Administration

Administration standard operation procedures to manage PostgreSQL clusters in production environment.

Module:

PGSQL

Cheatsheet

PGSQL playbooks and shortcuts:

bin/pgsql-add   <cls>                   # create pgsql cluster <cls>
bin/pgsql-user  <cls> <username>        # create pg user <username> on <cls>
bin/pgsql-db    <cls> <dbname>          # create pg database <dbname> on <cls>
bin/pgsql-svc   <cls> [...ip]           # reload pg service of cluster <cls>
bin/pgsql-hba   <cls> [...ip]           # reload postgres/pgbouncer HBA rules of cluster <cls>
bin/pgsql-add   <cls> [...ip]           # append replicas for cluster <cls>
bin/pgsql-rm    <cls> [...ip]           # remove replicas from cluster <cls>
bin/pgsql-rm    <cls>                   # remove pgsql cluster <cls>

Patroni admin command and shortcuts:

pg list        <cls>                    # print cluster info
pg edit-config <cls>                    # edit cluster config 
pg reload      <cls> [ins]              # reload cluster config
pg restart     <cls> [ins]              # restart pgsql cluster
pg reinit      <cls> [ins]              # reinit cluster members
pg pause       <cls>                    # entering maintenance mode (no auto failover)
pg resume      <cls>                    # exiting maintenance mode
pg switchover  <cls>                    # switchover on cluster <cls>
pg failover    <cls>                    # failover on cluster <cls>

pgBackRest backup & restore command and shortcuts:

pb info                                 # print pgbackrest repo info
pg-backup                               # make a backup, incr, or full backup if necessary
pg-backup full                          # make a full backup
pg-backup diff                          # make a differential backup
pg-backup incr                          # make a incremental backup
pg-pitr -i                              # restore to the time of latest backup complete (not often used)
pg-pitr --time="2022-12-30 14:44:44+08" # restore to specific time point (in case of drop db, drop table)
pg-pitr --name="my-restore-point"       # restore TO a named restore point create by pg_create_restore_point
pg-pitr --lsn="0/7C82CB8" -X            # restore right BEFORE a LSN
pg-pitr --xid="1234567" -X -P           # restore right BEFORE a specific transaction id, then promote
pg-pitr --backup=latest                 # restore to latest backup set
pg-pitr --backup=20221108-105325        # restore to a specific backup set, which can be checked with pgbackrest info

Systemd components quick reference

systemctl stop patroni                  # start stop restart reload
systemctl stop pgbouncer                # start stop restart reload
systemctl stop pg_exporter              # start stop restart reload
systemctl stop pgbouncer_exporter       # start stop restart reload
systemctl stop node_exporter            # start stop restart
systemctl stop haproxy                  # start stop restart reload
systemctl stop vip-manager              # start stop restart reload
systemctl stop postgres                 # only when patroni_mode == 'remove'

Create Cluster

To create a new Postgres cluster, define it in the inventory first, then init with:

bin/node-add <cls>                # init nodes for cluster <cls>           # ./node.yml  -l <cls> 
bin/pgsql-add <cls>               # init pgsql instances of cluster <cls>  # ./pgsql.yml -l <cls>

Beware, perform bin/node-add first, then bin/pgsql-add, PGSQL works on managed nodes only.

Example: Create Cluster

Create User

To create a new business user on the existing Postgres cluster, add user definition to all.children.<cls>.pg_users, then create the user as follows:

bin/pgsql-user <cls> <username>   # ./pgsql-user.yml -l <cls> -e username=<username>

Example: Create Business User

Create Database

To create a new database user on the existing Postgres cluster, add database definition to all.children.<cls>.pg_databases, then create the database as follows:

bin/pgsql-db <cls> <dbname>       # ./pgsql-db.yml -l <cls> -e dbname=<dbname>

Note: If the database has specified an owner, the user should already exist, or you’ll have to Create User first.

Example: Create Business Database

Reload Service

Services are exposed access point served by HAProxy.

