Distcc/fr

Distcc est un programme conçu pour répartir des tâches de compilation à travers un réseau vers des hôtes participants. Il comprend un serveur,, et un client,. Distcc peut travailler en toute transparence avec ccache, Portage et Automake moyennant un minimum de configuration.

Si vous envisagez d'utiliser pour vous aider à préparer la chaîne des outils de compilation pour une installation de Gentoo, assurez vous de lire préalablement la section Utiliser  distcc pour compiler les outils de compilation.

Installation
Avant de configurer, commençons par nous intéresser à l'installation de sur tous les hôtes.

Dépendances communes à tous les hôtes
Afin d'utiliser, tous les ordinateurs sur votre réseau doivent posséder la même version de GCC. Pour être plus précis, mélanger 3.3.x (avec x variable) est accepté, mais mélanger 3.3.x avec 3.2.x peut conduire à des erreurs de compilation ou des erreurs en exécution.

Installation du logiciel
Distcc comprend un utilitaire de surveillance graphique des tâches de compilation qu'un ordinateur envoie à l'extérieur. La présence de celui-ci est contrôlée par l'option  de la variable.

Une fois la variable USE configurée, installez le packet.

Démarrage automatique du daemon distcc
Afin de mettre en place le démarrage automatique de, suivez les instructions suivantes, en fonction du système d'initialisation que vous utilisez.

Avec OpenRC
Éditez le fichier en fonction de vos besoins et assurez-vous de définir la directive   pour seulement les hôtes auxquels vous accordez votre confiance. Pour une sécurité renforcée, utilisez aussi la directive  afin de dire au démon  quelles adresses IP écouter (pour les systèmes multi-adresses). Des informations complémentaires sur la sécurité avec distcc sont disponibles à l'adresse Distcc Security Design.

L'exemple suivant autorise les clients distcc tournant sur  et   à se connecter au serveur  local.

Maintenant démarrez votre démon sur tous les ordinateurs participants :

Avec systemd
Éditez afin d'ajouter les clients au format CIDR. Voici un exemple:

Reload the unit files after making such changes:

Activer le démarrage automatique de et démarrer le service :

Configuration
Jetons maintenant un œil à la configuration de.

Spécification des hôtes participants
Utilisez la commande pour définir la liste des participants.

Voici quelques exemples de définition d’hôtes. Dans la plupart des cas, des variations des lignes 1 et 2 suffisent. Cette dernière inclue la syntaxe  afin d'informer  du nombre maximal de taches à lancer sur le nœud. Plus d'informations sur la syntaxe employée aux lignes 3 et 4 sont disponibles sur le manuel de distcc.

Il y a aussi plusieurs autres méthodes pour définir des hôtes. Reportez-vous à la page de manuel de ( man distcc ) pour plus de détails.

Si la machine locale doit elle aussi compiler, indiquez  dans la liste des hôtes participants. À l'inverse, si la machine locale ne participe pas à la compilation (ce qui est souvent le cas), omettez la de la liste. Sur une machine lente, utiliser  peut ralentir les choses. Assurez vous de la performance de votre configuration en effectuant des tests.

Configurons afin d'utiliser les hôtes mentionnés par la première ligne de l'exemple :

Utiliser distcc avec Portage
Setting up Portage to use is easy. It is a matter of enabling the feature, and setting a decent value for the number of simultaneous build jobs (as  increases the amount of build resources).

Set the  variable and   variable as shown below.

A common strategy is to
 * set the value of  to twice the number of total (local + remote) CPU cores + 1, and
 * set the value of  to the number of local CPU cores

The use of  in the   variable will prevent spawning too many tasks when some of the  cluster hosts are unavailable (increasing the amount of simultaneous jobs on the other systems) or when an ebuild is configured to disallow remote builds (such as with gcc). This is accomplished by refusing to start additional jobs when the system load is at or above the value of.

Par exemple, lorsqu'il y à deux hôtes quadruple cœur qui exécute et que le PC local possède un processeur double cœur, la variable   peut ressembler à ceci :

While editing the file, make sure that it does not have   in the   or   variables. will not distribute work to other machines if  is set to. The appropriate  value can be obtained by running the following command:

See Inlining  for distcc for more information.

