File: README — Documentation for rq-ruby1.8 (3.4.7)

NAME

rq v3.4.6

SYNOPSIS

rq queue mode [mode_args]* [options]*

ruby queue (rq) is a zero-admin zero-configuration tool used to create
instant unix clusters on a multi-core machine, and/or multiple nodes in a
network, or in the Cloud. rq requires only a centrally mounted directory
(e.g. NFS) in order to manage a simple sqlite database as a distributed
priority work queue. See QUICK START below.

DESCRIPTION

ruby queue (rq) is a zero-admin zero-configuration tool used to create
instant unix clusters. the simple design allows researchers with minimal unix
experience to install and configure, in only a few minutes and without root
privileges, a robust unix cluster capable of distributing processes to many
nodes - bringing dozens of 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 one mr. j safran.

the central concept of rq is that n nodes work in isolation to pull jobs
from an centrally mounted nfs priority work queue in a synchronized fashion.
the nodes have absolutely no knowledge of each other and all communication
is 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.

although the rq system is simple in it's design it features powerful
functionality such as priority management, predicate and sql query, compact
streaming command-line processing, programmable api, hot-backup, and
input/capture of the stdin/stdout/stderr io streams of remote jobs. to date
rq has had no reported runtime failures and is in operation at
dozens of research centers around the world. while rq is written in
the Ruby programming language, there is no Ruby programming
involved in using rq.

QUICK START

install rq using rubygems, after installing sqlite 2.x

  gem1.8 install rq-ruby1.8

the binary is in /var/lib/gems/1.8/bin/, so add that to the path,
or create a symbolic link

  ln -sf `gem1.8 contents rq-ruby1.8|grep bin/rq$` /usr/local/bin/rq

now rq should work

  rq --help

run the integration test

  /var/lib/gems/1.8/bin/test_rq.rb

set up a directory for your queue - this can be a local, or an NFS/sshfs
mounted drive:

  rq dir create

on every node create a queue runner, specifying the number of cores (here 8)

  rq dir feed --daemon --log=rq.log --max_feed=8

submit two jobs - shell style

  rq dir submit 'sleep 10'
  rq dir submit 'sleep 9'

check status

  rq dir status

shows

      --- 
      jobs: 
        pending: 0
        holding: 0
        running: 2
        finished: 0
        dead: 0
        total: 2
      temporal: 
        running: 
          min: {2: 00h00m03.49s}
          max: {1: 00h00m03.60s}
      performance: 
        avg_time_per_job: 00h00m00.00s
        n_jobs_in_last_hrs: 
          1: 0
          12: 0
          24: 0
      exit_status: 
        successes: 0
        failures: 0
        ok: 0

Now, that was easy!!

INSTALL

See the ./INSTALL file, but quickly

gem >=3.4.6:

  - install sqlite2 (Debian apt-get install libsqlite0-dev)
  - gem1.8 install rq-ruby1.8 

  Also available from http://bio4.dnsalias.net/download/gem/ruby1.8/

manual (cluster wide):

    (note, this procedure is out of date and breaks on gcc 4.4 and later)
    - download latest release from http://codeforpeople.com/lib/ruby/rq/
    - tar xvfz rq-X.X.X.tgz
    - cd rq-X-X-X
    - cd all
    - ./install.sh /full/path/to/nfs/mounted/directory/

Debian flavours:

  see ./INSTALL file for latest

INVOCATION

the first argument to any rq command is the always the name of the queue
while the second is the mode of operation.  the queue name may be omitted
if, and only if, the environment variable RQ_Q has been set to contain the
absolute path of target queue.

for instance, the command

  ~ > rq queue list 

is equivalent to

  ~ > export RQ_Q=queue
  ~ > rq list

this facility can be used to create aliases for several queues, for example,
a .bashrc containing

  alias MYQ="RQ_Q=/path/to/myq rq"

  alias MYQ2="RQ_Q=/path/to/myq2 rq"

would allow syntax like

  MYQ2 submit < joblist

MODES

rq operates in modes create, submit, resubmit, list, status, delete, update,
query, execute, configure, snapshot, lock, backup, rotate, feed, recover,
ioview, cron, help, and a few others.  the meaning of 'mode_args' will
naturally change depending on the mode of operation.

