Postgres automatic failover

sudo vi /usr/lib/postgresql/13/bin/pgfailover


#!/bin/bash


# Postgres HA (Master / Replication) monitoring script

# This script must only be installed on postgres slave (hot standby) node 


POSTGRES_MASTER_IP=pi6

POSTGRES_SLAVE_IP=127.0.0.1

POSTGRES_CHECK_PORT=23267

POSTGRES_FAILOVER='/usr/lib/postgresql/13/bin/pg_ctl -D /data02/data promote'


status_master=$(curl --write-out %{http_code} --silent --output /dev/null $POSTGRES_MASTER_IP:$POSTGRES_CHECK_PORT)

status_slave=$(curl --write-out %{http_code} --silent --output /dev/null $POSTGRES_SLAVE_IP:$POSTGRES_CHECK_PORT)


if [[ "$status_master" -eq 200 ]]

then

   if [[ "$status_slave" -eq 206 ]]

   then

        echo "Master up - Slave Standbye - Do nothing"

   else

        echo "Master up - Slave down - Do nothing"

   fi

else

   if [[ "$status_slave" -eq 200 ]]

   then

        echo "Slave is Master - Do nothing"

   elif [[ "$status_slave" -eq 206 ]]

   then

        echo "Slave becomes Master - Do action"

        eval $POSTGRES_FAILOVER

        exit 1;

   else

        echo "Master and Slave down - Do nothing"

   fi

fi


exit 0;


sudo chown postgres:postgres /usr/lib/postgresql/13/bin/pgfailover

sudo chmod a+x /usr/lib/postgresql/13/bin/pgfailover


sudo crontab -u postgres -e

* * * * * /usr/lib/postgresql/13/bin/pgfailover

Postgres manually failover

How to failover from Master to Replication node and visa versa

Pi6 192.168.2.106 (MASTER)

Pi7 192.168.2.107 (REPLICATION)


Make Replication node master

# Goto pi7

su postgres

/usr/lib/postgresql/13/bin/pg_ctl -D /data02/data promote


Restore old master

# Goto to pi6

sudo cp /data02/data/*.conf ../.

/usr/lib/postgresql/13/bin/pg_ctl -D /data02/data stop

rm -rf /data02/data/*

/usr/lib/postgresql/13/bin/pg_basebackup --pgdata=/data02/data --format=p --write-recovery-conf --checkpoint=fast --label=mffb --progress --host=pi7 --port=5432 --username=plaatsoft

rm /data02/data/standby.signal

/usr/lib/postgresql/13/bin/pg_ctl -D /data02/data start

psql -c "select * from pg_create_physical_replication_slot('standby1_slot');"


# Goto to pi7

sudo cp /data02/data/*.conf ../.

/usr/lib/postgresql/13/bin/pg_ctl -D /data02/data stop

rm -rf /data02/data/*

/usr/lib/postgresql/13/bin/pg_basebackup --pgdata=/data02/data --format=p --write-recovery-conf --checkpoint=fast --label=mffb --progress --host=pi6 --port=5432 --username=plaatsoft

/usr/lib/postgresql/13/bin/pg_ctl -D /data02/data start


Check replication


CHECK MASTER NODE

postgres=# \x

postgres=# SELECT * FROM pg_stat_replication;


postgres=# select pg_is_in_recovery();

pg_is_in_recovery

-------------------

f

(1 row)


CHECK REPLICATION NODE

postgres=# \x

postgres=# SELECT * FROM pg_stat_wal_receiver;


postgres=# select pg_is_in_recovery();

pg_is_in_recovery

-------------------

t

(1 row)

HaProxy for Postgres HA

Execute on each Postgresql node the following actions

# Create check script
sudo vi /usr/lib/postgresql/13/bin/pgsqlchk

#!/bin/bash
# This script checks if a postgres server is healthy running on localhost. It will return:
# "HTTP/1.x 200 OK\r" (if postgres is running smoothly)
# - OR -
# "HTTP/1.x 500 Internal Server Error\r" (else)
# The purpose of this script is make haproxy capable of monitoring postgres properly
# It is recommended that a low-privileged postgres user is created to be used by this script.
# For eg. create user healthchkusr login password 'hc321';

PGBIN=/usr/pgsql-10/bin
PGSQL_HOST="localhost"
PGSQL_PORT="5432"
PGSQL_DATABASE="postgres"
PGSQL_USERNAME="postgres"
export PGPASSWORD="passwd"
TMP_FILE="/tmp/pgsqlchk.out"
ERR_FILE="/tmp/pgsqlchk.err"

# We perform a simple query that should return a few results

VALUE=`/usr/lib/postgresql/13/bin/psql -t -h localhost -U postgres -p 5432 -c "select pg_is_in_recovery()" 2> /dev/null`
# Check the output. If it is not empty then everything is fine and we return something. Else, we just do not return anything.

if [ $VALUE == "t" ]
then
/bin/echo -e "HTTP/1.1 206 OK\r\n"
/bin/echo -e "Content-Type: Content-Type: text/plain\r\n"
/bin/echo -e "\r\n"
/bin/echo "Standby"
/bin/echo -e "\r\n"
elif [ $VALUE == "f" ]
then
/bin/echo -e "HTTP/1.1 200 OK\r\n"
/bin/echo -e "Content-Type: Content-Type: text/plain\r\n"
/bin/echo -e "\r\n"
/bin/echo "Primary"
/bin/echo -e "\r\n"
else
/bin/echo -e "HTTP/1.1 503 Service Unavailable\r\n"
/bin/echo -e "Content-Type: Content-Type: text/plain\r\n"
/bin/echo -e "\r\n"
/bin/echo "DB Down"
/bin/echo -e "\r\n"
fi

# Make script executable
sudo chmod a+x /usr/lib/postgresql/13/bin/pgsqlchk

# install xinetd and telnet
sudo apt-get install xinetd telnet -y

# Create xinitd file
sudo vi /etc/xinetd.d/pgsqlchk

service pgsqlchk
{
flags = REUSE
socket_type = stream
port = 23267
wait = no
user = nobody
server = /usr/lib/postgresql/13/bin/pgsqlchk
log_on_failure += USERID
disable = no
only_from = 0.0.0.0/0
per_source = UNLIMITED
}

sudo bash -c 'echo "pgsqlchk 23267/tcp # pgsqlchk" >> /etc/services'
sudo systemctl restart xinetd

# Check if service is working
telnet 127.0.0.1 23267

Trying 127.0.0.1...
Connected to 127.0.0.1.
Escape character is '^]'.
HTTP/1.1 206 OK
Content-Type: Content-Type: text/plain
Standby
Connection closed by foreign host.

Execute on HaProxy following actions

# Install HaProxy
sudo apt-get install haproxy -y 

sudo vi /etc/hosts
Add pi6 192.168.2.106
Add pi7 192.168.2.107

sudo vi /etc/haproxy/haproxy.cfg  
  
global  
    maxconn 100  
   
defaults  
    log global  
    mode tcp  
    retries 2  
    timeout client 30m  
    timeout connect 4s  
    timeout server 30m  
    timeout check 5s  
   
listen stats  
    mode http  
    bind *:10000  
    stats enable   
    stats refresh 10s
    stats uri /
   
listen Postgres
    bind *:5432 
    option httpchk  
    http-check expect status 200  
    default-server inter 3s fall 3 rise 2 on-marked-down shutdown-sessions  
    server pi6 pi6:5432 maxconn 100 check port 23267  
    server pi7 pi7:5432 maxconn 100 check port 23267  
   
systemctl restart haproxy  

Check HaProxy

# Install postgres client
sudo apt-get install postgresql-client

# Start psql client
psql -h localhost -U postgres  
  
postgres=# select pg_is_in_recovery();  
pg_is_in_recovery  
-------------------  
f  
(1 row)

Check HaProxy portal http://192.168.2.107:5000

PostgreSQL HA setup

How to setup High Available PostgreSQL on two nodes.

Pi6 192.168.2.106 (MASTER)

Pi7 192.168.2.107 (REPLICATION)


Run below commands on both Pis:


sudo vi /etc/hosts

Add pi6 192.168.2.106

Add pi7 192.168.2.107


sudo apt-get update

sudo apt-get upgrade

sudo apt-get install postgresql


# Stop postgresql

sudo systemctl stop postgresql


# Create directories

sudo mkdir /data02

sudo mkdir /data02/data

sudo chmod a+wrx /data02

sudo chown postgres:postgres /data02/data

sudo chmod 0700 /data02/data


# Remove old databases

rm -rf /var/lib/postgresql/13/main

ln -s /data02/data /var/lib/postgresql/13/main

rm -rf /etc/postgresql/13/main

ln -s /data02/data /etc/postgresql/13/main


Run below commands only in Pi6 (MASTER):


# Create new database

/usr/lib/postgresql/13/bin/pg_ctl initdb -D /data02/data


# Update PostgresSQL configuration

vi /etc/postgresql/13/main/postgresql.conf

Change #listen_addresses = 'localhost' to listen_addresses = '*'

