Using Failover Manager for high availability#

Important

This page is under review and has not been updated for PEM 10. We plan to publish new documentation on HA patterns in PEM alongside some software changes to facilitate these patterns in PEM 10.1.

Note

This procedure is for setting up Failover Manager for a PEM server with a new installation, not with an existing one. The provided commands apply to the configuration on RHEL-based systems where HTTPD is used for the web server services.

Postgres Enterprise Manager (PEM) helps database administrators, system architects, and performance analysts to administer, monitor, and tune Postgres database servers.

Failover Manager is a high-availability tool from EDB that enables a Postgres primary node to failover to a standby node during a software or hardware failure on the primary. The examples that follow use these IP addresses:

172.16.161.200 - PEM Primary
172.16.161.201 - PEM Standby 1
172.16.161.202 - PEM Standby 2
172.16.161.203 - EFM Witness Node
172.16.161.245 - PEM VIP (used by agents and users to connect)

The following must use the VIP address:

The PEM agent binding of the monitored database servers
Accessing the PEM web client
Accessing the webserver services

Initial product installation and configuration#

Install the following on the primary and one or more standbys:

EDB Postgres Advanced Server (backend database for PEM Server)
PEM server
EDB Failover Manager 4.1

Refer to the installation instructions in the product documentation using these links or see the instructions on the EDB repos website . Replace USERNAME:PASSWORD with your username and password in the instructions to access the EDB repositories.

Make sure that the database server is configured to use the scram-sha-256 authentication method, as the PEM server configuration script doesn’t work with trust authentication.

You must install the java-1.8.0-openjdk package to install EFM.

Configure the PEM server on the primary server as well as on all the standby servers with an initial configuration of type 1 (web services and database):

/usr/edb/pem/bin/configure-pem-server.sh -t 1

For more detail on configuration types see, Configuring the PEM server on Linux .

Add the following ports in the firewall on the primary and all the standby servers to allow the access:

8443 for PEM Server (https)
5444 for EPAS 13
7800 for EFM
7908 for EFM Admin

For example:

$ sudo firewall-cmd --zone=public --add-port=5444/tcp --permanent
success
$ sudo firewall-cmd --zone=public --add-port=8443/tcp --permanent
success
$ sudo firewall-cmd --zone=public --add-port=7800/tcp --permanent
success
$ sudo firewall-cmd --zone=public --add-port=7809/tcp --permanent
success
$ sudo firewall-cmd --reload
success

Set up the primary node for streaming replication#

Create the replication role:

$ /usr/edb/as13/bin/psql -h 172.16.161.200 -p 5444 -U enterprisedb edb -c “CREATE ROLE repl REPLICATION LOGIN PASSWORD password”;
CREATE ROLE

Give the password of your choice.

Configure the following in the postgresql.conf file:

wal_level = replica
max_wal_senders = 10
wal_keep_size = 500
max_replication_slots = 10

For more information on configuring parameters for streaming replication, see the PostgreSQL documentation .

Note

The configuration parameters might differ for different versions of the database server. You can email EDB Support at techsupport@enterprisedb.com for help with setting up these parameters.

Add the following entry in the host-based authentication (/var/lib/edb/as13/data/pg_hba.conf ) file to allow the replication user to connect from all the standbys:

hostssl  replication  repl  172.16.161.201/24  scram-sha-256

Note

You can change the cidr range of the IP address, if needed.

Modify the host-based authentication (/var/lib/edb/as13/data/pg_hba.conf ) file for the pem_user role to connect to all databases using the scram-sha-256 authentication method:

# Allow local PEM agents and admins to connect to PEM server
hostssl all    +pem_user   172.16.161.201/24  scram-sha-256
hostssl pem    +pem_user   127.0.0.1/32       scram-sha-256
hostssl pem    +pem_agent  127.0.0.1/32         cert
# Allow remote PEM agents and users to connect to PEM server
hostssl pem   +pem_user    0.0.0.0/0          scram-sha-256
hostssl pem   +pem_agent   0.0.0.0/0          cert

Restart the EPAS 13 server.

systemctl restart edb-as-13.service

Set up the standby nodes for streaming replication#

Stop the service for EPAS 13 on all the standby nodes:

$ systemctl stop edb-as-13.service

Note

This example uses the pg_basebackup utility to create the replicas of the PEM backend database server on the standby servers. When using pg_basebackup, you need to stop the existing database server and remove the existing data directories.