the following mode abbreviations exist, note that not all modes have
abbreviations

  c  => create
  s  => submit
  r  => resubmit
  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
  io => ioview
  0  => stdin
  1  => stdout
  2  => stderr
  h  => help

create, c :

  creates a queue.  the queue must be located on an nfs mounted file system
  visible from all nodes intended to run jobs from it.  nfs locking must be
  functional on this file system.

  examples :

    0) to create a queue
        ~ > rq /path/to/nfs/mounted/q create

      or, using the abbreviation

        ~ > rq /path/to/nfs/mounted/q c

submit, s :

  submit jobs to a queue to be proccesed by some 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.  the leading '---' of yaml file may not be omitted.

  when submitting the '--priority, -p' option can be used here to determine
  the priority of jobs.  priorities may be any whole number including
  negative ones - zero is the default.  note that submission of a high
  priority job will NOT supplant a currently running low priority job, 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.  jobs submitted with the
  '--stage' option will not be eligible to be run by any node and will
  remain in a 'holding' state until updated (see update mode) into the
  'pending' mode, this option allows jobs to entered, or 'staged', in the
  queue and then made candidates for running at a later date.

  rq allows the stdin of commands to be provided and also captures the
  stdout and stderr of any job run (of course standard shell redirects may
  be used as well) and all three will be stored in a directory relative the
  the queue itself.  the stdin/stdout/stderr files are stored by job id and
  there location (though relative to the queue) is shown in the output of
  'list' (see docs for list).

  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 a list of jobs from file.  note the '-' used to specify
    reading jobs from stdin

      ~ > cat joblist
      job1.sh
      job2.sh
      job2.sh

      ~ > rq q submit --infile=joblist

    3) submit a joblist on stdin

      ~ > cat joblist | rq q submit -

      or

      ~ > rq q submit - <joblist

    4) submit cat as a job, providing the stdin for cat from the file cat.in

      ~ > rq q submit cat --stdin=cat.in

    5) submit cat as a job, providing the stdin for the cat job on stdin 

      ~ > cat cat.in | rq q submit cat --stdin=-

      or

      ~ > rq q submit cat --stdin=- <cat.in

    6) 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

    6) re-submit all the 'important' jobs (see 'query' section below)

      ~ > rq q query tag=important | rq q s -

    8) re-submit all jobs which are already finished (see 'list' section
       below) 

      ~ > rq q l f | rq q s 

    9) stage the job wont_run_yet to the queue in a 'holding' state.  no
       feeder will run this job until it's state is upgraded to 'pending'

      ~ > rq q s --stage wont_run_yet

resubmit, r :

  resubmit jobs back to a queue to be proccesed by a feeding node.  resubmit
  is essentially equivalent to submitting a job that is already in the queue
  as a new job and then deleting the original job except that using resubmit
  is atomic and, therefore, safer and more efficient.  resubmission respects
  any previous stdin provided for job input.  read docs for delete and
  submit for more info.

  examples :

    0) resubmit job 42 to the queue

      ~> rq q resubmit 42

    1) resubmit all failed jobs

      ~> rq q query exit_status!=0 | rq q resubmit -

    2) resubmit job 4242 with different stdin

      ~ rq q resubmit 4242 --stdin=new_stdin.in

list, l, ls :

  list mode lists jobs of a certain state or job id.  state may be one of
  pending, holding, 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
    h => holding
    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 finished 

    4) show job id 42 
        ~ > rq q l 42 

    5) show q's holding jobs
        ~ > rq q list holding 

status, t :

  status mode shows the global state the queue and statistics on it's the
  cluster's performance.  there are no 'mode_args'.  the meaning of each
  state is as follows:

    pending  => no feeder has yet taken this job
    holding  => a hold has been placed on this job, thus no feeder will start
                it
    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 subsequently
  died, or that it is simply taking a very long time to complete.  only the
  node that dies, upon restart, can determine that it owns jobs that 'were
  started before it started running jobs', an impossibility, 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 automatically restarted if, and only if, the job was
  submitted with the '--restartable' flag.

