docs: reproduce env from issue #361

demo/issues-esm/labo/361-transform-memory.js

@@ -0,0 +1,46 @@
+import fs from "fs";
+import { pipeline } from "stream/promises";
+import { transform } from "stream-transform";
+import desm from 'desm';
+const dirname = desm(import.meta.url);
+
+const format = (data) =>
+  `${Math.round((data / 1024 / 1024) * 100) / 100} MB`;
+let maxUsedHeap = 0;
+async function main() {
+  setInterval(() => {
+    const stats = process.memoryUsage();
+    maxUsedHeap = Math.max(maxUsedHeap, stats.heapUsed);
+    console.log(`head used: ${format(stats.heapUsed)}; max heap used: ${format(maxUsedHeap)}`)
+  }, 1000);
+
+  await pipeline(
+    function* () {
+      let i = -1;
+      // Original code with a record limit
+      // const n = 9999999;
+      // while (++i < n) {
+      //   yield { i };
+      // }
+      // Run with unlimited records
+      while (true) {
+        i++
+        yield { i };
+      }
+    },
+    transform({ parallel: +process.env.PARALLEL }, (chunk, next) =>
+      next(null, chunk.i)
+    ),
+    fs.createWriteStream(`${dirname}/361-transform-memory.csv`)
+  );
+
+  console.log(`${maxUsedHeap / (1000 * 1000)}mb`);
+}
+
+main();
+
+// $ PARALLEL=1 node example.js
+// 6.009856mb
+
+// $ PARALLEL=2 node example.js
+// 320.684144mb