Change #wal_level = replica to wal_level = replica

Change #max_wal_senders = 10 to max_wal_senders = 10

Change #wal_keep_size = 0 to wal_keep_size = 0


vi /etc/postgresql/13/main/pg_hba.conf

Add next line

host all all 192.168.2.0/24 trust

host replication plaatsoft 192.168.2.0/24 trust


# Start database

/usr/lib/postgresql/13/bin/pg_ctl -D /data02/data start

of

systemctl start postgresql


# Create replication user

psql -c "CREATE USER plaatsoft WITH PASSWORD 'plaatsoft' REPLICATION;"


5. Create replication slot on Primary Server

psql -c "select * from pg_create_physical_replication_slot('standby1_slot');"


Run below commands only in Pi7 (REPLICATION):


# Create replication database based on master

/usr/lib/postgresql/13/bin/pg_basebackup --pgdata=/data02/data --format=p --write-recovery-conf --checkpoint=fast --label=mffb --progress --host=pi6 --port=5432 --username=plaatsoft


# Update PostgresSQL configuration

vi /etc/postgresql/13/main/postgresql.conf


# Update PostgresSQL configuration

vi /etc/postgresql/13/main/postgresql.conf

Change primary_conninfo to 'host=pi6 port=5432 user=plaatsoft password=plaatsoft'

Change primary_slot_name to 'standby1_slot'


# Start database

/usr/lib/postgresql/13/bin/pg_ctl -D /data02/data start

of

systemctl start postgresql


Final Check Pi6:


postgres 5211 1 0 13:04 ? 00:00:00 /usr/lib/postgresql/13/bin/postgres -D /data02/data

postgres 5215 5211 0 13:04 ? 00:00:00 postgres: checkpointer

postgres 5216 5211 0 13:04 ? 00:00:00 postgres: background writer

postgres 5218 5211 0 13:04 ? 00:00:00 postgres: walwriter

postgres 5219 5211 0 13:04 ? 00:00:00 postgres: autovacuum launcher

postgres 5220 5211 0 13:04 ? 00:00:00 postgres: stats collector

postgres 5221 5211 0 13:04 ? 00:00:00 postgres: logical replication launcher

postgres 5970 5211 0 13:13 ? 00:00:00 postgres: walsender plaatsoft 192.168.2.107(46242) streaming 0/12013F58


Final Check Pi7:


postgres 23167 1 0 13:13 ? 00:00:00 /usr/lib/postgresql/13/bin/postgres -D /data02/data

postgres 23168 23167 0 13:13 ? 00:00:00 postgres: startup recovering 000000010000000000000012

postgres 23169 23167 0 13:13 ? 00:00:00 postgres: checkpointer

postgres 23170 23167 0 13:13 ? 00:00:00 postgres: background writer

postgres 23171 23167 0 13:13 ? 00:00:00 postgres: stats collector

postgres 23173 23167 0 13:13 ? 00:00:00 postgres: walreceiver streaming 0/12013F58

Raspberry Pi NFS

pi6 (NFS SERVER)

sudo apt-get install nfs-kernel-server


# Create directory structure

sudo mkdir /data03

sudo chmod a+wrx /data03


# Create NFS server file

vi /etc/exports

# Add below line at the end of the file

/data03 pi7(rw,sync,no_subtree_check)


# Reinit NFS server

sudo exportfs -ra


pi7 (NFS CLIENT)

sudo mkdir /data03

sudo chmod a+wrx /data03


# Temporary mount

sudo mount -t nfs -o proto=tcp,port=2049 pi6:/data03 /data03


# Final mount

sudo vi /etc/fstab

pi6:/data03 /data03 nfs auto 0 0

Ansible on Raspberry Pi example

# Create master ansible node
sudo apt-get install ansible
sudo apt-get install sshpass -y

# Check version if ansible
ansible --version

# Create host file and add below lines
sudo /etc/ansible/hosts

[plaatsoft]
pi1
pi4
pi5
pi9

# update hostfile (Add all ansible target clients)
sudo vi /etc/hosts
pi1 192.168.2.101
pi4 192.168.2.104
pi5 192.168.2.105
pi9 192.168.2.109

# Generate private/public ssh key
ssh-keygen -t rsa
cat /home/pi/.ssh/id_rsa.pub

# Login each target client / created authorized_keys and insert public ssh key of ansible master node
vi .ssh/authorized_keys

# Ping all clients nodes
ansible all -m ping

# expected output
pi9 | SUCCESS => {
    "changed": false,
    "ping": "pong"
}
pi5 | SUCCESS => {
    "changed": false,
    "ping": "pong"
}
pi1 | SUCCESS => {
    "changed": false,
    "ping": "pong"
}
pi4 | SUCCESS => {
    "changed": false,
    "ping": "pong"
}

