Add x-middleman-passthrough Header (#9)

Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "middleman"
-version = "0.1.3"
+version = "0.1.4"
 edition = "2021"
 
 # See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html

README.md

@@ -39,6 +39,10 @@ Starts a reverse proxy to <UPSTREAM>, listens on <BIND>:<PORT>.
 Records upstream responses to <TAPES> directory.
 Returns recorded response if url matches (does not call upstream in this case).
 
+The optional header `x-middleman-passthrough` can be specified in http requests to middleman to pass a request through to the <UPSTREAM>.
+Any value other than the exact string "false" will be considered Truthy.
+The `--replay-only` config flag takes precedence over the `x-middleman-passthrough` header.
+
 Usage: middleman [OPTIONS]
 
 Options:

src/config.rs

@@ -11,7 +11,7 @@ static DEFAULT_CONFIG_FILENAME: &str = "middleman.toml";
 #[command(
     author,
     version,
-    about = "Starts a reverse proxy to <UPSTREAM>, listens on <BIND>:<PORT>.\nRecords upstream responses to <TAPES> directory.\nReturns recorded response if url matches (does not call upstream in this case)."
+    about = "Starts a reverse proxy to <UPSTREAM>, listens on <BIND>:<PORT>.\nRecords upstream responses to <TAPES> directory.\nReturns recorded response if url matches (does not call upstream in this case).\n\nThe optional header `x-middleman-passthrough` can be specified in http requests to middleman to pass a request through to the <UPSTREAM>.\nAny value other than the exact string \"false\" will be considered Truthy.\nThe `--replay-only` config flag takes precedence over the `x-middleman-passthrough` header."
 )]
 pub struct CliArgs {
     /// the port to listen on

src/main.rs

@@ -16,6 +16,7 @@ use crate::tokiort::TokioIo;
 use std::net::{IpAddr, SocketAddr};
 use std::str::FromStr;
 
+use crate::clone::clone_incoming_response;
 use hyper::upgrade::Upgraded;
 use hyper::Method;
 
@@ -83,6 +84,16 @@ async fn proxy_handler(
         if config.replay_only {
             proxy::replay(config, req).await
         } else {
+            let passthrough = req.headers().contains_key("x-middleman-passthrough")
+                && req.headers().get("x-middleman-passthrough").unwrap() != "false";
+
+            if passthrough == true {
+                let (req, _) = clone::clone_incoming_request(req).await?;
+                let resp = proxy::make_request(req).await?;
+                let (_, resp) = clone_incoming_response(resp).await?;
+                return Ok(resp);
+            }
+
             if proxy::recording_exists(&proxy::recording_name(&config.tapes, &req)) {
                 return proxy::replay(config, req).await;
             }