An identity in Chat is unique to a user and may be signed in on multiple devices simultaneously. For example, identity "email@example.com" will stay synchronized on a number of endpoints including her iPhone, Android tablet and in-browser application. All destinations for the same user will receive identical channel and message notifications as well as display the same message history.
On the server, we must decide, based on the token request that was sent to us, who the user is and what they should be allowed to do. To figure out who the user is (their identity), you might use your existing login system or identity provider (e.g. using session cookies, an API token, or whatever mechanism you use to secure API requests or pages today). You might not care who a user is at all, and assign them a temporary identity as in our starter apps. Who the user is, what is their role, and how you determine that will vary from application to application.
If you determine that the user should indeed be allowed to access your Chat application, you must grant your user access to Chat and supply an identity. Here are the guidelines on how to generate JWT access tokens: Creating Access Tokens.
Programmable Chat also uses identity to track monthly usage and generate accounting reports, therefore be mindful about provisioning a reasonable amount of unique identities. Reusing identities too frequently and keeping uniqueness low may cause conflicts in the user and application logic. On the other end, using only random identities will result in a large number of redundant unique users, which also impacts monthly billing.
Twilio's Programmable Chat tracks unique user identities each month, and each unique
identity connecting to a Chat Service will create a User record. During a calendar month, if a user registers activity, they are considered "active." The following activities register users as "active users":
- User is created via the REST API
- User is updated via the REST API
- User authenticates via the SDK
- User sends a message from the SDK
- User sends a message from SDK
- A message is sent on behalf of a user from the REST API
- User joins a Channel via the SDK
- User is added to a Channel via REST API or SDK
- User is invited to a Channel
- User is removed from a channel via REST or SDK
To minimize costs related to active users:
- avoid creating the Chat client object (in the SDK) until you are certain that the User wants to read/send messages
- avoid unnecessary REST API updates to users (e.g., User attributes)