This section is a brief description of DaemonCore. DaemonCore is a library that is shared among most of the HTCondor daemons which provides common functionality. Currently, the following daemons use DaemonCore:
Most of DaemonCore’s details are not interesting for administrators. However, DaemonCore does provide a uniform interface for the daemons to various Unix signals, and provides a common set of command-line options that can be used to start up each daemon.
DaemonCore and Unix signals¶
One of the most visible features that DaemonCore provides for administrators is that all daemons which use it behave the same way on certain Unix signals. The signals and the behavior DaemonCore provides are listed below:
- Causes the daemon to reconfigure itself.
- Causes the daemon to gracefully shutdown.
- Causes the daemon to quickly shutdown.
Exactly what gracefully and quickly means varies from daemon to daemon.
For daemons with little or no state (the condor_kbdd,
condor_collector and condor_negotiator) there is no difference,
SIGQUIT signals result in the daemon
shutting itself down quickly. For the condor_master, a graceful
shutdown causes the condor_master to ask all of its children to
perform their own graceful shutdown methods. The quick shutdown causes
the condor_master to ask all of its children to perform their own
quick shutdown methods. In both cases, the condor_master exits after
all its children have exited. In the condor_startd, if the machine is
not claimed and running a job, both the
signals result in an immediate exit. However, if the condor_startd is
running a job, a graceful shutdown results in that job writing a
checkpoint, while a fast shutdown does not. In the condor_schedd, if
there are no jobs currently running, there will be no condor_shadow
processes, and both signals result in an immediate exit. However, with
jobs running, a graceful shutdown causes the condor_schedd to ask
each condor_shadow to gracefully vacate the job it is serving, while
a quick shutdown results in a hard kill of every condor_shadow, with
no chance to write a checkpoint.
For all daemons, a reconfigure results in the daemon re-reading its configuration file(s), causing any settings that have changed to take effect. See the Introduction to Configuration section for full details on what settings are in the configuration files and what they do.
DaemonCore and Command-line Arguments¶
The second visible feature that DaemonCore provides to administrators is a common set of command-line arguments that all daemons understand. These arguments and what they do are described below:
- -a string
- Append a period character (‘.’) concatenated with string to the file name of the log for this daemon, as specified in the configuration file.
- Causes the daemon to start up in the background. When a DaemonCore process starts up with this option, it disassociates itself from the terminal and forks itself, so that it runs in the background. This is the default behavior for HTCondor daemons.
- -c filename
- Causes the daemon to use the specified filename as a full path
and file name as its global configuration file. This overrides the
CONDOR_CONFIGenvironment variable and the regular locations that HTCondor checks for its configuration file.
Use dynamic directories. The
$(EXECUTE)directories are all created by the daemon at run time, and they are named by appending the parent’s IP address and PID to the value in the configuration file. These values are then inherited by all children of the daemon invoked with this -d argument. For the condor_master, all HTCondor processes will use the new directories. If a condor_schedd is invoked with the -d argument, then only the condor_schedd daemon and any condor_shadow daemons it spawns will use the dynamic directories (named with the condor_schedd daemon’s PID).
Note that by using a dynamically-created spool directory named by the IP address and PID, upon restarting daemons, jobs submitted to the original condor_schedd daemon that were stored in the old spool directory will not be noticed by the new condor_schedd daemon, unless you manually specify the old, dynamically-generated
SPOOLdirectory path in the configuration of the new condor_schedd daemon.
Causes the daemon to start up in the foreground. Instead of forking, the daemon runs in the foreground.
NOTE: When the condor_master starts up daemons, it does so with the -f option, as it has already forked a process for the new daemon. There will be a -f in the argument list for all HTCondor daemons that the condor_master spawns.
- -k filename
- For non-Windows operating systems, causes the daemon to read out a PID from the specified filename, and send a SIGTERM to that process. The daemon started with this optional argument waits until the daemon it is attempting to kill has exited.
- -l directory
- Overrides the value of
LOGas specified in the configuration files. Primarily, this option is used with the condor_kbdd when it needs to run as the individual user logged into the machine, instead of running as root. Regular users would not normally have permission to write files into HTCondor’s log directory. Using this option, they can override the value of
LOGand have the condor_kbdd write its log file into a directory that the user has permission to write to.
- -local-name name
- Specify a local name for this instance of the daemon. This local name will be used to look up configuration parameters. The Configuration File Macros section contains details on how this local name will be used in the configuration.
- -p port
- Causes the daemon to bind to the specified port as its command socket. The condor_master daemon uses this option to ensure that the condor_collector and condor_negotiator start up using well-known ports that the rest of HTCondor depends upon them using.
- -pidfile filename
Causes the daemon to write out its PID (process id number) to the specified filename. This file can be used to help shutdown the daemon without first searching through the output of the Unix ps command.
Since daemons run with their current working directory set to the value of
LOG, if a full path (one that begins with a slash character,
/) is not specified, the file will be placed in the
- Quiet output; write less verbose error messages to
stderrwhen something goes wrong, and before regular logging can be initialized.
- -r minutes
- Causes the daemon to set a timer, upon expiration of which, it sends itself a SIGTERM for graceful shutdown.
- Causes the daemon to print out its error message to
stderrinstead of its specified log file. This option forces the -f option.
- Causes the daemon to print out version information and exit.