Posts Tagged ‘Example’

A recipe for starting cloud images with virt-install

January 8, 2014

I’m a fan of using the same OS image across multiple environments. So, I’m a fan of using cloud images, those with cloud-init installed, even outside of a cloud.

The trick to this is properly triggering the NoCloud datasource. It’s actually more of a pain than you would think, and not very well documented. Here’s my recipe (from Fedora 19),

xz -d Fedora-x86_64-20-Beta-20131106-sda.raw.xz

echo "#cloud-config\npassword: fedora\nchpasswd: {expire: False}\nssh_pwauth: True" > user-data

cp Fedora-x86_64-20-Beta-20131106-sda.raw.xz $NAME.raw
echo "instance-id: $NAME; local-hostname: $NAME" > meta-data
genisoimage -output $NAME-cidata.iso -volid cidata -joliet -rock user-data meta-data
virt-install --import --name $NAME --ram 512 --vcpus 2 --disk $NAME.raw --disk $NAME-cidata.iso,device=cdrom --network bridge=virbr0

Login with username fedora and password fedora.

You’ll also want to boost the amount of RAM if you plan on doing anything interesting in the guest.

You can repeat lines 6 through 10 to start multiple guests, just make sure to change the name in line 6.

If you want to ssh into the guest, you can use virsh console, login and use ifconfig / ip addr to find the address. Or, you can use arp -e and virsh dumpxml to match MAC addresses. Or just arp -e before and after starting the guest.

Note, you need to follow the meta-data and user-data lines very closely. If you don’t you may not trigger the NoCloud datasource properly. It took me a number of tries to get it right. Also, the volid needs to be “cidata” or it won’t be found, which turns out to be a configurable parameter for NoCloud. The chpasswd bit is to prevent being prompted to change your password the first time you login.

Consider becoming a fan of consistent OS images across your environments too!

Configuration and policy evaluation

December 10, 2012

Figuring out how evaluation happens in configuration and policy is a common problem. The confusion is justified.

Configuration provides substitution with $() syntax, while policy is full ClassAd language evaluation without $() syntax.

Configuration is all the parameters listed in files discoverable with condor_config_val -config.

$ condor_config_val -config
Configuration source:
Local configuration sources:

Policy is the ClassAd expression found on the right-hand side of specific configuration parameters. For instance,

$ condor_config_val -v START
START: ( (KeyboardIdle > 15 * 60) && ( ((LoadAvg - CondorLoadAvg) <= 0.3) || (State != "Unclaimed" && State != "Owner")) )
  Defined in '/etc/condor/condor_config', line 753.

Configuration evaluation allows for substitution of configuration parameters with $().

$ cat /etc/condor/condor_config | head -n753 | tail -n1

$ condor_config_val -v UWCS_START
UWCS_START: ( (KeyboardIdle > 15 * 60) && ( ((LoadAvg - CondorLoadAvg) <= 0.3) || (State != "Unclaimed" && State != "Owner")) )
  Defined in '/etc/condor/condor_config', line 808.

$ cat /etc/condor/condor_config | head -n808 | tail -n3
UWCS_START	= ( (KeyboardIdle > $(StartIdleTime)) \
                    && ( $(CPUIdle) || \
                         (State != "Unclaimed" && State != "Owner")) )

Here START is actually the value of UWCS_START, provided by $(UWCS_START).

The substitution is recursive. Explore /etc/condor/condor_config and the JustCPU parameter. It is actually a parameter that is never read by daemons or tools. It is only useful in other configuration parameters. It’s shorthand.

Policy evaluation is full ClassAd expression evaluation. The evaluation happens at the appropriate times while daemons or tools are running.

Taking START as an example, the words KeyboardIdle, LoadAvg, CondorLoadAvg, State are attributes found on machine ads, and it is evaluated by the condor_startd and condor_negotiator to figure out if a job is allowed to start on a resource.

$ condor_status -l slot1@eeyore.local | grep -e ^KeyboardIdle -e ^LoadAvg -e ^CondorLoadAvg -e ^State
KeyboardIdle = 0
LoadAvg = 0.290000
CondorLoadAvg = 0.0
State = "Owner"

Evaluation happens by recursively evaluating those attributes. The expression ((KeyboardIdle > 15 * 60) && (((LoadAvg - CondorLoadAvg) <= 0.3) || (State != "Unclaimed" && State != "Owner"))) becomes ((0 > 15 * 60) && (((0.29 - 0.0) <= 0.3) || ("Owner" != "Unclaimed" && "Owner" != "Owner"))). And so forth.

That’s it.

Pre and Post job scripts

October 29, 2012

Condor has a few ways to run programs associated with a job, beyond the job itself. If you’re an administrator, you can use the USER_JOB_WRAPPER. If you’re a user who is friends with your administrator, you can use Job Hooks. If you are ambitious, you can wrap all your jobs in a script that runs programs before and after your actual job.

