我有两个PG服务器，一个主服务器，另一个从服务器-正常的流副本，工作得很好。
我需要把pgpool放在它们前面，这将使两台机器上的负载均衡器都可用——只需选择查询，因为流量很大。
但当我配置pgpool时，我不能强制它使用多个节点，总是第一个。。它不知道第二个。
当我尝试使用iptables并阻止第一台服务器时，pgpool没有从中恢复。
我试着使用权重，使用allow_to_failover，将guest backend0更改为backend1，打开/关闭主/从模式，什么都不做。
不管怎样，看起来它只连接到一个（第一个）服务器，而没有其他服务器。
正在附加配置pgPool。
# ----------------------------
# 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 = 5433
# Port number
# (change requires restart)
socket_dir = '/var/run/postgresql'
# 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)
# - 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 = '/var/run/postgresql'
# Unix domain socket path for pcp
# The Debian package defaults to
# /var/run/postgresql
# (change requires restart)
# - Backend Connection Settings -
backend_hostname0 = 'madmax'
# Host name or IP address to connect to for backend 0
backend_port0 = 5432
# Port number for backend 0
backend_weight0 = 1
# Weight for backend 0 (only in load balancing mode)
backend_data_directory0 = '/srv/postgresql/9.5/main'
# Data directory for backend 0
backend_flag0 = 'DISALLOW_TO_FAILOVER'
# Controls various backend behavior
# ALLOW_TO_FAILOVER or DISALLOW_TO_FAILOVER
backend_hostname1 = 'vengerberg'
backend_port1 = 5432
backend_weight1 = 1
backend_data_directory1 = '/srv/postgresql/9.5/main'
backend_flag1 = 'DISALLOW_TO_FAILOVER'
# - 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 = 60
# Delay in seconds to complete client authentication
# 0 means no timeout.
# - 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)
#------------------------------------------------------------------------------
# POOLS
#------------------------------------------------------------------------------
# - Concurrent session and pool size -
num_init_children = 32
# 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 = 0
# Connection to backend closes after being idle for this many seconds
# 0 means no close
client_idle_limit = 0
# 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 = 'stderr'
# 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_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 = on
# Log all statements
# with node and backend informations
log_standby_delay = 'none'
# 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 -
debug_level = 0
# Debug message verbosity level
# 0 means no message, 1 or more mean verbose
#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/postgresql/pgpool.pid'
# PID file name
# (change requires restart)
logdir = '/var/log/postgresql'
# Directory of pgPool status file
# (change requires restart)
#------------------------------------------------------------------------------
# CONNECTION POOLING
#------------------------------------------------------------------------------
connection_cache = off
# 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
# 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 = 'nextval,setval,nextval,setval'
# Comma separated list of function names
# that write to database
# Regexp are accepted
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
# 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).
#------------------------------------------------------------------------------
# MASTER/SLAVE MODE
#------------------------------------------------------------------------------
master_slave_mode = off
# Activate master/slave mode
# (change requires restart)
master_slave_sub_mode = 'stream'
# Master/slave sub mode
# Valid values are combinations slony or
# stream. Default is slony.
# (change requires restart)
# - Streaming -
sr_check_period = 0
# Streaming replication check period
# Disabled (0) by default
sr_check_user = 'pgpool'
# 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
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 = node id
# %h = host name
# %p = port number
# %D = database cluster path
# %m = new master node id
# %H = hostname of the new master node
# %M = old master node id
# %P = old primary node id
# %r = new master port number
# %R = new master database cluster path
# %% = '%' character
#------------------------------------------------------------------------------
# HEALTH CHECK
#------------------------------------------------------------------------------
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
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.
#------------------------------------------------------------------------------
# FAILOVER AND FAILBACK
#------------------------------------------------------------------------------
failover_command = ''
# Executes this command at failover
# Special values:
# %d = node id
# %h = host name
# %p = port number
# %D = database cluster path
# %m = new master node id
# %H = hostname of the new master node
# %M = old master node id
# %P = old primary node id
# %r = new master port number
# %R = new master database cluster path
# %% = '%' character
failback_command = ''
# Executes this command at failback.
# Special values:
# %d = node id
# %h = host name
# %p = port number
# %D = database cluster path
# %m = new master node id
# %H = hostname of the new master node
# %M = old master node id
# %P = old primary node id
# %r = new master port number
# %R = new master database cluster path
# %% = '%' character
fail_over_on_backend_error = on
# Initiates failover when reading/writing to the
# backend communication socket fails
# If set to off, pgpool will report an
# error and disconnect the session.
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.
#------------------------------------------------------------------------------
# ONLINE RECOVERY
#------------------------------------------------------------------------------
recovery_user = 'nobody'
# Online recovery user
recovery_password = ''
# Online recovery 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
.... rest是默认的。。。。
最佳答案
从http://www.pgpool.net/docs/pgpool-II-3.5.4/doc/pgpool-en.html：
要使查询实现负载平衡，必须满足以下所有要求：
PostgreSQL 7.4或更高版本，
在复制模式或主从模式下。。。
还有更多，但是在您的配置中，复制模式和主从机都被禁用。根据您的描述，最简单的可能是启用主从模式。
可能还应该通过设置“connection_cache=on”来启用连接缓存（pgpool的要点之一）。
关于postgresql - PgPool2负载平衡，我们在Stack Overflow上找到一个类似的问题：https://stackoverflow.com/questions/43276306/