How do I get pcp to automatically attach nodes to postgres pgpool?

Question

I'm using postgres 9.4.9, pgpool 3.5.4 on centos 6.8.

I'm having a major hard time getting pgpool to automatically detect when nodes are up (it often detects the first node but rarely detects the secondary) but if I use pcp_attach_node to tell it what nodes are up, then everything is hunky dory.

So I figured until I could properly sort the issue out, I would write a little script to check the status of the nodes and attach them as appropriate, but I'm having trouble with the password prompt. According to the documentation, I should be able to issue commands like

pcp_attach_node 10 localhost 9898 pgpool mypass 1

but that just complains

pcp_attach_node: Warning: extra command-line argument "localhost" ignored pcp_attach_node: Warning: extra command-line argument "9898" ignored pcp_attach_node: Warning: extra command-line argument "pgpool" ignored pcp_attach_node: Warning: extra command-line argument "mypass" ignored pcp_attach_node: Warning: extra command-line argument "1" ignored

it'll only work when I use parameters like

pcp_attach_node -U pgpool -h localhost -p 9898 -n 1 

and there's no parameter for the password, I have to manually enter it at the prompt.

Any suggestions for sorting this other than using Expect?

Answer 1

You have to create PCPPASSFILE . Search pgpool documentation for more info.

Example 1:

create PCPPASSFILE for logged user ( vi ~/.pcppass ), file content is 127.0.0.1:9897:user:pass (hostname:port:username:password), set file permissions 0600 ( chmod 0600 ~/.pcppass )

command should run without asking for password

pcp_attach_node -h 127.0.0.1 -U user -p 9897 -w -n 1

Example 2:

create PCPPASSFILE ( vi /usr/local/etc/.pcppass ), file content is 127.0.0.1:9897:user:pass (hostname:port:username:password), set file permissions 0600 ( chmod 0600 /usr/local/etc/.pcppass ), set variable PCPPASSFILE ( export PCPPASSFILE=/usr/local/etc/.pcppass )

command should run without asking for password

pcp_attach_node -h 127.0.0.1 -U user -p 9897 -w -n 1

Script for auto attach the node

You can schedule this script with for example crontab.

#!/bin/bash
#pgpool status
#0 - This state is only used during the initialization. PCP will never display it.
#1 - Node is up. No connections yet.
#2 - Node is up. Connections are pooled.
#3 - Node is down.

source $HOME/.bash_profile
export PCPPASSFILE=/appl/scripts/.pcppass
STATUS_0=$(/usr/local/bin/pcp_node_info -h 127.0.0.1 -U postgres -p 9897 -n 0 -w | cut -d " " -f 3)
echo $(date +%Y.%m.%d-%H:%M:%S.%3N)" [INFO] NODE 0 status "$STATUS_0;

if (( $STATUS_0 == 3 ))
then
    echo $(date +%Y.%m.%d-%H:%M:%S.%3N)" [WARN] NODE 0 is down - attaching node"
    TMP=$(/usr/local/bin/pcp_attach_node -h 127.0.0.1 -U postgres -p 9897 -n 0 -w -v)
    echo $(date +%Y.%m.%d-%H:%M:%S.%3N)" [INFO] "$TMP 
fi


STATUS_1=$(/usr/local/bin/pcp_node_info -h 127.0.0.1 -U postgres -p 9897 -n 1 -w | cut -d " " -f 3)
echo $(date +%Y.%m.%d-%H:%M:%S.%3N)" [INFO] NODE 1 status "$STATUS_1;

if (( $STATUS_1 == 3 ))
then
    echo $(date +%Y.%m.%d-%H:%M:%S.%3N)" [WARN] NODE 1 is down - attaching node"
    TMP=$(/usr/local/bin/pcp_attach_node -h 127.0.0.1 -U postgres -p 9897 -n 1 -w -v)
    echo $(date +%Y.%m.%d-%H:%M:%S.%3N)" [INFO] "$TMP 
fi

exit 0

Answer 2

是的，您可以使用自定义的failover_command（/etc/pgpool 中的failover.sh）触发此命令的执行

Answer 3

Automated way to up your pgpool down node:

1. copy this script into a file with execute permission to your desired location with postgres ownership into all nodes.
2. run crontab -e comamnd under postgres user
3. Finally set that script to run every minute at crontab. But to execute it for every second you may create your own service and run it.

#!/bin/bash
# This script will up all pgpool down node

#************************
#******NODE STATUS*******
#************************

# 0 - This state is only used during the initialization.
# 1 - Node is up. No connection yet.
# 2 - Node is up and connection is pooled.
# 3 - Node is down

#************************
#******SCRIPT*******
#************************
server_node_list=(0 1 2)    
for server_node in ${server_node_list[@]}
do
    source $HOME/.bash_profile
    export PCPPASSFILE=/var/lib/pgsql/.pcppass
    node_status=$(pcp_node_info -p 9898 -h localhost -U pgpool  -n $server_node -w | cut -d ' ' -f 3);

    if [[ $node_status == 3 ]]
    then
            pcp_attach_node -n $server_node -U pgpool -p 9898 -w -v
    fi

done