Or, you can use the PreCmd and PostCmd attributes on your job. They specify programs to run before and after your job executes. By example,

$ cat prepost.job
cmd = /bin/sleep
args = 1

log = prepost.log
output = prepost.out
error = prepost.err

+PreCmd = &quot;pre_script&quot;
+PostCmd = &quot;post_script&quot;

transfer_input_files = pre_script, post_script
should_transfer_files = always

$ cat pre_script
date &gt; prepost.pre

$ cat post_script
date &gt;


$ condor_submit prepost.job
Submitting job(s)
1 job(s) submitted to cluster 1.

...wait a few seconds, or 259...

$ cat prepost.pre
Sun Oct 14 18:06:00 UTC 2012

$ cat
Sun Oct 14 18:06:02 UTC 2012

That’s about it, except for some gotchas.

  • transfer_input_files is manual and required
  • The scripts are run from Iwd, you can’t use +PreCmd=”/bin/blah”, instead +PreCmd=”blah” and transfer_input_files=/bin/blah
  • should_transfer_files = always, scripts are run from Iwd, if run local to the Schedd Iwd will be in the EXECUTE directory but the scripts won’t be
  • Script stdout/err and exit code are ignored
  • You must use +Attr=”” syntax, +PreCmd=pre_script won’t work
  • There is no option of arguments for the scripts
  • There is no starter environment, thus no $_CONDOR_JOB_AD/$_CONDOR_MACHINE_AD, but you can find .job_ad and .machine_ad in $_CONDOR_SCRATCH_DIR
  • Make sure the scripts are executable, otherwise the job will be put on hold with a reason similar to: Error from 127-0-0-1.NO_DNS: Failed to execute ‘…/dir_30626/pre_script’: Permission denied
  • PostCmd is broken in condor 7.6, but works in 7.8

Advanced scheduling: Execute periodically with cron jobs

October 15, 2012

If you want to run a job periodically you could repeatedly submit jobs, or qedit existing jobs after they run, but both of those options are a kludge. Instead, the condor_schedd provides support for cron-like jobs as a first-class citizen.

The cron-like feature builds on the ability to defer job execution. However, instead of using deferral_time, commands analogous to crontab(5) fields are available. cron_month, cron_day_of_month, cron_day_of_week, cron_hour, and cron_minute all behave as you would expect, and default to * when not provided.

To run a job every two minutes,

executable = /bin/date
log = cron.log
output = cron.out
error = cron.err

cron_minute = 0-59/2
on_exit_remove = false


Note – on_exit_remove = false is required or the job will only be run once. It is arguable that on_exit_remove should default to false for jobs using cron_* commands.

After submitting and waiting 10 minutes, results can be found in the cron.log file.

$ grep ^00 cron.log
000 (009.000.000) 09/09 09:22:46 Job submitted from host: &lt;;
001 (009.000.000) 09/09 09:24:00 Job executing on host: &lt;;
006 (009.000.000) 09/09 09:24:00 Image size of job updated: 75
004 (009.000.000) 09/09 09:24:00 Job was evicted.
001 (009.000.000) 09/09 09:26:00 Job executing on host: &lt;;
004 (009.000.000) 09/09 09:26:00 Job was evicted.
001 (009.000.000) 09/09 09:28:00 Job executing on host: &lt;;
004 (009.000.000) 09/09 09:28:00 Job was evicted.
001 (009.000.000) 09/09 09:30:00 Job executing on host: &lt;;
004 (009.000.000) 09/09 09:30:00 Job was evicted.
001 (009.000.000) 09/09 09:32:00 Job executing on host: &lt;;
004 (009.000.000) 09/09 09:32:01 Job was evicted.

Note – the job appears to be evicted instead of terminated. What really happens is the job remains in the queue on termination. This is arguably a poor choice of wording in the log.

Just like for job deferral, there is no guarantee resources will be available at exactly the right time to run the job. cron_prep_time and cron_window provide a means to introduce tolerance.

Common question: What happens when a job takes longer than the time between defined starts, i.e. job takes 30 minutes to complete and is set to be run every 15 minutes?

Answer: The job will run serially. It will not stack up. The job does not need to serialize itself.

Note – a common complication, arguably a bug, which occurs only in pools with little or no new jobs being submitted, is that matchmaking must happen in time for the job dispatch. The Schedd does not publish a new Submitter Ad for the cron job’s owner when the job completes. This means that submitter ad the Negotiator sees may have zero idle jobs, resulting in no new match being handed out to dispatch the job on the next time it is set to execute.


Advanced scheduling: Execute in the future with job deferral

September 24, 2012

One advanced scheduling feature of Condor is the ability to set a time, in the future, when a job should be run. This is called a deferral time.

Using the deferral_time command, you simply specify a time, in seconds since EPOCH, when your job should run:

executable = /bin/date
log = deferral.log
output = deferral.out
error = deferral.err

deferral_time = 1357016400


Use date(1) to generate the deferral_time.

$ date -d @1357016400
Tue Jan  1 00:00:00 EST 2013
$ date +%s -d &quot;2013-01-01 00:00:00&quot;

After submitting the job and waiting until 1 Jan 2013, you can see the result by looking in deferral.log and deferral.out.

