Document feature flags

[gavincabbage]

Document procedure for adding, consuming and changing feature flags.

The PR below adds feature flag capabilities to InfluxDB to allow users to exercise experimental features before they are enabled by default.

A feature flag is created by updating flags.yml and running make flags. It includes a default value.

A feature flag is then consumed in code:

• On the backend, a flag can be used like this

if feature.MyFeatureFlag().Enabled(ctx) {
    // new code path...
} else {
    // old code path...
}

• On the frontend, a similar pattern can be used based on the response from /api/v2/flags

Finally, the value of a flag can be changed from the default using the INFLUXD_FEATURE_FLAGS environment variable or --feature-flags CLI flag. In the first case, the environment variable should be formatted as a JSON map of string keys to string values, e.g.

env INFLUXD_FEATURE_FLAGS="{\"flag1\":\value1\",\"key2\":\"value2\"}" influxd

In the the second case, the flag value should be formatted as a comma-delimted list of key-value pairs, with an equals sign as an assignment operator, e.g.

influxd --feature-flags flag1=value1,flag2=value2

Relevant URLs

• InfluxDB PR
• Existing internal documentation may provide a starting point (private link)
• Code documentation

What products and version are you using?

InfluxDB 2.0

[noramullen1]

Hi @gavincabbage , is this a feature just for internal use?

[sanderson]

@noramullen1 @gavincabbage There has been discussion around leaving this feature undocumented. I don't know that we've come to a consensus yet, but I think we better put this on hold.