PostgreSQL Configuration for HA and Load Balancing

posted May 7, 2019, 10:18 AM by

Andy Kerber (@dbakerber), Senior Consultant

In this blog, we will cover the installation and configuration of PostgreSQL for load balancing and High Availability (HA).  This is a fairly basic, traditional configuration that uses a hot standby rather than SQL replication.

Servers

First, a summary of the servers involved.

Pgstream1 and pgstream2 are the Postgres database servers. Pgstream1 includes the primary database, pgstream2 includes the hot standby.

Pgpool1 and pgpool2 are the load balancing connection pooling servers for the Postgres databases, which are set up as a watchdog cluster. Automatic activation of the hot standby is not configured, but  we will discuss it in a future blog.

The steps in the section titled ‘DB Server Setup’ to the start of ‘Hot Standby Setup’ must be done on both pgstream1 and pgstream2 and the steps are the same for both servers.

DB Server Setup

The host file is below.  This file is the same on all servers discussed in this blog.  The –priv ips are used for communication between the primary and standby Postgres instances. The –hb ips are used for communication between the two pgpool servers. Isolating the networks is a best practice:

127.0.0.1   localhost localhost.localdomain localhost4 localhost4.localdomain4
::1         localhost localhost.localdomain localhost6 localhost6.localdomain6


10.12.1.61  pgstream2 pgstream2.localdomain
10.12.1.225 pgstream1 pgstream1.localdomain


192.168.57.10 pgstream1-priv pgstream1-priv.localdomain
192.168.57.11 pgstream2-priv pgstream2-priv.localdomain


10.12.1.142   pgpool1  pgpool1.localdomain
10.12.1.204   pgpool2  pgpool2.localdomain


192.168.31.20   pgpool1-hb pgpool1-hb.localdomain
192.168.31.21   pgpool2-hb pgpool2-hb.localdomain


For this blog, we used the open source version of Postgres, with the open source repos.  Below are the commands we used to install the required repos:

yum install https://dl.fedoraproject.org/pub/epel/epel-release-latest-7.noarch.rpm

yum install

curl --header 'Host: download.postgresql.org' --user-agent 'Mozilla/5.0 (Windows NT 
6.1; Win64; x64; rv:66.0) Gecko/20100101 Firefox/66.0' --header 'Accept: 
text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8' --header 'Accept-Language: 
en-US,en;q=0.5' --referer 'https://yum.postgresql.org/repopackages.php' --header 'DNT: 1' 
--cookie '__utma=257560202.337789427.1552660161.1554995806.1555514629.5; 
__utmz=257560202.1555514629.5.4.utmcsr=google|utmccn=(organic)|utmcmd=organic|utmctr=(not%20provided);
 __utmc=257560202; __utmb=257560202.2.10.1555514629' --header 'Upgrade-Insecure-Requests: 1' 
'https://download.postgresql.org/pub/repos/yum/11/redhat/rhel-7-x86_64/pgdg-redhat-repo-latest.noarch.rpm'
 --output 'pgdg-redhat-repo-latest.noarch.rpm'

yum -y install pgdg-redhat-repo-latest.noarch.rpm

 

Next, with the repos configured and everything downloaded, install the Postgres software:

yum install postgresql11-server

 

Configure the data directories for Postgres, and use LVM for space management.  The steps below create a partition in a new disk device, put it in LVM, label it, and create an XFS file system on it.  While obviously the Postgres data can go on the root file system, it works best to put it in a separate volume group for simpler space management.

fdisk /dev/sdb

 

Create a new primary partition on /dev/sdb using all the space on the drive.  The name of the partition is /dev/sdb1.

[root@pgstream2 ~]# fdisk /dev/sdb
Welcome to fdisk (util-linux 2.23.2).

Changes will remain in memory only, until you decide to write them.
Be careful before using the write command.

Device does not contain a recognized partition table
Building a new DOS disklabel with disk identifier 0x57646c50.

Command (m for help): n
Partition type:
   p   primary (0 primary, 0 extended, 4 free)
   e   extended
Select (default p):
Using default response p
Partition number (1-4, default 1):
First sector (2048-41943039, default 2048):
Using default value 2048
Last sector, +sectors or +size{K,M,G} (2048-41943039, default 41943039):
Using default value 41943039
Partition 1 of type Linux and of size 20 GiB is set

Command (m for help): w
The partition table has been altered!

Calling ioctl() to re-read partition table.
Syncing disks.