This task is used when cluster membership has changed, e.g., append/remove replicas, switchover/failover / exposing new service or updating existing service’s config (e.g., LB Weight)

To create new services or reload existing services on entire proxy cluster or specific instances:

bin/pgsql-svc <cls>               # pgsql.yml -l <cls> -t pg_service -e pg_reload=true
bin/pgsql-svc <cls> [ip...]       # pgsql.yml -l ip... -t pg_service -e pg_reload=true

Example: Reload PG Service to Kick one Instance

Reload HBARule

This task is used when your Postgres/Pgbouncer HBA rules have changed, you may have to reload hba to apply changes.

If you have any role-specific HBA rules, you may have to reload hba after a switchover/failover, too.

To reload postgres & pgbouncer HBA rules on entire cluster or specific instances:

bin/pgsql-hba <cls>               # pgsql.yml -l <cls> -t pg_hba,pg_reload,pgbouncer_hba,pgbouncer_reload -e pg_reload=true
bin/pgsql-hba <cls> [ip...]       # pgsql.yml -l ip... -t pg_hba,pg_reload,pgbouncer_hba,pgbouncer_reload -e pg_reload=true

Example: Reload Cluster HBA Rules

Config Cluster

To change the config of a existing Postgres cluster, you have to initiate control command on admin node with admin user:

pg edit-config <cls>              # interactive config a cluster with patronictl

Change patroni parameters & postgresql.parameters, save & apply changes with the wizard.

Example: Config Cluster in Non-Interactive Manner

You can skip interactive mode and use -p option to override postgres parameters, for example:

pg edit-config -p log_min_duration_statement=1000 pg-test
pg edit-config --force -p shared_preload_libraries='timescaledb, pg_cron, pg_stat_statements, auto_explain'

Example: Change Cluster Config with Patroni REST API

You can also use Patroni REST API to change the config in a non-interactive mode, for example:

$ curl -s 10.10.10.11:8008/config | jq .  # get current config
$ curl -u 'postgres:Patroni.API' \
        -d '{"postgresql":{"parameters": {"log_min_duration_statement":200}}}' \
        -s -X PATCH http://10.10.10.11:8008/config | jq .

Note: patroni unsafe RestAPI access is limit from infra/admin nodes and protected with an HTTP basic auth username/password and an optional HTTPS mode.

Example: Config Cluster with patronictl

Append Replica

To add a new replica to the existing Postgres cluster, you have to add its definition to the inventory: all.children.<cls>.hosts, then:

bin/node-add <ip>                 # init node <ip> for the new replica               
bin/pgsql-add <cls> <ip>          # init pgsql instances on <ip> for cluster <cls>

It will add node <ip> to pigsty and init it as a replica of the cluster <cls>.

Cluster services will be reloaded to adopt the new member

Example: Add replica to pg-test

For example, if you want to add a pg-test-3 / 10.10.10.13 to the existing cluster pg-test, you’ll have to update the inventory first:

pg-test:
  hosts:
    10.10.10.11: { pg_seq: 1, pg_role: primary } # existing member
    10.10.10.12: { pg_seq: 2, pg_role: replica } # existing member
    10.10.10.13: { pg_seq: 3, pg_role: replica } # <--- new member
  vars: { pg_cluster: pg-test }

then apply the change as follows:

bin/node-add          10.10.10.13   # add node to pigsty
bin/pgsql-add pg-test 10.10.10.13   # init new replica on 10.10.10.13 for cluster pg-test

which is similar to cluster init but only works on single instance。

[ OK ] init instances  10.10.10.11 to pgsql cluster 'pg-test':
[WARN]   reminder: add nodes to pigsty, then install additional module 'pgsql'
[HINT]     $ bin/node-add  10.10.10.11  # run this ahead, except infra nodes
[WARN]   init instances from cluster:
[ OK ]     $ ./pgsql.yml -l '10.10.10.11,&pg-test'
[WARN]   reload pg_service on existing instances:
[ OK ]     $ ./pgsql.yml -l 'pg-test,!10.10.10.11' -t pg_service

Remove Replica

To remove a replica from the existing PostgreSQL cluster:

bin/pgsql-rm <cls> <ip...>        # ./pgsql-rm.yml -l <ip>

It will remove instance <ip> from cluster <cls>. Cluster services will be reloaded to kick the removed instance from load balancer.

