1. Instalação e Configuração

Para demonstrar como foi construída toda a instalação do PGPOOL-II para atender a arquitetura definida a cima considere os passos relatados no procedimento de instalação e configuração que se segue. A especificação abaixo considera que está sendo utilizada a distribuição RED-HAT 7.x., PostgreSQL versão 11 e PGPOOL-II 4.1.

Para mais informações a respeito do projeto acesse a Plataforma Digital do Poder Judiciário

1.1. Adicionar o repositório do PGPOOL-II

$ vi /etc/yum.repos.d/pgpool.repo
[pgpool]
name=PgPoolRepo
baseurl=https://www.pgpool.net/yum/rpms/4.1/redhat/rhel-$releasever-$basearch/
enabled=1
gpgcheck=0

1.2. Adicionar o repositório do PostgreSQL versão 11

Procedimento necessário, pois alguns pacotes dele são dependências do PGPOOL-II

$ yum install https://download.postgresql.org/pub/repos/yum/reporpms/EL-7-x86_64/pgdg-redhat-repo-latest.noarch.rpm
É importante nesse ponto ressaltar que a versão 4.1 deve ser utilizada, pois há correções no algoritmo de balanceamento que favorecem as consultas utilizadas pelo PJe.

Caso seja necessário proxy para acessar o repositório online do PGPOOL-II, configurar em:

$ vi /etc/yum.conf
# The proxy server - proxy server:port number
proxy=http://proxy.com.br:2386
proxy_username=usuario
proxy_password=senha

Verificar se o repositório está buscando os pacotes necessários:

$ yum search pgpool
Loaded plugins: enabled_repos_upload, langpacks, package_upload, product-id, search-disabled-repos, subscription-manager
pgpool-II-10.x86_64 :                      Pgpool is a connection pooling/replication server for PostgreSQL
pgpool-II-10-debuginfo.x86_64 :  Debug information for package pgpool-II-10
pgpool-II-10-devel.x86_64 :          The development files for pgpool-II
pgpool-II-10-extensions.x86_64 : Postgresql extensions for pgpool-II
pgpool-II-11.x86_64 :                     Pgpool is a connection pooling/replication server for PostgreSQL
pgpool-II-11-debuginfo.x86_64 :  Debug information for package pgpool-II-11
pgpool-II-11-devel.x86_64 :          The development files for pgpool-II
pgpool-II-11-extensions.x86_64 : Postgresql extensions for pgpool-II
pgpool-II-12.x86_64 :                      Pgpool is a connection pooling/replication server for PostgreSQL
pgpool-II-12-debuginfo.x86_64 :  Debug information for package pgpool-II-12
pgpool-II-12-devel.x86_64 :          The development files for pgpool-II
pgpool-II-12-extensions.x86_64 : Postgresql extensions for pgpool-II
O PGPOOL –II deve ter a mesma versão do banco do PostgreSQL

1.3. Instalar os pacotes do PGPOOL-II, para o PostgreSQL 11

# yum install -y  pgpool-II-11*

Dependencies Resolved
==============================================================================================
 Package                     Arch         Version           Repository                   Size
==============================================================================================
Reinstalling:
pgpool-II-11                 x86_64      4.1.0-1.rhel7       pgdg11                      705 k
pgpool-II-11-debuginfo       x86_64      4.1.0-1.rhel7       pgdg11                      2.2 M
pgpool-II-11-devel           x86_64      4.1.0-1.rhel7       pgdg11                       11 k
pgpool-II-11-extensions      x86_64      4.1.0-1.rhel7       pgdg11                       19 k

Transaction Summary
==============================================================================================
Installing  4 Packages

1.4. Configurando os arquivos

Para configurar o PGPOOL-II são necessários 4 arquivos básicos pool_passwd, pcp, pgpool.conf e pool_hba.conf que ficam no diretório /etc/pgpool-II-11/

1.4.1. Arquivo pcp.conf

O Pgpool-II fornece uma interface para os administradores executarem a operação de gerenciamento, como obter o status do Pgpool-II ou encerrar os processos do Pgpool-II remotamente. O pcp.conf é o arquivo de usuário e senha usado para autenticação por parte da interface. Todos os modos de operação exigem que o arquivo pcp.conf seja definido. Um arquivo $ prefix/etc/pcp.conf.sample é criado durante a instalação do Pgpool-II. Copie o arquivo como $ prefix / etc / pcp.conf e adicione seu nome de usuário e senha a ele.

$ cd /etc/pgpool-II-11/
$ cp pcp.conf.sample pcp.conf
Uma linha vazia ou uma linha começando com “#” é tratada como um comentário e será ignorada.

