %ROOT%\modules
CacheDir %ROOT%\data
Pidfile %ROOT%\data\nxlog.pid
SpoolDir %ROOT%\data
LogFile %ROOT%\data\nxlog.log

<Extension _syslog>
    Module      xm_syslog
</Extension>
<Extension uls_parser>
      Module xm_csv
      Fields Timestamp, Process, TID, Area, Category, EventID, Level, Message, \
      Correlation
      Delimiter \t
</Extension>
<Input trace_file>
         Module im_file
# Use a file mask to read from ULS trace log files only
         File '%SHAREPOINT_LOGS%\*-????????-????.log'
     <Exec>
     # Drop header lines and empty lines
            if $raw_event =~ /^(\xEF\xBB\xBF|Timestamp)/ drop();
            else
            {
     # Remove extra spaces
              $raw_event =~ s/ +(?=\t)//g;
     # Parse with uls_parser instance defined above
              uls_parser->parse_csv();
     # Set $EventTime field (second precision only)
              $EventTime = strptime($Timestamp, "%m/%d/%Y %H:%M:%S");
     # Add $Hostname field
              $Hostname = hostname_fqdn();
            }
    </Exec>
</Input>

#<Input in>
 #   Module      im_msvistalog
# For windows 2003 and earlier use the following:
#   Module      im_mseventlog
#</Input>

<Output out>
    Module      om_udp
    Host        192.168.99.52
    Port        514
    Exec        to_syslog_bsd();
</Output>
<Output out1>
    Module      om_udp
    Host        192.168.99.52
    Port        514
    Exec        to_syslog_bsd();
</Output>
<Route 1>
    Path        trace_file => out
</Route>

nxlog sends message to log server to the one moment when he stops with the work.why?