From 85fd147d0162e19999a1f27aea59d7bfbb0b47b4 Mon Sep 17 00:00:00 2001 From: Raya Fratkina Date: Tue, 29 Oct 2024 12:09:50 -0400 Subject: [PATCH] Expand README (#197880) MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit ## Summary Adds a bit more general background, intro to concepts, and guidelines about what to use FF for and what not to ### Checklist Delete any items that are not applicable to this PR. - [ ] Any text added follows [EUI's writing guidelines](https://elastic.github.io/eui/#/guidelines/writing), uses sentence case text and includes [i18n support](https://github.com/elastic/kibana/blob/main/packages/kbn-i18n/README.md) - [ ] [Documentation](https://www.elastic.co/guide/en/kibana/master/development-documentation.html) was added for features that require explanation or tutorials - [ ] [Unit or functional tests](https://www.elastic.co/guide/en/kibana/master/development-tests.html) were updated or added to match the most common scenarios - [ ] [Flaky Test Runner](https://ci-stats.kibana.dev/trigger_flaky_test_runner/1) was used on any tests changed - [ ] Any UI touched in this PR is usable by keyboard only (learn more about [keyboard accessibility](https://webaim.org/techniques/keyboard/)) - [ ] Any UI touched in this PR does not create any new axe failures (run axe in browser: [FF](https://addons.mozilla.org/en-US/firefox/addon/axe-devtools/), [Chrome](https://chrome.google.com/webstore/detail/axe-web-accessibility-tes/lhdoppojpmngadmnindnejefpokejbdd?hl=en-US)) - [ ] If a plugin configuration key changed, check if it needs to be allowlisted in the cloud and added to the [docker list](https://github.com/elastic/kibana/blob/main/src/dev/build/tasks/os_packages/docker_generator/resources/base/bin/kibana-docker) - [ ] This renders correctly on smaller devices using a responsive layout. (You can test this [in your browser](https://www.browserstack.com/guide/responsive-testing-on-local-server)) - [ ] This was checked for [cross-browser compatibility](https://www.elastic.co/support/matrix#matrix_browsers) ### Risk Matrix Delete this section if it is not applicable to this PR. Before closing this PR, invite QA, stakeholders, and other developers to identify risks that should be tested prior to the change/feature release. When forming the risk matrix, consider some of the following examples and how they may potentially impact the change: | Risk | Probability | Severity | Mitigation/Notes | |---------------------------|-------------|----------|-------------------------| | Multiple Spaces—unexpected behavior in non-default Kibana Space. | Low | High | Integration tests will verify that all features are still supported in non-default Kibana Space and when user switches between spaces. | | Multiple nodes—Elasticsearch polling might have race conditions when multiple Kibana nodes are polling for the same tasks. | High | Low | Tasks are idempotent, so executing them multiple times will not result in logical error, but will degrade performance. To test for this case we add plenty of unit tests around this logic and document manual testing procedure. | | Code should gracefully handle cases when feature X or plugin Y are disabled. | Medium | High | Unit tests will verify that any feature flag or plugin combination still results in our service operational. | | [See more potential risk examples](https://github.com/elastic/kibana/blob/main/RISK_MATRIX.mdx) | ### For maintainers - [ ] This was checked for breaking API changes and was [labeled appropriately](https://www.elastic.co/guide/en/kibana/master/contributing.html#_add_your_labels) - [ ] This will appear in the **Release Notes** and follow the [guidelines](https://www.elastic.co/guide/en/kibana/master/contributing.html#kibana-release-notes-process) --------- Co-authored-by: Alejandro Fernández Haro --- packages/core/feature-flags/README.mdx | 79 +++++++++++++------------- 1 file changed, 38 insertions(+), 41 deletions(-) diff --git a/packages/core/feature-flags/README.mdx b/packages/core/feature-flags/README.mdx index bd381269da8af..99e10b72aa68c 100644 --- a/packages/core/feature-flags/README.mdx +++ b/packages/core/feature-flags/README.mdx @@ -20,56 +20,53 @@ One example of invalid use cases are settings used during the `setup` lifecycle if an HTTP route is registered or not. Instead, you should always register the route, and return `404 - Not found` in the route handler if the feature flag returns a _disabled_ state. +In summary, Feature flagging is best suited for + - Phased rollout of the features (either to a specific customer, a subset of customers, or a % of overall users) + - Feature experimentation + +Feature flagging is NOT suitable for + - Applying feature availability for licensing and/or tiers + - Restricting or applying customer entitlement to specific GA features + For a code example, refer to the [Feature Flags Example plugin](https://github.com/elastic/kibana/blob/main/examples/feature_flags_example/README.md) -## Registering a feature flag +## Key concepts -> [!IMPORTANT] -> At the moment, we follow a manual process to manage our feature flags. Refer to [this repo](https://github.com/elastic/kibana-feature-flags) to learn more about our current internal process. -> Our goal is to achieve the _gitops_ approach detailed below. But, at the moment, it's not available, and you can skip it if you want. +### Feature Flag -Kibana follows a _gitops_ approach when managing feature flags. To declare a feature flag, add your flags definitions in -your plugin's `server/index.ts` file: +A config key that defines a set of [variations](#variations) that will be resolved at runtime when the app calls [the evaluation APIs](https://docs.elastic.dev/kibana-dev-docs/tutorials/feature-flags-service#evaluating-feature-flags). The variation is decided at runtime based on static binary state (ON -> `variationA` vs. OFF -> `variationB`), or via [evaluation/segmentation rules](#evaluationsegmentation-rules). -```typescript -// /server/index.ts -import type { FeatureFlagDefinitions } from '@kbn/core-feature-flags-server'; -import type { PluginInitializerContext } from '@kbn/core-plugins-server'; - -export const featureFlags: FeatureFlagDefinitions = [ - { - key: 'myPlugin.myCoolFeature', - name: 'My cool feature', - description: 'Enables the cool feature to auto-hide the navigation bar', - tags: ['my-plugin', 'my-service', 'ui'], - variationType: 'boolean', - variations: [ - { - name: 'On', - description: 'Auto-hides the bar', - value: true, - }, - { - name: 'Off', - description: 'Static always-on', - value: false, - }, - ], - }, - {...}, -]; - -export async function plugin(initializerContext: PluginInitializerContext) { - const { FeatureFlagsExamplePlugin } = await import('./plugin'); - return new FeatureFlagsExamplePlugin(initializerContext); -} -``` +### Variations + +All the potential values that a feature flag can return based on the [evaluation rules](#evaluationsegmentation-rules). A feature flag should define at least 2 variations: the ON and the OFF states. The typical use case sets the OFF state to match the `fallback` value provided to [the evaluation APIs](https://docs.elastic.dev/kibana-dev-docs/tutorials/feature-flags-service#evaluating-feature-flags), although it's not a hard requirement and Kibana contributors might require special configurations. + +### Evaluation/Segmentation rules + +Set of rules used to evaluate the variation to resolve, based on the [evaluation context](#evaluation-context) provided by the app. + +The rules can vary from a percentage rollout per evaluation context, or more complex IF...THEN filters and clauses. + +Refer to the [Evaluation Context guide's examples](https://github.com/elastic/kibana-feature-flags/blob/main/docs/evaluation-context.md#examples) for some typical scenarios. + +### Evaluation Context + +Kibana reports a set of properties specific to each ECH deployment/Serverless project to help define the [segmentation rules](#evaluationsegmentation-rules). A list of the currently reported context properties can be found in the [Evaluation Context guide](https://github.com/elastic/kibana-feature-flags/blob/main/docs/evaluation-context.md). + +### Feature Flag Code References + +In the Kibana repo we run a [GH Action](https://github.com/elastic/kibana/actions/workflows/launchdarkly-code-references.yml) that links existing Feature Flags to their code references. This helps us figure out which flags have been removed from the code and, which ones are still being used. + +> :information_source: New flags might take a few moments to be updated with their code references. +> The job runs on every commit to the `main` branch of the [Kibana repository](https://github.com/elastic/kibana), so the wait can take from a few minutes to a few hours, depending on the Kibana repo's activity. + +## Registering a feature flag -After merging your PR, the CI will create/update the flags in our third-party feature flags provider. +At the moment, we follow a manual process to manage our feature flags. Refer to [this repo](https://github.com/elastic/kibana-feature-flags) to learn more about our current internal process. +Our goal is to achieve a _gitops_ approach eventually. But, at the moment, it's not available. ### Deprecation/removal strategy -When your code doesn't use the feature flag anymore, it is recommended to clean up the feature flags when possible. +When your code doesn't use the feature flag anymore, it is recommended to clean up the feature flags. There are a few considerations to take into account when performing this clean-up: 1. Always deprecate first, remove after