Um nome de usuário e sua senha associada devem ser gravados como uma linha, usando o seguinte formato: nome de usuário : [senha criptografada md5] ou utilizar o utilitário pg_md5 para este fim conforme abaixo:

$ /usr/bin/pg_md5 -u postgres -m 123123

Irá gerar a seguinte saída no arquivo: postgres:md5c709cff0e4ede2c7beeb96a9738281d9
pcp.conf
$ cat pcp.conf
# PCP Client Authentication Configuration File
.
.
.
# be ignored. Again, no spaces or tabs allowed before '#'.
# USERID:MD5PASSWD
postgres:e10adc3949ba59abbe56e057f20f883e

1.4.2. Arquivo pool_hba.conf

O Pgpool-II fornece uma interface para os administradores executarem a operação de gerenciamento, como obter o status do Pgpool-II ou encerrar os processos do Pgpool-II remotamente. O pcp.conf é o arquivo de usuário e senha usado para autenticação por parte da interface. Todos os modos de operação exigem que o arquivo pcp.conf seja definido. Um arquivo $ prefix/etc/pcp.conf.sample é criado durante a instalação do Pgpool-II. Copie o arquivo como $ prefix / etc / pcp.conf e adicione seu nome de usuário e senha a ele.
pool_hba.conf
$ cat pool_hba.conf
# pgpool Client Authentication Configuration File
.
.
.
#
# TYPE  DATABASE       USER            CIDR-ADDRESS          METHOD
  host  BancoDeDados   usuário         ipServidorPJE/32      md5 #

1.4.3. Arquivo pool_passwd

Para usar o arquivo de autenticação pool_passwd, a autenticação md5 deve conter a senha do usuário no formato criptografado md5 em texto sem formatação ou no formato AES. O arquivo pool_passwd deve conter linhas no seguinte formato:

"nome de usuário: plain_text_passwd"
"nome de usuário: encrypted_passwd"

Exemplo do conteúdo do pool_passwd, supondo que os usuários (postgres, UserPje, UserLeitura) todos utilizem a senha 123123 para se conectar ao banco de dados:

pool_passwd
$ cat pool_passwd.conf
#usuario:md5[senha criptografada]
postgres: md5e10adc3949ba59abbe56e057f20f883e
UserPje: md5e10adc3949ba59abbe56e057f20f883e
UserLeitura: md5e10adc3949ba59abbe56e057f20f883e

1.4.4. Arquivo pgpool.conf

Neste arquivo devem constar todas as configurações do serviço PGPOOL-II, e qual seu comportamento com o banco de dados.

Supondo que as máquinas PostgreSQL são
  • 10.0.0.1 – Master

  • 10.0.0.2 – Slave 1

  • 10.0.0.3 – Slave 2

  • 10.0.0.4 – Slave 3

E o $PGDATA está configurado em /dados/data

Está liberado no pg_hba.conf de todos os servidores PostgreSQL o acesso ao servidor que irá servir o PGPOOL-II. A quantidade de conexões no postgresql.conf pode suportar de maneira mínima o valor configurado em num_init_children.

As principais propriedades que devem ser configuradas são:

pgpool.conf
listen_addresses = '*'
reserved_connections = 5
backend_hostname0 = '10.0.0.1'
backend_port0 = 5432
backend_weight0 = 0
backend_data_directory0 = '/dados/data'
backend_flag0 = 'ALWAYS_MASTER'

backend_application_name0 = 'MASTER'
backend_hostname1 = '10.0.0.2'
backend_port1 = 5432
backend_weight1 = 1
backend_data_directory1 = '/dados/data'
backend_flag1 = 'DISALLOW_TO_FAILOVER'
backend_application_name1 = 'SLAVE.01'

backend_hostname2 = '10.0.0.3'
backend_port2 = 5432
backend_weight2 = 1
backend_data_directory2 = '/dados/data'
backend_flag2 = 'DISALLOW_TO_FAILOVER'
backend_application_name2 = 'SLAVE.02'

backend_hostname3 = '10.0.0.4'
backend_port3 = 5432
backend_weight3 = 1
backend_data_directory3 = '/dados/data'
backend_flag3 = 'DISALLOW_TO_FAILOVER'
backend_application_name3 = 'SLAVE.03'

enable_pool_hba = on
authentication_timeout = 180
num_init_children = 605 #valor de conexões disponíveis a todos servidores
        #i.e.
        #Tem-se 3 nós de aplicação PJe, cada um com um pool de 200 conexões máximas,
        #então 3(servidores)_ x 200(conexões0) + 5(reserved_connections) = 605
log_destination = 'syslog'
log_line_prefix = '%t [%p]: [%l-1] client=%h '
log_standby_delay = 'always'
logdir = '/var/log/pgpool'
allow_sql_comments = on #parametro que possibilita as consultas com comentário serem balanceadas
disable_load_balance_on_write = 'transaction'
master_slave_mode = on
master_slave_sub_mode = 'stream'
sr_check_period = 0
delay_threshold = 0

health_check_period = 0

failover_on_backend_error = off

relcache_expire = 3600
relcache_query_target = load_balance_node

Criar as pastas a seguir:

$ mkdir /var/run/pgpool
$ mkdir /var/log/pgpool
$ chown postgres. /var/run/pgpool
$ chown postgres. /var/log/pgpool

Iniciar o serviço do PGPOOL-II

$ service pgpool-II-11 start

Para verificar utilize:

$ service pgpool-II-11 status
Redirecting to /bin/systemctl status pgpool-II-11.service
pgpool-II-11.service - PGPool-II Middleware Between PostgreSQL Servers And PostgreSQL Database Clients
Loaded: loaded (/usr/lib/systemd/system/pgpool-II-11.service; disabled; vendor preset: disabled)
Active: active (running) since Tue 2020-01-07 12:56:54 -03; 2h 22min ago
Process: 25223 ExecStop=/usr/pgpool-11/bin/pgpool -f /etc/pgpool-II-11/pgpool.conf -m fast stop (code=exited, status=0/SUCCESS)
 Main PID: 25227 (pgpool)
   Tasks: 15
   Memory: 58.9M
   CGroup: /system.slice/pgpool-II-11.service
           ├─25227 /usr/pgpool-11/bin/pgpool -f /etc/pgpool-II-11/pgpool.conf -n -D
           ├─25229 pgpool: wait for connection request
           ├─25230 pgpool: wait for connection request
           .
           .
           .
           ├─25239 pgpool: PCP: wait for connection request
           ├─25240 pgpool: worker process
           ├─25241 pgpool: health check process(0)
           └─25242 pgpool: health check process(1)

Jan 07 12:56:54 pgpool-2g-dev.pjmt.local systemd[1]: Started PGPool-II Middleware Between PostgreSQL Servers And PostgreSQL Database Clients.
Jan 07 12:56:54 pgpool-2g-dev.pjmt.local systemd[1]: Starting PGPool-II Middleware Between PostgreSQL Servers And PostgreSQL Database Clients...

Editar o arquivo de configuração acrescentando ou retirando os servers:

$ vi pgpool.conf

Duplique o ssh abra o journal para monitorar o log:

$ journalctl -f -u pgpool.service

Inicie o pgpool após todas as slaves tiver configurado:

$ service pgpool start

1.4.5. Arquivo pgpool.conf.sample-stream

Apesar de ser possível gerenciar as replicações pelo PGPool, esta prática esta em desuso, sendo assim foi decidido delegar para servidor de banco de dados PostgreSQL esta função pois nenhum sistema melhor do que ele para executar esta tarefa. Esta decisão foi tomada também para que o PGPool valide as autenticações e realize o balanceamento das conexões pois esta é a função principal do sistema, deixando assim cada sistema realizar a suas funções principais para as quais foram construídos, fazendo com que a arquitetura seja mais simples de se configurar e manter.

Para tal abordagem citada, foi utilizado o arquivo de exemplo /etc/pgpool-II-11/pgpool.conf.sample-stream como segue:

pgpool.conf.sample-stream
# ----------------------------
# pgPool-II configuration file
# ----------------------------
#
# This file consists of lines of the form:
#
#   name = value
#
# Whitespace may be used.  Comments are introduced with "#" anywhere on a line.
# The complete list of parameter names and allowed values can be found in the
# pgPool-II documentation.
#
# This file is read on server startup and when the server receives a SIGHUP
# signal.  If you edit the file on a running system, you have to SIGHUP the
# server for the changes to take effect, or use "pgpool reload".  Some
# parameters, which are marked below, require a server shutdown and restart to
# take effect.
#

#------------------------------------------------------------------------------
# CONNECTIONS
#------------------------------------------------------------------------------

# - pgpool Connection Settings -

listen_addresses = '*'
                                   # Host name or IP address to listen on:
                                   # '*' for all, '' for no TCP/IP connections
                                   # (change requires restart)
port = 9999
                                   # Port number
                                   # (change requires restart)
socket_dir = '/tmp'
                                   # Unix domain socket path
                                   # The Debian package defaults to
                                   # /var/run/postgresql
                                   # (change requires restart)
listen_backlog_multiplier = 2
                                   # Set the backlog parameter of listen(2) to
                                   # num_init_children * listen_backlog_multiplier.
                                   # (change requires restart)
serialize_accept = off
                                   # whether to serialize accept() call to avoid thundering herd problem
                                   # (change requires restart)
reserved_connections = 5
                                   # Number of reserved connections.
                                   # Pgpool-II does not accept connections if over
                                   # num_init_chidlren - reserved_connections.

# - pgpool Communication Manager Connection Settings -

pcp_listen_addresses = '*'
                                   # Host name or IP address for pcp process to listen on:
                                   # '*' for all, '' for no TCP/IP connections
                                   # (change requires restart)
pcp_port = 9898
                                   # Port number for pcp
                                   # (change requires restart)
pcp_socket_dir = '/tmp'
                                   # Unix domain socket path for pcp
                                   # The Debian package defaults to
                                   # /var/run/postgresql
                                   # (change requires restart)

# - Backend Connection Settings -


backend_hostname0 = '10.0.0.1'
backend_port0 = 5432
backend_weight0 = 0
backend_data_directory0 = '/dados/data'
backend_flag0 = 'ALWAYS_MASTER'

backend_application_name0 = 'MASTER'
backend_hostname1 = '10.0.0.2'
backend_port1 = 5432
backend_weight1 = 1
backend_data_directory1 = '/dados/data'
backend_flag1 = 'DISALLOW_TO_FAILOVER'
backend_application_name1 = 'SLAVE.02'

backend_hostname2 = '10.0.0.3'
backend_port2 = 5432
backend_weight2 = 1
backend_data_directory2 = '/dados/data'
backend_flag2 = 'DISALLOW_TO_FAILOVER'
backend_application_name2 = 'SLAVE.03'

backend_hostname3 = '10.0.0.4'
backend_port3 = 5432
backend_weight3 = 1
backend_data_directory3 = '/dados/data'
backend_flag3 = 'DISALLOW_TO_FAILOVER'
backend_application_name3 = 'SLAVE.04'
# - Authentication -

enable_pool_hba = on
                                   # Use pool_hba.conf for client authentication
pool_passwd = 'pool_passwd'
                                   # File name of pool_passwd for md5 authentication.
                                   # "" disables pool_passwd.
                                   # (change requires restart)
authentication_timeout = 180
                                   # Delay in seconds to complete client authentication
                                   # 0 means no timeout.

allow_clear_text_frontend_auth = off
                                   # Allow Pgpool-II to use clear text password authentication
                                   # with clients, when pool_passwd does not
                                   # contain the user password


# - SSL Connections -

ssl = off
                                   # Enable SSL support
                                   # (change requires restart)
#ssl_key = './server.key'
                                   # Path to the SSL private key file
                                   # (change requires restart)
#ssl_cert = './server.cert'
                                   # Path to the SSL public certificate file
                                   # (change requires restart)
#ssl_ca_cert = ''
                                   # Path to a single PEM format file
                                   # containing CA root certificate(s)
                                   # (change requires restart)
#ssl_ca_cert_dir = ''
                                   # Directory containing CA root certificate(s)
                                   # (change requires restart)

ssl_ciphers = 'HIGH:MEDIUM:+3DES:!aNULL'
                                   # Allowed SSL ciphers
                                   # (change requires restart)
ssl_prefer_server_ciphers = off
                                   # Use server's SSL cipher preferences,
                                   # rather than the client's
                                   # (change requires restart)
ssl_ecdh_curve = 'prime256v1'
                                   # Name of the curve to use in ECDH key exchange
ssl_dh_params_file = ''
                                   # Name of the file containing Diffie-Hellman parameters used
                                   # for so-called ephemeral DH family of SSL cipher.


#------------------------------------------------------------------------------
# POOLS
#------------------------------------------------------------------------------

# - Concurrent session and pool size -

num_init_children = 10
                                   # Number of concurrent sessions allowed
                                   # (change requires restart)
max_pool = 4
                                   # Number of connection pool caches per connection
                                   # (change requires restart)

# - Life time -

child_life_time = 300
                                   # Pool exits after being idle for this many seconds
child_max_connections = 0
                                   # Pool exits after receiving that many connections
                                   # 0 means no exit
connection_life_time = 10
                                   # Connection to backend closes after being idle for this many seconds
                                   # 0 means no close
##client_idle_limit = 0
client_idle_limit = 3600
#client_idle_limit = 3600
                                   # Client is disconnected after being idle for that many seconds
                                   # (even inside an explicit transactions!)
                                   # 0 means no disconnection

#------------------------------------------------------------------------------
# LOGS
#------------------------------------------------------------------------------

# - Where to log -

log_destination = 'syslog'
                                   # Where to log
                                   # Valid values are combinations of stderr,
                                   # and syslog. Default to stderr.

# - What to log -

##log_line_prefix = '%t: pid %p: '   # printf-style string to output at beginning of each log line.
log_line_prefix = '%t [%p]: [%l-1] client=%h '

log_connections = off
                                   # Log connections
log_hostname = off
                                   # Hostname will be shown in ps status
                                   # and in logs if connections are logged
log_statement = off
                                   # Log all statements
log_per_node_statement = off
                                   # Log all statements
                                   # with node and backend informations
log_client_messages = off
                                   # Log any client messages
##log_standby_delay = 'none'
log_standby_delay = 'always'
                                   # Log standby delay
                                   # Valid values are combinations of always,
                                   # if_over_threshold, none

# - Syslog specific -

syslog_facility = 'LOCAL0'
                                   # Syslog local facility. Default to LOCAL0
syslog_ident = 'pgpool'
                                   # Syslog program identification string
                                   # Default to 'pgpool'

# - Debug -

#log_error_verbosity = default          # terse, default, or verbose messages

#client_min_messages = notice           # values in order of decreasing detail:
                                        #   debug5
                                        #   debug4
                                        #   debug3
                                        #   debug2
                                        #   debug1
                                        #   log
                                        #   notice
                                        #   warning
                                        #   error

#log_min_messages = warning             # values in order of decreasing detail:
                                        #   debug5
                                        #   debug4
                                        #   debug3
                                        #   debug2
                                        #   debug1
                                        #   info
                                        #   notice
                                        #   warning
                                        #   error
                                        #   log
                                        #   fatal
                                        #   panic

#------------------------------------------------------------------------------
# FILE LOCATIONS
#------------------------------------------------------------------------------

pid_file_name = '/var/run/pgpool/pgpool.pid'
                                   # PID file name
                                   # Can be specified as relative to the"
                                   # location of pgpool.conf file or
                                   # as an absolute path
                                   # (change requires restart)
logdir = '/var/log/pgpool'
                                   # Directory of pgPool status file
                                   # (change requires restart)

#------------------------------------------------------------------------------
# CONNECTION POOLING
#------------------------------------------------------------------------------

connection_cache = on
                                   # Activate connection pools
                                   # (change requires restart)

                                   # Semicolon separated list of queries
                                   # to be issued at the end of a session
                                   # The default is for 8.3 and later
reset_query_list = 'ABORT; DISCARD ALL'
                                   # The following one is for 8.2 and before
#reset_query_list = 'ABORT; RESET ALL; SET SESSION AUTHORIZATION DEFAULT'

#------------------------------------------------------------------------------
# REPLICATION MODE
#------------------------------------------------------------------------------

replication_mode = off
                                   # Activate replication mode
                                   # (change requires restart)
replicate_select = off
                                   # Replicate SELECT statements
                                   # when in replication mode
                                   # replicate_select is higher priority than
                                   # load_balance_mode.

