After you have those installed (in particular the epel-release one) you can install the following : python2-pip<\/p>\n
yum install -y python2-pip<\/pre>\nNext you need to add the PostgreSQL Yum Repo from:\u00a0https:\/\/download.postgresql.org\/pub\/repos\/yum\/10\/redhat\/rhel-7-x86_64\/pgdg-centos10-10-2.noarch.rpm<\/a><\/p>\n
yum install -y https:\/\/download.postgresql.org\/pub\/repos\/yum\/10\/redhat\/rhel-7-x86_64\/pgdg-centos10-10-2.noarch.rpm<\/pre>\nOnce you have that RPM installed you can install the following packages: postgresql10-server postgresql10<\/p>\n
yum install -y postgresql10-server postgrseql10<\/pre>\n<\/p>\n
etcd server:<\/h2>\n
The following packages needs to be installed on the etcd server: gcc,python-devel, epel-release<\/p>\n
yum install -y gcc python-devel epel-release<\/pre>\nAfter epel is installed, you can then install etcd:<\/p>\n
yum install -y etcd <\/pre>\n<\/p>\n
haproxy server:<\/h2>\n
The following packages are needed on the haproxy server: epel-release and then haproxy.<\/p>\n
yum install -y epel-release<\/pre>\nyum install -y haproxy<\/pre>\n<\/p>\n
Software Configuration<\/h1>\n
Postgresql Servers<\/h2>\n
Now that the software has been installed, it is time to configure the components.\u00a0 (Everything here is ran as root)<\/p>\n
We will start with the PostgreSQL Servers, mine are named pg01 (10.0.2.124), pg02 (10.0.2.125), and pg03(10.0.2.126) respectively.\u00a0 The following needs to be done on each of the 3 servers:<\/p>\n
First some pip items:<\/p>\n
pip install --upgrade setuptools\r\npip install patroni\r\npip install python-etcd\r\npip install psycopg2-binary\r\n<\/pre>\nNext we are going to create a systemd service for patroni. So edit the file\u00a0\/etc\/systemd\/system\/patroni.service to contain the following:<\/p>\n
\r\n\r\n[Unit]\r\nDescription=Runners to orchestrate a high-availability PostgreSQL\r\nAfter=syslog.target network.target\r\n\r\n[Service]\r\nType=simple\r\n\r\nUser=postgres\r\nGroup=postgres\r\n\r\nExecStart=\/bin\/patroni \/etc\/patroni.yml\r\n\r\nKillMode=process\r\n\r\nTimeoutSec=30\r\n\r\nRestart=no\r\n\r\n[Install]\r\nWantedBy=multi-user.targ\r\n\r\n<\/pre>\nNext create a \/etc\/patroni.yml file. This file will control the startup\/shutdown, etc of the postgres instance. Here is an example of mine from my pg01 server. In it, you will need to replace IP addresses for your own servers and usernames and passwords.<\/p>\n
<\/p>\n
scope: postgres\r\nname: pg01\r\n\r\nrestapi:\r\n listen: 10.0.2.124:8008\r\n connect_address: 10.0.2.124:8008\r\n\r\netcd:\r\n host: 10.0.2.128:2379\r\n\r\nbootstrap:\r\n dcs:\r\n ttl: 30\r\n loop_wait: 10\r\n retry_timeout: 10\r\n maximum_lag_on_failover: 1048576\r\n postgresql:\r\n use_pg_rewind: true\r\n\r\n initdb:\r\n - encoding: UTF8\r\n - data-checksums\r\n\r\n pg_hba:\r\n - host replication replicator 127.0.0.1\/32 md5\r\n - host replication replicator 10.0.2.124\/0 md5\r\n - host replication replicator 10.0.2.125\/0 md5\r\n - host replication replicator 10.0.2.126\/0 md5\r\n - host all all 0.0.0.0\/0 md5\r\n\r\n users:\r\n admin:\r\n password: admin\r\n options:\r\n - createrole\r\n - createdb\r\n\r\npostgresql:\r\n listen: 10.0.2.124:5432\r\n bin_dir: \/usr\/pgsql-10\/bin\r\n connect_address: 10.0.2.124:5432\r\n data_dir: \/data\/patroni\r\n pgpass: \/tmp\/pgpass\r\n authentication:\r\n replication:\r\n username: replicator\r\n password: PASSWORD\r\n superuser:\r\n username: postgres\r\n password: PASSWORD\r\n parameters:\r\n unix_socket_directories: '.'\r\n\r\ntags:\r\n nofailover: false\r\n noloadbalance: false\r\n clonefrom: false\r\n nosync: false\r\n<\/pre>\netcd server<\/h2>\n
