Items tagged zerodowntime in 2024
Filters: Year: 2024 × zerodowntime × Sorted by date
Skew protection in Vercel (via) Version skew is a name for the bug that occurs when your user loads a web application and then unintentionally keeps that browser tab open across a deployment of a new version of the app. If you’re unlucky this can lead to broken behaviour, where a client makes a call to a backend endpoint that has changed in an incompatible way.
Vercel have an ingenious solution to this problem. Their platform already makes it easy to deploy many different instances of an application. You can now turn on “skew protection” for a number of hours which will keep older versions of your backend deployed.
The application itself can then include its desired deployment ID in a x-deployment-id header, a __vdpl cookie or a ?dpl= query string parameter. # 20th March 2024, 2:06 pm
pgroll (via) “Zero-downtime, reversible, schema migrations for Postgres”
I love this kind of thing. This one is has a really interesting design: you define your schema modifications (adding/dropping columns, creating tables etc) using a JSON DSL, then apply them using a Go binary.
When you apply a migration the tool first creates a brand new PostgreSQL schema (effectively a whole new database) which imitates your new schema design using PostgreSQL views. You can then point your applications that have been upgraded to the new schema at it, using the PostgreSQL search_path setting.
Old applications can continue talking to the previous schema design, giving you an opportunity to roll out a zero-downtime deployment of the new code.
Once your application has upgraded and the physical rows in the database have been transformed to the new schema you can run a --continue command to make the final destructive changes and drop the mechanism that simulates both schema designs at once. # 30th January 2024, 9:27 pm