Installation Reference

Install Zuul

To install a Zuul release from PyPI, run:

pip install zuul

Or from a git checkout, run:

pip install .

That will also install Zuul’s python dependencies. To minimize interaction with other python packages installed on a system, you may wish to install Zuul within a Python virtualenv.

Zuul has several system-level dependencies as well. You can find a list of operating system packages in bindep.txt in Zuul’s source directory.

Zuul Components

Zuul provides the following components:

  • zuul-scheduler: The main Zuul process. Handles receiving events, executing jobs, collecting results and posting reports. Coordinates the work of the other components. It also provides a gearman daemon which the other components use for coordination.
  • zuul-merger: Scale-out component that performs git merge operations. Zuul performs a large number of git operations in the course of its work. Adding merger processes can help speed Zuul’s processing. This component is optional (zero or more of these can be run).
  • zuul-executor: Scale-out component for executing jobs. At least one of these is required. Depending on system configuration, you can expect a single executor to handle up to about 100 simultaneous jobs. Can handle the functions of a merger if dedicated mergers are not provided. One or more of these must be run.
  • zuul-web: A web server that receives “webhook” events from external providers, supplies a web dashboard, and provides websocket access to live streaming of logs.
  • zuul-fingergw: A gateway which provides finger protocol access to live streaming of logs.

For more detailed information about these, see Components.

External Dependencies

Zuul interacts with several other systems described below.

Gearman

Gearman is a job distribution system that Zuul uses to communicate with its distributed components. The Zuul scheduler distributes work to Zuul mergers and executors using Gearman. You may supply your own gearman server, but the Zuul scheduler includes a built-in server which is recommended. Ensure that all Zuul hosts can communicate with the gearman server.

Zuul distributes secrets to executors via gearman, so be sure to secure it with TLS and certificate authentication. Obtain (or generate) a certificate for both the server and the clients (they may use the same certificate or have individual certificates). They must be signed by a CA, but it can be your own CA.

Nodepool

In order to run all but the simplest jobs, Zuul uses a companion program, Nodepool, to supply the nodes (whether dynamic cloud instances or static hardware) used by jobs. Before starting Zuul, ensure you have Nodepool installed and any images you require built. Zuul only makes one requirement of these nodes: that it be able to log in given a username and ssh private key.

Nodepool uses Zookeeper to communicate internally among its components, and also to communicate with Zuul. You can run a simple single-node Zookeeper instance, or a multi-node cluster. Ensure that the host running the Zuul scheduler has access to the cluster.

Ansible

Zuul uses Ansible to run jobs. Each version of Zuul is designed to work with a specific, contemporary version of Ansible. Zuul specifies that version of Ansible in its python package metadata, and normally the correct version will be installed automatically with Zuul. Because of the close integration of Zuul and Ansible, attempting to use other versions of Ansible with Zuul is not recommended.

Zuul Setup

At minimum you need to provide zuul.conf and main.yaml placed in /etc/zuul/. The following example uses the builtin gearman service in Zuul, and a connection to Gerrit.

zuul.conf:

[scheduler]
tenant_config=/etc/zuul/main.yaml

[gearman_server]
start=true

[gearman]
server=127.0.0.1

[connection my_gerrit]
driver=gerrit
server=git.example.com
port=29418
baseurl=https://git.example.com/gerrit/
user=zuul
sshkey=/home/zuul/.ssh/id_rsa

See Components and Connections for more details.

The following tells Zuul to read its configuration from and operate on the example-project project:

main.yaml:

- tenant:
    name: example-tenant
    source:
      my_gerrit:
        untrusted-projects:
          - example-project

Starting Zuul

You can run any zuul process with the -d option to make it not daemonize. It’s a good idea at first to confirm there’s no issues with your configuration.

To start, simply run:

zuul-scheduler

Once run you should have two zuul-scheduler processes (if using the built-in gearman server, or one process otherwise).

Before Zuul can run any jobs, it needs to load its configuration, most of which is in the git repositories that Zuul operates on. Start an executor to allow zuul to do that:

zuul-executor

Zuul should now be able to read its configuration from the configured repo and process any jobs defined therein.

Web Deployment Options

The zuul-web service provides a web dashboard, a REST API and a websocket log streaming service as a single holistic web application. For production use it is recommended to run it behind a reverse proxy, such as Apache or Nginx.

The zuul-web service is entirely self-contained and can be run with minimal configuration, however, more advanced users may desire to do one or more of the following:

White Label
Serve the dashboard of an individual tenant at the root of its own domain. https://zuul.openstack.org is an example of a Zuul dashboard that has been white labeled for the openstack tenant of its Zuul.
Static Offload
Shift the duties of serving static files, such as HTML, Javascript, CSS or images to the reverse proxy server.
Static External
Serve the static files from a completely separate location that does not support programmatic rewrite rules such as a Swift Object Store.
Sub-URL
Serve a Zuul dashboard from a location below the root URL as part of presenting integration with other application. https://softwarefactory-project.io/zuul/ is an example of a Zuul dashboard that is being served from a Sub-URL.