  status breaks down a variety of canned statistics about a nodes'
  performance based solely on the jobs currently in the queue.  only one
  option affects the ouput: '--exit'.  this option is used to specify
  additionaly exit code mappings on which to report.  normally rq will
  report any job with an exit code of 0 as being 'successes' and any job
  with an exit code that is not 0, or a status of 'dead', as being
  'failures'.  if the '--exit' switch is used then additional mappings can
  be specified, note that the the semantics for 'successes' and 'failures'
  does not change - this keyword specifies extra mappings.

  examples :

    0) show q's status

      ~ > rq q t 

    2) show q's status, consider any exit code of 42 will be listed as 'ok'

      ~ > rq q t --exit ok=42

    3) show q's status, consider any exit code of 42 or 43 will be listed as
    'ok' and 127 will be listed as 'command_not_found'.  notice the quoting
    required.

      ~ > rq q t --exit 'ok=42,43 command_not_found=127'

delete, d :

  delete combinations of pending, holding, 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
  prematurely using a facility such as an ssh command spawned on the remote
  host to kill it.  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 -

      an example ruby filter program (you have to love this)

        ~ > cat yaml_filter_prog
        require 'yaml'
        joblist = YAML::load STDIN
        y joblist.select{|job| job['command'] =~ /bombing_program/}

      this program reads the list of jobs (yaml) from stdin and then dumps
      only those jobs whose command matches 'bombing_program', which is
      subsequently piped to the delete command.

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 generically updated and the 'state' field
  may be toggled between pending and holding.

  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 

    3) place a hold on jid 2

      ~ > rq q u 2 state=holding

    4) place a hold on all jobs with tag=disk_filler

      ~ > rq q q tag=disk_filler | rq q u state=holding -

    5) remove the hold on jid 2

      ~ > rq q u 2 state=pending

query, q :

  query exposes the database more directly the user, evaluating the where
  clause specified on the command line (or read 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

      ~ > a='2004-06-29 22:51:00'

      ~ > b='2004-06-29 22:51:10'

      ~ > rq q query "started >= '$a' and started < '$b'"

    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 -

    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 

    6) in general all but numbers will need to be surrounded by single
    quotes unless the query is a 'simple' one.  a simple query is a query
    with no boolean operators, not quotes, and where every part of it looks
    like

          key op value

       with ** NO SPACES ** between key, op, and value.  if, and only if,
       the query is 'simple' rq will contruct the where clause
       appropriately.  the operators accepted, and their meanings, are

         =  : equivalence : sql =
         =~ : matches     : sql like
         !~ : not matches : sql not like

       match, in the context is ** NOT ** a regular expression but a sql
       style string match.  about all you need to know about sql matches is
       that the '%' char matches anything.  multiple simple queries will be
       joined with boolean 'and'

       this sounds confusing - it isn't.  here are some examples of simple
       queries

       6.a) 
         query :
           rq q query tag=important

         where_clause :
           "( tag = 'important' )"

       6.b) 
         query :
           rq q q priority=6 restartable=true 

         where_clause :
           "( priority = 6 ) and ( restartable = 'true' )"

       6.c) 
         query :
           rq q q command=~%bombing_job% runner=~%node_1% 

         where_clause :
           "( command like '%bombing_job%') and (runner like '%node_1%')"

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

  ** IMPORTANT **

    a really great way to hang all processing in your queue is to do this

      rq q list | less

    and then leave for the night.  you hold a read lock you won't release
    until less dies.  this is what snapshot is made for!  use it like

      rq q list -s | less

    now you've taken a snapshot of the queue to list so your locks affect no
    one.

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)

  ** IMPORTANT **

    this is another fantastic way to freeze your queue - use with care!

