Components

Overview

Zuul is a distributed system consisting of several components, each of which is described below.

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 or 2281.

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 required and configured in database section of /etc/zuul/zuul.conf. 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:

[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

[keystore]
password=MY_SECRET_PASSWORD

[web]
status_url=https://zuul.example.com/status

[scheduler]
log_config=/etc/zuul/scheduler-logging.yaml

A minimal Zuul system may consist of a Scheduler and 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.

Zuul stores private keys for each project it knows about in ZooKeeper. It is recommended that you periodically back up the private keys in case the ZooKeeper data store is lost or damaged. The Zuul Client provides two sub-commands for use in this case: export-keys and import-keys. Each takes an argument to a filesystem path and will write the keys to, or read the keys from that path. The data in the exported files are still secured with the keystore passphrase, so be sure to retain it as well.

Common

The following applies to all Zuul components.

Configuration

The following sections of zuul.conf are used by all Zuul components:

gearman

Client connection information for Gearman.

gearman.server (required)

Hostname or IP address of the Gearman server.

gearman.port
Default: 4730

Port on which the Gearman server is listening.

gearman.ssl_ca

An openssl file containing a set of concatenated “certification authority” certificates in PEM formet.

gearman.ssl_cert

An openssl file containing the client public certificate in PEM format.

gearman.ssl_key

An openssl file containing the client private key in PEM format.

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 Statsd reporting for more information.

statsd.server

Hostname or IP address of the statsd server.

statsd.port
Default: 8125

The UDP port on which the statsd server is listening.

statsd.prefix

If present, this will be prefixed to all of the keys before transmitting to the statsd server.

zookeeper

Client connection information for ZooKeeper. TLS is required.

zookeeper.hosts (required)

A list of zookeeper hosts for Zuul to use when communicating with Nodepool.

zookeeper.tls_cert (required)

The path to the PEM encoded certificate file.

zookeeper.tls_key (required)

The path to the PEM encoded key file.

zookeeper.tls_ca (required)

The path to the PEM encoded CA certificate file.

zookeeper.session_timeout
Default: 10.0

The ZooKeeper session timeout, in seconds.

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:

gearman_server

The builtin gearman server. Zuul can fork a gearman process from itself rather than connecting to an external one.

gearman_server.start
Default: false

Whether to start the internal Gearman server.

gearman_server.listen_address
Default: all addresses

IP address or domain name on which to listen.

gearman_server.port
Default: 4730

TCP port on which to listen.

gearman_server.log_config

Path to log config file for internal Gearman server.

gearman_server.ssl_ca

An openssl file containing a set of concatenated “certification authority” certificates in PEM formet.

gearman_server.ssl_cert

An openssl file containing the server public certificate in PEM format.

gearman_server.ssl_key

An openssl file containing the server private key in PEM format.

web

web.root (required)

The root URL of the web service (e.g., https://zuul.example.com/).

See tenant.web-root for additional options for whitelabeled tenant configuration.

web.status_url

URL that will be posted in Zuul comments made to changes when starting jobs for a change.

keystore

keystore.password (required)

Encryption password for private data stored in Zookeeper.

scheduler

scheduler.command_socket
Default: /var/lib/zuul/scheduler.socket

Path to command socket file for the scheduler process.

scheduler.tenant_config

Path to Tenant Configuration file. This attribute is exclusive with scheduler.tenant_config_script.

scheduler.tenant_config_script

Path to a script to execute and load the tenant config from. This attribute is exclusive with scheduler.tenant_config.

scheduler.default_ansible_version

Default ansible version to use for jobs that doesn’t specify a version. See job.ansible-version for details.

scheduler.log_config

Path to log config file.

scheduler.pidfile
Default: /var/run/zuul/scheduler.pid

Path to PID lock file.

scheduler.state_dir
Default: /var/lib/zuul

Path to directory in which Zuul should save its state.

scheduler.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.

scheduler.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.

scheduler.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.

scheduler.prometheus_port

Set a TCP port to start the prometheus metrics client.

scheduler.prometheus_addr
Default: 0.0.0.0

The IPv4 addr to listen for prometheus metrics poll. To use IPv6, python>3.8 is required issue24209.

Operation

To start the scheduler, run zuul-scheduler. To stop it, run zuul-scheduler stop.

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 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:

merger

merger.command_socket
Default: /var/lib/zuul/merger.socket

Path to command socket file for the merger process.

merger.git_dir
Default: /var/lib/zuul/merger-git

Directory in which Zuul should clone git repositories.

merger.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.

merger.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.

merger.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.

merger.git_user_email

Value to pass to git config user.email.

merger.git_user_name

Value to pass to git config user.name.

merger.log_config

Path to log config file for the merger process.

merger.pidfile
Default: /var/run/zuul/merger.pid

Path to PID lock file for the merger process.

Operation

To start the merger, run zuul-merger.

