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:title: Components
.. _components:
Components
==========
Zuul is a distributed system consisting of several components, each of
which is described below.
.. graphviz::
:align: center
graph {
node [shape=box]
Database [fontcolor=grey]
Gearman [shape=ellipse]
Gerrit [fontcolor=grey]
Statsd [shape=ellipse fontcolor=grey]
Zookeeper [shape=ellipse]
Nodepool
GitHub [fontcolor=grey]
Merger -- Gearman
Executor -- Gearman
Executor -- Statsd
Web -- Database
Web -- Gearman
Web -- Zookeeper
Web -- Executor
Finger -- Gearman
Finger -- Executor
Gearman -- Scheduler;
Scheduler -- Database;
Scheduler -- Gerrit;
Scheduler -- Zookeeper;
Zookeeper -- Nodepool;
Scheduler -- GitHub;
Scheduler -- Statsd;
}
Each of the Zuul processes may run on the same host, or different
hosts. Within Zuul, the components communicate with the scheduler via
the Gearman protocol, so each Zuul component needs to be able to
connect to the host running the Gearman server (the scheduler has a
built-in Gearman server which is recommended) on the Gearman port --
TCP port 4730 by default.
The Zuul scheduler communicates with Nodepool via the ZooKeeper
protocol. Nodepool requires an external ZooKeeper cluster, and the
Zuul scheduler needs to be able to connect to the hosts in that
cluster on TCP port 2181.
Both the Nodepool launchers and Zuul executors need to be able to
communicate with the hosts which nodepool provides. If these are on
private networks, the Executors will need to be able to route traffic
to them.
Only Zuul fingergw and Zuul web need to be publicly accessible;
executors never do. Executors should be accessible on TCP port 7900
by fingergw and web.
A database is only required if you create an sql driver in your Zuul
connections configuration. Both Zuul scheduler and Zuul web will need
access to it.
If statsd is enabled, the executors and scheduler needs to be able to
emit data to statsd. Statsd can be configured to run on each host
and forward data, or services may emit to a centralized statsd
collector. Statsd listens on UDP port 8125 by default.
All Zuul processes read the ``/etc/zuul/zuul.conf`` file (an alternate
location may be supplied on the command line) which uses an INI file
syntax. Each component may have its own configuration file, though
you may find it simpler to use the same file for all components.
Zuul will interpolate environment variables starting with the ``ZUUL_``
prefix given in the config file escaped as python string expansion.
``foo=%(ZUUL_HOME)s`` will set the value of ``foo`` to the same value
as the environment variable named ``ZUUL_HOME``.
An example ``zuul.conf``:
.. code-block:: ini
[gearman]
server=localhost
[gearman_server]
start=true
log_config=/etc/zuul/gearman-logging.yaml
[zookeeper]
hosts=zk1.example.com,zk2.example.com,zk3.example.com
[web]
status_url=https://zuul.example.com/status
[scheduler]
log_config=/etc/zuul/scheduler-logging.yaml
A minimal Zuul system may consist of a :ref:`scheduler` and
:ref:`executor` both running on the same host. Larger installations
should consider running multiple executors, each on a dedicated host,
and running mergers on dedicated hosts as well.
Common
------
The following applies to all Zuul components.
Configuration
~~~~~~~~~~~~~
The following sections of ``zuul.conf`` are used by all Zuul components:
.. attr:: gearman
Client connection information for Gearman.
.. attr:: server
:required:
Hostname or IP address of the Gearman server.
.. attr:: port
:default: 4730
Port on which the Gearman server is listening.
.. attr:: ssl_ca
An openssl file containing a set of concatenated “certification
authority” certificates in PEM formet.
.. attr:: ssl_cert
An openssl file containing the client public certificate in PEM format.
.. attr:: ssl_key
An openssl file containing the client private key in PEM format.
.. attr:: statsd
Information about the optional statsd server. If the ``statsd``
python module is installed and this section is configured,
statistics will be reported to statsd. See :ref:`statsd` for more
information.
.. attr:: server
Hostname or IP address of the statsd server.
.. attr:: port
:default: 8125
The UDP port on which the statsd server is listening.
