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hydra: 2020-02-06 -> 2020-03-{24,27}

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Upgrades Hydra to the latest master/flake branch. To perform this
upgrade, it's needed to do a non-trivial db-migration which provides a
massive performance-improvement[1].

The basic ideas behind multi-step upgrades of services between NixOS versions
have been gathered already[2]. For further context it's recommended to
read this first.

Basically, the following steps are needed:

* Upgrade to a non-breaking version of Hydra with the db-changes
  (columns are still nullable here). If `system.stateVersion` is set to
  something older than 20.03, the package will be selected
  automatically, otherwise `pkgs.hydra-migration` needs to be used.

* Run `hydra-backfill-ids` on the server.

* Deploy either `pkgs.hydra-unstable` (for Hydra master) or
  `pkgs.hydra-flakes` (for flakes-support) to activate the optimization.

The steps are also documented in the release-notes and in the module
using `warnings`.

`pkgs.hydra` has been removed as latest Hydra doesn't compile with
`pkgs.nixStable` and to ensure a graceful migration using the newly
introduced packages.

To verify the approach, a simple vm-test has been added which verifies
the migration steps.

[1] https://github.com/NixOS/hydra/pull/711
[2] https://github.com/NixOS/nixpkgs/pull/82353#issuecomment-598269471
This commit is contained in:
Maximilian Bosch 2020-03-27 22:09:13 +01:00
parent ea5c800175
commit bd5324c4fc
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GPG key ID: 091DBF4D1FC46B8E
9 changed files with 444 additions and 231 deletions
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33
nixos/modules/services/continuous-integration/hydra/default.nix
View file

@ -37,6 +37,8 @@ let
haveLocalDB = cfg.dbi == localDB;
inherit (config.system) stateVersion;
in
{
@ -63,8 +65,7 @@ in
};
package = mkOption {
type = types.path;
default = pkgs.hydra;
type = types.package;
defaultText = "pkgs.hydra";
description = "The Hydra package.";
};
@ -194,6 +195,34 @@ in
config = mkIf cfg.enable {
warnings = optional (cfg.package.migration or false) ''
You're currently deploying an older version of Hydra which is needed to
make some required database changes[1]. As soon as this is done, it's recommended
to run `hydra-backfill-ids` and set `services.hydra.package` to either `pkgs.hydra-unstable`
or `pkgs.hydra-flakes` after that.
[1] https://github.com/NixOS/hydra/pull/711
'';
services.hydra.package = with pkgs;
mkDefault (
if pkgs ? hydra
then throw ''
The Hydra package doesn't exist anymore in `nixpkgs`! It probably exists
due to an overlay. To upgrade Hydra, you need to take two steps as some
bigger changes in the database schema were implemented recently[1]. You first
need to deploy `pkgs.hydra-migration`, run `hydra-backfill-ids` on the server
and then deploy either `pkgs.hydra-unstable` or `pkgs.hydra-flakes`.
If you want to use `pkgs.hydra` from your overlay, please set `services.hydra.package`
explicitly to `pkgs.hydra` and make sure you know what you're doing.
[1] https://github.com/NixOS/hydra/pull/711
''
else if versionOlder stateVersion "20.03" then hydra-migration
else hydra-unstable
);
users.groups.hydra = {
gid = config.ids.gids.hydra;
};