What is tableflip
It is sometimes useful to update the running code and / or configuration of a network service, without disrupting existing connections. Usually, this is achieved by starting a new process, somehow transferring clients to it and then exiting the old process.
There are many ways to implement graceful upgrades. They vary wildly in the trade-offs they make, and how much control they afford the user. This library has the following goals:
- No old code keeps running after a successful upgrade
- The new process has a grace period for performing initialisation
- Crashing during initialisation is OK
- Only a single upgrade is ever run in parallel
- tableflip works on Linux and macOS.
- Build v0.0.1 demo.
go build -o demo main.go
- Run the demo and create a get request to
127.0.0.1:8080/version, here is the output:[PID: 123] v0.0.1
- Prepare a new version. change the main.go, let the version be "v0.0.2" and rebuild it.
go build -o demo main.go
- Now, kill the old one !
kill -s HUP 123 - Create the request to version api again, but output is changed:
[PID: 123] v0.0.2
The client is completely immune to server upgrades and reboots, and our application updates gracefully!