.. attr:: prefix
If present, this will be prefixed to all of the keys before
transmitting to the statsd server.
.. attr:: zookeeper
Client connection information for ZooKeeper
.. attr:: hosts
:required:
A list of zookeeper hosts for Zuul to use when communicating
with Nodepool.
.. attr:: session_timeout
:default: 10.0
The ZooKeeper session timeout, in seconds.
.. _scheduler:
Scheduler
---------
The scheduler is the primary component of Zuul. The scheduler is not
a scalable component; one, and only one, scheduler must be running at
all times for Zuul to be operational. It receives events from any
connections to remote systems which have been configured, enqueues
items into pipelines, distributes jobs to executors, and reports
results.
The scheduler includes a Gearman server which is used to communicate
with other components of Zuul. It is possible to use an external
Gearman server, but the built-in server is well-tested and
recommended. If the built-in server is used, other Zuul hosts will
need to be able to connect to the scheduler on the Gearman port, TCP
port 4730. It is also strongly recommended to use SSL certs with
Gearman, as secrets are transferred from the scheduler to executors
over this link.
The scheduler must be able to connect to the ZooKeeper cluster used by
Nodepool in order to request nodes. It does not need to connect
directly to the nodes themselves, however -- that function is handled
by the Executors.
It must also be able to connect to any services for which connections
are configured (Gerrit, GitHub, etc).
Configuration
~~~~~~~~~~~~~
The following sections of ``zuul.conf`` are used by the scheduler:
.. attr:: gearman_server
The builtin gearman server. Zuul can fork a gearman process from
itself rather than connecting to an external one.
.. attr:: start
:default: false
Whether to start the internal Gearman server.
.. attr:: listen_address
:default: all addresses
IP address or domain name on which to listen.
.. attr:: port
:default: 4730
TCP port on which to listen.
.. attr:: log_config
Path to log config file for internal Gearman server.
.. attr:: ssl_ca
An openssl file containing a set of concatenated “certification
authority” certificates in PEM formet.
.. attr:: ssl_cert
An openssl file containing the server public certificate in PEM
format.
.. attr:: ssl_key
An openssl file containing the server private key in PEM format.
.. attr:: web
.. attr:: root
:required:
The root URL of the web service (e.g.,
``https://zuul.example.com/``).
See :attr:`tenant.web-root` for additional options for
whitelabeled tenant configuration.
.. attr:: status_url
URL that will be posted in Zuul comments made to changes when
starting jobs for a change.
.. TODO: is this effectively required?
.. attr:: scheduler
.. attr:: command_socket
:default: /var/lib/zuul/scheduler.socket
Path to command socket file for the scheduler process.
.. attr:: tenant_config
Path to :ref:`tenant-config` file. This attribute
is exclusive with :attr:`scheduler.tenant_config_script`.
.. attr:: tenant_config_script
Path to a script to execute and load the tenant
config from. This attribute is exclusive with
:attr:`scheduler.tenant_config`.
.. attr:: default_ansible_version
Default ansible version to use for jobs that doesn't specify a version.
See :attr:`job.ansible-version` for details.
.. attr:: log_config
Path to log config file.
.. attr:: pidfile
:default: /var/run/zuul/scheduler.pid
Path to PID lock file.
.. attr:: state_dir
:default: /var/lib/zuul
Path to directory in which Zuul should save its state.
.. attr:: relative_priority
:default: False
A boolean which indicates whether the scheduler should supply
relative priority information for node requests.
In all cases, each pipeline may specify a precedence value which
is used by Nodepool to satisfy requests from higher-precedence
pipelines first. If ``relative_priority`` is set to ``True``,
then Zuul will additionally group items in the same pipeline by
pipeline queue and weight each request by its position in that
project's group. A request for the first change in a given
queue will have the highest relative priority, and the second
change a lower relative priority. The first change of each
queue in a pipeline has the same relative priority, regardless
of the order of submission or how many other changes are in the
pipeline. This can be used to make node allocations complete
faster for projects with fewer changes in a system dominated by
projects with more changes.
If this value is ``False`` (the default), then node requests are
sorted by pipeline precedence followed by the order in which
they were submitted. If this is ``True``, they are sorted by
pipeline precedence, followed by relative priority, and finally
the order in which they were submitted.