$ grep ^00 deferral.log
000 (001.000.000) 08/15 22:33:00 Job submitted from host: &lt;;
001 (001.000.000) 01/01 00:00:00 Job executing on host: &lt;;
006 (001.000.000) 01/01 00:00:00 Image size of job updated: 75
005 (001.000.000) 01/01 00:00:00 Job terminated.

$ cat deferral.out
Tue Jan  1 00:00:00 EST 2013

Of course there is no guarantee that a resource will be available at a precise time in the future. A job that does not run at its deferral_time will be put on Hold for manual intervention.

To reduce the likelihood of missing the deferral_time and needing manual intervention, the deferral_prep_time and deferral_window commands are available. Respectively, they specify the amount of time before the deferral_time that the job can be matched with a resource and how long after the deferral_time execution is acceptable.

executable = /bin/date
log = deferral.log
output = deferral.out
error = deferral.err

deferral_time = 1357016400

# 1 day = 24 hour * 60 min * 60 sec = 86,400 seconds
# 1/2 day = 86,400 sec / 2 = 43,200 seconds
deferral_prep_time = 86400
deferral_window = 43200


In the example above, the job may be matched to a resource, where it will keep the resource Claimed/Busy for up to a day (deferral_prep_time) in advance of its actual run. This will make it more likely that the job will run at precisely the deferral_time. It also means that for accounting purposes, you will be charged for using the resource, though the job has not yet run.

Additionally, if the job is not matched or otherwise does not start at precisely deferral_time, it has half a day (deferral_window) to run before it is put on hold for manual intervention.

That’s it.

Submitting a DAG via Aviary using Python

September 16, 2011

Submitting individual jobs through Condor’s various interfaces is, unsurprisingly, the first thing people do. A quick second is submitting DAGs. I have previously discussed this in Java with BirdBath.

Aviary is a suite of APIs that expose Condor features via powerful, easy to use developer interfaces. It builds on experience from other implementations and takes an approach of exposing common use cases through clean abstractions, while maintaining the Condor philosophy of giving experts access to extended features.

The code is maintained in the contributions section of the Condor repository and is documented in the Grid Developer Guide.

The current implementation provides a SOAP interface for job submission, control and query. It is broken in two parts: a plugin to the condor_schedd that exposes the submission and control; and, a daemon, aviary_query_server, exposing the data querying capabilities.

Installation on Fedora 15 and beyond is a simple yum install condor-aviary. The condor-aviary package includes configuration placed in /etc/condor/config.d. A reconfig of the condor_master, to start the aviary_query_server, and restart of the condor_schedd, to load the plugin, is necessary.

Once installed, there are examples in the repository, including a python submit script.

Starting with the above, is a straightforward extension following the example.

#!/usr/bin/env python
# -*- coding: utf-8 -*-
# Copyright 2009-2011 Red Hat, Inc.
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# See the License for the specific language governing permissions and
# limitations under the License.

# uses Suds -
from suds.client import Client
import sys, pwd, os, logging, argparse

def attr_builder(type_, format):
    def attr(name, value):
        attr = client.factory.create("ns0:Attribute") = name
        attr.type = type_
        attr.value = format % (value,)
        return attr
    return attr
string_attr=attr_builder('STRING', '%s')
int_attr=attr_builder('INTEGER', '%d')
expr_attr=attr_builder('EXPRESSION', '%s')

parser = argparse.ArgumentParser(description='Submit a job remotely via SOAP.')
parser.add_argument('-v', '--verbose', action='store_true',
                    default=False, help='enable SOAP logging')
parser.add_argument('-u', '--url', action='store', nargs='?', dest='url',
                    help='http or https URL prefix to be added to cmd')
parser.add_argument('dag', action='store', help='full path to dag file')
args =  parser.parse_args()

uid = pwd.getpwuid(os.getuid())[0] or "nobody"

client = Client('file:/var/lib/condor/aviary/services/job/aviary-job.wsdl')


if args.verbose:
    print client

    result = client.service.submitJob(
        '-f -l . -Debug 3 -AutoRescue 1 -DoRescueFrom 0 -Allowversionmismatch -Lockfile %s.lock -Dag %s' % (args.dag, args.dag),
        [string_attr('Env', '_CONDOR_MAX_DAGMAN_LOG=0;_CONDOR_DAGMAN_LOG=%s.dagman.out' % (args.dag,)),
         int_attr('JobUniverse', 7),
         string_attr('UserLog', args.dag + '.dagman.log'),
         string_attr('RemoveKillSig', 'SIGUSR1'),
         expr_attr('OnExitRemove', '(ExitSignal =?= 11 || (ExitCode =!= UNDEFINED && ExitCode >= 0 && ExitCode <= 2))')]
except Exception, e:
    print 'invocation failed at: ', args.url
    print e

if result.status.code != 'OK':
    print result.status.code,'; ', result.status.text

print args.verbose and result or

%d bloggers like this: