Client does not disconnect from relays upon Drop

[benthecarman]

When a Client is dropped it still persists the connections to the relays, this is an easy footgun that can cause resource exhaustion.

The user needs to remember to call disconnect() otherwise.

[yukibtc]

I tried to implement Drop for RelayPool but this cause many issues in a multi-threads env (like https://github.com/coinstr/coinstr) where the Client is cloned and dropped many times.

For now the only way to completely shutdown the client is to exit from the app (the threads will drop) or by calling the shutdown method.

[yukibtc]

An alternative to shutdown is the stop method: it allow to re-start a previously constructed Client (anyway it must be called manually) by calling the start method.

[benthecarman]

Just something to kill the connections on drop would be nice, have run into the problem multiple times on accident

[yukibtc]

Maybe you can wrap the Client:

pub struct CustomClient {
    inner: Client
}

impl Drop for CustomClient {
    fn drop(&mut self) {
        let client = self.clone();
        async_utility::thread::spawn(async move {
            client.shutdown().await.unwrap();
        });
    }
}

I can't implement the Drop because if a user do this

let client = self.clone();
thread::spawn(async move {
    // use client and then drop
});

the client shutdown everywhere.

[yukibtc]

Otherwise, I'll try to add a new filed in Options, like shutdown_on_drop: bool (by default will be disabled).
If you'll initialize the Client with that option enabled, the Client will shutdown on drop.
What do you think?

[benthecarman]

That sounds good

[yukibtc]

Done

So, init the Client in this way:

// ...
let opts = Options::new().shutdown_on_drop(true);
let client = Client::with_opts(&keys, opts);
// ...