Backend Settings

pgpool-II 3.6.5 Documentation
Prev | Up | Chapter 5. Server Configuration | Next

# 5.4. Backend Settings

## 5.4.1. Backend Connection Settings

`backend_hostname` (`string`)

  `backend_hostname` specifies the PostgreSQL backend to be connected to. It is used by Pgpool-II to communicate with the server.

  For TCP/IP communication, this parameter can take a hostname or an IP address. If this begins with a slash(`/`), it specifies Unix-domain communication rather than TCP/IP; the value is the name of the directory in which the socket file is stored. The default behavior when backend_hostname is empty (`''`) is to connect to a Unix-domain socket in `/tmp`.

  Multiple backends can be specified by adding a number at the end of the parameter name (e.g.backend_hostname0). This number is referred to as "DB node ID", and it starts from 0. The backend which was given the DB node ID of 0 will be called "master node". When multiple backends are defined, the service can be continued even if the master node is down (not true in some modes). In this case, the youngest DB node ID alive will be the new master node.

  Please note that the DB node which has id 0 has no special meaning if operated in streaming replication mode. Rather, you should care about if the DB node is the "primary node" or not. See Section 5.7, Section 5.9, Section 5.11 for more details.

  If you plan to use only one PostgreSQL server, specify it by backend_hostname0.

  New nodes can be added by adding parameter rows and reloading a configuration file. However, the existing values cannot be updated, so you must restart Pgpool-II in that case.

`backend_port` (`integer`)

  `backend_port` specifies the port number of the backends. Multiple backends can be specified by adding a number at the end of the parameter name (e.g. backend_port0). If you plan to use only one PostgreSQL server, specify it by backend_port0.

  New backend ports can be added by adding parameter rows and reloading a configuration file. However, the existing values cannot be updated, so you must restart Pgpool-II in that case.

`backend_weight` (`floating point`)

  `backend_weight` specifies the load balance ratio of the backends. It may be set to any interger or floating point value greater than or equeal zero. Multiple backends can be specified by adding a number at the end of the parameter name (e.g. backend_weight0). If you plan to use only one PostgreSQL server, specify it by backend_weight0.

  New `backend_weight` can be added in this parameter by reloading a configuration file. However, this will take effect only for new established client sessions. Pgpool-II V2.2.6, V2.3 or later allows alllow updating the values by reloading a configuration file. This is useful if you want to prevent any query sent to slaves to perform some administrative work in master/slave mode.

## 5.4.2. Backend Data Settings

`backend_data_directory` (`string`)

  `backend_data_directory` specifies the database cluster directory of the backend. Multiple backends can be specified by adding a number at the end of the parameter name (e.g. backend_data_directory0). If you plan to use only one PostgreSQL server, specify it by backend_data_directory0.

  New `backend data_directory` can be added by adding parameter rows and reloading a configuration file. However, the existing values cannot be updated, so you must restart Pgpool-II in that case.

`backend_flag` (`string`)

  `backend_flag` controls various backend behavior. Multiple backends can be specified by adding a number at the end of the parameter name (e.g. backend_flag0). If you plan to use only one PostgreSQL server, specify it by backend_flag0.

  New backend flags can be added by adding parameter rows and reloading a configuration file. Currently followings are allowed. Multiple flags can be specified by using "|".

  Table 5-3. Backend flags

  Flag | Description
  --- | ---
  `ALLOW_TO_FAILOVER` | Allow to failover or detaching backend. This is the default. You cannot specify with DISALLOW_TO_FAILOVER at a same time.
  `DISALLOW_TO_FAILOVER` | Disllow to failover or detaching backend This is useful when you protect backend by using HA (High Availability) softwares such as Heartbeat or Pacemaker. You cannot specify with ALLOW_TO_FAILOVER at a same time.

  This parameter can be changed by reloading the Pgpool-II configurations.

Prev | Home | Next
Running mode | Up | Connection Pooling