In order to stop the merger and under normal circumstances it is best to pause and wait for all currently running tasks to finish before stopping it. To do so run zuul-merger pause.

To stop the merger immediately, run zuul-merger stop.

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 config-project or an 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 1 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.

1

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:

executor

executor.command_socket
Default: /var/lib/zuul/executor.socket

Path to command socket file for the executor process.

executor.finger_port
Default: 7900

Port to use for finger log streamer.

executor.state_dir
Default: /var/lib/zuul

Path to directory in which Zuul should save its state.

executor.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 executor.job_dir so that when git repos are cloned into the job workspaces, they can be hard-linked to the local git cache.

executor.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 executor.git_dir so that when git repos are cloned into the job workspaces, they can be hard-linked to the local git cache.

executor.log_config

Path to log config file for the executor process.

executor.pidfile
Default: /var/run/zuul/executor.pid

Path to PID lock file for the executor process.

executor.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).

executor.default_username
Default: zuul

Username to use when logging into worker nodes, if none is supplied by Nodepool.

executor.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.

executor.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.

executor.winrm_operation_timeout_sec
Default: None. The Ansible default of 20 is used in this case.

The timeout for WinRM operations.

executor.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.

executor.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 User’s Guide for more information.

executor.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 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.

executor.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.

executor.ansible_setup_timeout
Default: 60

Timeout of the ansible setup playbook in seconds that runs before the first playbook of the job.

executor.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.

executor.trusted_ro_paths

List of paths, separated by : to read-only bind mount into trusted bubblewrap contexts.

executor.trusted_rw_paths

List of paths, separated by : to read-write bind mount into trusted bubblewrap contexts.

executor.untrusted_ro_paths

List of paths, separated by : to read-only bind mount into untrusted bubblewrap contexts.

executor.untrusted_rw_paths

List of paths, separated by : to read-write bind mount into untrusted bubblewrap contexts.

executor.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.

executor.max_starting_builds
Default: None

An executor is accepting up to as many starting builds as defined by the 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.

executor.min_avail_hdd
Default: 5.0

This is the minimum percentage of HDD storage available for the 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.

executor.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.

executor.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.

executor.paused_on_start
Default: false

Whether the executor should start in a paused mode. Such executor will not accept tasks until it is unpaused.

executor.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:

pools:
  - name: main
    node-attributes:
      executor-zone: vpn

executor.allow_unzoned
Default: False

If executor.zone is set it by default only processes jobs with nodes of that specific zone even if the nodes have no zone at all. Enabling allow_unzoned lets the executor also take jobs with nodes without zone.

executor.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.

executor.sigterm_method
Default: graceful

Determines how the executor responds to a SIGTERM signal.

graceful

Stop accepting new jobs and wait for all running jobs to complete before exiting.

stop

Abort all running jobs and exit as soon as possible.

keystore

keystore.password (required)

Encryption password for private data stored in Zookeeper.

merger

merger.git_user_email

Value to pass to git config user.email.

merger.git_user_name

Value to pass to git config user.name.

ansible_callback "<name>"

To whitelist ansible callback <name>. Any attributes found is this section will be added to the callback_<name> section in ansible.cfg.

An example of what configuring the builtin mail callback would look like. The configuration in zuul.conf.

[ansible_callback "mail"]
to = user@example.org
sender = zuul@example.org

Would generate the following in ansible.cfg:

[defaults]
callback_whitelist = mail

[callback_mail]
to = user@example.org
sender = zuul@example.org

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.

To pause the executor and prevent it from running new jobs you can run zuul-executor pause.

To cause the executor to stop accepting new jobs and exit when all running jobs have finished you can run zuul-executor graceful. Under most circumstances this will be the best way to stop Zuul.

To stop the executor immediately, run zuul-executor stop. Jobs that were running on the stopped executor will be rescheduled on other executors.

The executor normally responds to a SIGTERM signal in the same way as the graceful command, however you can change this behavior to match stop with the executor.sigterm_method setting.

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

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.

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.

Web Server

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 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:

web

web.listen_address
Default: 127.0.0.1

IP address or domain name on which to listen.

web.log_config

Path to log config file for the web server process.

web.pidfile
Default: /var/run/zuul/web.pid

Path to PID lock file for the web server process.

web.port
Default: 9000

Port to use for web server process.

web.websocket_url

Base URL on which the websocket service is exposed, if different than the base URL of the web app.

web.stats_url

Base URL from which statistics emitted via statsd can be queried.

web.stats_type
Default: graphite

Type of server hosting the statistics information. Currently only ‘graphite’ is supported by the dashboard.

web.static_path
Default: zuul/web/static

Path containing the static web assets.

web.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.zone

The zone in which zuul-web is deployed. This is only needed if there are executors with different zones in the environment and not all executors are directly addressable from zuul-web. The parameter specifies the zone where the executors are directly adressable. Live log streaming will go directly to the executors of the same zone and be routed to a finger gateway of the target zone if the zones are different.

