90 lines
3.2 KiB
Markdown
90 lines
3.2 KiB
Markdown
|
# Feature flags
|
||
|
|
|
||
|
|
When developing new features for Riot, we use feature flags to give us more
|
||
|
|
flexibility and control over when and where those features are enabled.
|
||
|
|
|
||
|
|
For example, flags make the following things possible:
|
||
|
|
|
||
|
|
* Extended testing of a feature via labs on develop
|
||
|
|
* Enabling features when ready instead of the first moment the code is released
|
||
|
|
* Testing a feature with a specific set of users (by enabling only on a specific
|
||
|
|
Riot instance)
|
||
|
|
|
||
|
|
The size of the feature controlled by a feature flag may vary widely: it could
|
||
|
|
be a large project like reactions or a smaller change to an existing algorithm.
|
||
|
|
A large project might use several feature flags if it's useful to control the
|
||
|
|
deployment of different portions independently.
|
||
|
|
|
||
|
|
Everyone involved in a feature (engineering, design, product, reviewers) should
|
||
|
|
think about its deployment plan up front as best as possible so we can have the
|
||
|
|
right feature flags in place from the start.
|
||
|
|
|
||
|
|
## Interaction with spec process
|
||
|
|
|
||
|
|
Historically, we have often used feature flags to guard client features that
|
||
|
|
depend on unstable spec features. Unfortunately, there was never clear agreement
|
||
|
|
about how long such a flag should live for, when it should be removed, etc.
|
||
|
|
|
||
|
|
Under the [new spec
|
||
|
|
process](https://github.com/matrix-org/matrix-doc/pull/2324), server-side
|
||
|
|
unstable features can be used by clients and enabled by default as long as
|
||
|
|
clients commit to doing the associated clean up work once a feature stabilises.
|
||
|
|
|
||
|
|
## Starting work on a feature
|
||
|
|
|
||
|
|
When starting work on a feature, we should create a matching feature flag:
|
||
|
|
|
||
|
|
* Add a new
|
||
|
|
[setting](https://github.com/matrix-org/matrix-react-sdk/blob/develop/src/settings/Settings.js)
|
||
|
|
of the form:
|
||
|
|
```js
|
||
|
|
"feature_cats": {
|
||
|
|
isFeature: true,
|
||
|
|
displayName: _td("Adds cats everywhere"),
|
||
|
|
supportedLevels: LEVELS_FEATURE,
|
||
|
|
default: false,
|
||
|
|
},
|
||
|
|
```
|
||
|
|
* Check whether the feature is enabled as appropriate:
|
||
|
|
```js
|
||
|
|
SettingsStore.isFeatureEnabled("feature_cats")
|
||
|
|
```
|
||
|
|
* Add the feature to the [set of labs on develop](../riot.im/develop/config.json):
|
||
|
|
```json
|
||
|
|
"features": {
|
||
|
|
"feature_cats": "labs"
|
||
|
|
},
|
||
|
|
```
|
||
|
|
* Document the feature in the [labs documentation](labs.md)
|
||
|
|
|
||
|
|
With these steps completed, the feature is disabled by default, but can be
|
||
|
|
enabled on develop by interested users for testing.
|
||
|
|
|
||
|
|
Different features may have different deployment plans for when to enable where. The
|
||
|
|
following lists a few common options.
|
||
|
|
|
||
|
|
## Enabling by default on develop
|
||
|
|
|
||
|
|
Set the feature to `enable` in the [develop config](../riot.im/develop/config.json):
|
||
|
|
|
||
|
|
```json
|
||
|
|
"features": {
|
||
|
|
"feature_cats": "enable"
|
||
|
|
},
|
||
|
|
```
|
||
|
|
|
||
|
|
## Enabling by default on staging and app
|
||
|
|
|
||
|
|
Set the feature to `enable` in the [app config](../riot.im/app/config.json).
|
||
|
|
|
||
|
|
## Feature deployed successfully
|
||
|
|
|
||
|
|
Once we're confident that a feature is working well, we should remove the flag:
|
||
|
|
|
||
|
|
* Remove the [setting](https://github.com/matrix-org/matrix-react-sdk/blob/develop/src/settings/Settings.js)
|
||
|
|
* Remove all `isFeatureEnabled` lines that test for the feature's setting
|
||
|
|
* Remove the feature from the [labs documentation](labs.md)
|
||
|
|
* Remove feature state from [develop](../riot.im/develop/config.json) and
|
||
|
|
[app](../riot.im/app/config.json) configs
|
||
|
|
* Celebrate! 🥳
|