#insert_lock = on
insert_lock = off
                                   # Automatically locks a dummy row or a table
                                   # with INSERT statements to keep SERIAL data
                                   # consistency
                                   # Without SERIAL, no lock will be issued
lobj_lock_table = ''
                                   # When rewriting lo_creat command in
                                   # replication mode, specify table name to
                                   # lock

# - Degenerate handling -

replication_stop_on_mismatch = off
                                   # On disagreement with the packet kind
                                   # sent from backend, degenerate the node
                                   # which is most likely "minority"
                                   # If off, just force to exit this session

failover_if_affected_tuples_mismatch = off
                                   # On disagreement with the number of affected
                                   # tuples in UPDATE/DELETE queries, then
                                   # degenerate the node which is most likely
                                   # "minority".
                                   # If off, just abort the transaction to
                                   # keep the consistency

#------------------------------------------------------------------------------
# LOAD BALANCING MODE
#------------------------------------------------------------------------------

load_balance_mode = on
                                   # Activate load balancing mode
                                   # (change requires restart)
ignore_leading_white_space = on
                                   # Ignore leading white spaces of each query
white_function_list = ''
                                   # Comma separated list of function names
                                   # that don't write to database
                                   # Regexp are accepted
black_function_list = 'currval,lastval,nextval,setval'
                                   # Comma separated list of function names
                                   # that write to database
                                   # Regexp are accepted

black_query_pattern_list = ''
                                   # Semicolon separated list of query patterns
                                   # that should be sent to primary node
                                   # Regexp are accepted
                                   # valid for streaming replicaton mode only.

database_redirect_preference_list = ''
                                   # comma separated list of pairs of database and node id.
                                   # example: postgres:primary,mydb[0-4]:1,mydb[5-9]:2'
                                   # valid for streaming replicaton mode only.
app_name_redirect_preference_list = ''
                                   # comma separated list of pairs of app name and node id.
                                   # example: 'psql:primary,myapp[0-4]:1,myapp[5-9]:standby'
                                   # valid for streaming replicaton mode only.
##allow_sql_comments = off
allow_sql_comments = on
                                   # if on, ignore SQL comments when judging if load balance or
                                   # query cache is possible.
                                   # If off, SQL comments effectively prevent the judgment
                                   # (pre 3.4 behavior).

disable_load_balance_on_write = 'transaction'
                                   # Load balance behavior when write query is issued
                                   # in an explicit transaction.
                                   # Note that any query not in an explicit transaction
                                   # is not affected by the parameter.
                                   # 'transaction' (the default): if a write query is issued,
                                   # subsequent read queries will not be load balanced
                                   # until the transaction ends.
                                   # 'trans_transaction': if a write query is issued,
                                   # subsequent read queries in an explicit transaction
                                   # will not be load balanced until the session ends.
                                   # 'always': if a write query is issued, read queries will
                                   # not be load balanced until the session ends.


####statement_level_load_balance = off
statement_level_load_balance = off
                                        # Enables statement level load balancing
                                        #Era OFF
                                        #Por definição será tentado ON
                                        #Tentativa não bem sucedida em 2019-11-26
                                        #statement_level_load_balance (boolean)
                                        #When set to on, the load balancing node is decided for each read query. When set to off, load balancing node is decided at
                                        #the session start time and will not be changed until the session ends. For example, in applications that use connection pooling
                                        #remain connections open to the backend server, because the session may be held for a long time, the load balancing node does
                                        #not change until the session ends. In such applications, When statement_level_load_balance is enabled, it is possible to decide
                                        #load balancing node per query, not per session. The default is off.

#------------------------------------------------------------------------------
# MASTER/SLAVE MODE
#------------------------------------------------------------------------------

#master_slave_mode = off
master_slave_mode = on
                                   # Activate master/slave mode
                                   # (change requires restart)
master_slave_sub_mode = 'stream'
                                   # Master/slave sub mode
                                   # Valid values are combinations stream, slony
                                   # or logical. Default is stream.
                                   # (change requires restart)

# - Streaming -

sr_check_period = 0
                                   # Streaming replication check period
                                   # Disabled (0) by default
sr_check_user = 'nobody'
                                   # Streaming replication check user
                                   # This is necessary even if you disable
                                   # streaming replication delay check with
                                   # sr_check_period = 0

sr_check_password = ''
                                   # Password for streaming replication check user.
                                   # Leaving it empty will make Pgpool-II to first look for the
                                   # Password in pool_passwd file before using the empty password

sr_check_database = 'postgres'
                                   # Database name for streaming replication check
delay_threshold = 0
                                   # Threshold before not dispatching query to standby node
                                   # Unit is in bytes
                                   # Disabled (0) by default