.. attr:: default_hold_expiration
:default: max_hold_expiration
The default value for held node expiration if not supplied. This
will default to the value of ``max_hold_expiration`` if not changed,
or if it is set to a higher value than the max.
.. attr:: max_hold_expiration
:default: 0
Maximum number of seconds any nodes held for an autohold request
will remain available. A value of 0 disables this, and the nodes
will remain held until the autohold request is manually deleted.
If a value higher than ``max_hold_expiration`` is supplied during
hold request creation, it will be lowered to this value.
Operation
~~~~~~~~~
To start the scheduler, run ``zuul-scheduler``. To stop it, kill the
PID which was saved in the pidfile specified in the configuration.
Reconfiguration
~~~~~~~~~~~~~~~
Most of Zuul's configuration is automatically updated as changes to
the repositories which contain it are merged. However, Zuul must be
explicitly notified of changes to the tenant config file, since it is
not read from a git repository. Zuul supports two kinds of reconfigurations.
The full reconfiguration refetches and reloads the configuration of
all tenants. To do so, run ``zuul-scheduler full-reconfigure``. For
example this can be used to fix eventual configuration inconsistencies
after connection problems to Gerrit/Github. The signal based method by
sending a `SIGHUP` signal to the scheduler PID is deprecated.
The smart reconfiguration reloads only the tenants that changed their
configuration in the tenant config file. To do so, run
``zuul-scheduler smart-reconfigure``. In multi tenant systems this can
be much faster than the full reconfiguration so it is recommended to
use the smart reconfiguration after changing the tenant configuration
file.
Merger
------
Mergers are an optional Zuul service; they are not required for Zuul
to operate, but some high volume sites may benefit from running them.
Zuul performs quite a lot of git operations in the course of its work.
Each change that is to be tested must be speculatively merged with the
current state of its target branch to ensure that it can merge, and to
ensure that the tests that Zuul perform accurately represent the
outcome of merging the change. Because Zuul's configuration is stored
in the git repos it interacts with, and is dynamically evaluated, Zuul
often needs to perform a speculative merge in order to determine
whether it needs to perform any further actions.
All of these git operations add up, and while Zuul executors can also
perform them, large numbers may impact their ability to run jobs.
Therefore, administrators may wish to run standalone mergers in order
to reduce the load on executors.
Mergers need to be able to connect to the Gearman server (usually the
scheduler host) as well as any services for which connections are
configured (Gerrit, GitHub, etc).
Configuration
~~~~~~~~~~~~~
The following section of ``zuul.conf`` is used by the merger:
.. attr:: merger
.. attr:: command_socket
:default: /var/lib/zuul/merger.socket
Path to command socket file for the merger process.
.. attr:: git_dir
:default: /var/lib/zuul/merger-git
Directory in which Zuul should clone git repositories.
.. attr:: git_http_low_speed_limit
:default: 1000
If the HTTP transfer speed is less then git_http_low_speed_limit for
longer then git_http_low_speed_time, the transfer is aborted.
Value in bytes, setting to 0 will disable.
.. attr:: git_http_low_speed_time
:default: 30
If the HTTP transfer speed is less then git_http_low_speed_limit for
longer then git_http_low_speed_time, the transfer is aborted.
Value in seconds, setting to 0 will disable.
.. attr:: git_timeout
:default: 300
Timeout for git clone and fetch operations. This can be useful when
dealing with large repos. Note that large timeouts can increase startup
and reconfiguration times if repos are not cached so be cautious when
increasing this value.
Value in seconds.
.. attr:: git_user_email
Value to pass to `git config user.email
<https://git-scm.com/book/en/v2/Getting-Started-First-Time-Git-Setup>`_.
.. attr:: git_user_name
Value to pass to `git config user.name
<https://git-scm.com/book/en/v2/Getting-Started-First-Time-Git-Setup>`_.
.. attr:: log_config
Path to log config file for the merger process.
.. attr:: pidfile
:default: /var/run/zuul/merger.pid
Path to PID lock file for the merger process.
