SHOW POOL_HEALTH_CHECK_STATS

Name

SHOW POOL_HEALTH_CHECK_STATS --  show health check statistics data

Synopsis

   SHOW POOL_HEALTH_CHECK_STATS
  

Description

SHOW POOL_HEALTH_CHECK_STATS displays health check (see Section 5.8) statistic data mostly collected by health check process. This command helps Pgpool-II admin to study events related to health check. For example, admin can easily locate the failover event in the log file by looking at "last_failed_health_check" column. Another example is finding unstable connection to backend by evaluating "average_retry_count" column. If particular node shows higher retry count than other node, there may be problem to the connection to the backend.

Table 1 shows each column name and its description.

Table 1. Statistics data shown by pool_health_check_stats command

Column NameDescription
node_id Backend node id.
hostname Backend hostname or UNIX domain socket path.
port Backend port number.
status Backend status. One of up, down, waiting, unused or quarantine.
role Role of the node. Either primary or standby in streaming replication mode. Either main or replica in other mode.
last_status_change Timestamp of last backend status changed.
total_count Number of health check count in total.
success_count Number of successful health check count in total.
fail_count Number of failed health check count in total.
skip_count Number of skipped health check count in total. If the node is already down, health check skips the node.
retry_count Number of retried health check count in total.
average_retry_count Number of average retried health check count in a health check session.
max_retry_count Number of maximum retried health check count in a health check session.
max_duration Maximum health check duration in Millie seconds. If a health check session retries, the health check duration is sum of each retried health check.
min_duration Minimum health check duration in Millie seconds. If a health check session retries, the health check duration is sum of each retried health check.
average_duration Average health check duration in Millie seconds. If a health check session retries, the health check duration is sum of each retried health check.
last_health_check Timestamp of last health check. If heath check does not performed yet, empty string.
last_successful_health_check Timestamp of last successful health check. If heath check does not succeeds yet, empty string.
last_skip_health_check Timestamp of last skipped health check. If heath check is not skipped yet, empty string. Note that it is possible that this field is an empty string even if the status is down. In this case failover was triggered by other than health check process.
last_failed_health_check Timestamp of last failed health check. If heath check does not fail yet, empty string. Note that it is possible that this field is an empty string even if the status is down. In this case failover was triggered by other than health check process.

Here is an example session:

test=# show pool_health_check_stats;
-[ RECORD 1 ]----------------+--------------------
node_id                      | 0
hostname                     | /tmp
port                         | 11002
status                       | up
role                         | primary
last_status_change           | 2020-01-26 19:08:45
total_count                  | 27
success_count                | 27
fail_count                   | 0
skip_count                   | 0
retry_count                  | 0
average_retry_count          | 0.000000
max_retry_count              | 0
max_duration                 | 9
min_duration                 | 2
average_duration             | 6.296296
last_health_check            | 2020-01-26 19:12:45
last_successful_health_check | 2020-01-26 19:12:45
last_skip_health_check       | 
last_failed_health_check     | 
-[ RECORD 2 ]----------------+--------------------
node_id                      | 1
hostname                     | /tmp
port                         | 11003
status                       | down
role                         | standby
last_status_change           | 2020-01-26 19:11:48
total_count                  | 19
success_count                | 12
fail_count                   | 1
skip_count                   | 6
retry_count                  | 3
average_retry_count          | 0.230769
max_retry_count              | 3
max_duration                 | 83003
min_duration                 | 0
average_duration             | 6390.307692
last_health_check            | 2020-01-26 19:12:48
last_successful_health_check | 2020-01-26 19:10:15
last_skip_health_check       | 2020-01-26 19:12:48
last_failed_health_check     | 2020-01-26 19:11:48