NAME
rq v3.0.0
SYNOPSIS
rq (queue | export RQ_Q=q) mode [mode_args]* [options]*
URIS
http://rubyforge.org/projects/codeforpeople
http://codeforpeople.com/lib/ruby/rq
INSTALL
gem install rq --no-wrappers
DESCRIPTION
ruby queue (rq) is a tool used to create instant linux clusters by managing
sqlite databases as nfs mounted priority work queues. multiple instances of
rq running from multiples hosts can work from these queues to distribute
processing load to n nodes - bringing many dozens of otherwise powerful cpus
to their knees with a single blow. clearly this software should be kept out
of the hands of free radicals, seti enthusiasts, and j. safran.
the central concept of rq is that n nodes work in isolation to pull jobs from
an central nfs mounted priority work queue in a synchronized fashion. the
nodes have absolutely no knowledge of each other and all communication if done
via the queue meaning that, so long as the queue is available via nfs and a
single node is running jobs from it, the system will continue to process jobs.
there is no centralized process whatsoever - all nodes work to take jobs from
the queue and run them as fast as possible. this creates a system which load
balances automatically and is robust in face of node failures.
the first argument to any rq command is the name of the queue. this name may
be omitted if, and only if, the environment variable RQ_Q has been set to
contain the absolute path of target queue.
rq operates in one of the modes create, submit, list, status, delete, update,
query, execute, configure, snapshot, lock, backup, rotate, feed, or help.
depending on the mode of operation and the options used the meaning of
'mode_args' may change.
MODES
the following mode abbreviations exist
c => create
s => submit
l => list
ls => list
t => status
d => delete
rm => delete
u => update
q => query
e => execute
C => configure
S => snapshot
L => lock
b => backup
r => rotate
f => feed
h => help
create, c :
create a queue. the queue must be located on an nfs mounted file system
visible from all nodes intended to run jobs from it.
examples :
0) to create a queue
~ > rq /path/to/nfs/mounted/q create
or simply
~ > rq /path/to/nfs/mounted/q c
submit, s :
submit jobs to a queue to be proccesed by a feeding node. any 'mode_args'
are taken as the command to run. note that 'mode_args' are subject to shell
expansion - if you don't understand what this means do not use this feature
and pass jobs on stdin.
when running in submit mode a file may by specified as a list of commands to
run using the '--infile, -i' option. this file is taken to be a newline
separated list of commands to submit, blank lines and comments (#) are
allowed. if submitting a large number of jobs the input file method is
MUCH, more efficient. if no commands are specified on the command line rq
automatically reads them from STDIN. yaml formatted files are also allowed
as input (http://www.yaml.org/) - note that the output of nearly all rq
commands is valid yaml and may, therefore, be piped as input into the submit
command.
when submitting the '--priority, -p' option can be used here to determine
the priority of jobs. priorities may be any whole number - zero is the
default. note that submission of a high priority job will NOT supplant
currently running low priority jobs, but higher priority jobs WILL always
migrate above lower priority jobs in the queue in order that they be run as
soon as possible. constant submission of high priority jobs may create a
starvation situation whereby low priority jobs are never allowed to run.
avoiding this situation is the responsibility of the user. the only
guaruntee rq makes regarding job execution is that jobs are executed in an
'oldest highest priority' order and that running jobs are never supplanted.
examples :
0) submit the job ls to run on some feeding host
~ > rq q s ls
1) submit the job ls to run on some feeding host, at priority 9
~ > rq -p9 q s ls
2) submit 42000 jobs (quietly) from a command file, marking them as
restartable should the node they are running on reboot.
~ > wc -l cmdfile
42000
~ > rq q s --quiet --restartable < cmdfile
3) submit 42 priority 9 jobs from a command file.
~ > wc -l cmdfile
42
~ > rq -p9 q s < cmdfile
4) submit 42 priority 9 jobs from a command file, marking them as
'important' using the '--tag, -t' option.
