14.6 Tracking System Failures
14.6.1 System Failures
The scheduler has a number of dependencies which may cause failures if not satisfied. These dependencies are in the areas of disk space, network access, memory, and processor utilization.
14.6.1.1 Disk Space
The scheduler utilizes a number of files. If the file system is full or otherwise inaccessible, the following behaviors might be noted:
| File | Failure |
| maui.pid | scheduler cannot perform single instance check |
| maui.ck* | scheduler cannot store persistent record of reservations, jobs, policies, summary statistics, etc. |
| maui.cfg | scheduler cannot load local configuration |
| log/* | scheduler cannot log activities |
| stats/* | scheduler cannot write job records |
14.6.1.2 Network
The scheduler utilizes a number of socket connections to perform basic functions. Network failures may affect the following facilities.
| Network Connection | Failure |
| scheduler client | scheduler client commands fail |
| resource manager | scheduler is unable to load/update information regarding nodes and jobs |
| allocation manager | scheduler is unable to validate account access or reserve/debit account balances |
14.6.1.3 Memory
Depending on cluster size and configuration, the scheduler may require up to 50 MB of memory on the server host. If inadequate memory is available, multiple aspects of scheduling may be negatively affected. The scheduler log files should indicate is memory failures are detected and mark any such messages with the ERROR or ALERT keywords.
14.6.1.4 Processor Utilization
On a heavily loaded system, the scheduler may appear sluggish and unresponsive. However no direct failures should result from this slowdown. Indirect failures may include timeouts of peer services (such as the resource manager or allocation manager) or timeouts of client commands. All timeouts should be recorded in the scheduler log files.
14.6.2 Internal Errors
The Maui scheduling system contains features to assist in diagnosing internal failures. If the scheduler exits unexpectedly, the scheduler logs may provide information regarding the cause. If no reason can be determined, use of a debugger may be required.
14.6.2.1 Logs
The first step in any exit failure is to check the last few lines of the scheduler log. In many cases, the scheduler may have exited due to misconfiguration or detected system failures. The last few lines of the log should indicate why the scheduler exited and what changes would be required to correct the situation. If the scheduler did not intentionally exit, increasing the LOGLEVEL parameter to 7 or higher, may help isolate the problem.
14.6.2.1 Tracing the Failure with a Debugger
If the scheduler did not intentionally exit due detected environmental conditions, use of a debugger may assist in pursuing the problem further. The fastest method to isolate such situations is to launch the scheduler under the debugger and run it until the failure occurs. Use of the MAUIDEBUG environment variable will prevent the scheduler from backgrounding itself and allow the debugger to remain attached. The example below describes a standard debugging session.
> export MAUIDEBUG=yes > gdb maui (gdb) r ... signal SIGILL received (gdb) where #0 MPBSJobStart() MPBSI.c:2013 #1 MRMJobStart() MRM.c:1107 #2 main() MSys.c:372
The debugger output should locate the source of the failure and help isolate the root cause.
14.6.3 Reporting Failures
If an internal failure is detected on your system, the information of greatest value to developers in isolating the problem will be the output of the gdb where subcommand and a printout of all variables associated with the failure. In addition, a level 7 log covering the failure can also help in determining the environment which caused the failure. This information should be sent to help@supercluster.org.