ps-ghostferry

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.

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

For a detailed tutorial, see the documentation.

Development Setup

Install:

• Have Docker installed
• Clone the repo
• docker-compose up -d mysql-1 mysql-2

Test copydb locally:

• mysql --protocol=tcp -u root -P 29291 < sql/n1create.sql to create databases on the source server
• mysql --protocol=tcp -u root -P 29291 < sql/n1users.sql to create ghostferry user on source server
• mysql --protocol=tcp -u root -P 29292 < sql/n2users.sql to create ghostferry user on destination server
• docker run --name ghostferry -p 8000:8000 -v $(pwd)/log:/log -v $(pwd)/config:/config pasientskyhosting/ps-ghostferry ghostferry-copydb -verbose -dryrun config/examplerun.json to perform a dry run
• docker run --name ghostferry -p 8000:8000 -d -v $(pwd)/log:/log -v $(pwd)/config:/config pasientskyhosting/ps-ghostferry ghostferry-copydb -verbose config/examplerun.json to start the run
• You can access the web UI on port 8000
• Log and state dump can be found in the log directory
• For a more detailed tutorial, see the documentation.