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.
use_skylog
foo.
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.
09/22/2008