Writing Policies

Greenwave policies are part of the server configuration and define which test cases are required to pass for specific decision contexts (or gating points), subject types, product versions or even for individual artifact names (packages, modules, images…).

When you ask Greenwave for a decision, it checks all the configured policies to find which ones are applicable to the subject of the decision. It then evaluates all the rules in each applicable policy and makes a decision based on whether they are all satisfied.

Greenwave decision requests need the following parameters to identify the policies to use:

  • decision_context

  • product_version

  • subject_type

Greenwave policies need the following parameters:

  • decision_contexts

  • product_versions

  • subject_type

  • rules

  • id

Optionally, policies can define applicable “package” (the name from NVR) allowlist and blocklist using parameters packages and excluded_packages. This works only for subject types that support NVR formatted subject identifiers (is_nvr in Subject types configuration).

Policies are YAML files, loaded from the directory given by the POLICIES_DIR configuration setting (by default, /etc/greenwave/policies).

The YAML format allows you to write one or more “documents” in a file. Greenwave considers each YAML document to be a policy.

Here is an example policy:

 1--- !Policy
 2id: taskotron_release_critical_tasks
 3decision_contexts:
 4- bodhi_update_push_stable
 5- bodhi_update_context1
 6- bodhi_update_context2
 7subject_type: bodhi_update
 8product_versions:
 9- fedora-26
10- fedora-27
11rules:
12- !PassingTestCaseRule {test_case_name: dist.rpmdeplint}
13- !PassingTestCaseRule {test_case_name: dist.upgradepath}
14excluded_packages:
15- python2-*

On line 1, the --- YAML document header marks the beginning of a new document.

The top-level document has the YAML tag !Policy to indicate that this is a Greenwave policy. Greenwave expects each YAML document to be tagged this way.

The document is a map (dictionary) with the following keys:

id

This is an arbitrary string identifying this policy. Each policy in the configuration must have a distinct id. Greenwave does not assign any meaning to this identifier, but it appears in Greenwave’s decision API responses so that you can map it back to the configuration where it is defined.

This is optional in gating.yaml files (see RemoteRule).

decision_contexts

Allows to specify many decision contexts for one policy. Previous parameter decision_context was kept for backward compatibility and its value is being used if this parameter is not specified. However only one parameter can be used in the same policy.

decision_context (obsolete)

This is an arbitrary string identifying the “context” of the decisions where this policy is applicable. In other words, if Greenwave is making decisions at gating points in a pipeline, this is how we identify which gate we are talking about.

Greenwave does not enforce anything about this identifier. It should be chosen in coordination with the tool asking Greenwave for a decision. In this example, the identifier is bodhi_update_push_stable. Bodhi passes this value when it asks Greenwave to decide whether a Bodhi update is ready to be pushed to the stable repositories.

subject_type

When you ask Greenwave for a decision, you ask it about a specific software artefact (the “subject” of the decision). Each policy applies to some type of software artefact – in this example, the policy applies to Bodhi updates.

The subject type can be any string. A list of commonly used subject types can be found in the Subject types section.

product_versions

A policy applies to one or more “product versions”. When you ask Greenwave for a decision, you must tell it which product version you are working with, and it only selects policies which are applicable for that product version.

This mechanism makes it possible to enforce different rules across different versions of a product. For example, the policy for Fedora could become increasingly stricter across versions as the quality and coverage of tests improves.

The “product version” strings used here (and in the Greenwave decision API) are expected to match the product version identifiers used in Product Definition Center (see the /product-versions endpoint), although Greenwave does not enforce this.

You can match many product versions by using a wildcard like fedora-*.

rules

A list of rules which this policy enforces. Each item in the list is a YAML map, tagged with the rule type.

Currently there are a few rule types, PassingTestCaseRule being one of them. See the Rule types section below for a full list.

List of rules can be empty if no tests are required for the specified decision contexts. This is useful in the remote rules. See RemoteRule: configure additional policies section for details.

packages (optional)

A list of binary RPM package names this policy applies to.

packages only takes effect when Greenwave is making a decision about subjects with "item": "koji_build". excluded_packages has a higher priority than packages.

excluded_packages (optional)

A list of binary RPM package names which are exempted from this policy. This supports Unix shell-style wildcards (e.g. python2-*).

excluded_packages only takes effect when Greenwave is making a decision about subjects with "item": "koji_build".

Subject types

Greenwave can make decisions about any type of software artefacts, the value of this field just needs to be a string.

The subject types can be configured in server (SUBJECT_TYPES_DIR points to the directory with the configuration YAML files). This customization can be listed via API GET /api/v1.0/subject_types.

These are common examples of types:

koji_build

A build stored in the Koji build system. Builds are identified by their Name-Version-Release (NVR) identifier, as in glibc-2.26-27.fc27. Note that Koji identifies builds by the NVR of their source RPM, regardless which binary packages were produced in the build.

bodhi_update

A distribution update in Bodhi. Updates are identified by their Bodhi update id, as in FEDORA-2018-ec7cb4d5eb.

To make decision about Koji builds in the update, they need to be explicitly listed in decision query.

compose

A distribution compose. The compose tool (typically Pungi) takes a snapshot of the distribution at a point in time, and produces a directory hierarchy containing packages, installer images, and other metadata. Composes are identified by the compose id in their metadata, which is typically also reflected in their directory name, for example Fedora-Rawhide-20170508.n.0.

