Unleash gradual rollouts with userId stickiness silently fail without a userId

TL;DR

Either pass a userId in the Unleash context on every evaluation or leave stickiness on default. If a rollout works for logged-in users and never for anonymous ones, check the stickiness setting first.

Steps

1. Either pass a userId in the Unleash context on every evaluation or leave stickiness on default.
2. If a rollout works for logged-in users and never for anonymous ones, check the stickiness setting first.

When to use

You are seeing this: If a rollout works for logged-in users and never for anonymous ones, check the stickiness setting first. Use this skill when you run into "Unleash gradual rollouts with userId stickiness silently fail without a userId".

When not to use

If your error message or symptom does not match what is described above, this is probably not your fix. Search for your exact error text instead of forcing this one to fit.

Versions

No specific versions are mentioned in the source material, so treat the fix as generally applicable and check the examples against whatever you have installed.

Why this happens

The original report does not dig into a root cause. It documents the symptom and the fix that resolved it.

Source: In Unleash, if your gradual rollout uses userId stickiness but the context has no userId, the strategy evaluates to false and the flag just looks broken. Default stickiness walks userId, then sessionId, then random, so it degrades gracefully, but explicit userId stickiness does not.

Verified resolution: Either pass a userId in the Unleash context on every evaluation or leave stickiness on default. If a rollout works for logged-in users and never for anonymous ones, check the stickiness setting first.

Source URL: https://docs.getunleash.io/guides/gradual-rollout