Streaming Replication Check
| pgpool-II 4.1.5 Documentation | |||
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Pgpool-II can work with PostgreSQL native Streaming Replication, that is available since PostgreSQL 9.0. To configure Pgpool-II with streaming replication, enable master_slave_mode and set master_slave_sub_mode to 'stream' .
Pgpool-II assumes that Streaming Replication is configured with Hot Standby on PostgreSQL, which means that the standby database can handle read-only queries.
- sr_check_period ( integer )
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Specifies the time interval in seconds to check the streaming replication delay. Default is 0, which means the check is disabled.
This parameter can be changed by reloading the Pgpool-II configurations.
- sr_check_user ( string )
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Specifies the PostgreSQL user name to perform streaming replication check. The user must have LOGIN privilege and exist on all the PostgreSQL backends.
Note: sr_check_user and sr_check_password are used even when sr_check_period is set to 0 (disabled) for the identification of the primary server.
This parameter can be changed by reloading the Pgpool-II configurations.
- sr_check_password ( string )
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Specifies the password of the sr_check_user PostgreSQL user to perform the streaming replication checks. Use '' (empty string) if the user does not requires a password.
If sr_check_password is left blank Pgpool-II will first try to get the password for sr_check_user from pool_passwd file before using the empty password.
Pgpool-II accepts following forms of password in either sr_check_password or pool_passwd file:
- AES256-CBC encrypted password
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Most secure and recommended way to store password. The password string must be prefixed with AES . You can use pg_enc utility to create the correctly formatted AES encrypted password strings. Pgpool-II will require a valid decryption key at the startup to use the encrypted passwords. see Section 6.4.2 for more details on providing the decryption key to Pgpool-II
- MD5 hashed password
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Not so secure as AES256, but still better than clear text password. The password string must be prefixed with MD5 . Note that the backend must set up MD5 authentication as well. You can use pg_md5 utility to create the correctly formatted MD5 hashed password strings.
- Plain text password
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Not encrypted, clear text password. You should avoid to use this if possible. The password string must be prefixed with TEXT . For example if you want to set mypass as a password, you should specify TEXTmypass in the password field. In the absence of a valid prefix, Pgpool-II will considered the string as a plain text password.
This parameter can be changed by reloading the Pgpool-II configurations.
- sr_check_database ( string )
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Specifies the database to perform streaming replication delay checks. The default is "postgres" .
This parameter can be changed by reloading the Pgpool-II configurations.
- delay_threshold ( integer )
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Specifies the maximum tolerance level of replication delay in WAL bytes on the standby server against the primary server. If the delay exceeds this configured level, Pgpool-II stops sending the SELECT queries to the standby server and starts routing everything to the primary server even if load_balance_mode is enabled, until the standby catches-up with the primary. Setting this parameter to 0 disables the delay checking. This delay threshold check is performed every sr_check_period . Default is 0.
This parameter can be changed by reloading the Pgpool-II configurations.
- log_standby_delay ( string )
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Specifies when to log the replication delay. Below table contains the list of all valid values for the parameter.
Table 5-9. Log standby delay options
Value Description 'none' Never log the standby delay 'always' Log the standby delay, every time the replication delay is checked 'if_over_threshold' Only log the standby delay, when it exceeds delay_threshold value This parameter can be changed by reloading the Pgpool-II configurations.