Operation
~~~~~~~~~
To start the merger, run ``zuul-merger``. To stop it, kill the
PID which was saved in the pidfile specified in the configuration.
.. _executor:
Executor
--------
Executors are responsible for running jobs. At the start of each job,
an executor prepares an environment in which to run Ansible which
contains all of the git repositories specified by the job with all
dependent changes merged into their appropriate branches. The branch
corresponding to the proposed change will be checked out (in all
projects, if it exists). Any roles specified by the job will also be
present (also with dependent changes merged, if appropriate) and added
to the Ansible role path. The executor also prepares an Ansible
inventory file with all of the nodes requested by the job.
The executor also contains a merger. This is used by the executor to
prepare the git repositories used by jobs, but is also available to
perform any tasks normally performed by standalone mergers. Because
the executor performs both roles, small Zuul installations may not
need to run standalone mergers.
Executors need to be able to connect to the Gearman server (usually
the scheduler host), any services for which connections are configured
(Gerrit, GitHub, etc), as well as directly to the hosts which Nodepool
provides.
Trusted and Untrusted Playbooks
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
The executor runs playbooks in one of two execution contexts depending
on whether the project containing the playbook is a
:term:`config-project` or an :term:`untrusted-project`. If the
playbook is in a config project, the executor runs the playbook in the
*trusted* execution context, otherwise, it is run in the *untrusted*
execution context.
Both execution contexts use `bubblewrap`_ [#nullwrap]_ to create a namespace to
ensure that playbook executions are isolated and are unable to access
files outside of a restricted environment. The administrator may
configure additional local directories on the executor to be made
available to the restricted environment.
The trusted execution context has access to all Ansible features,
including the ability to load custom Ansible modules. Needless to
say, extra scrutiny should be given to code that runs in a trusted
context as it could be used to compromise other jobs running on the
executor, or the executor itself, especially if the administrator has
granted additional access through bubblewrap, or a method of escaping
the restricted environment created by bubblewrap is found.
Playbooks run in the untrusted execution context are not permitted to
load additional Ansible modules or access files outside of the
restricted environment prepared for them by the executor. In addition
to the bubblewrap environment applied to both execution contexts, in
the untrusted context some standard Ansible modules are replaced with
versions which prohibit some actions, including attempts to access
files outside of the restricted execution context. These redundant
protections are made as part of a defense-in-depth strategy.
.. _bubblewrap: https://github.com/projectatomic/bubblewrap
.. _zuul-discuss: http://lists.zuul-ci.org/cgi-bin/mailman/listinfo/zuul-discuss
.. [#nullwrap] `bubblewrap` is integral to securely operating Zuul.
If it is difficult for you to use it in your environment, we
encourage you to let us know via the `zuul-discuss`_ mailing
list.
Configuration
~~~~~~~~~~~~~
The following sections of ``zuul.conf`` are used by the executor:
.. attr:: executor
.. attr:: command_socket
:default: /var/lib/zuul/executor.socket
Path to command socket file for the executor process.
.. attr:: finger_port
:default: 7900
Port to use for finger log streamer.
.. attr:: state_dir
:default: /var/lib/zuul
Path to directory in which Zuul should save its state.
.. attr:: git_dir
:default: /var/lib/zuul/executor-git
Directory that Zuul should clone local git repositories to. The
executor keeps a local copy of every git repository it works
with to speed operations and perform speculative merging.
This should be on the same filesystem as
:attr:`executor.job_dir` so that when git repos are cloned into
the job workspaces, they can be hard-linked to the local git
cache.
.. attr:: job_dir
:default: /var/lib/zuul/builds
Directory that Zuul should use to hold temporary job directories.
When each job is run, a new entry will be created under this
directory to hold the configuration and scratch workspace for
that job. It will be deleted at the end of the job (unless the
`--keep-jobdir` command line option is specified).
This should be on the same filesystem as :attr:`executor.git_dir`
so that when git repos are cloned into the job workspaces, they
can be hard-linked to the local git cache.
.. attr:: log_config
Path to log config file for the executor process.
.. attr:: pidfile
:default: /var/run/zuul/executor.pid
Path to PID lock file for the executor process.
