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3.9 DaemonCore
This section is a brief description of DaemonCore. DaemonCore
is a library that is shared among most of the Condor daemons which
provides common functionality. Currently, the following daemons use
DaemonCore:
- condor_master
- condor_startd
- condor_schedd
- condor_collector
- condor_negotiator
- condor_kbdd
- condor_quill
- condor_dbmsd
- condor_gridmanager
- condor_credd
- condor_had
- condor_replication
- condor_transferer
- condor_job_router
- condor_lease_manager
- condor_rooster
- condor_shared_port
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.
3.9.1 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:
- SIGHUP
- Causes the daemon to reconfigure itself.
- SIGTERM
- Causes the daemon to gracefully shutdown.
- SIGQUIT
- 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, and both SIGTERM and 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 SIGTERM and SIGQUIT 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 section 3.3 on
page , Configuring Condor for full
details on what settings are in the configuration files and what they do.
3.9.2 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.
- -b
- 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 Condor 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_CONFIG environment variable and the
regular locations that Condor checks for its configuration file
which are the condor user's
home directory and the file /etc/condor/condor_config.
- -d
- Use dynamic directories.
The $(LOG), $(SPOOL), and $(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 Condor 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
SPOOL directory path in the configuration of the
new condor_schedd daemon.
- -f
- 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
Condor 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 LOG as 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 Condor's log
directory. Using this option, they can override the value of
LOG and 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.
Section 3.3.1 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 Condor 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 you don't specify a full path
(one that begins with a ``/''),
the file will be placed in the LOG directory.
- -q
- Quiet output; write less verbose error
messages to stderr when 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.
- -t
- Causes the daemon to print out its error message to
stderr instead of its specified log file. This option forces
the -f option.
- -v
- Causes the daemon to print out version information and
exit.
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Up: 3. Administrators' Manual
Previous: 3.8 The Checkpoint Server
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