 

Next, create a new logical volume group for the Postgres data. The commands below create a new physical volume from /dev/sdb1.  They also create a new volume group called data, containing /dev/sdb1.  Next, a new logical volume named pgdata is created that contains the volume group. The logical volume will be used for the data.

pvcreate /dev/sdb1
vgcreate data /dev/sdb1
lvcreate -n pgdata -l 100%FREE data
mkfs.xfs /dev/data/pgdata
xfs_admin -L pgdata /dev/data/pgdata
mkdir -p /postgres/data

 

Next, do the same for /dev/sdc.  The name of the partition is /dev/sdc1. Create a new logical volume as indicated below, the logical volume will be used for the WAL (archive) logs.

fdisk /dev/sdc
vgcreate archive /dev/sdc1
lvcreate -n archive_vol -l 100%FREE archive
mkfs.xfs -L archive /dev/archive/archive_vol
mkdir -p /postgres/archive

 

Then, add lines in /etc/fstab for these two new file systems:

LABEL=pgdata /postgres/data                     xfs defaults 0 0
LABEL=archive /postgres/archive                     xfs defaults 0 0

Mount the devices using mount –a.  Mounting the devices this way accomplishes two things, it ensures that the fstab format is correct, and mounts the drives.

Next, we need to initialize the database.  Set the PGDATA environment variable to point to our data directory:

export PGDATA=/postgres/data/pgdata
/usr/pgsql-11/bin/postgresql-11-setup initdb

 

This creates the initial data directory (cluster, in Postgres parlance) with an empty database and the required configuration files.

Next, edit the pg_hba.conf file to allow connections as desired.  Our pg_hba.conf file is below:

local   all             all                                    trust
host    all             all             0.0.0.0/0              md5
host    all             all             pgstream1              trust
host    all             all             pgstream2              trust
# IPv4 local connections:
host    all             all             127.0.0.1/32            ident
# IPv6 local connections:
host    all             all             ::1/128                 ident
# Allow replication connections from localhost, by a user with the
# replication privilege.
local   replication     all                                    trust
host    replication     all             127.0.0.1/32            ident
host    replication     all             ::1/128                 ident
host    replication     all             0.0.0.0/0              md5

 

At this point, the initial basic setup is complete. Now we need to configure the database for hot standby replication.

Configure Postgres to start as a service.  First, edit the file /usr/lib/systemd/system/postgresql-11.service and edit the line beginning with ‘Environment=’.  Change the line to read:

Environment=PGDATA=/postgres/data/pgdata

 

Now, enable and start the service:

systemctl enable postgresql-11.service
systemctl start postgresql-11.service

 

Hot Standby Setup – Primary

On the primary server, make the following changes to the postgresql.conf file.  Only the non-default parameters are noted here:

listen_addresses = '*'
shared_buffers = 1024MB                 # min 128kB
wal_level = logical                     # minimal, replica, or logical
full_page_writes = on                   # recover from partial page writes
max_wal_size = 1GB
min_wal_size = 80MB
archive_mode = on               # enables archiving; off, on, or always
archive_command = 'test ! -f /postgres/archive/%f && cp %p /postgres/archive/%f'
hot_standby = on                        # "off" disallows queries during recovery

 

Create the replication user, which  is the user that has privileges to create the hot standby:

postgres=# create role replication with REPLICATION password 'mypassword' login;

Hot Standby Setup – Standby

On the standby server, stop the Postgres service:

systemctl stop postgresql-11.service

 

Then, delete all files in the PGDATA directory:

(rm –rf /postgres/data/pgdata)

 

Create the hot standby files using the pg_basebackup command:

pg_basebackup -h pgstream1-priv -U replication -D /postgres/data/pgdata

 

Next, before starting the database, create the recovery.conf file (with the contents below) in the PGDATA directory.  This tells Postgres where the source WAL logs are coming from:

standby_mode = 'on'
primary_conninfo = 'host=pgstream1-priv port=5432 user=replication password=replication'
trigger_file= '/var/lib/pgsql/activate.now'

 

Start the standby:

systemctl start postgresql-11.service

 

After starting the service, monitor the log file in $PGDATA/log/postgresql-dow.log.  Lines similar to those below indicate that the standby is working properly:

2019-04-30 14:29:47.664 CDT [20428] LOG:  database system is ready to accept read only connections
2019-04-30 14:29:47.675 CDT [20436] LOG:  started streaming WAL from primary at 0/7000000 on timeline 1

 

Should it become necessary to activate the standby in read-write mode, we will use the command ‘touch /var/lib/pgsql/activate.now’.  The existence of the file created by the ‘touch’ command is the signal to activate the standby. The file is created on the standby server.

Pgpool Setup

Pgpool is connection pooling software for the Postgres database. It can be used to direct communications to the standby or primary node, as well as manage failover.

More about managing failover will be discussed later blogs. In this blog, we are going set up a two-node Pgpool watchdog cluster.

First, install the Pgpool software. For this example, we are using the most recent available version pgpool-II-10. The command to install the software is yum install pgpool-II-10.  Note that for this version of Pgpool, the authors chose to leave the full version information on the directories, so you will use the Pgpool-II-10 directories rather than the Pgpool-II directories, which can be confusing.

