NAME

       queue_splitter - PgQ consumer that transports events from one queue into several target
       queues

SYNOPSIS

       queue_splitter.py [switches] config.ini

DESCRIPTION

       queue_spliter is PgQ consumer that transports events from source queue into several target
       queues. ev_extra1 field in each event shows into which target queue it must go.
       (pgq.logutriga() puts there the table name.)

       One use case is to move events from OLTP database to batch processing server. By using
       queue spliter it is possible to move all kinds of events for batch processing with one
       consumer thus keeping OLTP database less crowded.

QUICK-START

       Basic queue_splitter 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. Target database must also have pgq_ext schema installed.

        2. edit a queue_splitter configuration file, say
           queue_splitter_sourcedb_sourceq_targetdb.ini

        3. create source and target queues

               $ pgqadm.py ticker.ini create <queue>

        4. launch queue splitter in daemon mode

               $ queue_splitter.py queue_splitter_sourcedb_sourceq_targetdb.ini -d

        5. 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_splitter parameters
       src_db
           Source database.

       dst_db
           Target database.

   Example config file
           [queue_splitter]
           job_name        = queue_spliter_sourcedb_sourceq_targetdb

           src_db          = dbname=sourcedb
           dst_db          = dbname=targetdb

           pgq_queue_name  = sourceq

           logfile         = ~/log/%(job_name)s.log
           pidfile         = ~/pid/%(job_name)s.pid

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)

USECASE

       How to to process events created in secondary database with several queues but have only
       one queue in primary database. This also shows how to insert events into queues with
       regular SQL easily.

           CREATE SCHEMA queue;
           CREATE TABLE queue.event1 (
                -- this should correspond to event internal structure
                -- here you can put checks that correct data is put into queue
                id int4,
                name text,
                -- not needed, but good to have:
                primary key (id)
           );
           -- put data into queue in urlencoded format, skip actual insert
           CREATE TRIGGER redirect_queue1_trg BEFORE INSERT ON queue.event1
           FOR EACH ROW EXECUTE PROCEDURE pgq.logutriga('singlequeue', 'SKIP');
           -- repeat the above for event2

           -- now the data can be inserted:
           INSERT INTO queue.event1 (id, name) VALUES (1, 'user');

       If the queue_splitter is put on "singlequeue", it spreads the event on target to queues
       named "queue.event1", "queue.event2", etc. This keeps PgQ load on primary database minimal
       both CPU-wise and maintenance-wise.

                                            03/13/2012                          QUEUE_SPLITTER(1)