Skip to content

Frontend setup#

The ALICE build infrastructure is exposed via SSO.

Due to limitations of the SSO protocol this happens via single machine which runs apache and does the reverse proxying to the actual service.

The machine is setup in CERN/IT puppet + OpenStack facility in the hostgroup alibuild/frontend.

Disaster recovering#

Starting the frontend#

The quick recipe to restart the frontend is:

  • Login to aiadm.cern.ch.

  • Set up your OpenStack environment by doing:

    eval $(ai-rc "ALICE Release Testing")

  • To spawn a machine you need to use the ai-bs-vm wrapper, which will take care of provisioning the machine and putting it in Foreman, so that it will receive from it the Puppet configuration:

    MACHINE_NAME=

    ai-bs-vm -g alibuild/frontend \ --cc7 \ --nova-sshkey alibuild \ --nova-flavor m2.large \ --landb-mainuser alice-agile-admin \ --landb-responsible alice-agile-admin \ $MACHINE_NAME - Once you have the frontend created, you also need to grant it read-only permission to some CERN S3 bucket we use for storing logs. The policy for it can be found in the ali-marathon repository. The required policies are:

  • s3/alice-build-logs-policy.json

and they need to have the right Ip Address registered there.

Enabling / disabling one host in the load balancing#

Machines in the alibuild/frontend hostgroup participate in a load balanced DNS alias. In order to do so they must be in roger state production. To do so:

roger update --app_alarmed false --appstate production --message 'Fully operational' <hostname>

to do an intervention on them:

roger update --app_alarmed true --appstate intervention --message '<Some log message>' <hostname>
puppet agent -t -v

You can check their load balanced score with:

/usr/local/sbin/lbclient -d TRACE

CERN Single Sign-On (SSO) authentication#

Some web applications use Apache's OIDC support to authenticate with CERN SSO. Apache then sets various OIDC_CLAIM_* headers on the forwarded requests.

See also the CERN SSO documentation.

Adding a new application#

Applications must be configured on the CERN SSO side through the Application Portal and on the ALICE side though our Puppet-generated Apache configuration, specifically the file it-puppet-hostgroup-alibuild/data/hostgroup/alibuild/frontend.yaml.

  1. Add the application on the Application Portal
  2. Configure the client ID of the application in it-puppet-hostgroup-alibuild/data/hostgroup/alibuild/frontend.yaml, using oidc_client_id: <client ID>
  3. Store the generated client secret in Teigi as <app name>-oidc-client-secret
  4. Generate an OIDC crypto passphrase, e.g. using tr -dc '[:alnum:].+_-' < /dev/urandom | head -c 24; echo and save it in Teigi as <app name>-oidc-crypto-passphrase
  5. Add an OIDC (not SAML) registration to the new application
  6. Make sure you use https://<app name>.cern.ch/oidc-redirect as the redirect URI. Apache intercepts the /oidc-redirect path.
  7. Optionally, configure any required roles, e.g. alice-member:
  8. Add this role as documented here and map any required e-groups (e.g. alice-member) to it
  9. Configure oidc_require_role: <role identifier> for the application in it-puppet-hostgroup-alibuild/data/hostgroup/alibuild/frontend.yaml