Now lets move on to the etcd server. The only thing on the etcd server that needs edited is the \/etc\/etcd\/etcd.conf file. Here is what I changed in mine:<\/p>\n
\r\nETCD_LISTEN_PEER_URLS="http:\/\/10.0.2.128:2380"\r\nETCD_LISTEN_CLIENT_URLS="http:\/\/localhost:2379,http:\/\/10.0.2.128:2379"\r\nETCD_NAME="etcd0"\r\nETCD_INITIAL_ADVERTISE_PEER_URLS="http:\/\/10.0.2.128:2380"\r\nETCD_ADVERTISE_CLIENT_URLS="http:\/\/10.0.2.128:2379"\r\nETCD_INITIAL_CLUSTER="etcd0=http:\/\/10.0.2.128:2380"\r\nETCD_INITIAL_CLUSTER_TOKEN="cluster1"\r\nETCD_INITIAL_CLUSTER_STATE="new"\r\n<\/pre>\nSome of the above lines may be commented out, if so uncomment them and replace the values.<\/p>\n
HAProxy Server<\/p>\n
Now to config the HAProxy Server. Replace the \/etc\/haproxy\/haproxy.cfg with the following:<\/p>\n
<\/p>\n
global\r\n maxconn 100\r\n log 127.0.0.1 local2\r\n\r\ndefaults\r\n log global\r\n mode tcp\r\n retries 2\r\n timeout client 30m\r\n timeout connect 4s\r\n timeout server 30m\r\n timeout check 5s\r\n\r\nlisten stats\r\n mode http\r\n bind *:7000\r\n stats enable\r\n stats uri \/\r\n\r\nlisten postgres\r\n bind *:5000\r\n option httpchk\r\n http-check expect status 200\r\n default-server inter 3s fall 3 rise 2 on-marked-down shutdown-sessions\r\n server postgresql_pg01_5432 10.0.2.124:5432 maxconn 100 check port 8008\r\n server postgresql_pg02_5432 10.0.2.125:5432 maxconn 100 check port 8008\r\n server postgresql_pg03_5432 10.0.2.126:5432 maxconn 100 check port 8008<\/pre>\n<\/p>\n
N.B. The logging setup in the haproxy config requires that you set up rsyslog to allow logging to local files and to local2.*<\/p>\n
<\/p>\n
Starting it all up<\/h1>\n
So assuming that I haven’t missed anything above, and there are no typo’s on my or your part, we can start starting things up. But first some notes. Something in SElinux breaks some of this and I haven’t had enough time to look in to it, so disable SElinux for now (setenforce 0). In addition I did not add any ports to the firewalld, as this was just a test setup, so I disabled the firewall on all 5 machines. You can leave it enabled and then using the configs above add the appropriate ports to be allowed between the appropriate machines.<\/p>\n
So easy starts first:<\/p>\n
Start the etcd server: <\/p>\n
systemctl start etcd<\/pre>\nStart the haproxy server: <\/p>\n
systemctl start haproxy<\/pre>\nNow for the PostgreSQL servers there are a few things to do before we start them. On each PostgreSQL host do the following:<\/p>\n
\r\nmkdir -p \/data\/patroni\r\nchown -R postgres:postgres \/data\r\nchmod -R 700 \/data\r\n<\/pre>\nNow we can start Patroni and see if everything works. When you start Patroni, it will start PostgreSQL in the background and create the first database and set the username and password for the postgres user to what you specify in the \/etc\/patroni.yml file.<\/p>\n
systemctl start patroni<\/pre>\nOn the first host that you start Patroni on if you run systemctl status patroni you should see that it is running and active. In the \/var\/log\/messages you should see something like :<\/p>\n
\r\nSep 2 19:53:08 pg01 patroni: 2018-09-02 19:53:08,628 INFO: Lock owner: pg01; I am pg01\r\nSep 2 19:53:08 pg01 patroni: 2018-09-02 19:53:08,636 INFO: no action. i am the leader with the lock\r\n<\/pre>\nWhen you start the two slaves you should see something similar to this in the \/var\/log\/messages:<\/p>\n
\r\nSep 2 19:54:17 pg02 patroni: 2018-09-02 19:54:17,828 INFO: Lock owner: pg01; I am pg02\r\nSep 2 19:54:17 pg02 patroni: 2018-09-02 19:54:17,829 INFO: does not have lock\r\nSep 2 19:54:17 pg02 patroni: 2018-09-02 19:54:17,836 INFO: no action. i am a secondary and i am following a leader\r\n<\/pre>\n
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