fix: implement child_process IPC (#21490)

This PR implements the Node child_process IPC functionality in Deno on
Unix systems.

For `fd > 2` a duplex unix pipe is set up between the parent and child
processes. Currently implements data passing via the channel in the JSON
serialization format.

1 files changed, 64 insertions, 0 deletions

diff --git a/ext/node/benchmarks/child_process_ipc.mjs b/ext/node/benchmarks/child_process_ipc.mjs
new file mode 100644
index 000000000..0486972dc
--- /dev/null
+++ b/ext/node/benchmarks/child_process_ipc.mjs
@@ -0,0 +1,64 @@
+import { fork } from "node:child_process";
+import process from "node:process";
+import { setImmediate } from "node:timers";
+
+if (process.env.CHILD) {
+  const len = +process.env.CHILD;
+  const msg = ".".repeat(len);
+  const send = () => {
+    while (process.send(msg));
+    // Wait: backlog of unsent messages exceeds threshold
+    setImmediate(send);
+  };
+  send();
+} else {
+  function main(dur, len) {
+    const p = new Promise((resolve) => {
+      const start = performance.now();
+
+      const options = {
+        "stdio": ["inherit", "inherit", "inherit", "ipc"],
+        "env": { "CHILD": len.toString() },
+      };
+      const path = new URL("child_process_ipc.mjs", import.meta.url).pathname;
+      const child = fork(
+        path,
+        options,
+      );
+
+      let bytes = 0;
+      let total = 0;
+      child.on("message", (msg) => {
+        bytes += msg.length;
+        total += 1;
+      });
+
+      setTimeout(() => {
+        child.kill();
+        const end = performance.now();
+        const mb = bytes / 1024 / 1024;
+        const sec = (end - start) / 1000;
+        const mbps = mb / sec;
+        console.log(`${len} bytes: ${mbps.toFixed(2)} MB/s`);
+        console.log(`${total} messages`);
+        resolve();
+      }, dur * 1000);
+    });
+    return p;
+  }
+
+  const len = [
+    64,
+    256,
+    1024,
+    4096,
+    16384,
+    65536,
+    65536 << 4,
+    65536 << 6 - 1,
+  ];
+
+  for (const l of len) {
+    await main(5, l);
+  }
+}