# - Special commands -

follow_master_command = ''
                                   # Executes this command after master failover
                                   # Special values:
                                   #   %d = failed node id
                                   #   %h = failed node host name
                                   #   %p = failed node port number
                                   #   %D = failed node database cluster path
                                   #   %m = new master node id
                                   #   %H = new master node hostname
                                   #   %M = old master node id
                                   #   %P = old primary node id
                                   #   %r = new master port number
                                   #   %R = new master database cluster path
                                   #   %N = old primary node hostname
                                   #   %S = old primary node port number
                                   #   %% = '%' character

#------------------------------------------------------------------------------
# HEALTH CHECK GLOBAL PARAMETERS
#------------------------------------------------------------------------------

health_check_period = 0
                                   # Health check period
                                   # Disabled (0) by default
health_check_timeout = 20
                                   # Health check timeout
                                   # 0 means no timeout
health_check_user = 'nobody'
                                   # Health check user
health_check_password = ''
                                   # Password for health check user
                                   # Leaving it empty will make Pgpool-II to first look for the
                                   # Password in pool_passwd file before using the empty password

health_check_database = ''
                                   # Database name for health check. If '', tries 'postgres' frist, then 'template1'

health_check_max_retries = 0
                                   # Maximum number of times to retry a failed health check before giving up.
health_check_retry_delay = 1
                                   # Amount of time to wait (in seconds) between retries.
connect_timeout = 10000
                                   # Timeout value in milliseconds before giving up to connect to backend.
                                   # Default is 10000 ms (10 second). Flaky network user may want to increase
                                   # the value. 0 means no timeout.
                                   # Note that this value is not only used for health check,
                                   # but also for ordinary conection to backend.

#------------------------------------------------------------------------------
# HEALTH CHECK PER NODE PARAMETERS (OPTIONAL)
#------------------------------------------------------------------------------
#health_check_period0 = 0
#health_check_timeout0 = 20
#health_check_user0 = 'nobody'
#health_check_password0 = ''
#health_check_database0 = ''
#health_check_max_retries0 = 0
#health_check_retry_delay0 = 1
#connect_timeout0 = 10000

#------------------------------------------------------------------------------
# FAILOVER AND FAILBACK
#------------------------------------------------------------------------------

failover_command = ''
                                   # Executes this command at failover
                                   # Special values:
                                   #   %d = failed node id
                                   #   %h = failed node host name
                                   #   %p = failed node port number
                                   #   %D = failed node database cluster path
                                   #   %m = new master node id
                                   #   %H = new master node hostname
                                   #   %M = old master node id
                                   #   %P = old primary node id
                                   #   %r = new master port number
                                   #   %R = new master database cluster path
                                   #   %N = old primary node hostname
                                   #   %S = old primary node port number
                                   #   %% = '%' character
failback_command = ''
                                   # Executes this command at failback.
                                   # Special values:
                                   #   %d = failed node id
                                   #   %h = failed node host name
                                   #   %p = failed node port number
                                   #   %D = failed node database cluster path
                                   #   %m = new master node id
                                   #   %H = new master node hostname
                                   #   %M = old master node id
                                   #   %P = old primary node id
                                   #   %r = new master port number
                                   #   %R = new master database cluster path
                                   #   %N = old primary node hostname
                                   #   %S = old primary node port number
                                   #   %% = '%' character

failover_on_backend_error = off
                                   # Initiates failover when reading/writing to the
                                   # backend communication socket fails
                                   # If set to off, pgpool will report an
                                   # error and disconnect the session.

detach_false_primary = off
                                   # Detach false primary if on. Only
                                   # valid in streaming replicaton
                                   # mode and with PostgreSQL 9.6 or
                                   # after.

search_primary_node_timeout = 300
                                   # Timeout in seconds to search for the
                                   # primary node when a failover occurs.
                                   # 0 means no timeout, keep searching
                                   # for a primary node forever.

auto_failback = off
                                   # Dettached backend node reattach automatically
                                   # if replication_state is 'streaming'.
auto_failback_interval = 60
                                   # Min interval of executing auto_failback in
                                   # seconds.

#------------------------------------------------------------------------------
# ONLINE RECOVERY
#------------------------------------------------------------------------------

recovery_user = 'nobody'
                                   # Online recovery user
recovery_password = ''
                                   # Online recovery password
                                   # Leaving it empty will make Pgpool-II to first look for the
                                   # Password in pool_passwd file before using the empty password

recovery_1st_stage_command = ''
                                   # Executes a command in first stage
recovery_2nd_stage_command = ''
                                   # Executes a command in second stage
recovery_timeout = 90
                                   # Timeout in seconds to wait for the
                                   # recovering node's postmaster to start up
                                   # 0 means no wait
client_idle_limit_in_recovery = 0
                                   # Client is disconnected after being idle
                                   # for that many seconds in the second stage
                                   # of online recovery
                                   # 0 means no disconnection
                                   # -1 means immediate disconnection

#------------------------------------------------------------------------------
# WATCHDOG
#------------------------------------------------------------------------------

# - Enabling -

use_watchdog = off
                                    # Activates watchdog
                                    # (change requires restart)

# -Connection to up stream servers -

trusted_servers = ''
                                    # trusted server list which are used
                                    # to confirm network connection
                                    # (hostA,hostB,hostC,...)
                                    # (change requires restart)
ping_path = '/bin'
                                    # ping command path
                                    # (change requires restart)