Next, modify the files for the service to be run by root. Running it under root makes management easier. Just remove the line that tells it to run under Postgres, so the file /usr/lib/systemd/system/pgpool-II-10.service reads like this:

[Unit]
Description=PGPool-II Middleware Between PostgreSQL Servers And PostgreSQL Database Clients
After=syslog.target network.target

[Service]

EnvironmentFile=-/etc/sysconfig/pgpool-II-10
ExecStart=/usr/pgpool-10/bin/pgpool -f /etc/pgpool-II-10/pgpool.conf $OPTS
ExecStop=/usr/pgpool-10/bin/pgpool -f /etc/pgpool-II-10/pgpool.conf -m fast stop
ExecReload=/bin/kill -HUP $MAINPID
KillMode=mixed
KillSignal=SIGINT

[Install]
WantedBy=multi-user.target

 

Update the file on pgpool1 as follows (non-default settings are the only settings listed):

listen_addresses = '*'
port = 5432
pcp_listen_addresses = '*'
pcp_port = 9898
backend_hostname0 = '10.12.1.225'
backend_port0 = 5432
backend_data_directory0 = '/postgres/data/pgdata'
backend_flag0 = 'DISALLOW_TO_FAILOVER'
backend_hostname1 = '10.12.1.61'
backend_port1 = 5432
backend_weight1 = 1
backend_data_directory1 = '/postgres/data/pgdata'
backend_flag1 = 'DISALLOW_TO_FAILOVER'
enable_pool_hba = on
pool_passwd = 'pool_passwd'
log_destination = 'syslog'
syslog_facility = 'LOCAL6'
syslog_ident = 'pgpool-II-10'
load_balance_mode = on
master_slave_mode = on
master_slave_sub_mode = 'stream'
sr_check_user = 'postgres'
sr_check_password = 'password'
sr_check_database = 'postgres'
health_check_user = 'postgres'
health_check_password = 'password'
use_watchdog = on
wd_hostname = '192.168.31.20'
wd_port = 9000
delegate_IP = '10.12.1.111'
if_up_cmd = 'ip addr add $_IP_$/24 dev ens33 label ens33:111'
if_down_cmd = 'ip addr del $_IP_$/24 dev ens33'
arping_cmd = 'ping -w 1 $_IP_$'
wd_lifecheck_method = 'heartbeat'
wd_heartbeat_port = 9694
heartbeat_destination0 = '192.168.31.21'
heartbeat_destination_port0 = 9694
other_pgpool_hostname0 = '192.168.159.21'
other_pgpool_port0 = 5432
other_wd_port0 = 9000

 

On pgpool2, the changes are very similar, just reverse the node IP addresses:

listen_addresses = '*'
port = 5432
pcp_listen_addresses = '*'
pcp_port = 9898
backend_hostname0 = '10.12.1.225'
backend_port0 = 5432
backend_data_directory0 = '/postgres/data/pgdata'
backend_flag0 = 'DISALLOW_TO_FAILOVER'
backend_hostname1 = '10.12.1.61'
backend_port1 = 5432
backend_weight1 = 1
backend_data_directory1 = '/postgres/data/pgdata'
backend_flag1 = 'DISALLOW_TO_FAILOVER'
enable_pool_hba = on
pool_passwd = 'pool_passwd'
log_destination = 'syslog'
syslog_facility = 'LOCAL6'
syslog_ident = 'pgpool-II-10'
load_balance_mode = on
master_slave_mode = on
master_slave_sub_mode = 'stream'
sr_check_user = 'postgres'
sr_check_password = 'password'
sr_check_database = 'postgres'
health_check_user = 'postgres'
health_check_password = 'password'
use_watchdog = on
wd_hostname = '192.168.31.21'
wd_port = 9000
delegate_IP = '10.12.1.111'
if_up_cmd = 'ip addr add $_IP_$/24 dev ens33 label ens33:111'
if_down_cmd = 'ip addr del $_IP_$/24 dev ens33'
arping_cmd = 'ping -w 1 $_IP_$'
wd_lifecheck_method = 'heartbeat'
wd_heartbeat_port = 9694
heartbeat_destination0 = '192.168.31.20'
heartbeat_destination_port0 = 9694
other_pgpool_hostname0 = '192.168.159.20'
other_pgpool_port0 = 5432
other_wd_port0 = 9000

 

Next, on each server add this line to /etc/rsyslog.conf:

local6.*              /var/log/pgpool-II-10/pgpool-II-10.log

 

The line will cause pgpool-II-10 to log information to the file /var/log/pgpool-II-10/ pgpool-II-10.log.

Then, on either server, use the pg_md5 to populate the pool_passwd file:

pg_md5 --md5auth --username=postgres password

 

The file is located in /etc/pgpool-II-10.  Copy the password from the current server to the same directory on the other server.

Edit the pool_hba.conf to read as required.  Below is the pool_hba.conf for this configuration:

# "local" is for Unix domain socket connections only
local   all         all                               trust
# IPv4 local connections:
host    all         all         127.0.0.1/32          trust
host    all         all         ::1/128               trust
host    all             all             0.0.0.0/0              md5
host    all             all             pgstream1              trust
host    all             all             pgstream2              trust

 

Copy the file to both nodes.

