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PCP_NODE_INFO(1) pgpool-II 4.6.3 Documentation PCP_NODE_INFO(1)

NAME

pcp_node_info - displays the information on the given node ID

SYNOPSIS

pcp_node_info [option...] [node_id]

DESCRIPTION

pcp_node_info displays the information on the given node ID.

OPTIONS

-n node_id
--node-id=node_id

The index of backend node to get information of.

-a
--all

Display all backend nodes information.

Other options

See pcp_common_options(1).

EXAMPLE

Here is an example output:

$ pcp_node_info -w -p 11001 -n 1
/tmp 11003 1 0.500000 waiting up standby standby 0 streaming async 2021-02-27 14:51:30

The result is in the following order:

1. hostname
2. port number
3. status
4. load balance weight
5. status name
6. actual backend status (obtained using PQpingParams. Pgpool-II 4.3 or later)
7. backend role
8. actual backend role (obtained using pg_is_in_recovery. Pgpool-II 4.3 or later)
9. replication delay
10. replication state (taken from pg_stat_replication. Pgpool-II 4.1 or later)
11. sync replication state (taken from pg_stat_replication. Pgpool-II 4.1 or later)
12. last status change time

3 (status) is represented by a digit from [0 to 3].

•0 - This state is only used during the initialization. PCP will never display it.

•1 - Node is up. No connections yet.

•2 - Node is up. Connections are pooled.

•3 - Node is down.

4 (load balance weight) is displayed in normalized format (0 - 1).

5 (status name) indicates the status of a PostgreSQL node as recognized by Pgpool-II. It corresponds to the numeric value shown in "3 (status)" and represents the node's internal state in a human-readable format maintained by Pgpool-II.

6 (actual backend status) shows the backend status in real time. The info is obtained by calling PQpingParams at the time when the command is invoked. PQpingParams is only available in PostgreSQL 9.1 or later. If Pgpool-II was built with PostgreSQL 9.0 or earlier, the column shows "unknown". Also if health check is disabled, it shows "unknown". When a backend node is detached by pcp_detach_node(1), the status managed by Pgpool-II will be "down", while the actual backend status is "up". Thus it is possible that 5 does not match with 6. However it should not happen that 5 is "up" while 6 is "down".

7 (backend role) indicates the role of a PostgreSQL node (primary or standby) from the perspective of Pgpool-II, based on its internally maintained information.

8 (actual backend role) shows the backend status in real time. The result will be either "primary" or "standby", and possibly "unknown" if information retrieval failed. Since Pgpool-II searches backend nodes in the node id order and assumes the last found node is primary, it is possible that 7 does not match 8 when there are multiple nodes that are not standby by erroneous operations (this command is useful to find such that situation). In other than streaming replication mode, the status will be either "main" or "replica". Unlike streaming replication mode pg_is_in_recovery is not called and value for 7 and 8 will be always the same.

To correctly display 9, 10 and 11, sr_check_period must not be 0. Additionally, to correctly display 10 and 11, the following settings are required.

•backend_application_name must be configured.

The value set for each backend_application_nameX must match the value specified in application_name of primary_conninfo for the corresponding node.

In particular, when creating standby nodes using Pgpool-II's pcp_recovery_node(1) command and community-provided sample scripts, please ensure that the value of backend_application_nameX matches that of backend_hostnameX. For specific configuration examples, please refer to Section 8.2.7.6, “Backend Settings”, in the documentation.

•sr_check_user must either be a PostgreSQL superuser or have been granted the privileges of the pg_monitor role.


Note

To grant the privileges of the pg_monitor role to sr_check_user, execute following SQL command by PostgreSQL super user (replace "sr_check_user" with the setting of sr_check_user):

GRANT pg_monitor TO sr_check_user;

For PostgreSQL 9.6, there's no pg_monitor group and sr_check_user must be PostgreSQL super user.

From Pgpool-II 4.4, 9 (replication delay) is displayed in either bytes or seconds. See delay_threshold_by_time for more details.

The -a or --all option lists all backend nodes information.

$ pcp_node_info -w -p 11001 -a
/tmp 11002 1 0.500000 waiting up primary primary 0 none none 2021-02-27 14:51:30
/tmp 11003 1 0.500000 waiting up standby standby 0 streaming async 2021-02-27 14:51:30

The --verbose option can help understand the output. For example:

$ pcp_node_info -w -p 11001 --verbose 1
Hostname               : /tmp
Port                   : 11003
Status                 : 1
Weight                 : 0.500000
Status Name            : waiting
Backend Status Name    : up
Role                   : standby
Backend Role           : standby
Replication Delay      : 0
Replication State      : streaming
Replication Sync State : async
Last Status Change     : 2021-02-27 14:51:30
2023 pgpool-II 4.6.3