Hydra/de: Difference between revisions

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Hydra ist ein Werkzeug für kontinuierliche Integrationstests und Softwarefreigabe, das eine rein funktionale Sprache zur Beschreibung von Build-Jobs und deren Abhängigkeiten verwendet. Kontinuierliche Integration ist eine einfache Technik zur Verbesserung der Qualität des Softwareentwicklungsprozesses. Ein automatisiertes System prüft kontinuierlich oder periodisch den Quellcode eines Projekts, baut ihn, führt Tests durch und erstellt Berichte für die Entwickler. Auf diese Weise werden verschiedene Fehler, die versehentlich in die Codebasis aufgenommen werden könnten, automatisch erkannt.

   services.hydra = {

     enable = true;

     buildMachinesFiles = [];

     useSubstitutes = true;

   };

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außer die <code>services.hydra.dbi</code> wird geändert. Das Datenbanklayout wird automatisch erstellt vom Hydra-Service. Allerdings ist anzumerken, das zusätzliche Daten in der Datenbank gespeichert werden, was eine vollständige deklarative Konfiguration unmöglich macht. Daher sind Backups erforderlich.

* Siehe <code>nixos-option</code> oder die  [https://search.nixos.org/options?query=services.hydra Nixos Optionsseite] für eine Liste aller Optionen.

=== Webserverkonfiguration ===

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=== Virtuelle Maschinen ===

Hydra benutzt localhost als Standardbuildmaschine,

wenn nichts anderes konfiguriert ist.

   nix.buildMachines = [

     { hostName = "localhost";

       system = "x86_64-linux";

       supportedFeatures = ["kvm" "nixos-test" "big-parallel" "benchmark"];

Falls die Hydra-option <code>buildMachinesFiles</code> immer noch auf eine leere Liste gesetzt ist, wird diese Einstellung ignoriert. Deswegen muss diese Option wieder entfernt werden oder <code>/etc/nix/machines</code> hinzugefügt werden.

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* Flake URI: an URI to a repo containing a Flake like git+https://git.myserver.net/user/repo.git

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{

       ...

     };

       inherit (self)

         packages;

}

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nix.settings.allowed-uris = [

];

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Right now it is not possible to build a single package from nixpkgs with just that input. You will need to provide a supplementary repository which defines what to build. For examples you can check the [https://github.com/makefu/hydra-example hydra-example by makefu] and in the [https://nixos.org/hydra/manual/#idm140737315920320 Hydra Manual].

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=== Imperative Building ===

These steps are required to build the <code>hello</code> package.

# log into Hydra after creating a user with <code>hydra-create-user</code>

# create new project

* identifier: example-hello

* display name: example-hello

# Actions -> Create jobset

* identifier: hello

* Nix expression: <code>release.nix</code> in <code>hydra-example</code> -> will evaluate the file release.nix in the given input

* check interval: 60

* scheduling shares: 1

* Inputs:

{| class="wikitable"

|-

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=== Declarative Building ===

Since 2016, Hydra supports declarative creation of jobsets. Check out the [https://github.com/shlevy/declarative-hydra-example example repository and description by Shea Levy].

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== Hydra Internals ==

=== Definitions ===

This subsection provides an overview of the Hydra-specific definitions and how to configure them.

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A cluster of Jobs which are all coming from a single input (like a git checkout), the first thing you will need to create. Every Job should be able to be built independently from another. Most of the time the project maps to a single repository like <code>nixpkgs</code>. It is comparable to the project definition in Jenkins.

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==== Jobset ====

==== Job ====

==== Release Set ====

Definiert alle Jobs, die in Ihrem Release beschrieben sind. Konventionell wird eine Datei namens <code>release.nix</code> verwendet. Eine ausführliche Beschreibung der Struktur finden Sie im [https://nixos.org/hydra/manual/#idm140737315920320 Hydra Handbuch für Build Recipes].

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==== Evaluation ====

The process of interpreting nix code into a list of <code>.drv files</code>. These files are the build recipes for all related outputs. You can introspect these files by running <code>nix show-derivation nixpkgs.hello</code>.

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==== Build ====

Instantiation of a Job which is being triggered by being part of the release set.

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== Known Issues ==

* hydra-queue-runner sometimes gets stuck even with builds are in the queue, and the builds are not scheduled. The issue is being tracked [https://github.com/NixOS/hydra/issues/366 here]. In the meantime, a workaround is to add a cron job that regularly restarts the hydra-queue-runner systemd service. Possible fix: [https://github.com/NixOS/hydra/commit/73ca325d1c0f7914640a63764c9a6d448fde5bd0]

* If you see <code>error: unexpected end-of-file</code> it can mean multiple things, some of them are:

# You have a miss-match between nix versions on the Hydra server and the builder

# It can also mean that <code>hydra-queue-runner</code> needs privileges on the build server. Reference: [https://github.com/NixOS/nix/issues/2789]

* The default timeout for git operations is 600 seconds [https://github.com/NixOS/hydra/issues/1181], which might cause fetches of large repositories like [https://github.com/NixOS/nixpkgs nixos/nixpkgs] to fail: <code>error fetching latest change from git repo at `https://github.com/nixos/nixpkgs': timeout</code>. The timeout can be increased with the following configuration.nix snippet:

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{

}

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Hydra is used for managing official Nix project releases. The project Hydra server: https://hydra.nixos.org/

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Some Hydra trackers for Nix projects:

* [https://hydra.nixos.org/project/nixpkgs Nixpkgs]

* [https://hydra.nixos.org/project/nixos NixOS]

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== Resources ==

* [https://www.youtube.com/watch?v=RXV0Y5Bn-QQ Video: Setting up a Hydra Build Farm by Peter Simons (2016)]

* [https://gist.github.com/joepie91/c26f01a787af87a96f967219234a8723 Hydra Caveats by Joepie91]

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