Updated HA doc setup with new version of ETCD (#571)

* Updated HA doc setup with new version of ETCD

* Replaced ETCD config with yaml file

* Added a How to set up all ETCD nodes simultaneously

* Updated Enable extensions page

modified:   docs/solutions/ha-setup-apt.md
modified:   docs/solutions/ha-setup-yum.md

docs/enable-extensions.md

@@ -10,13 +10,7 @@ While setting up a high availability PostgreSQL cluster with Patroni, you will n
 
 - Patroni installed on every ``postresql`` node. 
 
-- Distributed Configuration Store (DCS). Patroni supports such DCSs as ETCD, zookeeper, Kubernetes though [ETCD](https://etcd.io/) is the most popular one. It is available upstream as DEB packages for Debian 10, 11, 12 and Ubuntu 20.04, 22.04.  
-
-     For CentOS 8, RPM packages for ETCD is available within Percona Distribution for PostreSQL.  You can install it using the following command: 
-
-     ```{.bash data-prompt="$"}
-     $ sudo yum install etcd python3-python-etcd
-     ```
+- Distributed Configuration Store (DCS). Patroni supports such DCSs as ETCD, zookeeper, Kubernetes though [ETCD](https://etcd.io/) is the most popular one. It is available within Percona Distribution for PostgreSQL for all supported operating systems.
 
 - [HAProxy](http://www.haproxy.org/).
 

docs/how-to.md

@@ -0,0 +1,75 @@
+# How to
+
+## How to configure ETCD nodes simultaneously
+
+!!! note 
+
+    We assume you have a deeper knowledge of how ETCD works. Otherwise, refer to the configuration where you add ETCD nodes one by one. 
+
+Instead of adding `etcd` nodes one by one, you can configure and start all nodes in parallel. 
+
+1. Create the ETCD configuration file on every node. You can edit the sample configuration file `/etc/etcd/etcd.conf.yaml` or create your own one. Replace the node names and IP addresses with the actual names and IP addresses of your nodes.
+
+    === "node1"
+
+         ```yaml title="/etc/etcd/etcd.conf.yaml"
+         name: 'node1'
+         initial-cluster-token: PostgreSQL_HA_Cluster_1
+         initial-cluster-state: new
+         initial-cluster: node1=http://10.104.0.1:2380,node2=http://10.104.0.2:2380,node3=http://10.104.0.3:2380
+         data-dir: /var/lib/etcd
+         initial-advertise-peer-urls: http://10.104.0.1:2380 
+         listen-peer-urls: http://10.104.0.1:2380
+         advertise-client-urls: http://10.104.0.1:2379
+         listen-client-urls: http://10.104.0.1:2379
+         ```
+
+    === "node2"
+
+         ```yaml title="/etc/etcd/etcd.conf.yaml"
+         name: 'node2'
+         initial-cluster-token: PostgreSQL_HA_Cluster_1
+         initial-cluster-state: new
+         initial-cluster: node1=http://10.104.0.1:2380,node2=http://10.104.0.2:2380,     node3=http://10.104.0.3:2380
+         data-dir: /var/lib/etcd
+         initial-advertise-peer-urls: http://10.104.0.2:2380 
+         listen-peer-urls: http://10.104.0.2:2380
+         advertise-client-urls: http://10.104.0.2:2379
+         listen-client-urls: http://10.104.0.2:2379
+         ```
+
+    === "node3"
+
+         ```yaml title="/etc/etcd/etcd.conf.yaml"
+         name: 'node1'
+         initial-cluster-token: PostgreSQL_HA_Cluster_1
+         initial-cluster-state: new
+         initial-cluster: node1=http://10.104.0.1:2380,node2=http://10.104.0.2:2380,     node3=http://10.104.0.3:2380
+         data-dir: /var/lib/etcd
+         initial-advertise-peer-urls: http://10.104.0.3:2380 
+         listen-peer-urls: http://10.104.0.3:2380
+         advertise-client-urls: http://10.104.0.3:2379
+         listen-client-urls: http://10.104.0.3:2379
+         ```
+
+2. Enable and start the `etcd` service on all nodes:
+
+    ```{.bash data-prompt="$"}
+    $ sudo systemctl enable --now etcd
+    ```
+
+    During the node start, ETCD searches for other cluster nodes defined in the configuration. If the other nodes are not yet running, the start may fail by a quorum timeout. This is expected behavior. Try starting all nodes again at the same time for the ETCD cluster to be created.
+
+3. Check the etcd cluster members.  Connect to one of the nodes and run the following command:
+
+    ```{.bash data-prompt="$"}
+    $ sudo etcdctl member list
+    ```
+
+    The output resembles the following:
+
+    ```
+    2d346bd3ae7f07c4: name=node2 peerURLs=http://10.104.0.2:2380 clientURLs=http://10.104.0.2:2379 isLeader=false
+    8bacb519ebdee8db: name=node3 peerURLs=http://10.104.0.3:2380 clientURLs=http://10.104.0.3:2379 isLeader=false
+    c5f52ea2ade25e1b: name=node1 peerURLs=http://10.104.0.1:2380 clientURLs=http://10.104.0.1:2379 isLeader=true
+    ```