At this point, you are ready to start pgpool.  On the first node, start the service using this command:

systemctl start pgpool-II-10.service

 

A successful startup of the first node will look like the following in the log file:

Apr 30 16:39:50 pgpool1 pgpool-II-10[17955]: [1-1] 2019-04-30 16:39:50: pid 17955: WARNING:  checking setuid bit of if_up_cmd
Apr 30 16:39:50 pgpool1 pgpool-II-10[17955]: [1-2] 2019-04-30 16:39:50: pid 17955: DETAIL:  ifup[/usr/sbin/ip] doesn't have setuid bit
Apr 30 16:39:50 pgpool1 pgpool-II-10[17955]: [2-1] 2019-04-30 16:39:50: pid 17955: WARNING:  checking setuid bit of if_down_cmd
Apr 30 16:39:50 pgpool1 pgpool-II-10[17955]: [2-2] 2019-04-30 16:39:50: pid 17955: DETAIL:  ifdown[/usr/sbin/ip] doesn't have setuid bit
Apr 30 16:39:50 pgpool1 pgpool-II-10[17955]: [3-1] 2019-04-30 16:39:50: pid 17955: WARNING:  checking setuid bit of arping command
Apr 30 16:39:50 pgpool1 pgpool-II-10[17955]: [3-2] 2019-04-30 16:39:50: pid 17955: DETAIL:  arping[/bin/ping] doesn't have setuid bit
Apr 30 16:39:50 pgpool1 pgpool-II-10[17955]: [4-1] 2019-04-30 16:39:50: pid 17955: LOG:  Backend status file /var/log/pgpool-II-10/pgpool_status discarded
Apr 30 16:39:50 pgpool1 pgpool-II-10[17955]: [5-1] 2019-04-30 16:39:50: pid 17955: LOG:  waiting for watchdog to initialize
Apr 30 16:39:50 pgpool1 pgpool-II-10[17956]: [5-1] 2019-04-30 16:39:50: pid 17956: LOG:  setting the local watchdog node name to "192.168.31.20:5432 Linux pgpool1.localdomain"
Apr 30 16:39:50 pgpool1 pgpool-II-10[17956]: [6-1] 2019-04-30 16:39:50: pid 17956: LOG:  watchdog cluster is configured with 1 remote nodes
Apr 30 16:39:50 pgpool1 pgpool-II-10[17956]: [7-1] 2019-04-30 16:39:50: pid 17956: LOG:  watchdog remote node:0 on 192.168.159.21:9000
Apr 30 16:39:50 pgpool1 pgpool-II-10[17956]: [8-1] 2019-04-30 16:39:50: pid 17956: LOG:  interface monitoring is disabled in watchdog
Apr 30 16:39:50 pgpool1 pgpool-II-10[17956]: [9-1] 2019-04-30 16:39:50: pid 17956: LOG:  watchdog node state changed from [DEAD] to [LOADING]
Apr 30 16:39:55 pgpool1 pgpool-II-10[17956]: [10-1] 2019-04-30 16:39:55: pid 17956: LOG:  watchdog node state changed from [LOADING] to [JOINING]
Apr 30 16:39:59 pgpool1 pgpool-II-10[17956]: [11-1] 2019-04-30 16:39:59: pid 17956: LOG:  watchdog node state changed from [JOINING] to [INITIALIZING]
Apr 30 16:40:00 pgpool1 pgpool-II-10[17956]: [12-1] 2019-04-30 16:40:00: pid 17956: LOG:  I am the only alive node in the watchdog cluster
Apr 30 16:40:00 pgpool1 pgpool-II-10[17956]: [12-2] 2019-04-30 16:40:00: pid 17956: HINT:  skipping stand for coordinator state
Apr 30 16:40:00 pgpool1 pgpool-II-10[17956]: [13-1] 2019-04-30 16:40:00: pid 17956: LOG:  watchdog node state changed from [INITIALIZING] to [MASTER]
Apr 30 16:40:00 pgpool1 pgpool-II-10[17956]: [14-1] 2019-04-30 16:40:00: pid 17956: LOG:  I am announcing my self as master/coordinator watchdog node
Apr 30 16:40:04 pgpool1 pgpool-II-10[17956]: [15-1] 2019-04-30 16:40:04: pid 17956: LOG:  I am the cluster leader node
Apr 30 16:40:04 pgpool1 pgpool-II-10[17956]: [15-2] 2019-04-30 16:40:04: pid 17956: DETAIL:  our declare coordinator message is accepted by all nodes
Apr 30 16:40:04 pgpool1 pgpool-II-10[17956]: [16-1] 2019-04-30 16:40:04: pid 17956: LOG:  setting the local node "192.168.31.20:5432 Linux pgpool1.localdomain" as watchdog cluster master
Apr 30 16:40:04 pgpool1 pgpool-II-10[17956]: [17-1] 2019-04-30 16:40:04: pid 17956: LOG:  I am the cluster leader node. Starting escalation process
Apr 30 16:40:04 pgpool1 pgpool-II-10[17956]: [18-1] 2019-04-30 16:40:04: pid 17956: LOG:  escalation process started with PID:17963
Apr 30 16:40:04 pgpool1 pgpool-II-10[17955]: [6-1] 2019-04-30 16:40:04: pid 17955: LOG:  watchdog process is initialized
Apr 30 16:40:04 pgpool1 pgpool-II-10[17956]: [19-1] 2019-04-30 16:40:04: pid 17956: LOG:  new IPC connection received
Apr 30 16:40:04 pgpool1 pgpool-II-10[17955]: [7-1] 2019-04-30 16:40:04: pid 17955: LOG:  Setting up socket for 0.0.0.0:5432
Apr 30 16:40:04 pgpool1 pgpool-II-10[17955]: [8-1] 2019-04-30 16:40:04: pid 17955: LOG:  Setting up socket for :::5432
Apr 30 16:40:04 pgpool1 pgpool-II-10[17955]: [9-1] 2019-04-30 16:40:04: pid 17955: LOG:  find_primary_node_repeatedly: waiting for finding a primary node
Apr 30 16:40:04 pgpool1 pgpool-II-10[17963]: [18-1] 2019-04-30 16:40:04: pid 17963: LOG:  watchdog: escalation started
Apr 30 16:40:04 pgpool1 pgpool-II-10[17956]: [20-1] 2019-04-30 16:40:04: pid 17956: LOG:  new IPC connection received
Apr 30 16:40:04 pgpool1 pgpool-II-10[17964]: [7-1] 2019-04-30 16:40:04: pid 17964: LOG:  2 watchdog nodes are configured for lifecheck
Apr 30 16:40:04 pgpool1 pgpool-II-10[17964]: [8-1] 2019-04-30 16:40:04: pid 17964: LOG:  watchdog nodes ID:0 Name:"192.168.31.20:5432 Linux pgpool1.localdomain"
Apr 30 16:40:04 pgpool1 pgpool-II-10[17964]: [8-2] 2019-04-30 16:40:04: pid 17964: DETAIL:  Host:"192.168.31.20" WD Port:9000 pgpool-II port:5432
Apr 30 16:40:04 pgpool1 pgpool-II-10[17964]: [9-1] 2019-04-30 16:40:04: pid 17964: LOG:  watchdog nodes ID:1 Name:"Not_Set"
Apr 30 16:40:04 pgpool1 pgpool-II-10[17964]: [9-2] 2019-04-30 16:40:04: pid 17964: DETAIL:  Host:"192.168.159.21" WD Port:9000 pgpool-II port:5432
Apr 30 16:40:04 pgpool1 pgpool-II-10[17955]: [10-1] 2019-04-30 16:40:04: pid 17955: LOG:  find_primary_node: primary node is 0
Apr 30 16:40:04 pgpool1 pgpool-II-10[17955]: [11-1] 2019-04-30 16:40:04: pid 17955: LOG:  find_primary_node: standby node is 1
Apr 30 16:40:04 pgpool1 pgpool-II-10[17955]: [12-1] 2019-04-30 16:40:04: pid 17955: LOG:  pgpool-II successfully started. version 4.0.3 (torokiboshi)
Apr 30 16:40:04 pgpool1 pgpool-II-10[17955]: [13-1] 2019-04-30 16:40:04: pid 17955: LOG:  node status[0]: 1
Apr 30 16:40:04 pgpool1 pgpool-II-10[17955]: [14-1] 2019-04-30 16:40:04: pid 17955: LOG:  node status[1]: 2
Apr 30 16:40:05 pgpool1 pgpool-II-10[17999]: [10-1] 2019-04-30 16:40:05: pid 17999: LOG:  set SO_REUSEPORT option to the socket
Apr 30 16:40:05 pgpool1 pgpool-II-10[17999]: [11-1] 2019-04-30 16:40:05: pid 17999: LOG:  creating socket for sending heartbeat
Apr 30 16:40:05 pgpool1 pgpool-II-10[17999]: [11-2] 2019-04-30 16:40:05: pid 17999: DETAIL:  set SO_REUSEPORT
Apr 30 16:40:05 pgpool1 pgpool-II-10[17998]: [10-1] 2019-04-30 16:40:05: pid 17998: LOG:  set SO_REUSEPORT option to the socket
Apr 30 16:40:05 pgpool1 pgpool-II-10[17998]: [11-1] 2019-04-30 16:40:05: pid 17998: LOG:  creating watchdog heartbeat receive socket.
Apr 30 16:40:05 pgpool1 pgpool-II-10[17998]: [11-2] 2019-04-30 16:40:05: pid 17998: DETAIL:  set SO_REUSEPORT
Apr 30 16:40:07 pgpool1 pgpool-II-10[17963]: [19-1] 2019-04-30 16:40:07: pid 17963: LOG:  successfully acquired the delegate IP:"10.12.1.111"
Apr 30 16:40:07 pgpool1 pgpool-II-10[17963]: [19-2] 2019-04-30 16:40:07: pid 17963: DETAIL:  'if_up_cmd' returned with success
Apr 30 16:40:07 pgpool1 pgpool-II-10[17956]: [21-1] 2019-04-30 16:40:07: pid 17956: LOG:  watchdog escalation process with pid: 17963 exit with SUCCESS.

