= Module Build Service Infra SOP

The MBS is a build orchestrator on top of Koji for "modules".

https://fedoraproject.org/wiki/Changes/ModuleBuildService

== Contact Information

Owner::
  Release Engineering Team, Infrastructure Team
Contact::
  fedora-admin, #fedora-releng
Persons::
  jkaluza, fivaldi, breilly, mikem
Public addresses::
  * mbs.fedoraproject.org
Servers::
  * mbs-frontend0[1-2].iad2.fedoraproject.org
  * mbs-backend01.iad2.fedoraproject.org
Purpose::
  Build modules for Fedora.

== Description

Users submit builds to _mbs.fedoraproject.org_ referencing their modulemd
file in https://src.fedoraproject.org/[dist-git]. (In the future,
users will not submit their own module
builds. The _freshmaker_ daemon (running in infrastructure)
will watch for `.spec` file changes and `modulemd.yaml` file changes -- it
will submit the relevant module builds to the MBS on behalf of users.)

The request to build a module is received by the MBS flask app running
on the `mbs-frontend` nodes.

Cursory validation of the submitted modulemd is performed on the
frontend: are the named packages valid? Are their branches valid? The
MBS keeps a copy of the modulemd and appends additional data describing
which branches pointed to which hashes at the time of submission.

A fedmsg from the frontend triggers the backend to start building the
module. First, tags and build/srpm-build groups are created. Then, a
module-build-macros package is synthesized and submitted as an srpm
build. When it is complete and available in the buildroot, the rest of
the rpm builds are submitted.

These are grouped and limited in two ways:

* First, there is a global `NUM_CONCURRENT_BUILDS` config option that
controls how many koji builds the MBS is allowed to have open at any
time. It serves as a throttle.
* Second, a given module may specify that it's components should have a
certain "build order". If there are 50 components, it may say that the
first 25 of them are in one buildorder batch, and the second 25 are in
another buildorder batch. The first batch will be submitted and, when
complete, tagged back into the buildroot. Only after they are available
will the second batch of 25 begin.

When the last component is complete, the MBS backend marks the build as
"done", and then marks it again as "ready". (There is currently no
meaning to the "ready" state beyond "done". We reserved that state for
future CI interactions.)

== Observing MBS Behavior

=== The mbs-build command

The https://pagure.io/fm-orchestrator[fm-orchestrator repo] and the
_module-build-service_ package provide an
_mbs-build_ command with a few subcommands. For general
help:

....
$ mbs-build --help
....

To generate a report of all currently active module builds:

....
$ mbs-build overview
  ID  State    Submitted             Components    Owner    Module
----  -------  --------------------  ------------  -------  -----------------------------------
 570  build    2017-06-01T17:18:11Z  35/134        psabata  shared-userspace-f26-20170601141014
 569  build    2017-06-01T14:18:04Z  14/15         mkocka   mariadb-f26-20170601141728
....

To generate a report of an individual module build, given its ID:

....
$ mbs-build info 569
NVR                                             State     Koji Task
----------------------------------------------  --------  ------------------------------------------------------------
libaio-0.3.110-7.module_414736cc                COMPLETE  https://koji.fedoraproject.org/koji/taskinfo?taskID=19803741
                                                BUILDING  https://koji.fedoraproject.org/koji/taskinfo?taskID=19804081
libedit-3.1-17.20160618cvs.module_414736cc      COMPLETE  https://koji.fedoraproject.org/koji/taskinfo?taskID=19803745
compat-openssl10-1.0.2j-6.module_414736cc       COMPLETE  https://koji.fedoraproject.org/koji/taskinfo?taskID=19803746
policycoreutils-2.6-5.module_414736cc           COMPLETE  https://koji.fedoraproject.org/koji/taskinfo?taskID=19803513
selinux-policy-3.13.1-255.module_414736cc       COMPLETE  https://koji.fedoraproject.org/koji/taskinfo?taskID=19803748
systemtap-3.1-5.module_414736cc                 COMPLETE  https://koji.fedoraproject.org/koji/taskinfo?taskID=19803742
libcgroup-0.41-11.module_ea91dfb0               COMPLETE  https://koji.fedoraproject.org/koji/taskinfo?taskID=19685834
net-tools-2.0-0.42.20160912git.module_414736cc  COMPLETE  https://koji.fedoraproject.org/koji/taskinfo?taskID=19804010
time-1.7-52.module_414736cc                     COMPLETE  https://koji.fedoraproject.org/koji/taskinfo?taskID=19803747
desktop-file-utils-0.23-3.module_ea91dfb0       COMPLETE  https://koji.fedoraproject.org/koji/taskinfo?taskID=19685835
libselinux-2.6-6.module_ea91dfb0                COMPLETE  https://koji.fedoraproject.org/koji/taskinfo?taskID=19685833
module-build-macros-0.1-1.module_414736cc       COMPLETE  https://koji.fedoraproject.org/koji/taskinfo?taskID=19803333
checkpolicy-2.6-1.module_414736cc               COMPLETE  https://koji.fedoraproject.org/koji/taskinfo?taskID=19803514
dbus-glib-0.108-2.module_ea91dfb0               COMPLETE  https://koji.fedoraproject.org/koji/taskinfo?taskID=19685836
....

