fix nodejs 17 localhost connection error with ipv4 fallback (#80)

Author: joe4dev

.github/workflows/integrations.go.yml

@@ -23,9 +23,12 @@ jobs:
     strategy:
       matrix:
         include:
-          - { language: go, node-version: '16.x', go-version: '1.16.15', region: us-east-1}
+        # The AWS CDK only supports third-party languages "until its EOL (End Of Life) shared by the vendor or community"
+        # https://github.com/aws/aws-cdk
+        # Golang EOL overview: https://endoflife.date/go
           - { language: go, node-version: '16.x', go-version: '1.17.8', region: us-east-1}
           - { language: go, node-version: '16.x', go-version: '1.18', region: us-east-1}
+          - { language: go, node-version: '18.x', go-version: '1.20', region: us-east-1}
 
     env:
       AWS_REGION: ${{ matrix.region }}

README.md

@@ -67,6 +67,7 @@ $ awslocal sns list-topics
 
 ## Change Log
 
+* 2.17.0: Fix IPv4 fallback check to prevent IPv6 connection issue with `localhost` on macOS
 * 2.16.0: Add check to prevent IPv6 connection issue with `localhost` on MacOS
 * 2.15.0: Fix issue with undefined BUCKET_NAME_OUTPUT variable; add CI build and eslint config
 * 2.14.0: Add switches in patches to accommodate new esbuild packaging mechanism in CDK v2.14.0+

bin/cdklocal

@@ -33,25 +33,53 @@ const getLocalHost = async () => {
   }
 
   var hostname = process.env.LOCALSTACK_HOSTNAME || DEFAULT_HOSTNAME;
-  // attempt to connect to the given host/port
-  const socket = new net.Socket();
-  try {
-    await socket.connect({ host: hostname, port });
-  } catch (e) {
-    if (hostname === "localhost") {
-      // fall back to using local IPv4 address - to fix IPv6 issue on MacOS
-      // see, https://github.com/localstack/serverless-localstack/issues/125
-      // and https://github.com/localstack/aws-cdk-local/issues/78
+  // Fall back to using local IPv4 address if connection to localhost fails.
+  // This workaround transparently handles systems (e.g., macOS) where
+  // localhost resolves to IPv6 when using Nodejs >=v17. See discussion:
+  // https://github.com/localstack/aws-cdk-local/issues/76#issuecomment-1412590519
+  // Issue: https://github.com/localstack/aws-cdk-local/issues/78
+  if (hostname === "localhost") {
+    try {
+      const options = { host: hostname, port: port };
+      await checkTCPConnection(options);
+    } catch (e) {
       hostname = "127.0.0.1";
     }
-  } finally {
-    socket.destroy();
   }
 
   resolvedHostname = hostname;
   return `${hostname}:${port}`;
 };
 
+/**
+ * Checks whether a TCP connection to the given "options" can be established.
+ * @param {object} options connection options of net.socket.connect()
+ *                 https://nodejs.org/api/net.html#socketconnectoptions-connectlistener
+ *                 Example: { host: "localhost", port: 4566 }
+ * @returns {Promise} A fulfilled empty promise on successful connection and
+ *                    a rejected promise on any connection error.
+ */
+const checkTCPConnection = async (options) => {
+  return new Promise((resolve, reject) => {
+    const socket = new net.Socket();
+    const client = socket.connect(options, () => {
+      client.end();
+      resolve();
+    });
+
+    client.setTimeout(500);  // milliseconds
+    client.on("timeout", err => {
+      client.destroy();
+      reject(err);
+    });
+
+    client.on("error", err => {
+      client.destroy();
+      reject(err);
+    });
+  });
+}
+
 const useLocal = () => {
   // TODO make configurable..?
   return true;

package-lock.json

@@ -1,7 +1,7 @@
 {
   "name": "aws-cdk-local",
   "description": "CDK Toolkit for use with LocalStack",
-  "version": "2.16.0",
+  "version": "2.17.0",
   "bin": {
     "cdklocal": "bin/cdklocal"
   },