A Caching HTTP Proxy using Titanium Web Proxy
At my work at Jetabroad I do a lot of integration with third-party webservices (like everyone these days). The webservices, especially the test endpoints, are of variable stability and responsiveness.
The responsiveness issue can be maddening when you’re trying to iterate quickly. I prefer doing the bulk of my development via unit tests or integration tests to isolate myself as much as possible. However, I still ultimately find myself developing directly against these third-party services from time to time.
I built Catchy to help solve this pain. When you start it, you provide a whitelist of domains to intercept. Catchy will examine your outbound REST or SOAP requests to those domains, and then cache the inbound response based on the hash of the outbound request.
Titanium Web Proxy – an amazing library
Early prototypes were originally built on top of Fiddler Core, but after Fiddler Core was killed by Telerik, I transitioned it over to the excellent Titanium Web Proxy project. It makes intercepting and analyzing requests, even over TLS, very straightforward.
The proxy code itself is straightforward. The following snippet of Titanium Web Proxy code allows you to intercept HTTP and HTTPS requests (via HTTP 1.1 and HTTP2!) and run arbitrary C# functions to inspect / modify the requests and responses:
var proxyServer = new ProxyServer();
var explicitEndPoint = new ExplicitProxyEndPoint(ipAddress, port, true);
proxyServer.EnableHttp2 = true;
proxyServer.CertificateManager.CreateRootCertificate(false);
proxyServer.CertificateManager.TrustRootCertificate();
proxyServer.AddEndPoint(explicitEndPoint);
// specify your callbacks here
explicitEndPoint.BeforeTunnelConnectRequest += BeforeTunnelConnectRequest;
proxyServer.BeforeRequest += OnRequestHandler;
proxyServer.BeforeResponse += OnResponseHandler;
proxyServer.ExceptionFunc = OnErrorFunc;
proxyServer.Start();
proxyServer.SetAsSystemProxy(explicitEndPoint, ProxyProtocolType.AllHttp);
It’s rare to find a network library that works completely as advertised, and exposes a complex concept behind an easy to understand API. Well done to them!