tarqd / ghost-darkly

Control live schema migrations with gh-ost and LauncHDarkly

ghost-darklyd

Example of controlling gh-ost schema migrations at runtime using LaunchDarkly.

A small daemon (ghost-darklyd) is started when gh-ost starts via a hook in ghost-hooks.d.

Updates to flags starting with ghost- are listened for and converted into commands sent to the gh-ost admin socket. For example, if you create a flag called ghost-chunk-size, you can dynamically change the chunk sized used when copying by updating the flag.

An example migration is included in example/add-col-expiry.sh. Bring the sample database up using docker-compose up --detach. You can run the example setting the following env variables:

export LD_SDK_KEY=<your sdk key>
#optional, trigger url that will be called when the migration suceeds
# for example, turn a flag on after the column is added
export GHOST_SUCCESS_URL=<launchdarkly trigger url>

Then start the example

bash example/add-col-expiry.sh --execute

Logs will be stored in /tmp/launchdarkly-ghost.log. You can complete the cutover by creating a flag called ghost-allow-cutover and having it return true.