table_dispatcher(1)

table_dispatcher - PgQ consumer that is used to write source records into partitoned table.

table_dispatcher is PgQ consumer that reads url encoded records from source queue and writes them into partitioned tables according to configuration file. Used to partiton data. For example change log's that need to kept online only shortly can be written to daily tables and then dropped as they become irrelevant. Also allows to select which columns have to be written into target database Creates target tables according to configuration file as needed.

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

1. PgQ must be installed in source database. See pgqadm man page for details. Target database must have pgq_ext schema installed.

2. edit a table_dispatcher configuration file, say table_dispatcher_sample.ini

3. create source queue

   $ pgqadm.py ticker.ini create <queue>

4. launch table dispatcher in daemon mode

   $ table_dispatcher.py table_dispatcher_sample.ini -d

5. start producing events

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

table_dispatcher parameters

src_db

Source database.

dst_db

Target database.

dest_table

Where to put data. when partitioning, will be used as base name

part_field

date field with will be used for partitioning.

part_template

SQL code used to create partition tables. Various magic replacements are done there:

_PKEY	comma separated list of primery key columns.
_PARENT	schema-qualified parent table name.
_DEST_TABLE	schema-qualified partition table.
_SCHEMA_TABLE	same as DEST_TABLE but dots replaced with "_", to allow use as index names.

Example config

[table_dispatcher]
job_name          = table_dispatcher_source_table_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

# where to put data.  when partitioning, will be used as base name
dest_table        = orders

# names of the fields that must be read from source records
fields            = id, order_date, customer_name

# date field with will be used for partitioning
part_field        = order_date

# template used for creating partition tables
part_template     =
     create table _DEST_TABLE () inherits (orders);
     alter table only _DEST_TABLE add constraint _DEST_TABLE_pkey primary key (id);
     grant select on _DEST_TABLE to group reporting;

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)

PgQ trigger function pgq.logutriga() sends table change event into queue in following format:

ev_type

(op || ":" || pkey_fields). Where op is either "I", "U" or "D", corresponging to insert, update or delete. And pkey_fields is comma-separated list of primary key fields for table. Operation type is always present but pkey_fields list can be empty, if table has no primary keys. Example: I:col1,col2

ev_data

Urlencoded record of data. It uses db-specific urlecoding where existence of = is meaningful - missing = means NULL, present = means literal value. Example: id=3&name=str&nullvalue&emptyvalue=

ev_extra1

Fully qualified table name.