feat: add AWS_LWA_PROXY_LAMBDA_RUNTIME_API to overwrite

AWS_LAMBDA_RUNTIME_API and use a proxy

Author: alexgallotta

README.md

@@ -106,6 +106,7 @@ The readiness check port/path and traffic port can be configured using environme
 | AWS_LWA_PASS_THROUGH_PATH                                    | the path for receiving event payloads that are passed through from non-http triggers | "/events"  |
 | AWS_LWA_AUTHORIZATION_SOURCE                                 | a header name to be replaced to `Authorization` | None  |
 | AWS_LWA_ERROR_STATUS_CODES                                  | comma-separated list of HTTP status codes that will cause Lambda invocations to fail (e.g. "500,502-504,422") | None  |
+| AWS_LWA_PROXY_LAMBDA_RUNTIME_API                             | overwrites `AWS_LAMBDA_RUNTIME_API` to allow proxying request (not affecting registration) | None  |
 
 > **Note:**
 > We use "AWS_LWA_" prefix to namespacing all environment variables used by Lambda Web Adapter. The original ones will be supported until we reach version 1.0.

src/lib.rs

@@ -310,6 +310,13 @@ impl Adapter<HttpConnector, Body> {
         let compression = self.compression;
         let invoke_mode = self.invoke_mode;
 
+        if let Ok(runtime_proxy) = env::var("AWS_LWA_PROXY_LAMBDA_RUNTIME_API") {
+            // overwrite the env variable since
+            // LambdaInvokeMode::Buffered => lambda_http::run(svc).await,
+            // calls the lambda lambda_runtime::run which doesn't allow to change the client URI
+            env::set_var("AWS_LAMBDA_RUNTIME_API", runtime_proxy);
+        }
+
         if compression {
             let svc = ServiceBuilder::new().layer(CompressionLayer::new()).service(self);
             match invoke_mode {