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   1 #PgBouncer Slony-I replication set follower
   2
   3 This script is a command-line utility to monitor the nodes in a Slony-I cluster
   4 and reconfigure pgbouncer to follow an origin or subscriber of replication sets.
   5
   6 The idea is pretty simple; periodically poll the slony schema to identify origin
   7 and subscriber nodes and repoint an existing pgbouncer instance to follow either
   8 the origin for read-write or a subscriber for read-only operation.  The script
   9 takes a template pgbouncer.ini file containing all the desired settings except
  10 for the target database and will write a copy with the target database and reload
  11 pgbouncer.  In 'ro' mode the script will try and choose a subscriber node  closest
  12 to pgbouncer host if IPv4 addressing has been used for the slony conninfos.
  13
  14 ##Example usage
  15
  16 The script can be either run on a schedule or as a daemon with the "D" flag:
  17
  18 ```bash
  19 $ pgbouncer_follower.pl -f <config file> [-D]
  20 ```
  21
  22 To run as a daemon in debian:
  23
  24 ```bash
  25 $ sudo cp init.debian /etc/init.d/pgbouncer_follower_rw
  26 $ cp pgbouncer_follower.pl /var/slony/pgbouncer_follower/pgbouncer_follower.pl
  27 $ cp pgbouncer_follower_rw.conf /var/slony/pgbouncer_follower/pgbouncer_follower_rw.conf
  28 $ sudo chmod +x /etc/init.d/pgbouncer_follower_rw
  29 $ sudo update-rc.d pgbouncer_follower_rw start 99 2 3 4 5 . stop 24 0 1 6
  30 $ sudo invoke-rc.d pgbouncer_follower_rw start
  31 ```
  32
  33 ##Configuration options
  34
  35 | Section   | Parameter              | Type    | Default                                     | Comment
  36 |:----------|:-----------------------|:--------|:--------------------------------------------|:-----------------------------------
  37 | Slony     | slony_user             | text    | *'slony'*                                   | Username used to connect to PostgreSQL and select from slony schema tables
  38 | Slony     | slony_pass             | text    | *''*                                        | Recommended to leave blank and use .pgpass file
  39 | Slony     | slony_cluster_name     | text    | *'replication'*                             | Name of slony cluster (without leading underscore of schema name)
  40 | Slony     | server_conninfo        | text    | *null*                                      | Conninfo string for slony a node, can be specified multiple times
  41 | pgBouncer | debug                  | boolean | *false*                                     | Churn out debugging info to log file / stdout
  42 | pgBouncer | follower_poll_interval | integer | *1000*                                      | Interval to poll slony cluster state when in daemon mode
  43 | pgBouncer | sets_to_follow         | text    | *1*                                         | Comma separated list of sets to follow or 'all' to follow all sets
  44 | pgBouncer | pool_mode              | 'ro/rw' | *'rw'*                                      | Select a read-only subscriber or the origin for read-write
  45 | pgBouncer | pool_all_databases     | boolean | *'false'*                                   | If true uses wildcard for database name in pgbouncer.ini, false uses slony database
  46 | pgBouncer | auth_user              | text    | *''*                                        | If set auth_user will be appended to conninfo written in [databases] section
  47 | pgBouncer | only_follow_origins    | boolean | *'false'*                                   | If true pgbouncer will only be reconfigured and reloaded when sets move origin
  48 | pgBouncer | status_file            | text    | *'/tmp/pgbouncer_follower_%mode.status'*    | File used to store a hash depicting the state of the cluster
  49 | pgBouncer | log_file               | text    | *'/tmp/pgbouncer_follower_%mode.log'*       | Log file for the script
  50 | pgBouncer | pid_file               | text    | *'/tmp/pgbouncer_follower_%mode.log'*       | PID file for the script when run as a daemon
  51 | pgBouncer | pool_conf_template     | text    | *'/etc/pgbouncer/pgbouncer_%mode.template'* | Template pgbouncer.ini file with your settings and a blank [databases] section
  52 | pgBouncer | pool_conf_target       | text    | *'/etc/pgbouncer/pgbouncer_%mode.ini'*      | Target pgbouncer.ini file to write a copy of pool_conf_template with a [databases] section to
  53 | pgBouncer | pool_reload_command    | text    | *'/etc/init.d/pgbouncer_%mode reload"'*     | System command to execute to reload pgbouncer instance
  54 | pgBouncer | max_ro_lag             | integer | *0*                                         | Maximum lag in seconds allowed for subscriber nodes when running in ro mode. 0 = don't monitor lag.
  55
  56 The status_file, log_file, pid_file, pool_conf_template, pool_conf_target and
  57 pool_reload_command parameters can contain the following special values:
  58
  59     %mode - Pool Mode
  60     %clname - Slony cluster name