Remove the data directory of the database server on all the standby nodes:

$ sudo su - enterprisedb

$ rm -rf /var/lib/edb/as13/data/*

Create the .pgpass file in the home directory of the enterprisedb user on all the standby nodes:

$ sudo su - enterprisedb

$ cat > ~/.pgpass << _EOF_
172.16.161.200:5444:replication:repl:CHANGE_ME
172.16.161.201:5444:replication:repl:CHANGE_ME
172.16.161.202:5444:replication:repl:CHANGE_ME
_EOF_

$ chmod 600 ~/.pgpass

Take the backup of the primary node on each of the standby nodes using pg_basebackup:

$ sudo su - enterprisedb /usr/edb/as13/bin/pg_basebackup -h 172.16.161.200 \
-D /var/lib/edb/as13/data -U repl -v -P -Fp -R -p 5444

The backup command creates the postgresql.auto.conf and standby.signal files on the standby nodes. The postgresql.auto.conf file has the following content:

sudo su - enterprisedb cat /var/lib/edb/as13/data/postgresql.auto.conf
# Do not edit this file manually
# It will be overwritten by the ALTER SYSTEM command.
primary_conninfo = ‘user=repl passfile=’’/var/lib/edb/.pgpass’’ channel_binding=prefer host=172.16.161.200 port=5444 sslmode=prefer sslcompression=0 ssl_min_protocol_version=TLSv1.2 gssencmode=prefer krbsvrname=postgres target_session_attrs=any’

In the postgresql.conf file on each of the standby nodes, edit the following parameter:

hot_standby = on

Start the EPAS 13 database server on each of the standby nodes:

$ systemctl enable edb-as-13

$ systemctl start edb-as-13

Copy the following files from the primary node to the standby nodes at the same location, overwriting any existing files. Set the permissions on the files:

/etc/httpd/conf.d/edb-pem.conf
/etc/httpd/conf.d/edb-ssl-pem.conf
/root/.pem/agent1.crt
/root/.pem/agent1.key
/usr/edb/pem/agent/etc/agent.cfg
/usr/edb/pem/share/.install-config
/usr/edb/pem/web/pem.wsgi
/usr/edb/pem/web/config_setup.py

For example:

$ mkdir -p /root/.pem
$ chown root:root /root/.pem
$ chmod 0755      /root/.pem
$ mkdir -p        /var/lib/pemhome/.pem
$ chown pem:pem   /var/lib/pemhome/.pem
$ chmod 0700      /var/lib/pemhome/.pem
$ mkdir -p        /usr/edb/pem/logs
$ chown root:root /usr/edb/pem/logs
$ chmod 0755      /usr/edb/pem/logs
$ for file in /etc/httpd/conf.d/edb-pem.conf     \
              /etc/httpd/conf.d/edb-ssl-pem.conf \
              /root/.pem/agent1.crt \
              /usr/edb/pem/agent/etc/agent.cfg \
              /usr/edb/pem/share/.install-config \
              /usr/edb/pem/web/pem.wsgi \
              /usr/edb/pem/web/config_setup.py; do \
       chown root:root ${file}; \
       chmod 0644      ${file}; \
    done;
$ chmod 0600 /root/.pem/agent1.key
$ chown root:root /root/.pem/agent1.key

This code ensures that the webserver is configured on the standby and is disabled by default. Switchover by EFM enables the webserver.

Note

Manually keep the certificates in sync on master and standbys whenever the certificates are updated.

Run the configure-selinux.sh script to configure the SELinux policy for PEM:

$ /usr/edb/pem/bin/configure-selinux.sh
getenforce found, now executing getenforce command
Configure the httpd to work with the SELinux
Allow the httpd to connect the database (httpd_can_network_connect_db = on)
Allow the httpd to connect the network (httpd_can_network_connect = on)
Allow the httpd to work with cgi (httpd_enable_cgi = on)
Allow to read & write permission on the pem user home directory
SELinux policy is configured for PEM

$ sudo chmod 640 /root/.pem/agent1.crt

Disable and stop HTTPD and PEM agent services if they’re running on all replica nodes:

systemctl stop pemagent
systemctl stop httpd
systemctl disable pemagent
systemctl disable httpd

Note

At this point, a PEM primary server and two standbys are ready to take over from the primary whenever needed.

