18.3. Collecting debugging information with strace, truss, or tusc

To properly troubleshoot certain situations, it can be useful to trace which system calls syslog-ng OSE performs. How this is performed depends on the platform running syslog-ng OSE. In general, note the following points:

  • When syslog-ng OSE is started, a supervisor process might stay in the foreground, while the actual syslog-ng daemon goes to the background. Always trace the background process.

  • Apart from the system calls, the time between two system calls can be important as well. Make sure that your tracing tool records the time information as well. For details on how to do that, refer to the manual page of your specific tool (for example, strace on Linux, or truss on Solaris and BSD).

  • Run your tracing tool in verbose mode, and if possible, set it to print long output strings, so the messages are not truncated.

  • When using strace, also record the output of lsof to see which files are accessed.

The following are examples for tracing system calls of syslog-ng on some platforms. The output is saved into the /tmp/syslog-ng-trace.txt file, sufficed with the PID of the related syslog-ng process.The path of the syslog-ng binary may be different for your installation, as distribution-specific packages may use different paths.

  • Linux: strace -o /tmp/trace.txt -s256 -ff -ttT /opt/syslog-ng/sbin/syslog-ng -f /opt/syslog-ng/etc/syslog-ng.conf -Fdv

  • HP-UX: tusc -f -o /tmp/syslog-ng-trace.txt -T /opt/syslog-ng/sbin/syslog-ng

  • IBM AIX and Solaris: truss -f -o /tmp/syslog-ng-trace.txt -r all -w all -u libc:: /opt/syslog-ng/sbin/syslog-ng -d -d -d

Tip

To execute these commands on an already running syslog-ng OSE process, use the -p <pid_of_syslog-ng> parameter.