Bandwidth Rate limiting

[staticgc]

Use-Case: Large buffers (~ 1MB) and large number of them (~millions) are to be transferred by the client and exploring hyper for it. Need a way to limit the network bandwidth used.

I see a similar ticket 2163 which was closed and hence opening a new one.

Is there a way to control n/w bandwidth in hyper?

[aeryz]

As @seanmonstar said (#2163 (comment)), hyper uses streamed bodies so you should be able to control the rate of reads and writes.

[staticgc]

How on earth did I miss that comment? It seems I read it but did not process it.
Thanks @aeryz

[staticgc]

hyper uses streamed bodies

I explored it and I am still confused.

My understanding is that hyper Client has a pool of tcp connections. So at a client level (i.e. hyper::client::Client) if I have to control the bytes written, how can I do that?

This implies that consumer of the client will specify say "do not use more than 20 MB/s". This needs to be split across underlying connections, which is further complicated by the fact that number of connections is dynamic.

[staticgc]

How about this?

I have used the limiter in the crate: async-speed-limit

Now we:

• Create a new type MyStream which wraps tokio::net::TcpStream and implements AsyncWrite & AsyncRead
• Implement a connector MyConnector similar to HttpConnector which helps to create new MyStream
• Instantiate Limiter and attach to MyConnector
• Make MyConnector to attach clone of Limiter to every new MyStream (done via fn call() in MyConnector)

The Limiter is thread-safe & cheaply clone-able. They all share the same bucket wrapped in Arc.

The MyStream's fn poll_write calls the limiter to "consume" and wait if not enough tokens.

Reference gist: here

Usage

    use hyper::{self, Body, body::HttpBody};


    let builder = hyper::client::Client::builder();
    let connector = MyConnector::with_limit(102400.0); // ~ 100KB/s Limit
    let client = Arc::new(builder.build::<MyConnector, Body>(connector));

Does it work?

Initial results does seem to suggest that it is working

[aeryz]

Hey, although I haven't tried it yet, your solution looks good to me. Since all connections use the same limiter, it would be able to limit the overall bandwidth rate perfectly.