25.3. Reference for the BiHA Extension

25.3. Reference for the BiHA Extension
Prev	Up	Chapter 25. Built-in High Availability (BiHA)	Home	Next

25.3.1. Configuration Parameters #

Configuration parameters that can be useful:

biha.can_be_leader (boolean) #: Determines the ability of a node to become the leader. The default value is true. If set to false, the node cannot stand as a candidate in elections of the new leader.
biha.can_vote (boolean) #: Determines whether a node is allowed to vote. The default value is true. If set to false, the node cannot vote, as well as cannot stand as a candidate in elections of the new leader.
biha.flw_ro (boolean) #: Determines whether a follower is available for read operations. If set to off, reading from this follower is prohibited. The default value is on.
biha.heartbeat_max_lost (integer) #: Specifies the maximum number of heartbeats that can be missed before the node is considered offline. The default value is 10.
biha.heartbeat_send_period (integer) #: Specifies the heartbeat sending frequency, in milliseconds. The default value is 1000.

25.3.2. BiHA Logging Levels #

biha.BihaLog_log_level (enum) #: Specifies the logging level to provide general information about the operation of BiHA components. The default value is LOG.
biha.BcpTransportDebug_log_level (enum) #: Specifies the logging level to provide debugging information about the control channel operation. The default value is DEBUG4.
biha.BcpTransportDetails_log_level (enum) #: Specifies the logging level to provide detailed information about the control channel operation. The default value is DEBUG4.
biha.BcpTransportLog_log_level (enum) #: Specifies the logging level to provide general information about the control channel operation. The default value is DEBUG4.
biha.BcpTransportWarn_log_level (enum) #: Specifies the logging level to provide warnings of likely problems in the control channel. The default value is DEBUG4.
biha.NodeControllerDebug_log_level (enum) #: Specifies the logging level to provide debugging information about the node controller operation. The default value is DEBUG4.
biha.NodeControllerDetails_log_level (enum) #: Specifies the logging level to provide detailed information about the node controller operation. The default value is DEBUG4.
biha.NodeControllerLog_log_level (enum) #: Specifies the logging level to provide general information about the node controller operation. The default value is DEBUG4.
biha.NodeControllerWarn_log_level (enum) #: Specifies the logging level to provide warnings of likely problems in the node controller. The default value is DEBUG4.

25.3.3. Functions #

All functions listed below should be called from the biha_db database:

biha.error_details () returns setof record #: Returns the description of why the node transferred to the NODE_ERROR state. The returned record contains the type of the error, its details, the place it occurred specifying begin_lsn, end_lsn, and identifier of the current and the next timeline, as well as replay_lsn.
biha.nodes () returns setof record #: Defines the biha.nodes_v view, which is described in detail in the biha.nodes_v section.
biha.status () returns setof record #: Defines the biha.status_v view, which is described in detail in the biha.status_v section. If the node does not respond when trying to display the view, try the same request on any other node to learn the actual state of cluster nodes.

25.3.4. Views #

To query the views listed below, you must first connect to the biha_db database.

25.3.4.1. `biha.nodes_v` #

This view displays the connection status of nodes in the cluster. For the node that the view is queried on, the following columns contain NULL: state, since_conn_start, conn_count.

Table 25.1. The biha.nodes_v view

Column Name	Description
`id`	The node ID.
`host`	The host of the node.
`port`	The port of the node.
`state`	The connection state of the node. This column may contain one of the following values: `ACTIVE`, `CONNECTING`, `IDLE`, or `INIT`.
`since_conn_start`	The time since the node connection.
`conn_count`	The number of times the node was connected since the start of the cluster.

25.3.4.2. `biha.status_v` #

This view displays the state of nodes in the cluster.

Table 25.2. The biha.status_v View

Column Name	Description
`id`	The node ID.
`leader_id`	The leader node ID.
`term`	The term of the node. This is used for the purposes of the leader election.
`online`	Shows whether the node is online.
`state`	The state of the node. This column may contain one of the following values: `PRESTARTUP` — the initial state of the node at the BiHA cluster launch. The node sends heartbeats and executes pg_rewind if scheduled. Otherwise, the node proceeds to `STARTUP`. `STARTUP` — the node waits for the Postgres Pro Shardman startup process to reach the consistency point. `CSTATE_FORMING` — the node receives and sends heartbeats to determine what state it must transfer to. `LEADER_RO` — the node is the leader available for read-only operations. `LEADER_RW` — the node is the leader available for read and write operations. `FOLLOWER` — the node is a replica of the leader. If biha.can_be_leader and biha.can_vote are set to `true`, the follower can be elected as the new leader. `FOLLOWER_OFFERED` — the node was manually nominated as the new leader. `CANDIDATE` — the node stands as a candidate in elections of the new leader. `REFEREE` — the node is the cluster referee. The state is the same both for the `referee` and `referee_with_wal` modes. `NODE_ERROR` — the node is non-operational due to an error. When the node is in the `NODE_ERROR` state, reading from this node is prohibited. To get more information about the error, use the biha.error_details function. To restore the faulty node, see Section 25.2.3. `UNKNOWN` — the node is offline for the current node.
`last_known_state`	The last known state of the node.
`since_last_hb`	The time since the last received heartbeat message.

Prev	Up	Next
25.2. Administration	Home	Chapter 26. Monitoring Database Activity