test: add new scenario for async-local storage

Add a new scenario of multiple clients sharing a single data callback function managing their response data through AsyncLocalStorage APIs Refs: #32063 Refs: #32060 Refs: #32062 (comment) Co-authored-by: Gireesh Punathil <gpunathi@in.ibm.com> PR-URL: #32082 Reviewed-By: Anna Henningsen <anna@addaleax.net> Reviewed-By: James M Snell <jasnell@gmail.com>
nodejs · ronag · Jan 22, 2020 · Jan 30, 2020 · Mar 4, 2020 · Mar 8, 2020
commit fc2909a96a3c48cafc6eeaab3f232ee23720c564
diff --git a/test/parallel/test-async-local-storage-http-multiclients.js b/test/parallel/test-async-local-storage-http-multiclients.js
@@ -0,0 +1,65 @@
+'use strict';
+const common = require('../common');
+const Countdown = require('../common/countdown');
+const assert = require('assert');
+const { AsyncLocalStorage } = require('async_hooks');
+const http = require('http');
+const cls = new AsyncLocalStorage();
+const NUM_CLIENTS = 10;
+
+// Run multiple clients that receive data from a server
+// in multiple chunks, in a single non-closure function.
+// Use the AsyncLocalStorage (ALS) APIs to maintain the context
+// and data download. Make sure that individual clients
+// receive their respective data, with no conflicts.
+
+// Set up a server that sends large buffers of data, filled
+// with cardinal numbers, increasing per request
+let index = 0;
+const server = http.createServer((q, r) => {
+  // Send a large chunk as response, otherwise the data
+  // may be sent in a single chunk, and the callback in the
+  // client may be called only once, defeating the purpose of test
+  r.end((index++ % 10).toString().repeat(1024 * 1024));
+});
+
+const countdown = new Countdown(NUM_CLIENTS, () => {
+  server.close();
+});
+
+server.listen(0, common.mustCall(() => {
+  for (let i = 0; i < NUM_CLIENTS; i++) {
+    cls.run(new Map(), common.mustCall(() => {
+      const options = { port: server.address().port };
+      const req = http.get(options, common.mustCall((res) => {
+        const store = cls.getStore();
+        store.set('data', '');
+
+        // Make ondata and onend non-closure
+        // functions and fully dependent on ALS
+        res.setEncoding('utf8');
+        res.on('data', ondata);
+        res.on('end', common.mustCall(onend));
+      }));
+      req.end();
+    }));
+  }
+}));
+
+// Accumulate the current data chunk with the store data
+function ondata(d) {
+  const store = cls.getStore();
+  assert.notStrictEqual(store, undefined);
+  let chunk = store.get('data');
+  chunk += d;
+  store.set('data', chunk);
+}
+
+// Retrieve the store data, and test for homogeneity
+function onend() {
+  const store = cls.getStore();
+  assert.notStrictEqual(store, undefined);
+  const data = store.get('data');
+  assert.strictEqual(data, data[0].repeat(data.length));
+  countdown.dec();
+}