Implementation of Bulletin Board in Elixir. Erlang VM which allows parallel processing and distributed Mechanism.
A bulletin board consists of a list of topics t1,t2,...,tk and users that can subscribe to specific topics and post new information about a topic. Newly posted information is forwarded to all currently subscribed users. The goal is to implement a distributed bulletin board system that supports the following operations: subscribe(ui,tj): subscribes user ui to topic tj . This ensures that user ui will be notified (by receiving a message) whenever an update is posted for topic tj in the future. If the topic tj does not exist yet, it is created with user ui as the (only) subscribed user. unsubscribe(ui,tj): unsubscribes user ui from topic tj such that ui is no longer notified of updates to the topic. post(ui,tj,content): user ui posts content regarding topic tj . This causes no- tification messages (attaching content) to be sent to all currently subscribed users. Your implementation should adhere to the following guidelines: � Initially, no user is subscribed to any topic. .For each topic tj , a topic manager is responsible for handling the subscription of users and implementing the broadcast of newly posted information to the current subscribers. To ensure fault-tolerance, a topic manager is replicated on all available nodes (described below). It is recommended that you imple- ment this functionality in a module TopicManager. To be discoverable by users, the topic manager for topic tj registers its process ID (PID) under the topic name in the process registry. Q.Write a module User that provides an API to facilitate the interaction of users with the topic managers. The module should include the functions subscribe(topic name,user name), unsubscribe(topic name,user name), post(user name,topic name,content), and fetch news(). A new user joins the system by executing User.start(user name), which registers the user's name (with this PID) in the global process registry. Example: User.subscribe("Alice","computing") :timer.sleep(5000) IO.puts("Updates to Alice's subscriptions: #{User.fetch_news()}") Meanwhile, Bob runs the following code: User.subscribe("Bob","computing") User.post("Bob","computing","Just found a new prime number.") User.unsubscribe("Bob","computing")
When Alice's process resumes its operation and executes User.fetch news(), she will receive the message previously posted by Bob, which was relayed to her by the topic manager of "computing".