In a mixed system (with zoned and unzoned executors) there may also be zoned and unzoned zuul-web services. Omit the zone parameter for any unzoned zuul-web servers.

If this is used the finger gateways should be configured accordingly.

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.

This optional section of zuul.conf, if present, will activate the protected endpoints and configure JWT validation:

auth <authenticator name>

auth <authenticator name>.driver

The signing algorithm to use. Accepted values are HS256, RS256, RS256withJWKS or OpenIDConnect. See below for driver-specific configuration options.

auth <authenticator name>.allow_authz_override
Default: false

Allow a JWT to override predefined access rules. See the section on JWT contents for more details on how to grant access to tenants with a JWT.

auth <authenticator name>.realm

The authentication realm.

auth <authenticator name>.default
Default: false

If set to true, use this realm as the default authentication realm when handling HTTP authentication errors.

auth <authenticator name>.client_id

The expected value of the “aud” claim in the JWT. This is required for validation.

auth <authenticator name>.issuer_id

The expected value of the “iss” claim in the JWT. This is required for validation.

auth <authenticator name>.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.

auth <authenticator name>.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.

auth <authenticator name>.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.

secret

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.

public_key

The path to the public key of the RSA key pair. It must be readable by Zuul.

private_key

Optional. The path to the private key of the RSA key pair. It must be readable by Zuul.

RS256withJWKS

Warning

This driver is deprecated, use OpenIDConnect instead.

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.

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

OpenIDConnect

Use a third-party Identity Provider implementing the OpenID Connect protocol. The issuer ID should be an URI, from which the “well-known” configuration URI of the Identity Provider can be inferred. This is intended to be used for authentication on Zuul’s web user interface.

scope
Default: openid profile

The scope(s) to use when requesting access to a user’s details. This attribute can be multivalued (values must be separated by a space). Most OpenID Connect Identity Providers support the default scopes “openid profile”. A full list of supported scopes can be found in the well-known configuration of the Identity Provider under the key “scopes_supported”.

keys_url

Optional. 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 The well-known configuration of the Identity Provider should provide this URL under the key “jwks_uri”, therefore this attribute is usually not necessary.

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

webclient

webclient.url

The root URL of Zuul’s web server.

webclient.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:

web

web.listen_address
Default: 127.0.0.1

IP address or domain name on which to listen.

web.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).

Finger gateways are optional. They may be run for either or both of the following purposes:

• Allowing end-users to connect to the finger port to stream logs.

• Providing an accessible log streaming port for remote zoned executors which are otherwise inacessible.

  In this case, log streaming requests from finger gateways or zuul-web will route to the executors via finger gateways in the same zone.

Configuration

In addition to the common configuration sections, the following sections of zuul.conf are used by the finger gateway:

fingergw

fingergw.command_socket
Default: /var/lib/zuul/fingergw.socket

Path to command socket file for the executor process.

fingergw.listen_address
Default: all addresses

IP address or domain name on which to listen.

fingergw.log_config

Path to log config file for the finger gateway process.

fingergw.pidfile
Default: /var/run/zuul/fingergw.pid

Path to PID lock file for the finger gateway process.

fingergw.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.

fingergw.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.

fingergw.hostname
Default: hostname of the server

When running finger gateways in a multi-zone configuration, the gateway 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.

fingergw.zone

The zone where the finger gateway is located. This is only needed for live log streaming if the zuul deployment is spread over multiple zones without the ability to directly connect to all executors from zuul-web. See executor.zone for further information.

In a mixed system (with zoned and unzoned executors) there may also be zoned and unzoned finger gateway services. Omit the zone parameter for any unzoned finger gateway servers.

If the Zuul installation spans an untrusted network (for example, if there are remote executor zones), it may be necessary to use TLS between the components that handle log streaming (zuul-executor, zuul-fingergw, and zuul-web). If so, set the following options.

Note that this section is also read by zuul-web in order to load a client certificate to use when connecting to a finger gateway which requires TLS, and it is also read by zuul-executor to load a server certificate for its console streaming port.

If any of these are present, all three certificate options must be provided.

fingergw.tls_cert

The path to the PEM encoded certificate file.

fingergw.tls_key

The path to the PEM encoded key file.

fingergw.tls_ca

The path to the PEM encoded CA certificate file.

fingergw.tls_verify_hostnames
Default: true

In the case of a private CA it may be both safe and convenient to disable hostname checks. However, if the certificates are issued by a public CA, hostname verification should be enabled.

fingergw.tls_client_only
Default: false

In order to provide a finger gateway which can reach remote finger gateways and executors which use TLS, but does not itself serve end-users via TLS (i.e., it runs within a protected network and users access it directly via the finger port), set this to true and the finger gateway will not listen on TLS, but will still use the supplied certificate to make remote TLS connections.

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.