 

Next, use the same command to start up the second node.  In the original log, a successful startup of the second node will look like this:

Apr 30 16:42:28 pgpool1 pgpool-II-10[17956]: [22-1] 2019-04-30 16:42:28: pid 17956: LOG:  new watchdog node connection is received from "192.168.159.21:11962"
Apr 30 16:42:28 pgpool1 pgpool-II-10[17956]: [23-1] 2019-04-30 16:42:28: pid 17956: LOG:  new node joined the cluster hostname:"192.168.31.21" port:9000 pgpool_port:5432
Apr 30 16:42:28 pgpool1 pgpool-II-10[17956]: [24-1] 2019-04-30 16:42:28: pid 17956: LOG:  new outbound connection to 192.168.159.21:9000
Apr 30 16:42:29 pgpool1 pgpool-II-10[17956]: [25-1] 2019-04-30 16:42:29: pid 17956: LOG:  adding watchdog node "192.168.31.21:5432 Linux pgpool2" to the standby list
Apr 30 16:42:29 pgpool1 pgpool-II-10[17955]: [15-1] 2019-04-30 16:42:29: pid 17955: LOG:  Pgpool-II parent process received watchdog quorum change signal from watchdog
Apr 30 16:42:29 pgpool1 pgpool-II-10[17956]: [26-1] 2019-04-30 16:42:29: pid 17956: LOG:  new IPC connection received
Apr 30 16:42:29 pgpool1 pgpool-II-10[17955]: [16-1] 2019-04-30 16:42:29: pid 17955: LOG:  watchdog cluster now holds the quorum
Apr 30 16:42:29 pgpool1 pgpool-II-10[17955]: [16-2] 2019-04-30 16:42:29: pid 17955: DETAIL:  updating the state of quarantine backend nodes
Apr 30 16:42:29 pgpool1 pgpool-II-10[17956]: [27-1] 2019-04-30 16:42:29: pid 17956: LOG:  new IPC connection received

 

On node 2, it will look something like this:

