Provided by: pgpool2_4.3.2-1_amd64 
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, “Health Check”, in
the documentation) 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 25, “Statistics data shown by pool_health_check_stats command” shows each column
name and its description.
Table 25. Statistics data shown by pool_health_check_stats command
┌─────────────────────────────┬──────────────────────────────────┐
│Column Name │ Description │
├─────────────────────────────┼──────────────────────────────────┤
│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