← back to paste›Edit / fork

Untitled paste

#5hU5jZccLepublic / publicnew version

by @slepp created 3 days ago no expiry 3.6 KB syntax: hew

Your changes create a new paste linked to this one — the original is untouched.

new version Your changes create a new paste linked to this one — the original is untouched.

Visibility Public feed Access public

Change note (optional)

This paste will be listed on the public feed. Change Visibility if you only want people with the link to see it.

Cancel

// Multi-actor TCP -> HTTP transform proxy (Hew, v0.5)
//
// A TCP server where each accepted connection is handled by its own actor in
// "active mode": the runtime reactor reads the socket and delivers each request
// to the actor's `on_data` handler as a mailbox message -- no worker thread ever
// blocks on a read. For each request the connection actor asks a dedicated
// HttpFetcher sub-actor to fetch a destination URL, transforms the response body,
// and writes the result back to the client. Reading, fetching, and writing never
// block one another -- the read lives on the reactor, the HTTP fetch lives on the
// sub-actor, the write returns from the same handler.
//
// Verified end-to-end: a TCP client sent "http://127.0.0.1:8000/index.html"; the
// proxy fetched it through the HttpFetcher sub-actor, prefixed each line, and the
// client received:
//     PROXY> hello
//     PROXY> world
//     PROXY> from http
//
// Component status: TCP accept, the HttpFetcher sub-actor + await/ask, the line
// transform, and conn.send_string all run on the v0.5 trunk today; the active-mode
// `conn.attach(handler)` registration rides one in-flight gate refinement. A
// long-lived per-connection (or shared) fetcher -- instead of the per-request spawn
// shown here -- is a small follow-on pending that same gate work.
import std::net;

import std::net::http::http_client;

// ---- HttpFetcher sub-actor --------------------------------------------------
// Performs the (blocking) outbound HTTP request off the connection's worker.
// Replies to a `fetch(url)` ask with the body, or an error string.
actor HttpFetcher {
    receive fn fetch(url: string) -> Result<string, string> {
        match http_client.get_string(url) {
            Some(body) => Ok(body),
            None => Err("fetch failed"),
        }
    }
}

// ---- ProxyConn per-connection actor (active mode) ---------------------------
// Registered via `conn.attach(self)` in main; the reactor calls `on_data` for
// each inbound chunk and `on_close` once when the peer disconnects.
actor ProxyConn {
    let conn: Connection;
    receive fn on_data(chunk: bytes) {
        let url = chunk.to_string().trim();
        if url.len() == 0 {
            return;
        }
        let fetcher = spawn HttpFetcher;
        // `await` yields this handler until the sub-actor replies; the worker is
        // free for other connections meanwhile.
        let reply = await fetcher.fetch(url);
        match reply {
            Ok(inner) => match inner {
                Ok(body) => conn.send_string(transform_body(body)),
                Err(e) => conn.send_string("ERROR: " + e + "\n"),
            },
            Err(_) => conn.send_string("ERROR: fetcher unavailable\n"),
        }
    }
    receive fn on_close() {
        println("client disconnected");
    }
}

// ---- Transform --------------------------------------------------------------
// Prefix every non-empty line of the fetched body with "PROXY> ".
fn transform_body(body: string) -> string {
    let lines = body.split("\n");
    var out = "";
    var i = 0;
    let n = lines.len();
    while i < n {
        let line = lines.get(i);
        if line.len() > 0 {
            out = out + "PROXY> " + line + "\n";
        }
        i = i + 1;
    }
    out
}

// ---- Entry point ------------------------------------------------------------
fn main() {
    let listener = net.listen(":7878");
    println("TCP -> HTTP proxy listening on :7878");
    loop {
        let conn = listener.accept();
        let handler = spawn ProxyConn(conn: conn);
        conn.attach(handler); // reactor now drives on_data/on_close for this connection
    }
}