~ > wc -l cmdfile
42
~ > rq -p9 -timportant q s < cmdfile
5) re-submit all the 'important' jobs (see 'query' section below)
~ > rq q query tag=important | rq q s
6) re-submit all jobs which are already finished (see 'list' section
below)
~ > rq q l f | rq q s
list, l, ls :
list mode lists jobs of a certain state or job id. state may be one of
pending, running, finished, dead, or all. any 'mode_args' that are numbers
are taken to be job id's to list.
states may be abbreviated to uniqueness, therefore the following shortcuts
apply :
p => pending
r => running
f => finished
d => dead
a => all
examples :
0) show everything in q
~ > rq q list all
or
~ > rq q l all
or
~ > export RQ_Q=q
~ > rq l
1) show q's pending jobs
~ > rq q list pending
2) show q's running jobs
~ > rq q list running
3) show q's finished jobs
~ > rq q list finshed
4) show job id 42
~ > rq q l 42
status, t :
status mode shows the global state the queue. there are no 'mode_args'.
the meaning of each state is as follows:
pending => no feeder has yet taken this job
running => a feeder has taken this job
finished => a feeder has finished this job
dead => rq died while running a job, has restarted, and moved
this job to the dead state
note that rq cannot move jobs into the dead state unless it has been
restarted. this is because no node has any knowledge of other nodes and
cannot possibly know if a job was started on a node that died, or is simply
taking a very long time. only the node that dies, upon restart, can
determine that is has jobs that 'were started before it started' and move
these jobs into the dead state. normally only a machine crash would cause a
job to be placed into the dead state. dead jobs are never automatically
restarted, this is the responsibility of an operator.
examples :
0) show q's status
~ > rq q t
delete, d :
delete combinations of pending, finished, dead, or jobs specified by jid.
the delete mode is capable of parsing the output of list and query modes,
making it possible to create custom filters to delete jobs meeting very
specific conditions.
'mode_args' are the same as for list.
note that it is NOT possible to delete a running job. rq has a
decentralized architechture which means that compute nodes are completely
independant of one another; an extension is that there is no way to
communicate the deletion of a running job from the queue the the node
actually running that job. it is not an error to force a job to die using a
facility such as an ssh command spawned on the remote host. once a job has
been noted to have finished, whatever the exit status, it can be deleted
from the queue.
examples :
0) delete all pending, finished, and dead jobs from a queue
~ > rq q d all
1) delete all pending jobs from a queue
~ > rq q d p
2) delete all finished jobs from a queue
~ > rq q d f
3) delete jobs via hand crafted filter program
~ > rq q list | yaml_filter_prog | rq q d
update, u :
update assumes all leading arguments are jids to update with subsequent
key=value pairs. currently only the 'command', 'priority', and 'tag' fields
of pending jobs can be updated.
examples:
0) update the priority of job 42
~ > rq q update 42 priority=7
1) update the priority of all pending jobs
~ > rq q update pending priority=7
2) query jobs with a command matching 'foobar' and update their command
to be 'barfoo'
~ > rq q q "command like '%foobar%'" |\
rq q u command=barfoo
query, q :
query exposes the database more directly the user, evaluating the where
clause specified on the command line (or from STDIN). this feature can be
used to make a fine grained slection of jobs for reporting or as input into
the delete command. you must have a basic understanding of SQL syntax to
use this feature, but it is fairly intuitive in this limited capacity.
examples:
0) show all jobs submitted within a specific 10 minute range
~ > rq q query "started >= '2004-06-29 22:51:00' and started < '2004-06-29 22:51:10'"
1) shell quoting can be tricky here so input on STDIN is also allowed to
avoid shell expansion
~ > cat constraints.txt
started >= '2004-06-29 22:51:00' and
started < '2004-06-29 22:51:10'
~ > rq q query < contraints.txt
or (same thing)
~ > cat contraints.txt| rq q query
** in general all but numbers will need to be surrounded by single quotes **
2) this query output might then be used to delete those jobs
~ > cat contraints.txt | rq q q | rq q d
3) show all jobs which are either finished or dead
~ > rq q q "state='finished' or state='dead'"
4) show all jobs which have non-zero exit status
~ > rq q query exit_status!=0
5) if you plan to query groups of jobs with some common feature consider
using the '--tag, -t' feature of the submit mode which allows a user to
tag a job with a user defined string which can then be used to easily
query that job group
~ > rq q submit --tag=my_jobs < joblist
~ > rq q query tag=my_jobs
execute, e :
execute mode is to be used by expert users with a knowledge of sql syntax
only. it follows the locking protocol used by rq and then allows the user
to execute arbitrary sql on the queue. unlike query mode a write lock on
the queue is obtained allowing a user to definitively shoot themselves in
the foot. for details on a queue's schema the file 'db.schema' in the queue
directory should be examined.