To actively watch a module build in flight, given its ID:

....
$ mbs-build watch 570
Still building:
   libXrender https://koji.fedoraproject.org/koji/taskinfo?taskID=19804885
   libXdamage https://koji.fedoraproject.org/koji/taskinfo?taskID=19805153
Failed:
   libXxf86vm https://koji.fedoraproject.org/koji/taskinfo?taskID=19804903

Summary:
   2 components in the BUILDING state
   34 components in the COMPLETE state
   1 components in the FAILED state
   97 components in the undefined state
psabata's build #570 of shared-userspace-f26 is in the "build" state
....

=== The releng repo

There are more tools located in the `scripts/mbs/` directory
of the releng repo: https://pagure.io/releng/blob/main/f/scripts/mbs

== Cancelling a module build

Users can cancel their own module builds with:

....
$ mbs-build cancel $BUILD_ID
....

MBS admins can also cancel builds of any user.

[NOTE]
====
MBS admins are defined as members of the groups listed in the
`ADMIN_GROUPS` configuration options in
`roles/mbs/common/templates/config.py`.
====
== Logs

The frontend logs are on mbs-frontend0[1-2] in
`/var/log/httpd/error_log`.

The backend logs are on mbs-backend01. Look in the journal for the
`fedmsg-hub` service.

== Upgrading

The package in question is `module-build-service`. Please
use the `playbooks/manual/upgrade/mbs.yml` playbook.

== Managing Bootstrap Modules

In general, modules use other modules to define their buildroots, but
what defines the buildroot of the very first module? For this, we use
"bootstrap" modules which are manually selected. For some history on
this, see these tickets:

* https://pagure.io/releng/issue/6791
* https://pagure.io/fedora-infrastructure/issue/6097

The tag for a bootstrap module needs to be manually created and
populated by Release Engineering. Builds for that tag are curated and
selected from other Fedora tags, with care to ensure that only as many
builds are added as needed.

The existence of the tag is not enough for the bootstrap module to be
useable by MBS. MBS discovers the bootstrap module as a possible
dependency for other yet-to-be-built modules by querying PDC. During
normal operation, these entries in PDC are automatically created by
`pdc-updater` on _pdc-backend02_, but for the bootstrap tag they need to be
manually created and linked to the new bootstrap tag.

To be usable, you'll need a token with rights to speak to staging/prod
PDC. See the PDC SOP for information on client configuration in
`/etc/pdc.d/` and on where to find those tokens.

== Things that could go wrong

=== Overloading koji

If koji is overloaded, it should be acceptable to _stop_ the fedmsg-hub
daemon on _mbs-backend01_ at any time.

[NOTE]
====
As builds finish in koji, they will be _missed_ by the backend.. but
when it restarts it should find them in datagrepper. If that fails as
well, the mbs backend has a poller which should start up ~5 minutes
after startup that checks koji for anything it may have missed, at which
point it will resume functioning.
====
If koji continues to be overloaded after startup, try decreasing the
`NUM_CONCURRENT_BUILDS` option in the config file in
`roles/mbs/common/templates/`.