.. attr:: private_key_file
:default: ~/.ssh/id_rsa
SSH private key file to be used when logging into worker nodes.
.. note:: If you use an RSA key, ensure it is encoded in the PEM
format (use the ``-t rsa -m PEM`` arguments to
`ssh-keygen`).
.. attr:: default_username
:default: zuul
Username to use when logging into worker nodes, if none is
supplied by Nodepool.
.. attr:: winrm_cert_key_file
:default: ~/.winrm/winrm_client_cert.key
The private key file of the client certificate to use for winrm
connections to Windows nodes.
.. attr:: winrm_cert_pem_file
:default: ~/.winrm/winrm_client_cert.pem
The certificate file of the client certificate to use for winrm
connections to Windows nodes.
.. note:: Currently certificate verification is disabled when
connecting to Windows nodes via winrm.
.. attr:: winrm_operation_timeout_sec
:default: None. The Ansible default of 20 is used in this case.
The timeout for WinRM operations.
.. attr:: winrm_read_timeout_sec
:default: None. The Ansible default of 30 is used in this case.
The timeout for WinRM read. Increase this if there are intermittent
network issues and read timeout errors keep occurring.
.. _admin_sitewide_variables:
.. attr:: variables
Path to an Ansible variables file to supply site-wide variables.
This should be a YAML-formatted file consisting of a single
dictionary. The contents will be made available to all jobs as
Ansible variables. These variables take precedence over all
other forms (job variables and secrets). Care should be taken
when naming these variables to avoid potential collisions with
those used by jobs. Prefixing variable names with a
site-specific identifier is recommended. The default is not to
add any site-wide variables. See the :ref:`User's Guide
<user_jobs_sitewide_variables>` for more information.
.. attr:: manage_ansible
:default: True
Specifies wether the zuul-executor should install the supported ansible
versions during startup or not. If this is ``True`` the zuul-executor
will install the ansible versions into :attr:`executor.ansible_root`.
It is recommended to set this to ``False`` and manually install Ansible
after the Zuul installation by running ``zuul-manage-ansible``. This has
the advantage that possible errors during Ansible installation can be
spotted earlier. Further especially containerized deployments of Zuul
will have the advantage of predictable versions.
.. attr:: ansible_root
:default: <state_dir>/ansible-bin
Specifies where the zuul-executor should look for its supported ansible
installations. By default it looks in the following directories and uses
the first which it can find.
* ``<zuul_install_dir>/lib/zuul/ansible``
* ``<ansible_root>``
The ``ansible_root`` setting allows you to override the second location
which is also used for installation if ``manage_ansible`` is ``True``.
.. attr:: ansible_setup_timeout
:default: 60
Timeout of the ansible setup playbook in seconds that runs before
the first playbook of the job.
.. attr:: disk_limit_per_job
:default: 250
This integer is the maximum number of megabytes that any one job
is allowed to consume on disk while it is running. If a job's
scratch space has more than this much space consumed, it will be
aborted. Set to -1 to disable the limit.
.. attr:: trusted_ro_paths
List of paths, separated by ``:`` to read-only bind mount into
trusted bubblewrap contexts.
.. attr:: trusted_rw_paths
List of paths, separated by ``:`` to read-write bind mount into
trusted bubblewrap contexts.
.. attr:: untrusted_ro_paths
List of paths, separated by ``:`` to read-only bind mount into
untrusted bubblewrap contexts.
.. attr:: untrusted_rw_paths
List of paths, separated by ``:`` to read-write bind mount into
untrusted bubblewrap contexts.
.. attr:: load_multiplier
:default: 2.5
When an executor host gets too busy, the system may suffer
timeouts and other ill effects. The executor will stop accepting
more than 1 job at a time until load has lowered below a safe
level. This level is determined by multiplying the number of
CPU's by `load_multiplier`.
So for example, if the system has 2 CPUs, and load_multiplier
is 2.5, the safe load for the system is 5.00. Any time the
system load average is over 5.00, the executor will quit
accepting multiple jobs at one time.
The executor will observe system load and determine whether
to accept more jobs every 30 seconds.
