Add Feature Toggles

[branimir-vujicic]

Feature Toggles should allow teams to modify system behavior without changing code. Feature Toggles are configured using google guice. Basic definition of toggles are crated using FeatureToggleBinder. FeatureToggleBinder creates FeatureToggle and additional configuration can be done using feature configuration.
In current stage Feature Toggles supports:

• if / else based feature toggles
• Dependency Injection based Hot reloading implementation without restart require code refactoring to add an interface when injecting the new implementation/class
• using various toggle strategies along with simple on / off toggles

configuration:

to allow feature toggle configuration four lines are needed in config.properties file

features.config-source-type=file
features.refresh-period=30s

configuration-source-type is source type for Feature Toggles configuration features.config-source is a source (file) of the configuration features.config-type format in which configuration is stored (json or properties) features.refresh-period configuration refresh period

Defining Feature Toggles

Feature toggle definition is done in google guice module using FeatureToggleBinder

simple feature toggle definition

    featureToggleBinder(binder)
                        .featureId("featureXX")
                        .bind()

This example creates bindings for @Inject

    @Inject
    public Runner(@FeatureToggle("featureXX") Supplier<Boolean> isFeatureXXEnabled)
    {
        this.isFeatureXXEnabled = isFeatureXXEnabled;
    }

isFeatureXXEnabled can be used to test if feature is enabled or disabled:

    boolean testFeatureXXEnabled()
    {
        return isFeatureXXEnabled.get();
    }

hot reloadable feature toggle definition

featureToggleBinder(binder, Feature01.class)
                        .featureId("feature01")
                        .baseClass(Feature01.class)
                        .defaultClass(Feature01Impl01.class)
                        .allOf(Feature01Impl01.class, Feature01Impl02.class)
                        .bind()

adding Feature Toggle switching strategy

featureToggleBinder(binder)
                        .featureId("feature04")
                        .toggleStrategy("AllowAll")
                        .toggleStrategyConfig(ImmutableMap.of("key", "value", "key2", "value2"))

feature-config.properties file example

# feature query-logger
feature.query-logger.enabled=true
feature.query-logger.strategy=OsToggle
feature.query-logger.strategy.os_name=.*Linux.*

#feature.query-rate-limiter
feature.query-rate-limiter.currentInstance=com.facebook.presto.server.protocol.QueryBlockingRateLimiter

# feature.query-cancel
feature.query-cancel.strategy=AllowList
feature.query-cancel.strategy.allow-list-source=.*IDEA.*
feature.query-cancel.strategy.allow-list-user=.*prestodb

in this example for first feature query-logger
changing value of feature.query-logger.enabled to false will 'disable' this feature. Changes will be effective within refresh period.

Test plan - Unit Tests

== RELEASE NOTES ==

General Changes
 * Add support for Feature Toggles.

[v-jizhang]

@bot kick off tests

[ericyuliu]

Shall we add more documentation/comments inside code, for each new component, annotation use case, and each test case as a living doc.

[tdcmeehan]

Can you remove the custom parsing code and reuse the code in airlift/configuration to parse individual FeatureConfigurations?

[tdcmeehan]

One major thing that seems to be missing is: I thought there would be a plugin mechanism that would allow one to change how the toggles are persisted and loaded? Without that, how does one even use the FileBasedFeatureToggleModule, since it seems to be unused in this PR?

[tdcmeehan]

Is this unused?

[branimir-vujicic]

FileBasedFeatureToggleModule is a FeatureToggle module for file-based configuration.
For other configuration sources, we can create and initialize other modules. for example: DatabaseBasedFeatureToggleModule.

I'll try to refactor this and extract the configuration sources parser in a separate class, and we will have a FeatureToggleModule and configuration parsers based on configuration sources

[branimir-vujicic]

HI @tdcmeehan,
I updated the configuration loading to use the plugin mechanism.

[tdcmeehan]

Thank you for refactoring this into a plugin. Can you please make sure that all the file-based loading code is in one module, and all the core code to wire in feature toggles is in a separate module? One may want to swap out the file reading code with something e.g. db backed, without depending on the file loading code.

What happens if we add a feature toggle in the code, but the operator hasn't added a configuration source plugin?

[branimir-vujicic]

HI @tdcmeehan,
I separated the feature toggle module and the feature toggle plugin. Now, the file configuration is in presto-feature-toggle-plugin.
If no configuration source is configured feature toggles work with a dummy configuration source.

[ajaygeorge]

@branimir-vujicic This requires a release note since this is introducing a new feature. Can you please add that in.

[ajaygeorge]

@branimir-vujicic Are the Velox changes needed as a part of this PR. ? Seems unrelated. Can you please remove them.

[branimir-vujicic]

@ajaygeorge Velox updates are included by mistake.
updated release notes.