What are Feature Flags?

Feature flags are a quality control measure for Citrix to be able to dynamically roll back to the previous working version of the app before a new feature was introduced. Since a bug fix on the public app stores is subject to delays due to app store submission and approval times, this provides Citrix with a faster resolution time until a fix is available for a subsequent app store update.

Citrix uses a 3rd party service called Launch Darkly to enable and disable feature flags within the app code. No user or app data is passed to the Launch Darkly service. The app contacts the Launch Darkly service only to query the value of a specific feature flag key and retrieve the value (on or off). This will enable or disable a feature.

Why do devices need to be able to reach Launch Darkly’s service?

Currently, Secure Mail and Secure Hub use Launch Darkly’s APIs and service to enable and disable feature flags with every release. Without communication to the Launch Darkly service, the app will not be able to retrieve the value for the flag and disable or enable the feature on the device -

• Features are turned off by default when a release ships and communication to the service is required to enable the feature (if it has been turned on for the release).
• If a new feature presents an issue in production, the feature flag will be turned off to disable the feature and resolve the issue as an intermediate bug fix until the next release.

When would you need to specifically enable traffic to Launch Darkly?

You do not need to make any configurations to enable traffic to Launch Darkly, except when you have a firewall or proxy blocking outbound traffic. In that case, you enable traffic to Launch Darkly via specific URLs or IP addresses, depending on your policy requirements.

How to enable traffic/communication to Launch Darkly:

You can either enable traffic out to the below URLs or if your internal policies require only IP addresses to be listed, these are also provided below. app.launchdarkly.com:

List of IPs:

https://docs.fastly.com/guides/securing-communications/accessing-fastlys-ip-ranges

events.launchdarkly.com

Address: 34.205.234.124
Address: 34.206.27.142

stream.launchdarkly.com

Address: 34.192.196.169
Address: 34.231.253.69
Address: 34.193.119.86
Address: 34.235.217.178
Address: 54.156.199.48
Address: 34.232.235.135
Address: 34.205.207.124
Address: 34.197.0.51

clientstream.launchdarkly.com

Address: 34.201.185.120

Address: 34.199.172.173

Address: 52.22.57.175 Address: 54.173.82.102

firehose.launchdarkly.com

Address: 34.207.23.28

Address: 34.206.111.62