ml / warsawjs-workshop-5-chat Goto Github PK

Currently, Authenticator#register allows overwriting of other users' accounts. This can be eliminated by checking the database for existing accounts of the same name. Care should be taken to avoid a race condition.

In particular, a race condition might occur with the following sequence of operations taking place:

• Read (existence check) is done for connection A → user does not exist
• Read is done for connection B → user does not exist
• Write for connection A
• Write for connection B → overwrites the user account of A

This can be avoided using an in-process lock, possibly with a single Promise that controls access and makes other such checks/writes wait until the last/current procedure finishes.