Example: Remove replica from pg-test

For example, if you want to remove pg-test-3 / 10.10.10.13 from the existing cluster pg-test:

bin/pgsql-rm pg-test 10.10.10.13  # remove pgsql instance 10.10.10.13 from pg-test
bin/node-rm  10.10.10.13          # remove that node from pigsty (optional)
vi pigsty.yml                     # remove instance definition from inventory
bin/pgsql-svc pg-test             # refresh pg_service on existing instances to kick removed instance from load balancer

[ OK ] remove pgsql instances from  10.10.10.13 of 'pg-test':
[WARN]   remove instances from cluster:
[ OK ]     $ ./pgsql-rm.yml -l '10.10.10.13,&pg-test'

And remove instance definition from the inventory:

pg-test:
  hosts:
    10.10.10.11: { pg_seq: 1, pg_role: primary }
    10.10.10.12: { pg_seq: 2, pg_role: replica }
    10.10.10.13: { pg_seq: 3, pg_role: replica } # <--- remove this after execution
  vars: { pg_cluster: pg-test }

Finally, you can update pg service and kick the removed instance from load balancer:

bin/pgsql-svc pg-test             # reload pg service on pg-test

Remove Cluster

To remove the entire Postgres cluster, just run:

bin/pgsql-rm <cls>                # ./pgsql-rm.yml -l <cls>

Example: Remove Cluster

Example: Force removing a cluster

Note: if pg_safeguard is configured for this cluster (or globally configured to true), pgsql-rm.yml will abort to avoid removing a cluster by accident.

You can use playbook command line args to explicitly overwrite it to force the purge:

./pgsql-rm.yml -l pg-meta -e pg_safeguard=false    # force removing pg cluster pg-meta

Switchover

You can perform a PostgreSQL cluster switchover with patroni cmd.

pg switchover <cls>   # interactive mode, you can skip that with following options
pg switchover --leader pg-test-1 --candidate=pg-test-2 --scheduled=now --force pg-test

Example: Switchover pg-test

$ pg switchover pg-test
Master [pg-test-1]:
Candidate ['pg-test-2', 'pg-test-3'] []: pg-test-2
When should the switchover take place (e.g. 2022-12-26T07:39 )  [now]: now
Current cluster topology
+ Cluster: pg-test (7181325041648035869) -----+----+-----------+-----------------+
| Member    | Host        | Role    | State   | TL | Lag in MB | Tags            |
+-----------+-------------+---------+---------+----+-----------+-----------------+
| pg-test-1 | 10.10.10.11 | Leader  | running |  1 |           | clonefrom: true |
|           |             |         |         |    |           | conf: tiny.yml  |
|           |             |         |         |    |           | spec: 1C.2G.50G |
|           |             |         |         |    |           | version: '15'   |
+-----------+-------------+---------+---------+----+-----------+-----------------+
| pg-test-2 | 10.10.10.12 | Replica | running |  1 |         0 | clonefrom: true |
|           |             |         |         |    |           | conf: tiny.yml  |
|           |             |         |         |    |           | spec: 1C.2G.50G |
|           |             |         |         |    |           | version: '15'   |
+-----------+-------------+---------+---------+----+-----------+-----------------+
| pg-test-3 | 10.10.10.13 | Replica | running |  1 |         0 | clonefrom: true |
|           |             |         |         |    |           | conf: tiny.yml  |
|           |             |         |         |    |           | spec: 1C.2G.50G |
|           |             |         |         |    |           | version: '15'   |
+-----------+-------------+---------+---------+----+-----------+-----------------+
Are you sure you want to switchover cluster pg-test, demoting current master pg-test-1? [y/N]: y
2022-12-26 06:39:58.02468 Successfully switched over to "pg-test-2"
+ Cluster: pg-test (7181325041648035869) -----+----+-----------+-----------------+
| Member    | Host        | Role    | State   | TL | Lag in MB | Tags            |
+-----------+-------------+---------+---------+----+-----------+-----------------+
| pg-test-1 | 10.10.10.11 | Replica | stopped |    |   unknown | clonefrom: true |
|           |             |         |         |    |           | conf: tiny.yml  |
|           |             |         |         |    |           | spec: 1C.2G.50G |
|           |             |         |         |    |           | version: '15'   |
+-----------+-------------+---------+---------+----+-----------+-----------------+
| pg-test-2 | 10.10.10.12 | Leader  | running |  1 |           | clonefrom: true |
|           |             |         |         |    |           | conf: tiny.yml  |
|           |             |         |         |    |           | spec: 1C.2G.50G |
|           |             |         |         |    |           | version: '15'   |
+-----------+-------------+---------+---------+----+-----------+-----------------+
| pg-test-3 | 10.10.10.13 | Replica | running |  1 |         0 | clonefrom: true |
|           |             |         |         |    |           | conf: tiny.yml  |
|           |             |         |         |    |           | spec: 1C.2G.50G |
|           |             |         |         |    |           | version: '15'   |
+-----------+-------------+---------+---------+----+-----------+-----------------+