Rule types

PassingTestCaseRule

For this rule to be satisfied, there must be a result in ResultsDB for the given test_case_name with an outcome of PASSED or INFO, or there must be a corresponding waiver in WaiverDB for the given test case.

The rule requires all matching latest test results with distinct triplets system_architecture, system_variant and scenario (which are defined in result data) to pass or be waived.

Optional scenario property can be specified to consider only results with a given scenario name.

Optional valid_since and valid_until properties declare a date/time range for which the rule is applicable. The range is compared to subject’s build time from Koji if available or the current date/time. The default value is null for both, indicating that the rule is always valid. The comparison logic is following:

if valid_since != null and subject_time < valid_since then
   rule is not applicable
else if valid_until != null and subject_time >= valid_until then
   rule is not applicable
else
   rule is applicable

Removing the rule is equivalent to setting valid_until to the current date/time. This is preferable since it won’t affect previous decisions. Similarly, adding new rule with valid_since set to the current or a future date/time does not affect previous decisions.

In the following example, on 2021-10-02 (if not specified, the time defaults to 00:00 UTC), compose test results for test case compose.autocloud start requiring scenario x86_64.uefi instead of x86_64.64bit.

 1--- !Policy
 2id: "compose_required_tests"
 3product_versions:
 4  - fedora-rawhide
 5decision_context: compose_required_tests
 6subject_type: compose
 7rules:
 8  - !PassingTestCaseRule
 9    valid_until: 2021-10-02
10    test_case_name: compose.autocloud
11    scenario: x86_64.64bit
12  - !PassingTestCaseRule
13    valid_since: 2021-10-02
14    test_case_name: compose.autocloud
15    scenario: x86_64.uefi

RemoteRule

See the RemoteRule: configure additional policies section below for some information about how RemoteRule works and how to configure it.

Testing your policy changes

Before requesting a new policy, you can verify the rules for the policy by passing rules to API POST /api/v1.0/decision instead of the decision_context attribute.

curl https://greenwave.fedoraproject.org/api/v1.0/decision \
  --json '{
    "product_version": "fedora-27",
    "subject_identifier": "akonadi-calendar-tools-17.12.1-1.fc27",
    "subject_type": "koji_build",
    "rules": [
      {"type": "PassingTestCaseRule", "test_case_name": "example1.test.case.name"},
      {"type": "PassingTestCaseRule", "test_case_name": "example2.test.case.name"},
      {
        "type": "RemoteRule",
        "source": "https://gitlab.example.com/ci/policies/-/raw/master/{subject_id}.yml"
      }
    ]}'

Updating existing policies

Modifying rules in policies would normally break previous gating decisions. To avoid this, use valid_since when adding new rules and valid_until instead of removing rules.

For details, see: PassingTestCaseRule

RemoteRule: configure additional policies

This rule allows the packager to configure some additional policies in a gating.yaml file configured in the repo. To “activate” this feature is necessary to configure a policy among the others policies configured in the default directory.

If you want to add a policy for the Fedora Greenwave, you need to change this file committing and pushing a change with the new policy: https://infrastructure.fedoraproject.org/cgit/ansible.git/tree/roles/openshift-apps/greenwave/templates/configmap.yml

Then you need to login to batcave and run the ansible repo to apply the changes:

sudo rbac-playbook openshift-apps/greenwave.yml

If you have permission problems ask in the IRC freenode channel #fedora-apps.

You can:

  • add a rule to an existing Policy

  • add a Policy

Here’s an example of a RemoteRule:

--- !Policy
id: "test_remoterule"
product_versions:
  - fedora-29
decision_contexts: [osci_compose_gate]
subject_type: koji_build
excluded_packages: []
rules:
  - !RemoteRule {}

Once the code is pushed, Greenwave will start to check if there is a remote rule file in your repo. If you didn’t configure any remote rule file nothing will change.

Greenwave will check if a remote rule file exists, if it does, it pulls it down, loads it, and uses it to additionally evaluate the subject of the decision.

If a remote rule file exists it should contain a policy for each required decision context. If no tests are required for the particular decision context, there should be empty rules set, i.e. rules: []. In this case the evaluation result will be No tests are required. If there is no decision context matching the original policy, the result will be Cannot find any applicable policies.

To be able to get remote rule file, Greenwave requires REMOTE_RULE_POLICIES option to be set.

REMOTE_RULE_POLICIES is a map, where the key is the subject type. There could be a default pattern “*” used when no subject type matched. Old parameter DIST_GIT_URL_TEMPLATE if used will override the default subject type, but please note that it is obsolete and should not be used in new configurations. Each subject should contain an URL template.

Below is an example configuration of remote rule URLs:

REMOTE_RULE_POLICIES = {
    'brew-build-group': [
        'https://greenwave.example.com/policies/{subject_id}.yaml',
        'https://greenwave.example.com/policies/{pkg_name}.yaml',
    ],
    '*': (
        'https://src.fedoraproject.org/{pkg_namespace}'
        '{pkg_name}/raw/{rev}/f/gating.yaml'
    )
}
KOJI_BASE_URL = 'https://koji.fedoraproject.org/kojihub'

In the URL templates the following parameters can be used: {pkg_name}, {pkg_namespace} and {rev}. Values for all of these parameters are being retrieved from Koji.

If any of these parameters are used in the template, KOJI_BASE_URL option must be set.

Parameter {subject_id} can also be used in URL template. If the subject identifier contains a hash starting with the sha256: prefix, this prefix would be removed.

For details about fetching the remote policy files, see How is the remote rule file being retrieved?.