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 --min_sleep=2 --max_sleep=4

    1) same as above, but viewing the executed sql as it is sent to the
    database

      ~ > RQ_SQL_DEBUG=1 rq q feed -v4 --min_sleep=2 --max_sleep=4

    2) feed from a queue in daemon mode - logging to /home/ahoward/rq.log

      ~ > rq q feed --daemon -l/home/$USER/rq.log

       log rolling in daemon mode is automatic so your logs should never
       need to be deleted to prevent disk overflow.

start :

  the start mode is equivalent to running the feed mode except the --daemon
  is implied so the process instantly goes into the background.  also, if no
  log (--log) is specified in start mode a default one is used.  the default
  is /home/$USER/$BASENAME_OF_Q.log

  examples :

    0) start a daemon process feeding from q

      ~ > rq q start

    1) 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.  output is only created when the
    daemon is started so your mailbox will not fill up with this crontab
    entry:

      #
      # crontab.sample 
      #

      */15 * * * * /path/to/bin/rq /path/to/q start

    and entry like this on every node in your cluster is all that's needed
    to keep your cluster going - even after a reboot.

shutdown :

  tell a running feeder to finish any pending jobs and then to exit.  this
  is equivalent to sending signal 'SIGTERM' to the process - this is what
  using 'kill pid' does by default.

  examples :

    0) stop a feeding process, if any, that is feeding from q.  allow all
    jobs to be finished first.

      ~ > rq q shutdown 

  ** VERY IMPORTANT **

    if you are keeping your feeder alive with a crontab entry you'll need to
      comment it out before doing this or else it will simply re-start!!!

stop :

  tell any running feeder to stop NOW.  this sends signal 'SIGKILL' (-9) to
  the feeder process.  the same warning as for shutdown applies!!!

  examples :

    0) stop a feeding process, if any, that is feeding from q.  allow NO
    jobs to be finished first - exit instantly.

      ~ > rq q stop 

cron :

  when given 'start' for 'mode_args' this option automatically adds a
  crontab entry to keep a feeder alive indefinitely and starts a feeder in
  the background.  this is a shortcut to start a feeder and ensure it stays
  running forever, even across re-boots.

  'stop' as an argument applys the inverse option: any crontab entry is
  removed and the daemon shutdown nicely.  a second argument of 'hard' will
  do a stop instead of a shutdown.

  the addition and subtraction of crontab entries is robust, however, if you
  already have crontab lines maintaining your feeders with a vastly
  different syntax it would be best to shut down, remove them, and then let
  rq manage them.  then again, some people are quite brave...

  examples :

    0) automatically add crontab entry and start daemon feeder

      ~ > rq q cron start

    1) automatically remove crontab entry and shutdown daemon feeder nicely 

      ~ > rq q cron shutdown

    2) the same, but using stop instead of shutdown

      ~ > rq q cron stop

pid :

  show the pid, if any, of the feeder on this host

  ~ > rq q feeder
  ---
  pid : 3176

ioview, io :

  as shown in the description for submit, a job maybe be provided stdin
  during job submission.  the stdout and stderr of the job are also captured
  as the job is run.  all three streams are captured in files located
  relative to the queue.  so, if one has submitted a job, and it's jid was
  shown to be 42, by using something like

    ~ > rq /path/to/q submit myjob --stdin=myjob.in
    ---
    -
      jid : 42
      priority : 0
      ...
      stdin : stdin/42
      stdout : stdout/42
      stderr : stderr/42
      ...
      command : myjob

  the stdin file will exists as soon as the job is submitted and the others
  will exist once the job has begun running.  note that these paths are
  shown relative to the queue.  in this case the actual paths would be

    /path/to/q/stdin/42
    /path/to/q/stdout/42
    /path/to/q/stderr/42

  but, since our queue is nfs mounted the /path/to/q may or may not be the
  same on every host.  thus the path is a relative one.  this can make it
  anoying to view these files, but rq assists here with the ioview command.
  the ioview command spawns an external editor to view all three files.
  it's use is quite simple

  examples :

    0) view the stdin/stdout/stderr of job id 42

       ~ > rq q ioview 42

  by default this will open up all three files in vim.  the editor command
  can be specified using the '--editor' option or the ENV var RQ_EDITOR.
  the default value is 'vim -R -o' which allows all three files to be opened
  in a single window.

