Installing the software

Follow these steps to install PostgreSQL, Patroni, etcd, and HAProxy for the HA setup.

• Install the PostgreSQL database by using YUM repository:
  1. Optional: If you install the PostgreSQL binary files, create user postgres. If you install by using YUM repository, skip this step.

     For more information about creating users, see Managing Users via Command-Line Tools.

  2. Configure the YUM repository:

     yum -y install 
     https://download.postgresql.org/pub/repos/yum/reporpms/EL-8-x86_64/pgdg-redhat-repo-latest.noarch.rpm

  3. Install PostgreSQL by using the following command:

     dnf -y install postgresql12 postgresql12-server

• Install Patroni by using the following steps:
  1. Install Python and Python pip and other dependencies by using the following command:

     yum install -y gcc python-devel python2-pip

     For more information, see Installing pip/setuptools/wheel with Linux Package Managers

  2. Install Patroni and supporting libraries by using Python pip.

     
     pip install --upgrade setuptools
     pip install psycopg2-binary
     pip install patroni
     pip install python-etcd
     

     For more information, see Patroni- Technical Requirements/Installation.
  3. Enable Patroni as service by using the following steps:
     1. Create system file for patroni Service with the following command:

        vi /etc/systemd/system/patroni.service

     2. Add the following lines:

        
        [Unit]
        Description=Patroni
        After=syslog.target network.target
        [Service]
        Type=simple
        User=postgres
        Group=postgres
        ExecStart=/bin/patroni <path>/patroni.yml
        KillMode=process
        TimeoutSec=30
        Restart=no
        [Install]
        WantedBy=multi-user.target

        <path> is location of the patroni_config.yaml file.

• Install etcd with the following steps:
  1. Download etcd binary files from the following link:
     etcd-v2.2.5-linux-amd64.tar.gz
  2. Extract archive with the following command:

     tar -xvf etcd-v2.2.5-linux-amd64.tar.gz

  3. Move the etcd and etcdctl binary files with the following command:

     mv etcd etcdctl  /usr/local/bin

  4. Enable etcd service with the following steps:
     1. Create data directory for etcd with the following command:

        mkdir -p /var/lib/etcd && mkdir -p /etc/etcd

     2. Create etcd user with the following commands:

        groupadd –-system etcd
        useradd -s /sbin/nologin –-system -g etcd etcd
        

     3. Change data directory ownership with the following command:

        chown -R etcd:etcd /var/lib/etcd

     4. Create system file for etcd service

        vi /etc/systemd/system/etcd.service

     5. Add the following lines:

        
        [Unit]
        Description=etcd cluster
        Documentation=https://github.com/etcd-io/etcd
        After=syslog.target network.target
        [Service]
        User=etcd
        Type-notify
        Environment file=/etc/etcd/default
        Environment=ETCD_DATA_DIR=/var/lib/etcd
        Environment=
        ExecStart=/usr/local/bin/etcd
        Restart=always
        RestartSec=10s
        LimitNOFILE=40000
        [Install]
        WantedBy=multi-user.target

• Install HAProxy by using the following command:

  yum install -y haproxy

  For more information, see Install and Configure HAProxy.