Module E - Async and Rust for Web
Channels are a very useful way to communicate between threads and
async tasks. They allow for decoupling your application into many tasks. You'll see how that can come in nicely in exercise E.2. In this exercise, you'll implement two variants: a oneshot channel and a multi-producer-single-consumer (MPSC) channel. If you're up for a challenge, you can write a broadcast channel as well.
E.1.A MPSC channel ⭐⭐
A multi-producer-single-consumer (MPSC) channel is a channel that allows for multiple
Senders to send many messages to a single
exercises/E/1-channels in your editor. You'll find the scaffolding code there. For part A, you'll work in
src/mpsc.rs. Fix the
todo!s in that file in order to make the test pass. To test, run:
cargo test -- mpsc
If your tests are stuck, probably either your implementation does not use the
Waker correctly, or it returns
Poll::Pending where it shouldn't.
E.1.B Oneshot channel ⭐⭐⭐
A oneshot is a channel that allows for one
Sender to send exactly one message to a single
For part B, you'll work in
src/broadcast.rs. This time, you'll have to do more yourself. Intended behavior:
Future. It returns
inner.wakerwith the one from the
selfon send, allowing the it to be used no more than once. Sending sets
Some(T). It returns
Receiverwas dropped before sending.
inner.wakerafter putting the data in
- Once the
Senderis dropped, it marks itself dropped with
- Once the
Receiveris dropped, it marks itself dropped with
- Upon succesfully sending the message, the consumed
Senderis not marked as dropped. Instead
std::mem::forgetis used to avoid running the destructor.
To test, run:
cargo test -- broadcast
E.1.B Broadcast channel (bonus) ⭐⭐⭐⭐
A Broadcast channel is a channel that supports multiple senders and receivers. Each message that is sent by any of the senders, is received by every receiver. Therefore, the implemenentation has to hold on to messages until they have been sent to every receiver that has not yet been dropped. This furthermore implies that the message shoud be cloned upon broadcasting.
For this bonus exercise, we provide no scaffolding. Take your inspiration from the
oneshot modules, and implement a
broadcast module yourself.
E.2 Chat app
In this exercise, you'll write a simple chat server and client based on Tokio. Open
exercises/E/2-chat in your editor. The project contains a
lib.rs file, in which a type
Message resides. This
Message defines the data the chat server and clients use to communicate.
E.2.A Server ⭐⭐⭐
The chat server, which resides in
src/bin/server.rs listens for incoming TCP connections on port 8000, and spawns two tasks (futures):
handle_incoming: reads lines coming in from the TCP connection. It reads the username the client provides, and broadcasts incoming
Messages, possibly after some modification.
handle_outgoing: sends messages that were broadcasted by the
handle_incomingtasks to the client over TCP.
handle_outgoing contain a number to
todos. Fix them.
To start the server, run
cargo run --bin server
E.2.B Client ⭐⭐
The chat client, residing in
src/bin/client.rs contains some todo's as well. Fix them to allow for registration and sending
Messages to the server.
To start the client, run
cargo run --bin client
If everything works well, you should be able to run multiple clients and see messages sent from each client in every other.
E.3 Pastebin ⭐⭐⭐
This exercise is about writing a simple pastebin web server. Like the quizzer app, you will need to set up the project yourself. This webserver will be powered by
- Data is kept in memory. Bonus if you use a database or
sqlite, but first make the app function properly without.
- Expose a route to which a POST request can be sent, that accepts some plain text, and stores it along with a freshly generated UUID. The UUID is sent in the response. You can use the
uuidcrate to generate UUIDs.
- Expose a route to which a GET request can be sent, that accepts a UUID and returns the plain text corresponding to the UUID, or a 404 error if it doesn't exist.
- Expose a route to which a DELETE request can be sent, that accepts a UUID and deletes the plain text corresonding to that UUID.