stdin, 0 :

  dump the stdinput (if any) provided to the job 

  examples :

    0)  dump the stdin for jid 42

      ~ > rq q stdin 42

stdout, 1 :

  dump the stdoutput (if any) created by the job 

  examples :

    0)  dump the stdout for jid 42

      ~ > rq q stdout 42

stderr, 2 :

  dump the stderrput (if any) created by the job 

  examples :

    0)  dump the stderr for jid 42

      ~ > rq q stderr 42

stdin4 :

  show the path used for the stdin of a jid 

  examples :

    0) show which file has job 42's stdin

      ~ > rq q stdin4 42

stdout4 :

  show the path used for the stdout of a jid 

  examples :

    0) show which file has job 42's stdout

      ~ > rq q stdout4 42

stderr4 :

  show the path used for the stderr of a jid 

  examples :

    0) show which file has job 42's stderr

      ~ > rq q stderr4 42

recover :

  it is possible that a hardware failure might corrupt an rq database.  this
  isn't the kind of thing people like hearing, but it's true - hardware has
  errors.  in these situations a database can sometimes be readable, but not
  writable, or some other combination.  this has been reported only a
  handful of times, nevertheless, this command wraps sqlite recovery to get
  you rolling again, it's acceptable to perform recovery on a live rq
  database with active feeders

  examples :

    0) recover!

      ~ > rq q recover

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.

- know that it is a VERY bad idea to spawn several dozen process all
  reading/writing huge output files to a single NFS server.  use this
  paradigm instead

    * copy/move data from global input space to local disk
    * process data
    * move data on local disk to global output space

  this, of course, applies to any nfs processing, not just those jobs
  submitted to rq

  the vsftp daemon is an excellent utility to have running on hosts in your
  cluster so anonymous ftp can be used to get/put data between any two
  hosts.

- know that nfs locking is very, very easy to break with firewalls put in
  place by overzealous system administrators.  be postive not only that nfs
  locking works, but that lock recovery server/client crash or reboot works
  as well.  http://nfs.sourceforge.net/ is the place to learn about NFS.  my
  experience thus far is that there are ZERO properly configured NFS
  installations in the world.  please test yours.  contact me for a simple
  script which can assist you.  beer donations required as payment.

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.  

  a shell script like this can also be used to avoid needing to type the
  queue name each and every time

    ~ > cat my_q
      #!/bin/sh
      rq /full/path/to/my/q "$@"

  and then all operations become, for example

    ~> my_q submit my_mob
    ~> my_q status 
    ~> my_q delete 42

RQ_OPTS | RQ_OPTIONS: specify extra options 

  this ENV var can be used to specify options which should always apply, for
  example

    ~ > export RQ_OPTS=--restartable

  and shell script like this might be used to mark jobs submitted by a
  certain user and to always submit them at a negative priority

    ~ > cat username_q
      #!/bin/sh
      export RQ_OPTS="--tag=username --priority=-42"
      rq /full/path/to/my/q "$@"

  actual command line options wil always override options given this way

DIAGNOSTICS

success : $? == 0
failure : $? != 0

URIS

https://github.com/pjotrp/rq - main website
http://www.linuxjournal.com/article/7922
http://rubyforge.org/projects/codeforpeople/ (original)

LICENSE

rq is distributed under the BSD license, see the ./LICENSE file

CREDITS

- kim baugh       : patient tester and design input
- jeff safran     : the guy can break anything
- chris elvidge   : boss who made it possible 
- trond myklebust : tons of help with nfs
- jamis buck      : for writing the sqlite bindings for ruby
- _why            : for writing yaml for ruby
- matz            : for writing ruby

INSTALL

gem1.8 install rq-ruby1.8 (see top of page)

TEST

Install rq and

  test_rq.rb

AUTHOR

Ara Howard <[email protected]> and Pjotr Prins <[email protected]>

BUGS

0 < bugno && bugno <= 42

reports on github, or to Pjotr Prins <[email protected]> and Ara Howard <[email protected]>