Time Out an Apache HttpClient 5 Proxy That Stalls During CONNECT

The proxy accepted TCP but never finished its CONNECT reply. The website response has not begun; a timeout aimed only at that later response may leave this setup wait unbounded.

For Apache HttpClient 5.3.1, set the connection manager's defaults:

var connection = ConnectionConfig.custom()
    .setConnectTimeout(Timeout.ofSeconds(5))
    .setSocketTimeout(Timeout.ofSeconds(10))
    .build();

var manager = PoolingHttpClientConnectionManagerBuilder.create()
    .setDefaultConnectionConfig(connection)
    .build();

var client = HttpClients.custom()
    .setConnectionManager(manager)
    .setProxy(new HttpHost("http", "proxy.example", 8080))
    .build();

Use the Apache HttpComponents 5 classes under org.apache.hc, with Timeout in the core5 utility package. Retain and close the client for its workload. For an isolated public HTTP test, a candidate from the HTTP proxy list supplies the endpoint; keep the destination steady when comparing timeouts.

After CONNECT, TLS can need its own setup limit through HttpClient 5's TLS configuration. Also distinguish inactivity from a total deadline: intermittent bytes or repeated authentication exchanges can extend aggregate time. Use the application's supported deadline/cancellation policy for one whole-operation budget.