.. attr:: max_starting_builds
:default: None
An executor is accepting up to as many starting builds as defined by the
:attr:`executor.load_multiplier` on systems with more than four CPU cores,
and up to twice as many on systems with four or less CPU cores. For
example, on a system with two CPUs: 2 * 2.5 * 2 - up to ten starting
builds may run on such executor; on systems with eight CPUs: 2.5 * 8 - up
to twenty starting builds may run on such executor.
On systems with high CPU/vCPU count an executor may accept too many
starting builds. This can be overwritten using this option providing a
fixed number of maximum starting builds on an executor.
.. attr:: min_avail_hdd
:default: 5.0
This is the minimum percentage of HDD storage available for the
:attr:`executor.state_dir` directory. The executor will stop accepting
more than 1 job at a time until more HDD storage is available. The
available HDD percentage is calculated from the total available
disk space divided by the total real storage capacity multiplied by
100.
.. attr:: min_avail_mem
:default: 5.0
This is the minimum percentage of system RAM available. The
executor will stop accepting more than 1 job at a time until
more memory is available. The available memory percentage is
calculated from the total available memory divided by the
total real memory multiplied by 100. Buffers and cache are
considered available in the calculation.
.. attr:: hostname
:default: hostname of the server
The executor needs to know its hostname under which it is reachable by
zuul-web. Otherwise live console log streaming doesn't work. In most cases
This is automatically detected correctly. But when running in environments
where it cannot determine its hostname correctly this can be overridden
here.
.. attr:: paused_on_start
:default: false
Whether the executor should start in a paused mode. Such executor will not
accept tasks until it is unpaused.
.. attr:: zone
:default: None
Name of the nodepool executor-zone to exclusively execute all jobs that
have nodes with the specified executor-zone attribute. As an example,
it is possible for nodepool nodes to exist in a cloud without public
accessable IP address. By adding an executor to a zone nodepool nodes
could be configured to use private ip addresses.
To enable this in nodepool, you'll use the node-attributes setting in a
provider pool. For example:
.. code-block:: yaml
pools:
- name: main
node-attributes:
executor-zone: vpn
.. attr:: merge_jobs
:default: True
To disable global merge job, set it to false. This is useful for zoned
executors that are running on slow network where you don't want them to
perform merge operations for any events. The executor will still perform
the merge operations required for the build they are executing.
.. attr:: merger
.. attr:: git_user_email
Value to pass to `git config user.email
<https://git-scm.com/book/en/v2/Getting-Started-First-Time-Git-Setup>`_.
.. attr:: git_user_name
Value to pass to `git config user.name
<https://git-scm.com/book/en/v2/Getting-Started-First-Time-Git-Setup>`_.
Operation
~~~~~~~~~
To start the executor, run ``zuul-executor``.
There are several commands which can be run to control the executor's
behavior once it is running.
In order to stop the executor and under normal circumstances it is
best to pause and wait for all currently running jobs to finish
before stopping it. To do so run ``zuul-executor pause``.
To stop the executor immediately, run ``zuul-executor stop``. Jobs that were
running on the stopped executor will be rescheduled on other executors.
To enable or disable running Ansible in verbose mode (with the
``-vvv`` argument to ansible-playbook) run ``zuul-executor verbose``
and ``zuul-executor unverbose``.
.. _ansible-and-python-3:
Ansible and Python 3
~~~~~~~~~~~~~~~~~~~~
As noted above, the executor runs Ansible playbooks against the remote
node(s) allocated for the job. Since part of executing playbooks on
remote hosts is running Python scripts on them, Ansible needs to know
what Python interpreter to use on the remote host. With older
distributions, ``/usr/bin/python2`` was a generally sensible choice.
However, over time a heterogeneous Python ecosystem has evolved where
older distributions may only provide Python 2, most provide a mixed
2/3 environment and newer distributions may only provide Python 3 (and
then others like RHEL8 may even have separate "system" Python versions
to add to confusion!).
Ansible's ``ansible_python_interpreter`` variable configures the path
to the remote Python interpreter to use during playbook execution.
This value is set by Zuul from the ``python-path`` specified for the
node by Nodepool; see the `nodepool configuration documentation
<https://zuul-ci.org/docs/nodepool/configuration.html>`__.
