forward RequestContext in a http header (#108)

Author: bnusunny

Cargo.lock

@@ -19,7 +19,7 @@ exclude = ["examples"]
 [dependencies]
 http = "0.2.4"
 lambda-extension = "0.7.0"
-lambda_http = "0.7.1"
+lambda_http = "0.7.2"
 reqwest = { version = "0.11", default-features = false, features = ["json"] }
 tokio = { version = "1.20.0", features = ["macros", "io-util", "sync", "rt-multi-thread", "time"] }
 tokio-retry = "0.3"

Cargo.toml

@@ -13,8 +13,10 @@ use std::{
     time::Duration,
 };
 
+use http::header::{HeaderName, HeaderValue};
 use http_body::Body as HttpBody;
 use lambda_extension::Extension;
+use lambda_http::aws_lambda_events::serde_json;
 pub use lambda_http::Error;
 use lambda_http::{Body, Request, RequestExt, Response};
 use reqwest::{redirect, Client, Url};
@@ -220,6 +222,7 @@ async fn fetch_response(
         ready_at_init.store(true, Ordering::SeqCst);
     }
 
+    let request_context = event.request_context();
     let path = event.raw_http_path();
     let mut path = path.as_str();
     let (parts, body) = event.into_parts();
@@ -229,7 +232,13 @@ async fn fetch_response(
         path = path.trim_start_matches(base_path);
     }
 
-    let req_headers = parts.headers;
+    let mut req_headers = parts.headers;
+
+    // include request context in http header "x-amzn-request-context"
+    req_headers.append(
+        HeaderName::from_static("x-amzn-request-context"),
+        HeaderValue::from_bytes(serde_json::to_string(&request_context).unwrap().as_bytes()).unwrap(),
+    );
 
     let mut app_url = domain;
     app_url.set_path(path);