Gülçin Yıldırım Jelínek
Main Organizer @ Prague PostgreSQL Meetup - MSc, Computer and Systems Engineering @ Tallinn University of Technology - BSc, Applied Mathematics @ Yildiz Technical University
Near-Zero Downtime Automated Upgrades of PostgreSQL Clusters in Cloud
Gülçin Yıldırım 156398IASM
Master's Thesis, June 2017
Supervisor: Tarmo Robal, PhD
Agenda
Goals & Motivation
Problems & How to Solve?
Platform Implementation
Case Studies & Results
Outlook
Conclusion & Summary
Problems?
DOWNTIME
Revenue Loss
Reputation Loss
High Availability?
SLAs?
Low Capacity?
Database Anyone?
Banks
Social Networks
Desktop Apps
Startups
Medium-size
Enterprises
To Upgrade, or not to Upgrade
-
New features
-
Security patches
-
Perfomance Updates
-
Bug fixes
-
Outdated, no support
-
Vulnerable to attacks
-
Poor Perfomance
-
Buggy, hard to maintain
Why Automate?
- Risk & Errors
- Cost
- Time-to-market
- Reproducibility
- Repeatability
- Efficiency
- Updating nasa.gov: 1 hr to 5 mins
- Patching updates: Multi-day to 45 mins
- Application stack setup: 1-2 hrs to 10 mins
Ansible Loves PostgreSQL
( in the s )
Postgres Modules: 6
AWS Modules: 100
PostgreSQL
252
Database
208
Cloud
116
Upgrade
50
Power of Logical Replication
-
Offline Conversion
-
pg_dump/pg_restore
-
pg_upgrade
-
-
Online Conversion
-
pglogical
-
pglupgrade
-
1
2
Elements of the solution
pglogical
pgbouncer
Ansible
AWS
pglupgrade
How
Does It Work?
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
First Case: High Availability
First Case: High Availability (2)
Second Case: Read Scalability
Second Case: Read Scalability(2)
Results
| Metric (1st case) | pg_dump/pg_restore | pg_upgrade | pglupgrade |
|---|---|---|---|
| Primary Downtime | 00:24:27 | 00:16:25 | 00:00:03 |
| Partial cluster HA | 00:24:27 | 00:28:56 | 00:00:03 |
| Full cluster capacity | 01:02:27 | 00:28:56 | 00:38:00 |
| Length of upgrade | 01:02:27 | 00:28:56 | 01:38:10 |
| Extra disk space | 800 MB | 27 GB | 10 GB |
| Metric (2nd case) | pg_dump/pg_restore | pg_upgrade | pglupgrade |
|---|---|---|---|
| Primary Downtime | 00:23:52 | 00:17:03 | 00:00:05 |
| Partial cluster HA | 00:23:52 | 00:54:29 | 00:00:05 |
| Full cluster capacity | 00:23:52 | 03:19:16 | 00:00:05 |
| Length of upgrade | 00:23:52 | 03:19:16 | 01:02:10 |
| Extra disk space | 800 MB | 27 GB | 10 GB |
Back to the Future
- There is a need for a near-zero downtime automated upgrade solution for PostgreSQL [PgCon 2017 Developer Meeting]
- Solution will be introduced to the community at PGDay'17 Russia on 6th July
- The tool will have a use in 2ndQuadrant and our customers
- Applicable to other DBMSs through logical replication
- Applicable to other Operating Systems
- PostgreSQL 10 will have built-in logical replication
Conclusion
-
Database clusters can be upgraded with minimal downtime without users being affected while the upgrade is happening.
-
An application can still respond to the request only with a small drop in performance.
-
Thesis and the case studies prove that pglupgrade minimizes the downtime to the level of 3-5 seconds.
Summary
-
THE GOAL: Minimize the downtime for database upgrades, specifically on PostgreSQL
-
METHODOLOGY: Engineer logical replication as an upgrade method
-
IMPLEMENTATION: Develop pglupgrade tool to automate the upgrade process using Ansible
-
CASE STUDIES: Benchmark on two different PostgreSQL clusters in cloud
-
RESULTS & CONCLUSION: Near-Zero downtime achieved without affecting the users
Thanks!
Questions
First Question
[old-primary]
54.171.211.188
[new-primary]
54.246.183.100
[old-standbys]
54.77.249.81
54.154.49.180
[new-standbys:children]
old-standbys
[pgbouncer]
54.154.49.180
Inventory file hosts.ini
$ ansible-playbook -i hosts.ini pglupgrade.yml
Running pglupgrade playbook
Second Question
- name: Switch the pgbouncer (and applications) to new primary
hosts: pgbouncer
become: true
become_user: postgres
vars_files:
- config.yml
roles:
- role: pgbouncer
tags:
- pgbouncer
pgbouncer play in pglupgrade playbook
remove
add
Near-Zero Downtime Automated Upgrades of PostgreSQL Clusters in Cloud
By Gülçin Yıldırım Jelínek
Near-Zero Downtime Automated Upgrades of PostgreSQL Clusters in Cloud
This presentation is prepared as Master's Thesis defence of Gulcin Yildirim at Tallinn University of Technology. All rights are reserved. Copying without permission is not allowed.