This defaults to ``auto``, where Ansible will automatically discover
the interpreter available on the remote host. However, this setting
only became available in Ansible >=2.8, so Zuul will translate
``auto`` into the old default of ``/usr/bin/python2`` when configured
to use older Ansible versions.
Thus for modern Python 3-only hosts no further configuration is needed
when using Ansible >=2.8 (e.g. Fedora, Bionic onwards). If using
earlier Ansible versions you may need to explicitly set the
``python-path`` if ``/usr/bin/python2`` is not available on the node.
Ansible roles/modules which include Python code are generally Python 3
safe now, but there is still a small possibility of incompatibility.
See also the Ansible `Python 3 support page
<https://docs.ansible.com/ansible/latest/reference_appendices/python_3_support.html>`__.
.. _web-server:
Web Server
----------
.. TODO: Turn REST API into a link to swagger docs when we grow them
The Zuul web server serves as the single process handling all HTTP
interactions with Zuul. This includes the websocket interface for live
log streaming, the REST API and the html/javascript dashboard. All three are
served as a holistic web application. For information on additional supported
deployment schemes, see :ref:`web-deployment-options`.
Web servers need to be able to connect to the Gearman server (usually
the scheduler host). If the SQL reporter is used, they need to be
able to connect to the database it reports to in order to support the
dashboard. If a GitHub connection is configured, they need to be
reachable by GitHub so they may receive notifications.
Configuration
~~~~~~~~~~~~~
In addition to the common configuration sections, the following
sections of ``zuul.conf`` are used by the web server:
.. attr:: web
.. attr:: listen_address
:default: 127.0.0.1
IP address or domain name on which to listen.
.. attr:: log_config
Path to log config file for the web server process.
.. attr:: pidfile
:default: /var/run/zuul/web.pid
Path to PID lock file for the web server process.
.. attr:: port
:default: 9000
Port to use for web server process.
.. attr:: websocket_url
Base URL on which the websocket service is exposed, if different
than the base URL of the web app.
.. attr:: stats_url
Base URL from which statistics emitted via statsd can be queried.
.. attr:: stats_type
:default: graphite
Type of server hosting the statistics information. Currently only
'graphite' is supported by the dashboard.
.. attr:: static_path
:default: zuul/web/static
Path containing the static web assets.
.. attr:: static_cache_expiry
:default: 3600
The Cache-Control max-age response header value for static files served
by the zuul-web. Set to 0 during development to disable Cache-Control.
.. _web-server-tenant-scoped-api:
Enabling tenant-scoped access to privileged actions
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
A user can be granted access to protected REST API endpoints by providing a
valid JWT (JSON Web Token) as a bearer token when querying the API endpoints.
JWTs are signed and therefore Zuul must be configured so that signatures can be
verified. More information about the JWT standard can be found on the `IETF's
RFC page <https://tools.ietf.org/html/rfc7519>`_.
This optional section of ``zuul.conf``, if present, will activate the
protected endpoints and configure JWT validation:
.. attr:: auth <authenticator name>
.. attr:: driver
The signing algorithm to use. Accepted values are ``HS256``, ``RS256`` or
``RS256withJWKS``. See below for driver-specific configuration options.
.. attr:: allow_authz_override
:default: false
Allow a JWT to override predefined access rules. See the section on
:ref:`JWT contents <jwt-format>` for more details on how to grant access
to tenants with a JWT.
.. attr:: realm
The authentication realm.
.. attr:: default
:default: false
If set to ``true``, use this realm as the default authentication realm
when handling HTTP authentication errors.
.. attr:: client_id
The expected value of the "aud" claim in the JWT. This is required for
validation.
.. attr:: issuer_id
The expected value of the "iss" claim in the JWT. This is required for
validation.
.. attr:: uid_claim
:default: sub
The JWT claim that Zuul will use as a unique identifier for the bearer of
a token. This is "sub" by default, as it is usually the purpose of this
claim in a JWT. This identifier is used in audit logs.
.. attr:: max_validity_time
Optional value to ensure a JWT cannot be valid for more than this amount
of time in seconds. This is useful if the Zuul operator has no control
over the service issueing JWTs, and the tokens are too long-lived.