Most deployments shouldn’t need these, so the following discussion will assume that the zuul-web service is exposed via a reverse proxy. Where rewrite rule examples are given, they will be given with Apache syntax, but any other reverse proxy should work just fine.

Reverse Proxy

Using Apache as the reverse proxy requires the mod_proxy, mod_proxy_http and mod_proxy_wstunnel modules to be installed and enabled.

All of the cases require a rewrite rule for the websocket streaming, so the simplest reverse-proxy case is:

RewriteEngine on
RewriteRule ^/api/tenant/(.*)/console-stream ws://localhost:9000/api/tenant/$1/console-stream [P]
RewriteRule ^/(.*)$ http://localhost:9000/$1 [P]

This is the recommended configuration unless one of the following features is required.

Static Offload

To have the reverse proxy serve the static html/javascript assets instead of proxying them to the REST layer, enable the mod_rewrite Apache module, register the location where you unpacked the web application as the document root and add rewrite rules:

<Directory /usr/share/zuul>
  Require all granted
</Directory>
Alias / /usr/share/zuul/
<Location />
  RewriteEngine on
  RewriteBase /
  # Rewrite api to the zuul-web endpoint
  RewriteRule api/tenant/(.*)/console-stream ws://localhost:9000/api/tenant/$1/console-stream [P,L]
  RewriteRule api/(.*)$ http://localhost:9000/api/$1 [P,L]
  # Backward compatible rewrite
  RewriteRule t/(.*)/(.*).html(.*) /t/$1/$2$3 [R=301,L,NE]

  # Don't rewrite files or directories
  RewriteCond %{REQUEST_FILENAME} !-f
  RewriteCond %{REQUEST_FILENAME} !-d
  RewriteRule . /index.html [L]
</Location>

Sub directory serving

The web application needs to be rebuilt to update the internal location of the static files. Set the homepage setting in the package.json to an absolute path or url. For example, to deploy the web interface through a ‘/zuul/’ sub directory:

Note

The web dashboard source code and package.json are located in the web directory. All the yarn commands need to be executed from the web directory.

sed -e 's#"homepage": "/"#"homepage": "/zuul/"#' -i package.json
yarn build

Then assuming the web application is unpacked in /usr/share/zuul, enable the mod_rewrite Apache module and add the following rewrite rules:

<Directory /usr/share/zuul>
  Require all granted
</Directory>
Alias /zuul /usr/share/zuul/
<Location /zuul>
  RewriteEngine on
  RewriteBase /zuul
  # Rewrite api to the zuul-web endpoint
  RewriteRule api/tenant/(.*)/console-stream ws://localhost:9000/api/tenant/$1/console-stream [P,L]
  RewriteRule api/(.*)$ http://localhost:9000/api/$1 [P,L]
  # Backward compatible rewrite
  RewriteRule t/(.*)/(.*).html(.*) /t/$1/$2$3 [R=301,L,NE]

  # Don't rewrite files or directories
  RewriteCond %{REQUEST_FILENAME} !-f
  RewriteCond %{REQUEST_FILENAME} !-d
  RewriteRule . /zuul/index.html [L]
</Location>

White Labeled Tenant

Running a white-labeled tenant is similar to the offload case, but adds a rule to ensure connection webhooks don’t try to get put into the tenant scope.

Note

It’s possible to do white-labeling without static offload, but it is more complex with no benefit.

Enable the mod_rewrite Apache module, and assuming the Zuul tenant name is example, the rewrite rules are:

<Directory /usr/share/zuul>
  Require all granted
</Directory>
Alias / /usr/share/zuul/
<Location />
  RewriteEngine on
  RewriteBase /
  # Rewrite api to the zuul-web endpoint
  RewriteRule api/connection/(.*)$ http://localhost:9000/api/connection/$1 [P,L]
  RewriteRule api/console-stream ws://localhost:9000/api/tenant/example/console-stream [P,L]
  RewriteRule api/(.*)$ http://localhost:9000/api/tenant/example/$1 [P,L]
  # Backward compatible rewrite
  RewriteRule t/(.*)/(.*).html(.*) /t/$1/$2$3 [R=301,L,NE]

  # Don't rewrite files or directories
  RewriteCond %{REQUEST_FILENAME} !-f
  RewriteCond %{REQUEST_FILENAME} !-d
  RewriteRule . /index.html [L]
</Location>

Static External

Note

Hosting the Zuul dashboard on an external static location that does not support dynamic url rewrite rules only works for white-labeled deployments.

In order to serve the zuul dashboard code from an external static location, REACT_APP_ZUUl_API must be set at javascript build time:

REACT_APP_ZUUL_API='http://zuul-web.example.com' yarn build