# Now create first playbook

mkdir /etc/ansible/playbook
mkdir /etc/ansible/playbook/files

vi /etc/ansible/playbook/hello1.yml

---
- name: first playbook example
  hosts: pi1 pi4 pi5 pi9
  tasks:
    - name: Create a file called '/tmp/hello1.txt' with the content 'hello world'.
      copy:
        content: hello world
        dest: /tmp/hello1.txt

# Execute first playbook
ansible-playbook hello1.yml

PLAY [This is a hello-world example] ************************************************************************************************************

TASK [Gathering Facts] **************************************************************************************************************************
ok: [pi5]
ok: [pi9]
ok: [pi1]
ok: [pi4]

TASK [Create a file called '/tmp/hello.txt' with the content 'hello world'.] ********************************************************************
ok: [pi9]
ok: [pi5]
ok: [pi1]
ok: [pi4]

PLAY RECAP **************************************************************************************************************************************
pi1                        : ok=2    changed=1    unreachable=0    failed=0
pi4                        : ok=2    changed=1    unreachable=0    failed=0
pi5                        : ok=2    changed=1    unreachable=0    failed=0
pi9                        : ok=2    changed=1    unreachable=0    failed=0

# Now create second playbook

vi /etc/ansible/playbook/files/hello.txt 

ENTER SOME TEXT

vi /etc/ansible/playbook/hello2.yml

---
- name: This is a second example
  hosts: pi1 pi4 pi5 pi9
  tasks:
    - name: Create a file called '/tmp/hello.txt' with content
      copy:
        src: ./files/hello2.txt
        dest: /tmp/hello2.txt

# Execute second playbook
ansible-playbook hello2.yml

PLAY [This is a second example] *****************************************************************************************************************

TASK [Gathering Facts] **************************************************************************************************************************
ok: [pi5]
ok: [pi9]
ok: [pi1]
ok: [pi4]

TASK [Create a file called '/tmp/hello.txt' with content] ***************************************************************************************
changed: [pi9]
ok: [pi5]
changed: [pi1]
changed: [pi4]

PLAY RECAP **************************************************************************************************************************************
pi1                        : ok=2    changed=1    unreachable=0    failed=0
pi4                        : ok=2    changed=1    unreachable=0    failed=0
pi5                        : ok=2    changed=0    unreachable=0    failed=0
pi9                        : ok=2    changed=1    unreachable=0    failed=0

Maven settings.xml with Nexus entry

<?xml version="1.0" encoding="UTF-8"?>
<settings xmlns="http://maven.apache.org/SETTINGS/1.1.0"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/SETTINGS/1.1.0 http://maven.apache.org/xsd/settings-1.1.0.xsd">

<mirrors>
<mirror>
<id>nexus</id>
<mirrorOf>*</mirrorOf>
<url>https://nexus.plaatsoft.nl/repository/maven-public/</url>
</mirror>
</mirrors>

<profiles>
<profile>
<id>nexus</id>
<properties>
<altSnapshotDeploymentRepository>nexus::default::https://nexus.plaatsoft.nl/repository/maven-snapshots/</altSnapshotDeploymentRepository>
<altReleaseDeploymentRepository>nexus::default::https://nexus.plaatsoft.nl/repository/maven-releases/</altReleaseDeploymentRepository>
</properties>
</profile>
</profiles>

<activeProfiles>
<activeProfile>nexus</activeProfile>
</activeProfiles>

<servers>
<server>
<id>nexus</id>
<username>XXX</username>
<password>XXX</password>
</server>
</servers>

</settings>

BassieMusic Android App 2.3

PlaatSoft has released a new version of the BassieMusic Android App in the Google Play Store.

The following changes were made:
– Added fast alphabetic scrollbar
– Fixed music sort order to be case insensitive
– Added more animations and polished the UI experience more
– Added remember last song feature
– Cleaned up the source code a lot

Click here to download the latest version.

WarQuest 7.3 (Game update!)

Today there is a new update of WarQuest online!
This is the next release of WarQuest. This release contain the following changes and bug fixes:

Game Server
– Fixed bug that prevent registering of new players
– Fixed bug that prevent players of level zero to spend skill points on attack or defence
– Make all language code files UTF-8 complaint
– Update all copyright years to right year (2020)
– Removed some weird black bars in the announcement images
– Removed obsolete store links on the login page
– Add new Google Play Store download link
– Fixed some small layout issues
– Add theme Modern (Tablet / Desktop)
– Fixed the announcements when using an ad blocker
– Fixed gravatar http image loading bug on Android
– Update all http links to https and fixed all old domain names
– Added simple JSON REST API that the renewed WarQuest Android App uses
– Add bplaat (b.b.b.) to the developers (because he made this update)

Play

Click here to enter directly the game!