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

web3.js/src/agent-manager.js

@@ -0,0 +1,38 @@
+// @flow
+
+import {Agent} from 'http';
+
+export const DESTROY_TIMEOUT_MS = 5000;
+
+export class AgentManager {
+  _agent: Agent = AgentManager._newAgent();
+  _activeRequests = 0;
+  _destroyTimeout: TimeoutID | null = null;
+
+  static _newAgent(): Agent {
+    return new Agent({keepAlive: true, maxSockets: 25});
+  }
+
+  requestStart(): Agent {
+    // $FlowExpectedError - Don't manage agents in the browser
+    if (process.browser) return;
+
+    this._activeRequests++;
+    clearTimeout(this._destroyTimeout);
+    this._destroyTimeout = null;
+    return this._agent;
+  }
+
+  requestEnd() {
+    // $FlowExpectedError - Don't manage agents in the browser
+    if (process.browser) return;
+
+    this._activeRequests--;
+    if (this._activeRequests === 0 && this._destroyTimeout === null) {
+      this._destroyTimeout = setTimeout(() => {
+        this._agent.destroy();
+        this._agent = AgentManager._newAgent();
+      }, DESTROY_TIMEOUT_MS);
+    }
+  }
+}

web3.js/src/connection.js

@@ -20,6 +20,7 @@ import type {Blockhash} from './blockhash';
 import type {FeeCalculator} from './fee-calculator';
 import type {Account} from './account';
 import type {TransactionSignature} from './transaction';
+import {AgentManager} from './agent-manager';
 
 export const BLOCKHASH_CACHE_TIMEOUT_MS = 30 * 1000;
 
@@ -502,10 +503,13 @@ type ConfirmedBlock = {
 };
 
 function createRpcRequest(url): RpcRequest {
+  const agentManager = new AgentManager();
   const server = jayson(async (request, callback) => {
+    const agent = agentManager.requestStart();
     const options = {
       method: 'POST',
       body: request,
+      agent,
       headers: {
         'Content-Type': 'application/json',
       },
@@ -539,6 +543,8 @@ function createRpcRequest(url): RpcRequest {
       }
     } catch (err) {
       callback(err);
+    } finally {
+      agentManager.requestEnd();
     }
   });