To do so with Patroni API (schedule a switchover from 2 to 1 at a specific time):

curl -u 'postgres:Patroni.API' \
  -d '{"leader":"pg-test-2", "candidate": "pg-test-1","scheduled_at":"2022-12-26T14:47+08"}' \
  -s -X POST http://10.10.10.11:8008/switchover

Backup Cluster

To create a backup with pgBackRest, run as local dbsu:

pg-backup                         # make a postgres base backup
pg-backup full                    # make a full backup
pg-backup diff                    # make a differential backup
pg-backup incr                    # make a incremental backup
pb info                           # check backup information

Check Backup & PITR for details.

Example: Make Backups

Example: Create routine backup crontab

You can add crontab to node_crontab to specify your backup policy.

# make a full backup 1 am everyday
- '00 01 * * * postgres /pg/bin/pg-backup full'

# rotate backup: make a full backup on monday 1am, and an incremental backup during weekdays
- '00 01 * * 1 postgres /pg/bin/pg-backup full'
- '00 01 * * 2,3,4,5,6,7 postgres /pg/bin/pg-backup'

Restore Cluster

To restore a cluster to a previous time point (PITR), run as local dbsu:

pg-pitr -i                              # restore to the time of latest backup complete (not often used)
pg-pitr --time="2022-12-30 14:44:44+08" # restore to specific time point (in case of drop db, drop table)
pg-pitr --name="my-restore-point"       # restore TO a named restore point create by pg_create_restore_point
pg-pitr --lsn="0/7C82CB8" -X            # restore right BEFORE a LSN
pg-pitr --xid="1234567" -X -P           # restore right BEFORE a specific transaction id, then promote
pg-pitr --backup=latest                 # restore to latest backup set
pg-pitr --backup=20221108-105325        # restore to a specific backup set, which can be checked with pgbackrest info

And follow the instructions wizard, Check Backup & PITR for details.

Example: PITR with raw pgBackRest Command

# restore to the latest available point (e.g. hardware failure)
pgbackrest --stanza=pg-meta restore

# PITR to specific time point (e.g. drop table by accident)
pgbackrest --stanza=pg-meta --type=time --target="2022-11-08 10:58:48" \
   --target-action=promote restore

# restore specific backup point and then promote (or pause|shutdown)
pgbackrest --stanza=pg-meta --type=immediate --target-action=promote \
  --set=20221108-105325F_20221108-105938I restore

Adding Packages

To add newer version of RPM packages, you have to add them to repo_packages and repo_url_packages

Then rebuild repo on infra nodes with ./infra.yml -t repo_build subtask, Then you can install these packages with ansible module package:

ansible pg-test -b -m package -a "name=pg_cron_15,topn_15,pg_stat_monitor_15*"  # install some packages

Update Packages Manually

# add repo upstream on admin node, then download them manually
cd ~/pigsty; ./infra.yml -t repo_upstream,repo_cache # add upstream repo (internet)
cd /www/pigsty;  repotrack "some_new_package_name"   # download the latest RPMs

# re-create local repo on admin node, then refresh yum/apt cache on all nodes
cd ~/pigsty; ./infra.yml -t repo_create              # recreate local repo on admin node
./node.yml -t node_repo                              # refresh yum/apt cache on all nodes

# alternatives: clean and remake cache on all nodes with ansible command
ansible all -b -a 'yum clean all'                         # clean node repo cache
ansible all -b -a 'yum makecache'                         # remake cache from the new repo
ansible all -b -a 'apt clean'                             # clean node repo cache (Ubuntu/Debian)
ansible all -b -a 'apt update'                            # remake cache from the new repo (Ubuntu/Debian)

For example, you can then install or upgrade packages with:

ansible pg-test -b -m package -a "name=postgresql15* state=latest"

Install Extension

If you want to install extension on pg clusters, Add them to pg_extensions and make sure them installed with:

./pgsql.yml -t pg_extension     # install extensions

Some extension needs to be loaded in shared_preload_libraries, You can add them to pg_libs, or Config an existing cluster.