Set up EFM to manage failover on all hosts#

Prepare the primary node to support EFM:

Create a database user efm to connect to the database servers.
Grant the execute privileges on the functions related to WAL logs and the monitoring privileges to the user.
Add entries in pg_hba.conf to allow the efm database user to connect to the database server from all nodes on all the hosts.
Reload the configurations on all the database servers. For example:

$ cat > /tmp/efm-role.sql << _EOF_
-- Create a role for EFM
CREATE ROLE efm LOGIN PASSWORD password;

-- Give privilege to efm user to connect to a database
GRANT CONNECT ON DATABASE edb TO efm;

-- Give privilege to efm user to do backup operations
GRANT EXECUTE ON FUNCTION pg_current_wal_lsn() TO efm;
GRANT EXECUTE ON FUNCTION pg_last_wal_replay_lsn() TO efm;
GRANT EXECUTE ON FUNCTION pg_wal_replay_resume() TO efm;
GRANT EXECUTE ON FUNCTION pg_wal_replay_pause() TO efm;
GRANT EXECUTE ON FUNCTION pg_reload_conf() TO efm;

-- Grant monitoring privilege to the efm user
GRANT pg_monitor TO efm;
_EOF_

$ /usr/edb/as13/bin/psql -h 172.16.161.200 -p 5444 -U enterprisedb edb -f /tmp/efm-role.sql
CREATE ROLE
GRANT
GRANT
GRANT
GRANT
GRANT
GRANT
GRANT ROLE

$ rm -f /tmp/efm-role.sql

$ cat > /var/lib/edb/as13/data/pg_hba.conf <<< _EOF_
hostssl      edb     efm     172.16.161.200/32     scram-sha-256
hostssl      edb     efm     172.16.161.201/32     scram-sha-256
hostssl      edb     efm     172.16.161.202/32     scram-sha-256
hostssl      edb     efm     172.16.161.203/32     scram-sha-256
_EOF_

$ /usr/edb/as13/bin/psql -h 172.16.161.200 -p 5444 -U enterprisedb edb -c “SELECT pg_reload_conf();”

Create the scripts on each node to start/stop the PEM agent:

$ sudo cat > /usr/local/bin/start-httpd-pemagent.sh << _EOF_
#!/bin/sh
/bin/sudo /bin/systemctl enable httpd
/bin/sudo /bin/systemctl start httpd
/bin/sudo /bin/systemctl enable pemagent
/bin/sudo /bin/systemctl start pemagent
_EOF_
$ sudo cat > /usr/local/bin/stop-httpd-pemagent.sh << _EOF_
#!/bin/sh

/bin/sudo /bin/systemctl stop pemagent
/bin/sudo /bin/systemctl disable pemagent
/bin/sudo /bin/systemctl stop httpd
/bin/sudo /bin/systemctl disable httpd
_EOF_
$ sudo chmod 770 /usr/local/bin/start-pemagent.sh
$ sudo chmod 770 /usr/local/bin/stop-pemagent.sh

Create a sudoers file (/etc/sudoers.d/efm-pem ) on each node to allow the efm user to start/stop the pemagent:

$ sudo cat > /etc/sudoers.d/efm-pem << _EOF_
efm    ALL=(ALL)           NOPASSWD:   /bin/systemctl enable pemagent
efm    ALL=(ALL)           NOPASSWD:   /bin/systemctl disable pemagent
efm    ALL=(ALL)           NOPASSWD:   /bin/systemctl stop pemagent
efm    ALL=(ALL)           NOPASSWD:   /bin/systemctl start pemagent
efm    ALL=(ALL)           NOPASSWD:   /bin/systemctl status pemagent
_EOF_

Create an efm.nodes file on all nodes using the sample file (/etc/edb/efm-4.1/efm.nodes.in ), and give read-write access to the efm OS user:

$ sudo cp /etc/edb/efm-4.1/efm.nodes.in /etc/edb/efm-4.1/efm.nodes
$ sudo chown efm:efm /etc/edb/efm-4.1/efm.nodes
$ sudo chmod 600 /etc/edb/efm-4.1/efm.nodes

Add the IP address and efm port of the primary node in the /etc/edb/efm-4.1/efm.nodes file on the standby nodes:

$ sudo cat > /etc/edb/efm-4.1/efm.nodes <<< _EOF_
172.16.161.200:7800
_EOF_

Create the efm.properties file on all the nodes using the sample file (/etc/edb/efm-4.1/efm.properties.in ). Grant read access to all the users:

$ sudo cp /etc/edb/efm-4.1/efm.properties.in /etc/edb/efm-4.1/efm.properties
$ sudo chown efm:efm /etc/edb/efm-4.1/efm.properties
$ sudo chmod a+r /etc/edb/efm-4.1/efm.properties

Encrypt the efm user’s password using the efm utility:

$ export EFMPASS=password
$ /usr/edb/efm-4.1/bin/efm encrypt efm --from-env
096666746b05b081d1a98e43d94c9dad