Apr 30 16:42:28 pgpool2 pgpool-II-10[17193]: [1-1] 2019-04-30 16:42:28: pid 17193: WARNING:  checking setuid bit of if_up_cmd
Apr 30 16:42:28 pgpool2 pgpool-II-10[17193]: [1-2] 2019-04-30 16:42:28: pid 17193: DETAIL:  ifup[/usr/sbin/ip] doesn't have setuid bit
Apr 30 16:42:28 pgpool2 pgpool-II-10[17193]: [2-1] 2019-04-30 16:42:28: pid 17193: WARNING:  checking setuid bit of if_down_cmd
Apr 30 16:42:28 pgpool2 pgpool-II-10[17193]: [2-2] 2019-04-30 16:42:28: pid 17193: DETAIL:  ifdown[/usr/sbin/ip] doesn't have setuid bit
Apr 30 16:42:28 pgpool2 pgpool-II-10[17193]: [3-1] 2019-04-30 16:42:28: pid 17193: WARNING:  checking setuid bit of arping command
Apr 30 16:42:28 pgpool2 pgpool-II-10[17193]: [3-2] 2019-04-30 16:42:28: pid 17193: DETAIL:  arping[/bin/ping] doesn't have setuid bit
Apr 30 16:42:28 pgpool2 pgpool-II-10[17193]: [4-1] 2019-04-30 16:42:28: pid 17193: LOG:  Backend status file /var/log/pgpool-II-10/pgpool_status discarded
Apr 30 16:42:28 pgpool2 pgpool-II-10[17193]: [5-1] 2019-04-30 16:42:28: pid 17193: LOG:  waiting for watchdog to initialize
Apr 30 16:42:28 pgpool2 pgpool-II-10[17194]: [5-1] 2019-04-30 16:42:28: pid 17194: LOG:  setting the local watchdog node name to "192.168.31.21:5432 Linux pgpool2"
Apr 30 16:42:28 pgpool2 pgpool-II-10[17194]: [6-1] 2019-04-30 16:42:28: pid 17194: LOG:  watchdog cluster is configured with 1 remote nodes
Apr 30 16:42:28 pgpool2 pgpool-II-10[17194]: [7-1] 2019-04-30 16:42:28: pid 17194: LOG:  watchdog remote node:0 on 192.168.159.20:9000
Apr 30 16:42:28 pgpool2 pgpool-II-10[17194]: [8-1] 2019-04-30 16:42:28: pid 17194: LOG:  interface monitoring is disabled in watchdog
Apr 30 16:42:28 pgpool2 pgpool-II-10[17194]: [9-1] 2019-04-30 16:42:28: pid 17194: LOG:  watchdog node state changed from [DEAD] to [LOADING]
Apr 30 16:42:28 pgpool2 pgpool-II-10[17194]: [10-1] 2019-04-30 16:42:28: pid 17194: LOG:  new outbound connection to 192.168.159.20:9000
Apr 30 16:42:28 pgpool2 pgpool-II-10[17194]: [11-1] 2019-04-30 16:42:28: pid 17194: LOG:  setting the remote node "192.168.31.20:5432 Linux pgpool1.localdomain" as watchdog cluster master
Apr 30 16:42:28 pgpool2 pgpool-II-10[17194]: [12-1] 2019-04-30 16:42:28: pid 17194: LOG:  watchdog node state changed from [LOADING] to [INITIALIZING]
Apr 30 16:42:28 pgpool2 pgpool-II-10[17194]: [13-1] 2019-04-30 16:42:28: pid 17194: LOG:  new watchdog node connection is received from "192.168.159.20:7321"
Apr 30 16:42:28 pgpool2 pgpool-II-10[17194]: [14-1] 2019-04-30 16:42:28: pid 17194: LOG:  new node joined the cluster hostname:"192.168.31.20" port:9000 pgpool_port:5432
Apr 30 16:42:29 pgpool2 pgpool-II-10[17194]: [15-1] 2019-04-30 16:42:29: pid 17194: LOG:  watchdog node state changed from [INITIALIZING] to [STANDBY]
Apr 30 16:42:29 pgpool2 pgpool-II-10[17194]: [16-1] 2019-04-30 16:42:29: pid 17194: LOG:  successfully joined the watchdog cluster as standby node
Apr 30 16:42:29 pgpool2 pgpool-II-10[17194]: [16-2] 2019-04-30 16:42:29: pid 17194: DETAIL:  our join coordinator request is accepted by cluster leader node "192.168.31.20:5432 Linux pgpool1.localdomain"
Apr 30 16:42:29 pgpool2 pgpool-II-10[17193]: [6-1] 2019-04-30 16:42:29: pid 17193: LOG:  watchdog process is initialized
Apr 30 16:42:29 pgpool2 pgpool-II-10[17193]: [7-1] 2019-04-30 16:42:29: pid 17193: LOG:  Pgpool-II parent process received watchdog quorum change signal from watchdog
Apr 30 16:42:29 pgpool2 pgpool-II-10[17194]: [17-1] 2019-04-30 16:42:29: pid 17194: LOG:  new IPC connection received
Apr 30 16:42:29 pgpool2 pgpool-II-10[17193]: [8-1] 2019-04-30 16:42:29: pid 17193: LOG:  watchdog cluster now holds the quorum
Apr 30 16:42:29 pgpool2 pgpool-II-10[17193]: [8-2] 2019-04-30 16:42:29: pid 17193: DETAIL:  updating the state of quarantine backend nodes
Apr 30 16:42:29 pgpool2 pgpool-II-10[17194]: [18-1] 2019-04-30 16:42:29: pid 17194: LOG:  new IPC connection received
Apr 30 16:42:29 pgpool2 pgpool-II-10[17194]: [19-1] 2019-04-30 16:42:29: pid 17194: LOG:  new IPC connection received
Apr 30 16:42:29 pgpool2 pgpool-II-10[17193]: [9-1] 2019-04-30 16:42:29: pid 17193: LOG:  we have joined the watchdog cluster as STANDBY node
Apr 30 16:42:29 pgpool2 pgpool-II-10[17193]: [9-2] 2019-04-30 16:42:29: pid 17193: DETAIL:  syncing the backend states from the MASTER watchdog node
Apr 30 16:42:29 pgpool2 pgpool-II-10[17194]: [20-1] 2019-04-30 16:42:29: pid 17194: LOG:  new IPC connection received
Apr 30 16:42:29 pgpool2 pgpool-II-10[17194]: [21-1] 2019-04-30 16:42:29: pid 17194: LOG:  received the get data request from local pgpool-II on IPC interface
Apr 30 16:42:29 pgpool2 pgpool-II-10[17194]: [22-1] 2019-04-30 16:42:29: pid 17194: LOG:  get data request from local pgpool-II node received on IPC interface is forwarded to master watchdog node "192.168.31.20:5432 Linux pgpool1.localdomain"
Apr 30 16:42:29 pgpool2 pgpool-II-10[17194]: [22-2] 2019-04-30 16:42:29: pid 17194: DETAIL:  waiting for the reply...
Apr 30 16:42:29 pgpool2 pgpool-II-10[17193]: [10-1] 2019-04-30 16:42:29: pid 17193: LOG:  master watchdog node "192.168.31.20:5432 Linux pgpool1.localdomain" returned status for 2 backend nodes
Apr 30 16:42:29 pgpool2 pgpool-II-10[17193]: [11-1] 2019-04-30 16:42:29: pid 17193: LOG:  Setting up socket for 0.0.0.0:5432
Apr 30 16:42:29 pgpool2 pgpool-II-10[17193]: [12-1] 2019-04-30 16:42:29: pid 17193: LOG:  Setting up socket for :::5432
Apr 30 16:42:29 pgpool2 pgpool-II-10[17194]: [23-1] 2019-04-30 16:42:29: pid 17194: LOG:  new IPC connection received
Apr 30 16:42:29 pgpool2 pgpool-II-10[17195]: [7-1] 2019-04-30 16:42:29: pid 17195: LOG:  2 watchdog nodes are configured for lifecheck
Apr 30 16:42:29 pgpool2 pgpool-II-10[17195]: [8-1] 2019-04-30 16:42:29: pid 17195: LOG:  watchdog nodes ID:0 Name:"192.168.31.21:5432 Linux pgpool2"
Apr 30 16:42:29 pgpool2 pgpool-II-10[17195]: [8-2] 2019-04-30 16:42:29: pid 17195: DETAIL:  Host:"192.168.31.21" WD Port:9000 pgpool-II port:5432
Apr 30 16:42:29 pgpool2 pgpool-II-10[17195]: [9-1] 2019-04-30 16:42:29: pid 17195: LOG:  watchdog nodes ID:1 Name:"192.168.31.20:5432 Linux pgpool1.localdomain"
Apr 30 16:42:29 pgpool2 pgpool-II-10[17195]: [9-2] 2019-04-30 16:42:29: pid 17195: DETAIL:  Host:"192.168.159.20" WD Port:9000 pgpool-II port:5432
Apr 30 16:42:29 pgpool2 pgpool-II-10[17193]: [13-1] 2019-04-30 16:42:29: pid 17193: LOG:  pgpool-II successfully started. version 4.0.3 (torokiboshi)
Apr 30 16:42:29 pgpool2 pgpool-II-10[17193]: [14-1] 2019-04-30 16:42:29: pid 17193: LOG:  node status[0]: 0
Apr 30 16:42:29 pgpool2 pgpool-II-10[17193]: [15-1] 2019-04-30 16:42:29: pid 17193: LOG:  node status[1]: 0
Apr 30 16:42:30 pgpool2 pgpool-II-10[17233]: [10-1] 2019-04-30 16:42:30: pid 17233: LOG:  set SO_REUSEPORT option to the socket
Apr 30 16:42:30 pgpool2 pgpool-II-10[17233]: [11-1] 2019-04-30 16:42:30: pid 17233: LOG:  creating socket for sending heartbeat
Apr 30 16:42:30 pgpool2 pgpool-II-10[17233]: [11-2] 2019-04-30 16:42:30: pid 17233: DETAIL:  set SO_REUSEPORT
Apr 30 16:42:30 pgpool2 pgpool-II-10[17232]: [10-1] 2019-04-30 16:42:30: pid 17232: LOG:  set SO_REUSEPORT option to the socket
Apr 30 16:42:30 pgpool2 pgpool-II-10[17232]: [11-1] 2019-04-30 16:42:30: pid 17232: LOG:  creating watchdog heartbeat receive socket.
Apr 30 16:42:30 pgpool2 pgpool-II-10[17232]: [11-2] 2019-04-30 16:42:30: pid 17232: DETAIL:  set SO_REUSEPORT