Finally, CREATE EXTENSION <extname>; on the cluster primary instance to install it.

Example: Install pg_cron on pg-test cluster

ansible pg-test -b -m package -a "name=pg_cron_15"          # install pg_cron packages on all nodes
# add pg_cron to shared_preload_libraries
pg edit-config --force -p shared_preload_libraries='timescaledb, pg_cron, pg_stat_statements, auto_explain'
pg restart --force pg-test                                  # restart cluster
psql -h pg-test -d postgres -c 'CREATE EXTENSION pg_cron;'  # install pg_cron on primary

Check PGSQL Extensions: Install for details.

Minor Upgrade

To perform a minor server version upgrade/downgrade, you have to add packages to yum/apt repo first.

Then perform a rolling upgrade/downgrade from all replicas, then switchover the cluster to upgrade the leader.

ansible <cls> -b -a "yum upgrade/downgrade -y <pkg>"    # upgrade/downgrade packages
pg restart --force <cls>                                # restart cluster

Example: Downgrade PostgreSQL 15.2 to 15.1

Add 15.1 packages to yum/apt repo and refresh node package manager cache:

cd ~/pigsty; ./infra.yml -t repo_upstream               # add upstream repo backup
cd /www/pigsty; repotrack postgresql15-*-15.1           # add 15.1 packages to yum repo
cd ~/pigsty; ./infra.yml -t repo_create                 # re-create repo
ansible pg-test -b -a 'yum clean all'                   # clean node repo cache (use apt in debian/ubuntu)
ansible pg-test -b -a 'yum makecache'                   # remake yum cache from the new repo

Perform a downgrade and restart the cluster:

ansible pg-test -b -a "yum downgrade -y postgresql15*"  # downgrade packages
pg restart --force pg-test                              # restart entire cluster to finish upgrade

Example: Upgrade PostgreSQL 15.1 back to 15.2

This time we upgrade in a rolling fashion:

ansible pg-test -b -a "yum upgrade -y postgresql15*"    # upgrade packages
ansible pg-test -b -a '/usr/pgsql/bin/pg_ctl --version' # check binary version is 15.2
pg restart --role replica --force pg-test               # restart replicas
pg switchover --leader pg-test-1 --candidate=pg-test-2 --scheduled=now --force pg-test    # switchover
pg restart --role primary --force pg-test               # restart primary

Major Upgrade

The simplest way to achieve a major version upgrade is to create a new cluster with the new version, then migration with logical replication & green/blue deployment.

You can also perform an in-place major upgrade, which is not recommended especially when certain extensions are installed. But it is possible.

Assume you want to upgrade PostgreSQL 14 to 15, you have to add packages to yum/apt repo, and guarantee the extensions has exact same version too.

./pgsql.yml -t pg_pkg -e pg_version=15                         # install packages for pg 15
sudo su - postgres; mkdir -p /data/postgres/pg-meta-15/data/   # prepare directories for 15
pg_upgrade -b /usr/pgsql-14/bin/ -B /usr/pgsql-15/bin/ -d /data/postgres/pg-meta-14/data/ -D /data/postgres/pg-meta-15/data/ -v -c # preflight
pg_upgrade -b /usr/pgsql-14/bin/ -B /usr/pgsql-15/bin/ -d /data/postgres/pg-meta-14/data/ -D /data/postgres/pg-meta-15/data/ --link -j8 -v -c
rm -rf /usr/pgsql; ln -s /usr/pgsql-15 /usr/pgsql;             # fix binary links 
mv /data/postgres/pg-meta-14 /data/postgres/pg-meta-15         # rename data directory
rm -rf /pg; ln -s /data/postgres/pg-meta-15 /pg                # fix data dir links

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Last modified 2024-08-13: update extension list (1fef2bfc)