examples :
0) list all jobs
~ > rq q execute 'select * from jobs'
configure, C :
this mode is not supported yet.
snapshot, p :
snapshot provides a means of taking a snapshot of the q. use this feature
when many queries are going to be run; for example when attempting to figure
out a complex pipeline command your test queries will not compete with the
feeders for the queue's lock. you should use this option whenever possible
to avoid lock competition.
examples:
0) take a snapshot using default snapshot naming, which is made via the
basename of the q plus '.snapshot'
~ > rq /path/to/nfs/q snapshot
1) use this snapshot to chceck status
~ > rq ./q.snapshot status
2) use the snapshot to see what's running on which host
~ > rq ./q.snapshot list running | grep `hostname`
note that there is also a snapshot option - this option is not the same as
the snapshot command. the option can be applied to ANY command. if in
effect then that command will be run on a snapshot of the database and the
snapshot then immediately deleted. this is really only useful if one were
to need to run a command against a very heavily loaded queue and did not
wish to wait to obtain the lock. eg.
0) get the status of a heavily loaded queue
~ > rq q t --snapshot
1) same as above
~ > rq q t -s
lock, L :
lock the queue and then execute an arbitrary shell command. lock mode uses
the queue's locking protocol to safely obtain a lock of the specified type
and execute a command on the user's behalf. lock type must be one of
(r)ead | (sh)ared | (w)rite | (ex)clusive
examples :
0) get a read lock on the queue and make a backup
~ > rq q L read -- cp -r q q.bak
(the '--' is needed to tell rq to stop parsing command line
options which allows the '-r' to be passed to the 'cp' command)
backup, b :
backup mode is exactly the same as getting a read lock on the queue and
making a copy of it. this mode is provided as a convenience.
0) make a backup of the queue using default naming ( qname + timestamp + .bak )
~ > rq q b
1) make a backup of the queue as 'q.bak'
~ > rq q b q.bak
rotate, r :
rotate mode is conceptually similar to log rolling. normally the list of
finished jobs will grow without bound in a queue unless they are manually
deleted. rotation is a method of trimming finished jobs from a queue
without deleting them. the method used is that the queue is copied to a
'rotation'; all jobs that are dead or finished are deleted from the original
queue and all pending and running jobs are deleted from the rotation. in
this way the rotation becomes a record of the queue's finished and dead jobs
at the time the rotation was made.
0) rotate a queue using default rotation name
~ > rq q rotate
1) rotate a queue naming the rotation
~ > rq q rotate q.rotation
2) a crontab entry like this could be used to rotate a queue daily
59 23 * * * rq q rotate `date +q.%Y%m%d`
feed, f :
take jobs from the queue and run them on behalf of the submitter as quickly
as possible. jobs are taken from the queue in an 'oldest highest priority'
first order.
feeders can be run from any number of nodes allowing you to harness the CPU
power of many nodes simoultaneously in order to more effectively clobber
your network, anoy your sysads, and set output raids on fire.
the most useful method of feeding from a queue is to do so in daemon mode so
that if the process loses it's controling terminal it will not exit when you
exit your terminal session. use the '--daemon, -d' option to accomplish
this. by default only one feeding process per host per queue is allowed to
run at any given moment. because of this it is acceptable to start a feeder
at some regular interval from a cron entry since, if a feeder is alreay
running, the process will simply exit and otherwise a new feeder will be
started. in this way you may keep feeder processing running even acroess
machine reboots without requiring sysad intervention to add an entry to the
machine's startup tasks.
examples :
0) feed from a queue verbosely for debugging purposes, using a minimum and
maximum polling time of 2 and 4 respectively. you would NEVER specify
polling times this brief except for debugging purposes!!!
