jm + migrations   9

'shift is a [web] application that helps you run schema migrations on MySQL databases'
databases  mysql  sql  migrations  ops  square  ddl  percona 
february 2017 by jm
'Continuous Deployment: The Dirty Details'
Good slide deck from Etsy's Mike Brittain regarding their CD setup. Some interesting little-known details:

Slide 41: database schema changes are not CD'd -- they go out on "Schema change Thursdays".

Slide 44: only the webapp is CD'd -- PHP, Apache, memcache components (, support and back-office tools, developer API, gearman async worker queues). The external "services" are not -- databases, Solr/JVM search (rolling restarts), photo storage (filters, proxy cache, S3), payments (PCI-DSS, controlled access).

They avoid schema changes and breaking changes using an approach they call "non-breaking expansions" -- expose new version in a service interface; support multiple versions in the consumer. Example from slides 50-63, based around a database schema migration.

Slide 66: "dev flags" (rollout oriented) are promoted to "feature flags" (long lived degradation control).

Slide 71: some architectural philosophies: deploying is cheap; releasing is cheap; gathering data should be cheap too; treat first iterations as experiments.

Slide 102: "Canary pools". They have multiple pools of users for testing in production -- the staff pool, users who have opted in to see prototypes/beta stuff, 0-100% gradual phased rollout.
cd  deploy  etsy  slides  migrations  database  schema  ops  ci  version-control  feature-flags 
april 2015 by jm
devbook/ at master · barsoom/devbook
How to avoid the shitty behaviour of ActiveRecord wrt migration safety, particularly around removing/renaming columns. ugh, ActiveRecord
activerecord  fail  rails  mysql  sql  migrations  databases  schemas  releasing 
march 2015 by jm
The Large Hadron Migrator is a tool to perform live database migrations in a Rails app without locking.

The basic idea is to perform the migration online while the system is live, without locking the table. In contrast to OAK and the facebook tool, we only use a copy table and triggers. The Large Hadron is a test driven Ruby solution which can easily be dropped into an ActiveRecord or DataMapper migration. It presumes a single auto incremented numerical primary key called id as per the Rails convention. Unlike the twitter solution, it does not require the presence of an indexed updated_at column.
migrations  database  sql  ops  mysql  rails  ruby  lhm  soundcloud  activerecord 
march 2015 by jm
Rails migrations with no downtime
Ugh, Rails fail. It is impossible to drop a column from a Rails-managed table without downtime, even if nothing in the code accesses it (!!), without ugly hacks that don't even seem to work on recent versions of ActiveRecord.
activerecord  deploy  migrations  rails  ruby  sql  fail  downtime 
november 2014 by jm
Manages migrations for your Cassandra data stores. Pillar grew from a desire to automatically manage Cassandra schema as code. Managing schema as code enables automated build and deployment, a foundational practice for an organization striving to achieve Continuous Delivery.

Pillar is to Cassandra what Rails ActiveRecord migrations or Play Evolutions are to relational databases with one key difference: Pillar is completely independent from any application development framework.
migrations  database  ops  pillar  cassandra  activerecord  scala  continuous-delivery  automation  build 
june 2014 by jm
Database Migrations Done Right
The rule is simple. You should never tie database migrations to application deploys or vice versa. By minimising dependencies you enable faster, easier and cleaner deployments.

A solid description of why this is a good idea, from an ex-Guardian dev.
migrations  database  sql  mysql  postgres  deployment  ops  dependencies  loose-coupling 
may 2014 by jm
Netflix Queue: Data migration for a high volume web application
There will come a time in the life of most systems serving data, when there is a need to migrate data to [another] data store while maintaining or improving data consistency, latency and efficiency. This document explains the data migration technique we used at Netflix to migrate the user’s queue data between two different distributed NoSQL storage systems [SimpleDB to Cassandra].
cassandra  netflix  migrations  data  schema  simpledb  storage 
march 2013 by jm
Online Schema Change for MySQL
A tool written by Facebook to ease the pain of online MySQL schema-change migrations.
Some ALTER TABLE statements take too long form the perspective of some MySQL users. The fast index create feature for the InnoDB plugin in MySQL 5.1 makes this less of an issue but this can still take minutes to hours for a large table and for some MySQL deployments that is too long.
A workaround is to perform the change on a slave first and then promote the slave to be the new master. But this requires a slave located near the master. MySQL 5.0 added support for triggers and some replication systems have been built using triggers to capture row changes. Why not use triggers for this? The openarkkit toolkit did just that with oak-online-alter-table. We have published our version of an online schema change utility (OnlineSchemaChange.php aka OSC).
facebook  mysql  sql  schema  database  migrations  ops  alter-table 
march 2013 by jm

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