Using distcc with automake
This is, in some cases, easier than the Portage setup. All that is needed is to update the  variable to include  in front of the directory that contains. However, there is a caveat. If is used, then put the  location after the  one:

Put this in the user's or equivalent file to have the   set every time the user logs in, or set it globally through an  file.

Instead of calling alone, add in   (where   is an integer). The value of  depends on the network and the types of computers that are used to compile. A heuristic approach to the right value is given earlier in this article.

Using distcc to bootstrap
Using to bootstrap (i.e. build a working toolchain before installing the remainder of the system) requires some additional steps to take.

Step 1: configure Portage
Boot the new box with a Gentoo Linux LiveCD and follow the installation instructions, while keeping track of the instructions in the Gentoo FAQ for information about bootstrapping. Then configure Portage to use :

Update the  variable in the installation session as well:

Step 2: getting distcc
Install :

Step 3: setting up distcc
Run to setup distcc; substitute the   in the example with the IP addresses or hostnames of the participating nodes.

Distcc is now set up to bootstrap! Continue with the proper installation instructions and do not forget to run after running. This is to make sure that all of the necessary dependencies are installed.

Distcc extras
The application has additional features and applications to support working in a  environment.

Distcc monitors
Distcc ships with two monitoring utilities. The text-based monitoring utility is always built and is called. Running it for the first time can be a bit confusing, but it is really quite easy to use. If the program is run with no parameter it will run just once. However, if it is passed a number it will update every  seconds, where   is the argument that was passed.

The other monitoring utility is only enabled when the  USE flag is set. This one is GTK+ based, runs in an X environment, and it is quite lovely. For Gentoo, the GUI monitor has been renamed to to make it less confusing (it is originally called ).

To monitor Portage's usage:

A trick is to set  in environment variables:

Now update the environment:

Finally, start the GUI application:

Using SSH for distcc communication
Setting up distcc via SSH includes some pitfalls. First, generate an SSH key pair without password setup. Be aware that portage compiles programs as the Portage user (or as root if  is not set). The home folder of the Portage user is, which means the keys need to be stored in

Second, create a section for each host in the SSH configuration file:

Send the public key to each compilation node:

Also make sure that each host is available in the file:

Fix the file permissions as follows:

To set up the hosts  and , run:

Please note the  (@ sign), which specifies ssh hosts for distcc.

Finally, tell which SSH binary to use:

It is not necessary to run the initscript on the hosts when  communicates via SSH.

Dépannage
If a problem occurs while using, then this section might help in resolving the problem.

ERROR: failed to open
As of January 22nd, 2015 emerging fails to create the proper file in. This apparently only effects version 3.1-r8 of distcc. This bug is in the process of being corrected (see ). It is possible to work around this by manually creating the log file, giving it proper ownership, and restarting the distccd daemon:

Next update the path of the  configuration file in  to the  directory created in the step before:

Finally, restart the distccd service:

Some packages do not use distcc
As various packages are installed, users will notice that some of them aren't being distributed (and aren't being built in parallel). This may happen because the package' doesn't support parallel operations, or the maintainer of the ebuild has explicitly disabled parallel operations due to a known problem.

Sometimes might cause a package to fail to compile. If this happens, please report it.

Mixed GCC versions
If the environment hosts different GCC versions, there will likely be very weird problems. The solution is to make certain all hosts have the same GCC version.

Recent Portage updates have made Portage use  (minus gcc) instead of. This means that if i686 machines are mixed with other types (i386, i586) then the builds will run into troubles. A workaround for this may be to run:

It is also possible to set the  and   variables in  to the values list in the command above.

-march=native
Starting with GCC 4.3.0, the compiler supports the  option which turns on CPU auto-detection and optimizations that are worth being enabled on the processor on which GCC is running. This creates a problem when using because it allows the mixing of code optimized for different processors. For example, running with   on a system that has an AMD Athlon processor and doing the same on another system that has an Intel Pentium processor will mix code compiled on both processors together.

Heed the following warning:

To know the flags that GCC would enable when called with, execute the following:

External resources

 * Inlining  for distcc
 * Distcc homepage