Highly available databases are essential to organizations depending on mission-critical, 24/7 access to data. Postgres is widely recognized as an excellent open-source database, with critical maturity and features that allow organizations to scale and achieve high availability. This webinar will explore: - Evolution of replication in Postgres - Streaming replication - Logical replication - Replication for high availability - Important high availability parameters - Options to monitor high availability - HA infrastructure to patch the database with minimal downtime - EDB Postgres Failover Manager (EFM) - EDB tools to create a highly available Postgres architecture

1. © Copyright EnterpriseDB Corporation, 2020. All rights reserved.
How to Design for Database
High Availability
Vibhor Kumar, Chief Performance Architect
Marc Linster, Senior Vice President of Product
Development
Bruce Momjian, Postgres Evangelist
1

2. Welcome – Housekeeping
Items
• Slides and recording will be available in next 48 hours
• Submit questions via GotoWebinar – will be answering at end
• We will be sharing info about EDB and Postgres later
2

3. Webinar Series
3
April 29 2020 My Favorite Postgres books
May 13 2020
Database Administration for
Postgres
June 3 2020
New Approaches to Integrating
Oracle and Postgres Database
Strategies
June 17 2020 How to Design for Database
High Availability
July 15 2020 Using the Postgres Tuning
Wizard in PEM
Every other Monday at
8:00 AM PDT/ 11:00 AM EDT
16:00 BST/ 17:00 CET
https://www.enterprisedb.com/postgres-pulse

4. Agenda
● Evolution of replication in Postgres
○ Streaming replication
○ Logical replication
● Replication for high availability
● Important high availability parameters
● Monitor high availability
● Patch the database with minimal downtime
● EDB Postgres Failover Manager (EFM)
● EDB tools to create a highly available Postgres architecture
4

5. High Availability
5

6. High Availability
High availability (HA) is a characteristic of a system, which aims to ensure an
agreed level of operational performance, usually uptime, for a higher than normal
period.
● Key Principles
○ Eliminate single point of failure
○ Reliable crossover
○ Detection of failures
6

7. ● RPO – Recovery Point Objective
○ How much data can I lose?
○ Ex: RPO = 2 hours 🡺 In case of a crash
I may forget everything that I did in the
last 2 hours!
● RTO - Recovery Time Objective
○ How much time do I have to recover the
database after a crash?
○ Includes:
■ Load the initial backup
■ Play back the WAL files
Key Metrics for HA/DR
7
● MTTR - Mean Time to Recovery
○ On average – how long will RTO be
○ More WAL files to re-play if the last full backup was a
long time ago
● GRO – Geographic Recovery Objective
○ If my datacenter becomes unavailable, how long will
it take for the service to become available again?
● Maintenance Windows
○ How many hours of planned maintenance per year?

8. Evolution of Replication in Postgres
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PostgreSQL 7.x (~2000)
● Replication should not be part of
core Postgres
● Londiste – Slony (trigger based
logical replication)
PostgreSQL 8.0 (~2005)
● Point-In-Time Recovery (WAL)
PostgreSQL 9.4 (~2014)
● Logical Decoding (changeset
extraction)
PostgreSQL 9.0 (~2010)
● Streaming Replication (physical)
PostgreSQL 8.2 (~2006)
● Warm Standby
● EFM for

9. High Availability
9
Eliminate Single Point of Failure

10. Eliminate Single Point of
Failure
● WAL shipping based replication
○ Replication based on the archived WAL
● Streaming replication (SR)
○ Streaming WAL files to one or more standbys
● Logical replication
○ Streaming logical data modifications from the WAL.
10

11. Hot Standby
● Identical to primary system
○ Data is still mirrored in real time
○ Allows READ
○ On failure, can replace primary
● Approaches
○ WAL shipping based
○ Streaming WAL (widely used after 9.0)
11

12. Hot Standby: WAL Shipping
12

13. Monitor: WAL Shipping
● Functions on standby
○ pg_is_in_recovery()
○ pg_last_xlog/wal_replay_location/lsn()
○ pg_last_xact_replay_timestamp()
13

14. Hot standby: Streaming WAL
14

15. Streaming Replication
● Asynchronous Streaming Replication
● Synchronous Streaming Replication
○ synchronous_standby_names
■ e.g.
■ FIRST 1 (standby_east, standby_west)
■ ANY 3 (standby_east, standby_west, eu_standby_east,
eu_standby_west)
■ 'standby_east, standby_west'
○ synchronous_commit - off/local/remote_write/on/remote_apply
15

16. Monitor: Streaming Replication
● Views
○ Master: pg_stat_replication
○ Standby: pg_wal_receiver
16

17. High Availability
17
Reliable Crossover & Detection

18. 18
EDB POSTGRES FAILOVER
MANAGER (EFM)
Protect Your Mission
Critical Applications
from Costly Outages
High Availability
Infrastructure for
EDB Postgres Clusters
Ensure Data Remains
Available in the
Event of a Failure
ELIMINATE SINGLE
POINTS OF FAILURE
DETECTS AND
AUTOMATES FAILOVER
PEACE OF MIND FAILOVER
WILL BE INITIATED

19. 19
Streaming
Replication &
EFM

20. High Availability
20
Software Updates/Patching

21. Software Updates: Postgres H.A.
cluster
● Three reasons for software updates
○ Remedy known software issues
○ General stability and reliability of the software
○ Security problem
21

22. Software Updates: Strategies
● Three strategies
○ All Nodes Patching
○ Rolling Patching
○ Minimum Downtime Patching
22

23. High Availability
23
Postgres H.A Architecture

24. USE CASE - Architecture
24
Highly Available Postgres Cluster with Automatic Failover, Backups and Monitoring enabled
High Availability & Resiliency
• Master & Replica spread across
• Failover to most recent standby
• Reconfigure remaining standby to the new
master
• Allow switching the roles of Master-standby
Monitoring, Alerting & Tuning
• Monitor multiple database servers with intuitive
dashboards, email, SNMP alerts, and rich APIs
• Alerts on load, bloat, memory utilization,
server/agent down
• Track slow queries, analyze and tune it
Backup & Recovery
• Fast Backups and trouble free Disaster Recovery
Architecture

25. Conclusion
● High Availability components
○ Hot Standby (Streaming Replication)
○ EDB Postgres Failover Manager
○ Postgres Enterprise Manager
● Design consideration
○ Near zero downtime software maintenance
○ RPO/RTO/GRO
25

26. Resources
Blog series
● What Does High Availability Really Mean
● Patching Minor Version in Postgres High Availability (HA) Database Cluster
● Plans & Strategies for DBAs
● Key Parameters and Configuration for Streaming Replication in Postgres 12
● Quick and Reliable Failure Detection with EDB Postgres Failover Manager
26

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