gitolite/doc/big-config.mkd

what is a "big-config"

In this document:

• when/why do we need it?
• how do we use it?
• other optimisations
• what are the downsides?
• (extra coolness) usergroups and LDAP/similar tools

when/why do we need it?

A "big config" is anything that has a few thousand users and a few thousand repos, organised into groups that are much smaller in number (like maybe a few hundreds of repogroups and a few dozens of usergroups).

So let's say you have

@wbr    =   lynx firefox
@devs   =   alice bob

repo @wbr
    RW+     next    =   @devs
    RW    master    =   @devs

Gitolite internally translates this to

repo lynx firefox
    RW+     next    =   alice bob
    RW    master    =   alice bob

Not just that -- it now generates the actual config rules once for each user-repo-ref combination (there are 8 combinations above; the compiled config file looks partly like this:

%repos = (
  'firefox' => {
    'R' => {
      'alice' => 1,
      'bob' => 1
    },
    'W' => {
      'alice' => 1,
      'bob' => 1
    },
    'alice' => [
      {
        'refs/heads/next' => 'RW+'
      },
      {
        'refs/heads/master' => 'RW'
      }
    ],
    'bob' => [
      {
        'refs/heads/next' => 'RW+'
      },
      {
        'refs/heads/master' => 'RW'
      }
    ]
  },
  'lynx' => {
    'R' => {
      'alice' => 1,
      'bob' => 1
    },
    'W' => {
      'alice' => 1,
      'bob' => 1
    },
    'alice' => [
      {
        'refs/heads/next' => 'RW+'
      },
      {
        'refs/heads/master' => 'RW'
      }
    ],
    'bob' => [
      {
        'refs/heads/next' => 'RW+'
      },
      {
        'refs/heads/master' => 'RW'
      }
    ]
  }
);

Phew!

You can imagine what that does when you have 10,000 users and 10,000 repos. Let's just say it's not pretty :)

how do we use it?

Now, if you had all those 10,000 users and repos explicitly listed (no groups), then there is no help. But if, like the above example, you had groups like we used above, there is hope.

Just set

$GL_BIG_CONFIG = 1;

in the ~/.gitolite.rc file on the server (see next section for more variables). When you do that, and push this configuration, the compiled file looks like this:

%repos = (
  '@wbr' => {
    '@devs' => [
      {
        'refs/heads/next' => 'RW+'
      },
      {
        'refs/heads/master' => 'RW'
      }
    ],
    'R' => {
      '@devs' => 1
    },
    'W' => {
      '@devs' => 1
    }
  },
);
%groups = (
  '@devs' => {
    'alice' => 'master',
    'bob' => 'master'
  },
  '@wbr' => {
    'firefox' => 'master',
    'lynx' => 'master'
  }
);

That's a lot smaller, and allows orders of magintude more repos and groups to be supported.

other optimisations

The default RC file contains the following lines (we've already discussed the first one):

$GL_BIG_CONFIG = 0;
$GL_NO_DAEMON_NO_GITWEB = 0;
$GL_NO_CREATE_REPOS = 0;
$GL_NO_SETUP_AUTHKEYS = 0;

GL_NO_DAEMON_NO_GITWEB is a very useful optimisation that you must enable if you do have a large number of repositories, and do not use gitolite's support for gitweb or git-daemon access (see "easier to specify gitweb description and gitweb/daemon access" for details). This will save a lot of time when you push the gitolite-admin repo with changes. This variable also control whether "git config" lines (such as config hooks.emailprefix = "[gitolite]") will be processed or not.

Setting this is relatively harmless to a normal installation, unlike the next two variables :-) GL_NO_CREATE_REPOS and GL_NO_SETUP_AUTHKEYS are meant for installations where some backend system already exists that does all the actual repo creation, and all the authentication setup (ssh auth keys), respectively.

Summary: Please leave those two variables alone unless you're initials are "JK" ;-)

Also note that using all 3 of the GL_NO_* variables will result in everything after the config compile being skipped. In other words, gitolite is being used only for its access control language.

what are the downsides?

There is one minor issue.

If you use the delegation feature, you can no longer define or extend @groups in a fragment, for security reasons. It will also not let you use any group other than the @fragname itself (specifically, groups which contained a subset of the allowed @fragname, which would work normally, do not work now).

(If you didn't understand all that, you're probably not using delegation, so feel free to ignore it!)

(extra coolness) usergroups and LDAP/similar tools

[Please NOTE: this is all about user groups, not repo groups]

Gitolite now allows usergroup information to be passed in from outside. The gl-auth-commmand can now take an optional list of usergroup names after the first argument (which is the username).

To understand why this is useful, consider the following:

Some people have an LDAP-backed ssh daemon (or some other similar mechanism that can speak "ssh" to the client), with pubkeys stored in LDAP, etc., and some way (not using ~/.ssh/authorized_keys) of invoking gitolite.

Such setups also have "usergroups", and a way to tell, for each user, what groups he/she is a member of. So let's say "alice" works on projects "foo" and "bar", while "bob" works on project "bar" and is a member of the L3_support team.

You can use those group names in the gitolite config file for access control as "@foo", "@bar", @L3_support, etc.; please note the "@" prefix because gitolite requires it.

However, that still leaves a wee little inconvenience. You still have to add lines like this to the gitolite config file:

@foo        = alice
@bar        = alice bob
@L3_support = bob

You don't need to do that anymore now. Tell your authentication system that, after authenticating alice, instead of running:

/some/path/to/gl-auth-command alice

it should first find the groups that alice is a member of, and then run:

/some/path/to/gl-auth-command alice foo bar

That's it. Internally, gitolite will behave as if the config file had also specified:

@foo = alice
@bar = alice