From 8cb039a32e8905709957c5272dee9f88750f9706 Mon Sep 17 00:00:00 2001
From: Dan Greaves <dan@dangreaves.com>
Date: Fri, 20 Sep 2024 11:02:52 +1000
Subject: [PATCH] feat: configure lambda web adapter health check

---
 src/adapter/handler.ts | 8 ++++++++
 src/cdk/GatsbySite.ts  | 3 ++-
 2 files changed, 10 insertions(+), 1 deletion(-)

diff --git a/src/adapter/handler.ts b/src/adapter/handler.ts
index acb4f57..0632da8 100644
--- a/src/adapter/handler.ts
+++ b/src/adapter/handler.ts
@@ -32,6 +32,14 @@ const app = express();
 // Disable X-Powered-By header.
 app.disable("x-powered-by");
 
+/**
+ * Endpoint used by AWS Lambda Web Adapter for readiness checks.
+ * @see https://github.com/awslabs/aws-lambda-web-adapter#readiness-check
+ */
+app.get("/__ping", (_req, res) => {
+  res.status(200).send("Pong");
+});
+
 // Register a route which listens to all requests.
 app.all("*", async (req, res) => {
   /**
diff --git a/src/cdk/GatsbySite.ts b/src/cdk/GatsbySite.ts
index 3f32b9c..7ba9f2f 100644
--- a/src/cdk/GatsbySite.ts
+++ b/src/cdk/GatsbySite.ts
@@ -209,8 +209,9 @@ export class GatsbySite extends Construct {
                 layers: [webAdapterLayer, ...(functionOptions.layers ?? [])],
                 environment: {
                   ...functionOptions.environment,
-                  // Required by web adapter.
+                  // Configuration for AWS Lambda Web Adapter.
                   AWS_LAMBDA_EXEC_WRAPPER: "/opt/bootstrap",
+                  AWS_LWA_READINESS_CHECK_PATH: "/__ping",
                 },
               });