[ANN] rq-1.0.0

Discussion in 'Ruby' started by Ara.T.Howard, Nov 10, 2004.

  1. Ara.T.Howard

    Ara.T.Howard Guest

    URLS
    http://raa.ruby-lang.org/project/rq/
    http://www.codeforpeople.com/lib/ruby/rq/
    (http://rubyforge.org/projects/rqueue/ - under construction)

    NAME
    rq v1.0.0

    SYNOPSIS
    rq (queue | export RQ_Q=q) mode [mode_args]* [options]*


    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, help, or
    feed. 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
    h => help
    f => feed

    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.

    ~ > wc -l cmdfile
    42000
    ~ > rq q s -q < 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, running, 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 while it is possible to
    delete a running job, but there is no way to actually STOP it mid execution
    since the node doing the deleteing has no way to communicate this
    information to the (probably) remote execution node. therefore you should
    use the 'delete running' feature with care and only for housekeeping
    purposes or to prevent future jobs from being scheduled.

    examples :

    0) delete all pending, running, and finished 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

    help, h :

    this message

    examples :

    0) get this message

    ~> rq q help
    or
    ~> rq help


    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.


    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


    BUGS
    0 < bugno && bugno <= 42

    reports to

    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
    --infile=infile, -i
    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, -f
    modes <feed> : the maximum number of concurrent jobs run
    --retries=retries, -r
    modes <feed> : specify transaction retries
    --min_sleep=min_sleep, -m
    modes <feed> : specify min sleep
    --max_sleep=max_sleep, -M
    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



    enjoy.

    -a
    --
    ===============================================================================
    | EMAIL :: Ara [dot] T [dot] Howard [at] noaa [dot] gov
    | PHONE :: 303.497.6469
    | When you do something, you should burn yourself completely, like a good
    | bonfire, leaving no trace of yourself. --Shunryu Suzuki
    ===============================================================================
    Ara.T.Howard, Nov 10, 2004
    #1
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