fix: use socket pooling for http requests in Node.js (#12480)

web3.js/test/agent-manager.test.js

@@ -0,0 +1,40 @@
+// @flow
+
+import {AgentManager, DESTROY_TIMEOUT_MS} from '../src/agent-manager';
+import {sleep} from '../src/util/sleep';
+
+jest.setTimeout(10 * 1000);
+
+test('agent manager', async () => {
+  const manager = new AgentManager();
+  const agent = manager._agent;
+  expect(manager._activeRequests).toBe(0);
+  expect(manager._destroyTimeout).toBeNull();
+
+  manager.requestStart();
+
+  expect(manager._activeRequests).toBe(1);
+  expect(manager._destroyTimeout).toBeNull();
+
+  manager.requestEnd();
+
+  expect(manager._activeRequests).toBe(0);
+  expect(manager._destroyTimeout).not.toBeNull();
+
+  manager.requestStart();
+  manager.requestStart();
+
+  expect(manager._activeRequests).toBe(2);
+  expect(manager._destroyTimeout).toBeNull();
+
+  manager.requestEnd();
+  manager.requestEnd();
+
+  expect(manager._activeRequests).toBe(0);
+  expect(manager._destroyTimeout).not.toBeNull();
+  expect(manager._agent).toBe(agent);
+
+  await sleep(DESTROY_TIMEOUT_MS);
+
+  expect(manager._agent).not.toBe(agent);
+});