Ghostferry is a library that enables you to selectively copy data from one mysql instance to another with minimal amount of downtime.
It is inspired by Github's gh-ost, although instead of copying data from and to the same database, Ghostferry copies data from one database to another and have the ability to only partially copy data.
There is an example application called ghostferry-copydb included (under the
copydb directory) that demonstrates this library by copying an entire database from one machine to another.
Talk to us on IRC at irc.freenode.net #ghostferry.
- Tutorial and General Documentations: https://shopify.github.io/ghostferry
- Code documentations: https://godoc.org/github.com/Shopify/ghostferry
Overview of How it Works
An overview of Ghostferry's high-level design is expressed in the TLA+ specification, under the
tlaplus directory. It maybe good to consult with that as it has a concise definition. However, the specification might not be entirely correct as proofs remain elusive.
On a high-level, Ghostferry is broken into several components, enabling it to copy data. This is documented at https://shopify.github.io/ghostferry/master/technicaloverview.html
- Have Docker installed
- Clone the repo
docker-compose up -d mysql-1 mysql-2
make copydb && ghostferry-copydb -verbose examples/copydb/conf.json
- For a more detailed tutorial, see the documentation.
Ruby Integration Tests
Kindly take note of following options:
DEBUG=1: To see more detailed debug output by
TESTOPTS=...: As detailed under https://docs.ruby-lang.org/en/2.1.0/Rake/TestTask.html
bundle exec rake test DEBUG=1 TESTOPTS="-v --name=TrivialIntegrationTests#test_logged_query_omits_columns"