 

At this point, Pgpool should be properly configured.  To test, login as the Postgres user on either of the Pgpool nodes and set the variables below:

export PGPORT=5432
export PGDATA=/postgres/data/pgdata
export PGHOSTADDR=10.12.1.111

 

Then enter the command psql.

It should prompt for the password, and if it does, configuration was successful.

-bash-4.2$ psql
Password:
psql (10.7, server 11.2)
WARNING: psql major version 10, server major version 11.
Some psql features might not work.
Type "help" for help.

postgres=# select inet_server_addr();
inet_server_addr
------------------
10.12.1.61
(1 row)

postgres-# \quit
-bash-4.2$ psql
Password:
psql (10.7, server 11.2)
WARNING: psql major version 10, server major version 11.
Some psql features might not work.
Type "help" for help.

postgres=# select inet_server_addr();
inet_server_addr
------------------
10.12.1.225
(1 row)

postgres=#

 

Connect again, as shown above, to verify that load balancing is working properly. As we can see, it successfully connected to both nodes, so we can connect to both instances. Pgpool is designed to send update queries to the primary node, and will send select queries to the standby nodes. The configuration of PostgreSQL with pgpool is complete.

Conclusion

In this blog, we have installed and configured PostgreSQL and pgpool for high availability. We did not cover automatic failover, and typically you will not want to fail over automatically.  My next blog will cover failover and recovery for PostgreSQL.

Please note: this blog contains code examples provided for your reference. All sample code is provided for illustrative purposes only. Use of information appearing in this blog is solely at your own risk. Please read our full disclaimer for details.

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