.. attr:: skew
:default: 0
Optional integer value to compensate for skew between Zuul's and the
JWT emitter's respective clocks. Use a negative value if Zuul's clock
is running behind.
This section can be repeated as needed with different authenticators, allowing
access to privileged API actions from several JWT issuers.
Driver-specific attributes
..........................
HS256
,,,,,
This is a symmetrical encryption algorithm that only requires a shared secret
between the JWT issuer and the JWT consumer (ie Zuul). This driver should be
used in test deployments only, or in deployments where JWTs will be issued
manually.
.. attr:: secret
:noindex:
The shared secret used to sign JWTs and validate signatures.
RS256
,,,,,
This is an asymmetrical encryption algorithm that requires an RSA key pair. Only
the public key is needed by Zuul for signature validation.
.. attr:: public_key
The path to the public key of the RSA key pair. It must be readable by Zuul.
.. attr:: private_key
Optional. The path to the private key of the RSA key pair. It must be
readable by Zuul.
RS256withJWKS
,,,,,,,,,,,,,
Some Identity Providers use key sets (also known as **JWKS**), therefore the key to
use when verifying the Authentication Token's signatures cannot be known in
advance; the key's id is stored in the JWT's header and the key must then be
found in the remote key set.
The key set is usually available at a specific URL that can be found in the
"well-known" configuration of an OpenID Connect Identity Provider.
.. attr:: keys_url
The URL where the Identity Provider's key set can be found. For example, for
Google's OAuth service: https://www.googleapis.com/oauth2/v3/certs
Operation
~~~~~~~~~
To start the web server, run ``zuul-web``. To stop it, kill the
PID which was saved in the pidfile specified in the configuration.
Web Client
----------
Zuul's command line client may be configured to make calls to Zuul's web
server. The client will then look for a ``zuul.conf`` file with a ``webclient``
section to set up the connection over HTTP.
Configuration
~~~~~~~~~~~~~
.. attr:: webclient
.. attr:: url
The root URL of Zuul's web server.
.. attr:: verify_ssl
:default: true
Enforce SSL verification when sending requests over to Zuul's web server.
This should only be disabled when working with test servers.
Configuration
~~~~~~~~~~~~~
In addition to the common configuration sections, the following
sections of ``zuul.conf`` are used by the web server:
.. attr:: web
.. attr:: listen_address
:default: 127.0.0.1
IP address or domain name on which to listen.
.. attr:: log_config
Path to log config file for the web server process.
Finger Gateway
--------------
The Zuul finger gateway listens on the standard finger port (79) for
finger requests specifying a build UUID for which it should stream log
results. The gateway will determine which executor is currently running that
build and query that executor for the log stream.
This is intended to be used with the standard finger command line client.
For example::
finger UUID@zuul.example.com
The above would stream the logs for the build identified by `UUID`.
Finger gateway servers need to be able to connect to the Gearman
server (usually the scheduler host), as well as the console streaming
port on the executors (usually 7900).
Configuration
~~~~~~~~~~~~~
In addition to the common configuration sections, the following
sections of ``zuul.conf`` are used by the finger gateway:
.. attr:: fingergw
.. attr:: command_socket
:default: /var/lib/zuul/fingergw.socket
Path to command socket file for the executor process.
.. attr:: listen_address
:default: all addresses
IP address or domain name on which to listen.
.. attr:: log_config
Path to log config file for the finger gateway process.
.. attr:: pidfile
:default: /var/run/zuul/fingergw.pid
Path to PID lock file for the finger gateway process.
.. attr:: port
:default: 79
Port to use for the finger gateway. Note that since command line
finger clients cannot usually specify the port, leaving this set to
the default value is highly recommended.
.. attr:: user
User ID for the zuul-fingergw process. In normal operation as a
daemon, the finger gateway should be started as the ``root``
user, but if this option is set, it will drop privileges to this
user during startup. It is recommended to set this option to an
unprivileged user.
Operation
~~~~~~~~~
To start the finger gateway, run ``zuul-fingergw``. To stop it, kill the
PID which was saved in the pidfile specified in the configuration.
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