QUEUE_MOVER(1)

NAME
queue_mover - PgQ consumer that copies data from one queue to another.

SYNOPSIS

queue_mover.py [switches] config.ini

DESCRIPTION

queue_mover is PgQ consumer that transports events from source queue into target queue. One use case is when events are produced in several databases then queue_mover is used to consolidate these events into single queue that can then be processed by consumers who need to handle theses events. For example in case of patitioned databases it’s convenient to move events from each partition into one central queue database and then process them there. That way configuration and dependancies of partiton databases are simpler and more robust. Another use case is to move events from OLTP database to batch processing server.

Transactionality: events will be inserted as one transaction on target side. That means only batch_id needs to be tracked on target side.

QUICK-START

Basic PgQ setup and usage can be summarized by the following steps:

    1. PgQ must be installed both in source and target databases. See pgqadm man page for details.

    2. Target database must also have pgq_ext schema installed. It is used to keep sync between two databases.

    3. Create a queue_mover configuration file, say qmover_sourceq_to_targetdb.ini

    4. create source and target queues

        $ pgqadm.py sourcedb_ticker.ini create <srcqueue>
        $ pgqadm.py targetdb_ticker.ini create <dstqueue>

    5. launch queue mover in daemon mode

        $ queue_mover.py -d qmover_sourceq_to_targetdb.ini

    6. start producing and consuming events

CONFIG

  Common configuration parameters

job_name
    Name for particulat job the script does. Script will log under this name to logdb/logserver. The name is also used as default for PgQ consumer name. It should be unique.

pidfile
    Location for pid file. If not given, script is disallowed to daemonize.

logfile
    Location for log file.

loop_delay
    If continuisly running process, how long to sleep after each work loop, in seconds. Default: 1.

connection_lifetime
    Close and reconnect older database connections.

log_count
    Number of log files to keep. Default: 3

log_size
    Max size for one log file. File is rotated if max size is reached. Default: 10485760 (10M)

use_skylog
    If set, search for [./skylog.ini, ~/.skylog.ini, /etc/skylog.ini]. If found then the file is used as config file for Pythons logging module. It allows setting up fully customizable logging setup.

  Common PgQ consumer parameters

pgq_queue_name
    Queue name to attach to. No default.

pgq_consumer_id
    Consumers ID to use when registering. Default: %(job_name)s

  queue_mover parameters

src_db
    Source database.

dst_db
    Target database.

dst_queue_name
    Target queue name.

  Example config file

    [queue_mover]
    job_name = eventlog_to_target_mover
    src_db = dbname=sourcedb
    dst_db = dbname=targetdb
    pgq_queue_name = eventlog
    dst_queue_name = copy_of_eventlog
    pidfile = log/%(job_name)s.pid
    logfile = pid/%(job_name)s.log

COMMAND LINE SWITCHES

Following switches are common to all skytools.DBScript-based Python programs.

-h, --help
    show help message and exit

-q, --quiet
    make program silent

-v, --verbose
    make program more verbose

-d, --daemon
    make program go background

Following switches are used to control already running process. The pidfile is read from config then signal is sent to process id specified there.

-r, --reload
    reload config (send SIGHUP)

-s, --stop
    stop program safely (send SIGINT)

-k, --kill
    kill program immidiately (send SIGTERM)

BUGS

Event ID is not kept on target side. If needed is can be kept, then event_id seq at target side need to be increased by hand to inform ticker about new events.