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## variables

Those will be required.

 * PGSQL_VIP - vip for PostgreSQL
 * MAAS_REGIOND_VIP - vip for MAAS regiond on pxe line
 * MAAS_REGIOND_VIP_EXT - vip for MAAS regiond on public line if any
 * NODE1_IP_ADDRESS, NODE2_IP_ADDRESS, NODE3_IP_ADDRESS - each IP address
 * NODE1_HOSTNAME, NODE2_HOSTNAME, NODE3_HOSTNAME - each hostname
 * REPLICATION_PASSWORD - password for PostgreSQL replication user

## Package installation

Install PostgreSQL, corosync and pacemaker packages on all 3 infrastructure nodes.

    $ sudo apt install postgresql corosync pacemaker

Edit corosync.conf and copy it.

    $ sudo cp -v corosync.conf /etc/corosync/corosync.conf

Start corosync/pacemaker on all 3 infrastructure nodes.

    $ sudo service corosync restart
    $ sudo service pacemaker restart

Make sure all 3 nodes are listed up as online in status after starting corosync/pacemaker on all 3 nodes.

    $ sudo crm status

Stop all PostgreSQL running on all 3 infrastructure nodes for now.

    $ sudo service postgresql stop

Disable auto start of PostgreSQL on all 3 infrastructure nodes to prevent unnecessary cluster disruptions on reboot.

    $ echo manual | sudo tee /etc/postgresql/9.5/main/start.conf


## Setup PostgreSQL replication

Edit pg_hba.conf first.

Write ACL as pg_hba.conf on all 3 infrastructure nodes.

    $ sudo cp -v pg_hba.conf /etc/postgresql/9.5/main/pg_hba.conf

Write postgresql.conf on all 3 infrastructure nodes for replication.

    $ sudo cp -v postgresql.conf \
        /etc/postgresql/9.5/main/postgresql.conf

Prepare necessary directories and files on all 3 infrastructure nodes.

    $ sudo install -o postgres -g postgres -m 0700 \
        -d /var/lib/postgresql/9.5/main/pg_archive
    $ sudo install -o postgres -g postgres -m 0700 \
        -d /var/lib/postgresql/9.5/tmp
    $ sudo install -o postgres -g postgres -m 0600 \
        /dev/null /var/lib/postgresql/9.5/tmp/rep_mode.conf

Start PostgreSQL only on the primary node.

    $ sudo pg_ctlcluster 9.5 main start

Create a replication user as “repuser” in PostgreSQL. You can specify arbitrary password here.

    $ sudo -u postgres createuser \
        -U postgres repuser \
        -P -c 10 --replication

Start the replication only on non-primary nodes.

    $ sudo mv -v /var/lib/postgresql/9.5/main{,.old}

    $ sudo -u postgres pg_basebackup \
        -h <NODE1_IP_ADDRESS> \
        -D /var/lib/postgresql/9.5/main \
        -U repuser \
        -v -P --xlog-method=stream


## Enable PostgreSQL management with corosync/pacemaker

Stop PostgreSQL on the primary node and double check no PostgreSQL is running anywhere.

    $ sudo pg_ctlcluster 9.5 main stop


Edit pgsql.crm. Please note that "node_list" should contain hostnames (uname -n) regardless you have DNS or not.

Load crm configuration on 1 of 3 nodes.

    $ sudo crm configure load update - < base.crm

    $ sudo crm configure load update - < pgsql.crm

Wait for a while until the master node will be chosen by corosync/pacemaker. You can watch the status by the following command.

    $ sudo crm_mon -fAr


## MAAS package installation

After the master PostgreSQL node is chosen, install "maas" package only on the master node, please double check which one is master with the crm status.

    $ sudo apt install maas jq

Install only necessary packages on the remaining 2 nodes.

    $ sudo apt install maas-common
    $ sudo apt install maas-region-api maas-dns maas-rack-controller jq


## Enable MAAS HA

First, get maasdb password by executing the following command on the primary node.

    $ sudo maas-region local_config_get --plain --database-pass

Get MAAS secret string by executing the following command on the primary node.

    $ sudo cat /var/lib/maas/secret; echo

Execute the following commands on all 3 infrastructure nodes to update configuration to use vip endpoints.

    $ sudo maas-region local_config_set \
        --maas-url http://<MAAS_REGIOND_VIP>/MAAS \
        --database-host <PGSQL_VIP> \
        --database-name maasdb \
        --database-user maas \
        --database-pass <MAASDB_PASSWORD>

    $ sudo maas-region edit_named_options \
        --migrate-conflicting-options

    $ sudo service bind9 restart
    $ sudo service maas-regiond restart

    $ sudo maas-rack register \
        --url http://<MAAS_REGION_VIP>/MAAS \
        --secret <MAAS_SECRET>

Edit MAAS crm file.

Load MAAS crm configuration.

    $ sudo crm configure load update - < maas.crm

You can watch the crm status by the following command.

    $ sudo crm_mon -fAr -1


## Expected status

sudo crm_mon -fAr -1
Last updated: Wed Apr 19 04:03:58 2017          Last change: Wed Apr 12 09:19:33 2017 by root via cibadmin on node01
Stack: corosync
Current DC: node02 (version 1.1.14-70404b0) - partition with quorum
3 nodes and 15 resources configured

Online: [ node01 node02 node03 ]

Full list of resources:

 Resource Group: grp_pgsql_vip
     res_pgsql_vip      (ocf::heartbeat:IPaddr2):       Started node03
 Master/Slave Set: ms_pgsql [res_pgsql]
     Masters: [ node03 ]
     Slaves: [ node01 node02 ]
 Resource Group: grp_regiond_vip
     res_regiond_vip    (ocf::heartbeat:IPaddr2):       Started node01
     res_regiond_vip_ext        (ocf::heartbeat:IPaddr2):       Started node01
 Clone Set: cl_apache2 [res_apache2]
     Started: [ node01 node02 node03 ]
 Clone Set: cl_bind9 [res_bind9]
     Started: [ node01 node02 node03 ]
 Clone Set: cl_maas-regiond [res_maas-regiond]
     Started: [ node01 node02 node03 ]

Node Attributes:
* Node node01:
    + master-res_pgsql                  : -INFINITY 
    + res_pgsql-data-status             : STREAMING|ASYNC
    + res_pgsql-receiver-status         : normal    
    + res_pgsql-status                  : HS:async  
* Node node02:
    + master-res_pgsql                  : 100       
    + res_pgsql-data-status             : STREAMING|SYNC
    + res_pgsql-receiver-status         : normal    
    + res_pgsql-status                  : HS:sync   
    + res_pgsql-xlog-loc                : 0000000006000060
* Node node03:
    + master-res_pgsql                  : 1000      
    + res_pgsql-data-status             : LATEST    
    + res_pgsql-master-baseline         : 0000000004000000
    + res_pgsql-receiver-status         : normal (master)
    + res_pgsql-status                  : PRI       
    + res_pgsql-xlog-loc                : 0000000004000000

Migration Summary:
* Node node02:
* Node node03:
* Node node01: