fix(http): guard socket.setKeepAlive for proxy agent streams (#10917)

Co-authored-by: Maks Pikov <mixelburg@users.noreply.github.com>
Co-authored-by: Jay <jasonsaayman@gmail.com>

PRE_RELEASE_CHANGELOG.md

@@ -1 +1,7 @@
 # Pre-Release Changelog
+
+## Unreleased
+
+## Bug Fixes
+
+- **Proxy Agent Streams:** Guarded Node HTTP adapter TCP keep-alive setup so proxy agents that return generic Duplex streams do not throw when `setKeepAlive` is unavailable. (**#10917**, closes **#10908**)

lib/adapters/http.js

@@ -1205,7 +1205,11 @@ export default isHttpAdapterSupported &&
 
       req.on('socket', function handleRequestSocket(socket) {
         // default interval of sending ack packet is 1 minute
-        socket.setKeepAlive(true, 1000 * 60);
+        // proxy agents (e.g. agent-base) may return a generic Duplex stream
+        // that doesn't have setKeepAlive, so guard before calling
+        if (typeof socket.setKeepAlive === 'function') {
+          socket.setKeepAlive(true, 1000 * 60);
+        }
 
         // Install a single 'error' listener per socket (not per request) to avoid
         // accumulating listeners on pooled keep-alive sockets that get reassigned

tests/unit/adapters/http.test.js

@@ -6169,6 +6169,58 @@ describe('supports http with nodejs', () => {
         'second request should be destroyed by its own active socket error'
       );
     });
+
+    it('should not throw TypeError when a proxy agent stream does not define setKeepAlive (regression #10908)', async () => {
+      // proxy agents (e.g. agent-base) may provide a generic Duplex stream as
+      // the socket; that stream does not define setKeepAlive.
+      const socket = new stream.Duplex({
+        read() {},
+        write(_chunk, _encoding, callback) {
+          callback();
+        },
+      });
+      assert.strictEqual(typeof socket.setKeepAlive, 'undefined');
+
+      const transport = {
+        request(_, cb) {
+          return new (class MockRequest extends EventEmitter {
+            constructor() {
+              super();
+              this.destroyed = false;
+            }
+
+            setTimeout() {}
+            write() {}
+
+            end() {
+              this.emit('socket', socket);
+
+              setImmediate(() => {
+                const response = stream.Readable.from(['ok']);
+                response.statusCode = 200;
+                response.headers = {};
+                cb(response);
+                this.emit('close');
+              });
+            }
+
+            destroy(err) {
+              if (this.destroyed) return;
+              this.destroyed = true;
+              err && this.emit('error', err);
+              this.emit('close');
+            }
+          })();
+        },
+      };
+
+      const result = await axios.get('http://example.com/', {
+        transport,
+        maxRedirects: 0,
+      });
+
+      assert.strictEqual(result.status, 200);
+    });
   });
 
   describe('redirect listener accumulation', () => {