Lifecycle of a WAL segment on Heroku Postgres

A lightning talk about what happens with Write-Ahead Logs in Heroku Postgres from creation to destruction, and the features enabled by it.

Given at PG Conf Europe 2013, Dublin.

Transcript

1. Lifecycle of a WAL segment on Heroku Postgres Harold Giménez @hgmnz @herokupostgres
2. Heroku Postgres?
4. Adding heroku-postgresql on demo-app… done, v129 (free) Attached as HEROKU_POSTGRESQL_ORANGE_URL Database has been created and is available Use `heroku addons:docs heroku-postgresql` to view documentation. $ $ heroku addons:add heroku-postgresql --app demo-app
5. Adding heroku-postgresql on demo-app… done, v129 (free) Attached as HEROKU_POSTGRESQL_ORANGE_URL Database has been created and is available Use `heroku addons:docs heroku-postgresql` to view documentation. $ $ heroku addons:add heroku-postgresql --app demo-app Plan: Dev Status: available Connections: 1 PG Version: 9.2.4 Data Size: 6.3 MB Tables: 0 Rows: 0/10000 (In compliance) Fork/Follow: Unsupported heroku pg:info -a demo-app
6. INSERT INTO … 1. Write to WAL ! ! 2. Data pages in memory 3. Respond to client 4. Flush data pages to heap
7. pg_xlog separate /wal partition 64GB ext4 options: nosuid, noatime, nodev
8. archive_command invoked by postgres to archive WAL segments we built WAL-E github.com/wal-e/wal-e
9. archive_command multi-datacenter storage
10. forks byte-by-byte copy of your database heroku addons:add heroku-postgresql --fork=blue
11. fork
12. followers read replicas heroku addons:add heroku-postgresql --follow=blue
13. follower
14. problem
15. eventual consistency auth issues instability
16. Archive reaper
17. Archive reaper
18. thanks! Harold Giménez @hgmnz @herokupostgres