fix: redirect static-router/doc/master to stable docs (#568) (#571)

Co-authored-by: Marco Ieni <[email protected]>

terragrunt/modules/release-distribution/fastly-static.tf

@@ -47,6 +47,16 @@ resource "fastly_service_vcl" "static" {
     VCL
   }
 
+  snippet {
+    name    = "detect doc-master requests"
+    type    = "recv"
+    content = <<-VCL
+      if (req.url ~ "^\/doc\/master\/") {
+        error 619 "redirect";
+      }
+    VCL
+  }
+
   snippet {
     name    = "enable segmented caching"
     type    = "recv"
@@ -115,6 +125,21 @@ resource "fastly_service_vcl" "static" {
     VCL
   }
 
+  snippet {
+    # This was an abandoned copy of Rust 1.17.0-era docs; redirect to current docs
+    name    = "redirect doc-master to stable"
+    type    = "error"
+    content = <<-VCL
+      if (obj.status == 619 && obj.response == "redirect") {
+        set obj.status = 301;
+        set obj.response = "Moved permanently";
+        set obj.http.Location = regsub(req.url, "^\/doc\/master", "https://doc.rust-lang.org/stable");
+
+        return (deliver);
+      }
+    VCL
+  }
+
   logging_datadog {
     name  = "datadog"
     token = data.aws_ssm_parameter.datadog_api_key.value

terragrunt/modules/release-distribution/lambdas/static-router/index.js

@@ -35,5 +35,16 @@ echo "    curl https://sh.rustup.rs -sSf | sh"
         return redirect('https://sh.rustup.rs', body, callback);
     }
 
+    // Links to `/doc/master/*` are probably from old external sources, so send
+    // them back through the doc site to take advantage of any helpful error
+    // handling that may be defined there
+    if (request.uri.startsWith('/doc/master')) {
+        // The slice method is used to remove the '/doc/master' prefix from the
+        // URI. 11 is the length of '/doc/master'.
+        const newUri = 'https://doc.rust-lang.org/stable' + request.uri.slice(11);
+        const body = "The documentation now lives under doc.rust-lang.org";
+        return redirect(newUri, body, callback);
+    }
+
     callback(null, request);
 };