Using Failover Manager for high availability v8
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.
You can set up Failover Manager only with a fresh installation of a Postgres Enterprise Manager (PEM) server. You can't set it for an existing PEM installation.
The examples in the following sections 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:PASSWORDwith 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-openjdkpackage 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:
8443for PEM Server (https)5444for EPAS 137800for EFM7908for 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.conffile: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-256Note
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
.pgpassfile 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
backupcommand creates thepostgresql.auto.confandstandby.signalfiles on the standby nodes. Thepostgresql.auto.conffile 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.conffile 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-13Copy 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.shscript 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.confto 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
sudoersfile (/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.nodesfile 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.nodesfile on the standby nodes:$ sudo cat > /etc/edb/efm-4.1/efm.nodes <<< _EOF_ 172.16.161.200:7800 _EOF_
Create the
efm.propertiesfile 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.witnessconfiguration parameter on the witness node totrue:is.witness=true
Enable and start the EFM service on the primary node:
$ systemctl enable edb-efm-4.1 $ systemctl start edb-efm-4.1Allow 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-4.1Check 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.