What is context?

Context is a collection of all the facts available in a single Tweek evaluation. Context is evaluated against key’s rules to retrieve the value, meaning:

Context + key definition = value

For example, assuming we have a key is_allowed_to_drive with rule:

default value: false
User.Age > 18 then true

If we send these requests to Tweek:

GET http://localhost:8081/api/v2/values/is_allowed_to_drive -> false
GET http://localhost:8081/api/v2/values/is_allowed_to_drive?User.Age=20 -> true

In order to get the right values from Tweek, we need to provide Tweek the relevant context for the request.

Inline context vs remote context

While we can always pass context parameters in url, a different approach is to save context in Tweek for identity. For example:

GET http://localhost:8081/api/v2/values/is_allowed_to_drive?User=john -> false

We’ve asked for the value of “is_allowed_to_drive” for user John, but Tweek doesn’t know any facts about him, let’s change it:

POST http://localhost:8081/api/v2/context/user/john
    "Age": 20

After adding the data, let’s retry our first request:

GET http://localhost:8081/api/v2/keys/is_allowed_to_drive?User=john -> true

Identities & Properties

You’ve noticed that we used “User.Age” and not simply “Age”, the reason is that Tweek treat facts as properties on top of identities, for example:

GET http://localhost:8081/api/v2/keys/path/to/key?User=john&User.Country=england
  1. Tweek understands that it need to get the values for identity user “john”.
  2. Tweek look at inline context to see relevant properties for this identity, for example “User.Country=england”
  3. Tweek look at remote context to get all properties for identity user “john”, from previous example it would be Age=20
  4. Tweek merge inline and remote context to a single context.
  5. Tweek evaluate the context against the requested key definition (rules)
  6. Tweek send the results back to the user