~ > rq q feed -v4 -m2 -M4
1) same as above, but viewing the executed sql as it is sent to the
database
~ > RQ_SQL_DEBUG=1 rq q f -v4 -m2 -M4
2) feed from a queue in daemon mode - logging to /home/ahoward/rq.log
~ > rq q f -d -l/home/ahoward/rq.log
log rolling in daemon mode is automatic so your logs should never need
to be deleted to prevent disk overflow.
3) use something like this sample crontab entry to keep a feeder running
forever - it attempts to (re)start every fifteen minutes but exits if
another process is already feeding.
···
#
# your crontab file - sample only
#
*/15 * * * * /full/path/to/bin/rq /full/path/to/nfs/mounted/q f -d -l/home/username/cfq.log -q
the '--quiet, -q' here tells rq to exit quietly (no STDERR)
when another process is found to already be feeding so that no cron
message would be sent under these conditions.
help, h :
this message
examples :
0) get this message
~> rq q help
or
~> rq help
NOTES
- realize that your job is going to be running on a remote host and this has
implications. paths, for example, should be absolute, not relative.
specifically the submitted job script must be visible from all hosts
currently feeding from a queue as must be the input and output
files/directories.
- jobs are currently run under the bash shell using the --login option.
therefore any settings in your .bashrc will apply - specifically your PATH
setting. you should not, however, rely on jobs running with any given
environment.
- you need to consider __CAREFULLY__ what the ramifications of having multiple
instances of your program all potentially running at the same time will be.
for instance, it is beyond the scope of rq to ensure multiple instances of a
given program will not overwrite each others output files. coordination
of programs is left entirely to the user.
- the list of finished jobs will grow without bound unless you sometimes
delete some (all) of them. the reason for this is that rq cannot know when
the user has collected the exit_status of a given job, and so keeps this
information in the queue forever until instructed to delete it. if you have
collected the exit_status of you job(s) it is not an error to then delete
that job from the finished list - the information is kept for your
informational purposes only. in a production system it would be normal to
periodically save, and then delete, all finished jobs.
ENVIRONMENT
RQ_Q: set to the full path of nfs mounted queue
the queue argument to all commands may be omitted if, and only if, the
environment variable 'RQ_Q' contains the full path to the q. eg.
~ > export RQ_Q=/full/path/to/my/q
this feature can save a considerable amount of typing for those weak of
wrist.
DIAGNOSTICS
success : $? == 0
failure : $? != 0
AUTHOR
ara.t.howard@noaa.gov
BUGS
0 < bugno && bugno <= 42
reports to ara.t.howard@noaa.gov
OPTIONS
--priority=priority, -p
modes <submit> : set the job(s) priority - lowest(0) .. highest(n) -
(default 0)
--tag=tag, -t
modes <submit> : set the job(s) user data tag
--runner=runner
modes <submit> : set the job(s) required runner(s)
--restartable
modes <submit> : set the job(s) to be restartable on node reboot
--infile=infile
modes <submit> : infile
--quiet, -q
modes <submit, feed> : do not echo submitted jobs, fail silently if
another process is already feeding
--daemon, -D
modes <feed> : spawn a daemon
--max_feed=max_feed
modes <feed> : the maximum number of concurrent jobs run
--retries=retries
modes <feed> : specify transaction retries
--min_sleep=min_sleep
modes <feed> : specify min sleep
--max_sleep=max_sleep
modes <feed> : specify max sleep
--snapshot, -s
operate on snapshot of queue
--verbosity=verbostiy, -v
0|fatal < 1|error < 2|warn < 3|info < 4|debug - (default info)
--log=path, -l
set log file - (default stderr)
--log_age=log_age
daily | weekly | monthly - what age will cause log rolling (default
nil)
--log_size=log_size
size in bytes - what size will cause log rolling (default nil)
--help, -h
this message
--version
show version number
-a
--
be kind whenever possible... it is always possible.
- the dalai lama