Edit the following parameters in the properties file:

db.user=efm
db.password.encrypted=096666746b05b081d1a98e43d94c9dad
db.port=5444
db.database=edb
db.service.owner=enterprisedb
db.service.name=edb-as-13
db.bin=/usr/edb/as13/bin
db.data.dir=/var/lib/edb/as13/data
jdbc.sslmode=require
user.email=username@example.com
from.email=node1@efm-pem
notification.level=INFO
notification.text.prefix=[PEM/EFM]
bind.address=172.16.161.200:7800
admin.port=7809
is.witness=false
local.period=10
local.timeout=60
local.timeout.final=10
remote.timeout=10
node.timeout=50
encrypt.agent.messages=true
stop.isolated.primary=true
stop.failed.primary=true
primary.shutdown.as.failure=false
update.physical.slots.period=0
ping.server.ip=8.8.8.8
ping.server.command=/bin/ping -q -c3 -w5
auto.allow.hosts=false
stable.nodes.file=false
db.reuse.connection.count=0
auto.failover=true
auto.reconfigure=true
promotable=true
use.replay.tiebreaker=true
standby.restart.delay=0
reconfigure.num.sync=false
reconfigure.sync.primary=false
minimum.standbys=0
recovery.check.period=1
restart.connection.timeout=60
auto.resume.period=0
virtual.ip=172.16.161.245
virtual.ip.interface=ens33
virtual.ip.prefix=24
virtual.ip.single=true
check.vip.before.promotion=true
pgpool.enable=false
sudo.command=sudo
sudo.user.command=sudo -u %u
syslog.host=localhost
syslog.port=514
syslog.protocol=UDP
syslog.facility=LOCAL1
file.log.enabled=true
syslog.enabled=false
jgroups.loglevel=INFO
efm.loglevel=INFO
jvm.options=-Xmx128m
script.remote.post.promotion=/usr/local/bin/stop-pemagent.sh
script.post.promotion=/usr/local/bin/start-pemagent.sh

Set the value of the is.witness configuration parameter on the witness node to true :

is.witness=true

Enable and start the EFM service on the primary node:

$ systemctl enable edb-efm-4.1
$ systemctl start edb-efm-4.1

Allow the standbys to join the cluster started on the primary node:

/usr/edb/efm-4.1/bin/efm allow-node  efm  172.16.161.201
/usr/edb/efm-4.1/bin/efm allow-node  efm  172.16.161.202
/usr/edb/efm-4.1/bin/efm allow-node  efm  172.16.161.203

Enable and start the EFM service on the standby nodes and the EFM witness node:

$ systemctl enable edb-efm-4.1
$ systemctl start edb-efm-4.1

Check the EFM cluster status from any node:

$ sudo /usr/edb/efm-4.1/bin/efm cluster-status efm
Cluster Status: efm
    Agent Type  Address              DB       VIP
    ----------------------------------------------------------------
    Primary     172.16.161.200      UP       172.16.161.245*
    Standby     172.16.161.201      UP       172.16.161.245
    Standby     172.16.161.202      UP       172.16.161.245
    Witness     172.16.161.203      N/A      172.16.161.245

Allowed node host list:
    172.16.161.200 172.16.161.201 172.16.161.202 172.16.161.203

Membership coordinator: 172.16.161.200

Standby priority host list:
    172.16.161.201 172.16.161.202

Promote Status:

    DB Type     Address              WAL Received LSN   WAL Replayed LSN   Info
    ---------------------------------------------------------------------------
    Primary     172.16.161.200                         0/F7A3808
    Standby     172.16.161.201      0/F7A3808          0/F7A3808
    Standby     172.16.161.202      0/F7A3808          0/F7A3808

    Standby database(s) in sync with primary. It is safe to promote.

This status confirms that EFM is set up successfully and managing the failover for the PEM server.

In case of failover, any of the standbys are promoted as the primary node, and PEM agents connect to the new primary node. You can replace the failed primary node with a new standby using this procedure.

Current limitations#

The current limitations include:

Web console sessions for the users are lost during the switchover.
Per-user settings set from the Preferences dialog box are lost, as they’re stored in local configuration files on the file system.
Background processes, started by the Backup, Restore, and Maintenance dialogs boxes, and their logs aren’t shared between the systems. They are lost during switchover.

Using Failover Manager for high availability

Contents

Using Failover Manager for high availability#

Initial product installation and configuration#

Set up the primary node for streaming replication#

Set up the standby nodes for streaming replication#

Set up EFM to manage failover on all hosts#

Current limitations#