# - Watchdog communication Settings -

wd_hostname = ''
                                    # Host name or IP address of this watchdog
                                    # (change requires restart)
wd_port = 9000
                                    # port number for watchdog service
                                    # (change requires restart)
wd_priority = 1
                                    # priority of this watchdog in leader election
                                    # (change requires restart)

wd_authkey = ''
                                    # Authentication key for watchdog communication
                                    # (change requires restart)

wd_ipc_socket_dir = '/var/run/postgresql'
                                    # Unix domain socket path for watchdog IPC socket
                                    # The Debian package defaults to
                                    # /var/run/postgresql
                                    # (change requires restart)

# - Virtual IP control Setting -

delegate_IP = ''
                                    # delegate IP address
                                    # If this is empty, virtual IP never bring up.
                                    # (change requires restart)
if_cmd_path = '/sbin'
                                    # path to the directory where if_up/down_cmd exists
                                    # If if_up/down_cmd starts with "/", if_cmd_path will be ignored.
                                    # (change requires restart)
if_up_cmd = '/usr/bin/sudo /sbin/ip addr add $_IP_$/24 dev eth0 label eth0:0'
                                    # startup delegate IP command
                                    # (change requires restart)
if_down_cmd = '/usr/bin/sudo /sbin/ip addr del $_IP_$/24 dev eth0'
                                    # shutdown delegate IP command
                                    # (change requires restart)
arping_path = '/usr/sbin'
                                    # arping command path
                                    # If arping_cmd starts with "/", if_cmd_path will be ignored.
                                    # (change requires restart)
arping_cmd = '/usr/bin/sudo /usr/sbin/arping -U $_IP_$ -w 1 -I eth0'
                                    # arping command
                                    # (change requires restart)

# - Behaivor on escalation Setting -

clear_memqcache_on_escalation = on
                                    # Clear all the query cache on shared memory
                                    # when standby pgpool escalate to active pgpool
                                    # (= virtual IP holder).
                                    # This should be off if client connects to pgpool
                                    # not using virtual IP.
                                    # (change requires restart)
wd_escalation_command = ''
                                    # Executes this command at escalation on new active pgpool.
                                    # (change requires restart)
wd_de_escalation_command = ''
                                    # Executes this command when master pgpool resigns from being master.
                                    # (change requires restart)

# - Watchdog consensus settings for failover -

failover_when_quorum_exists = on
                                    # Only perform backend node failover
                                    # when the watchdog cluster holds the quorum
                                    # (change requires restart)

failover_require_consensus = on
                                    # Perform failover when majority of Pgpool-II nodes
                                    # aggrees on the backend node status change
                                    # (change requires restart)

allow_multiple_failover_requests_from_node = off
                                    # A Pgpool-II node can cast multiple votes
                                    # for building the consensus on failover
                                    # (change requires restart)

enable_consensus_with_half_votes = off
                                    # apply majority rule for consensus and quorum computation
                                    # at 50% of votes in a cluster with even number of nodes.
                                    # when enabled the existence of quorum and consensus
                                    # on failover is resolved after receiving half of the
                                    # total votes in the cluster, otherwise both these
                                    # decisions require at least one more vote than
                                    # half of the total votes.
                                    # (change requires restart)

# - Lifecheck Setting -

# -- common --

wd_monitoring_interfaces_list = ''  # Comma separated list of interfaces names to monitor.
                                    # if any interface from the list is active the watchdog will
                                    # consider the network is fine
                                    # 'any' to enable monitoring on all interfaces except loopback
                                    # '' to disable monitoring
                                    # (change requires restart)


wd_lifecheck_method = 'heartbeat'
                                    # Method of watchdog lifecheck ('heartbeat' or 'query' or 'external')
                                    # (change requires restart)
wd_interval = 10
                                    # lifecheck interval (sec) > 0
                                    # (change requires restart)

# -- heartbeat mode --

wd_heartbeat_port = 9694
                                    # Port number for receiving heartbeat signal
                                    # (change requires restart)
wd_heartbeat_keepalive = 2
                                    # Interval time of sending heartbeat signal (sec)
                                    # (change requires restart)
wd_heartbeat_deadtime = 30
                                    # Deadtime interval for heartbeat signal (sec)
                                    # (change requires restart)
heartbeat_destination0 = 'host0_ip1'
                                    # Host name or IP address of destination 0
                                    # for sending heartbeat signal.
                                    # (change requires restart)
heartbeat_destination_port0 = 9694
                                    # Port number of destination 0 for sending
                                    # heartbeat signal. Usually this is the
                                    # same as wd_heartbeat_port.
                                    # (change requires restart)
heartbeat_device0 = ''
                                    # Name of NIC device (such like 'eth0')
                                    # used for sending/receiving heartbeat
                                    # signal to/from destination 0.
                                    # This works only when this is not empty
                                    # and pgpool has root privilege.
                                    # (change requires restart)

#heartbeat_destination1 = 'host0_ip2'
#heartbeat_destination_port1 = 9694
#heartbeat_device1 = ''

# -- query mode --

wd_life_point = 3
                                    # lifecheck retry times
                                    # (change requires restart)
wd_lifecheck_query = 'SELECT 1'
                                    # lifecheck query to pgpool from watchdog
                                    # (change requires restart)
wd_lifecheck_dbname = 'template1'
                                    # Database name connected for lifecheck
                                    # (change requires restart)
wd_lifecheck_user = 'nobody'
                                    # watchdog user monitoring pgpools in lifecheck
                                    # (change requires restart)
wd_lifecheck_password = ''
                                    # Password for watchdog user in lifecheck
                                    # Leaving it empty will make Pgpool-II to first look for the
                                    # Password in pool_passwd file before using the empty password
                                    # (change requires restart)

# - Other pgpool Connection Settings -

#other_pgpool_hostname0 = 'host0'
                                    # Host name or IP address to connect to for other pgpool 0
                                    # (change requires restart)
#other_pgpool_port0 = 5432
                                    # Port number for other pgpool 0
                                    # (change requires restart)
#other_wd_port0 = 9000
                                    # Port number for other watchdog 0
                                    # (change requires restart)
#other_pgpool_hostname1 = 'host1'
#other_pgpool_port1 = 5432
#other_wd_port1 = 9000

#------------------------------------------------------------------------------
# OTHERS
#------------------------------------------------------------------------------
relcache_expire = 3600
                                   # Life time of relation cache in seconds.
                                   # 0 means no cache expiration(the default).
                                   # The relation cache is used for cache the
                                   # query result against PostgreSQL system
                                   # catalog to obtain various information
                                   # including table structures or if it's a
                                   # temporary table or not. The cache is
                                   # maintained in a pgpool child local memory
                                   # and being kept as long as it survives.
                                   # If someone modify the table by using
                                   # ALTER TABLE or some such, the relcache is
                                   # not consistent anymore.
                                   # For this purpose, cache_expiration
                                   # controls the life time of the cache.

relcache_size = 256
                                   # Number of relation cache
                                   # entry. If you see frequently:
                                   # "pool_search_relcache: cache replacement happend"
                                   # in the pgpool log, you might want to increate this number.

check_temp_table = catalog
                                   # Temporary table check method. catalog, trace or none.
                                   # Default is catalog.

check_unlogged_table = on
                                   # If on, enable unlogged table check in SELECT statements.
                                   # This initiates queries against system catalog of primary/master
                                   # thus increases load of master.
                                   # If you are absolutely sure that your system never uses unlogged tables
                                   # and you want to save access to primary/master, you could turn this off.
                                   # Default is on.
enable_shared_relcache = on
                                   # If on, relation cache stored in memory cache,
                                   # the cache is shared among child process.
                                   # Default is on.
                                   # (change requires restart)

relcache_query_target = load_balance_node     # Target node to send relcache queries. Default is master (primary) node.
                                   # If load_balance_node is specified, queries will be sent to load balance node.
#------------------------------------------------------------------------------
# IN MEMORY QUERY MEMORY CACHE
#------------------------------------------------------------------------------
memory_cache_enabled = off
                                   # If on, use the memory cache functionality, off by default
                                   # (change requires restart)
memqcache_method = 'shmem'
                                   # Cache storage method. either 'shmem'(shared memory) or
                                   # 'memcached'. 'shmem' by default
                                   # (change requires restart)
memqcache_memcached_host = 'localhost'
                                   # Memcached host name or IP address. Mandatory if
                                   # memqcache_method = 'memcached'.
                                   # Defaults to localhost.
                                   # (change requires restart)
memqcache_memcached_port = 11211
                                   # Memcached port number. Mondatory if memqcache_method = 'memcached'.
                                   # Defaults to 11211.
                                   # (change requires restart)
memqcache_total_size = 67108864
                                   # Total memory size in bytes for storing memory cache.
                                   # Mandatory if memqcache_method = 'shmem'.
                                   # Defaults to 64MB.
                                   # (change requires restart)
memqcache_max_num_cache = 1000000
                                   # Total number of cache entries. Mandatory
                                   # if memqcache_method = 'shmem'.
                                   # Each cache entry consumes 48 bytes on shared memory.
                                   # Defaults to 1,000,000(45.8MB).
                                   # (change requires restart)
memqcache_expire = 0
                                   # Memory cache entry life time specified in seconds.
                                   # 0 means infinite life time. 0 by default.
                                   # (change requires restart)
memqcache_auto_cache_invalidation = on
                                   # If on, invalidation of query cache is triggered by corresponding
                                   # DDL/DML/DCL(and memqcache_expire).  If off, it is only triggered
                                   # by memqcache_expire.  on by default.
                                   # (change requires restart)
memqcache_maxcache = 409600
                                   # Maximum SELECT result size in bytes.
                                   # Must be smaller than memqcache_cache_block_size. Defaults to 400KB.
                                   # (change requires restart)
memqcache_cache_block_size = 1048576
                                   # Cache block size in bytes. Mandatory if memqcache_method = 'shmem'.
                                   # Defaults to 1MB.
                                   # (change requires restart)
memqcache_oiddir = '/var/log/pgpool/oiddir'
                                   # Temporary work directory to record table oids
                                   # (change requires restart)
white_memqcache_table_list = ''
                                   # Comma separated list of table names to memcache
                                   # that don't write to database
                                   # Regexp are accepted
black_memqcache_table_list = ''
                                   # Comma separated list of table names not to memcache
                                   # that don't write to database
                                   # Regexp are accepted