Connection cache 100 continue

[Verdent]

Description

Fixes ##9736

This issue introduces a new way of idle connection handling. It splits the desired idle timeout and uses small 500 ms timeouts until the overall desired timeout is reached. This helps to interrupt the idle timeout mechanism.

FYI: I will add some more comments to the code

Documentation

None

[spericas]

After looking at the final version of this, I think there's no need for the "remainder" logic TBH. Timeouts are approximations (especially at the socket layer), so it should be enough to divide by TIMEOUT or maybe add 1 to that. No need for finer control than that. That should simplify your logic a bit, making it easier to read.

[romain-grecourt]

+1 the loop should just increment until max iterations

[romain-grecourt]

Something like this maybe ?

Should the idle "tick" timeout (500) be configurable ?
If both are configurable then it's up to the user to pick multiple numbers.

maxIterations = (int) Math.ceilDiv(Math.max(1, idleTimout.getSeconds()), 500);

// idleTimout=0   -> maxIterations=1
// idleTimout=499 -> maxIterations=1
// idleTimout=501 -> maxIterations=2
// idleTimout=999 -> maxIterations=2

try {
    int timeout = -1; // always at least one iteration
    for (int i = 0; i < maxIterations && !cancelled; i++) {
        try {
            int t = socket.getSoTimeout();
            if (t != 500) {
                timeout = t;
            }
            socket.setSoTimeout(500);
            next = upstream.read();
            if (next <= 0) {
                closed = true;
                // no need to restore timeout
                return;
            }
            // sucessful read
            break;
        } catch (SocketTimeoutException ignored) {
            // ignore socket timeout, retry until maxIterations
        }
    }
    // restore original timeout
    // read sucessful, canceled (endIdle) or max iterations (idle timeout)
    socket.setSoTimeout(timeout);
} catch (IOException e) {
    closed = true;
    throw new UncheckedIOException(e);
}