nstdlib-nightly/lib/internal/cluster/round_robin_handle.mjs

Node.js standard library converted to runtime-agnostic ES modules.

// Source: https://github.com/nodejs/node/blob/65eff1eb/lib/internal/cluster/round_robin_handle.js

import * as assert from "nstdlib/lib/internal/assert";
import * as net from "nstdlib/lib/net";
import { sendHelper } from "nstdlib/lib/internal/cluster/utils";
import {
  append,
  init,
  isEmpty,
  peek,
  remove,
} from "nstdlib/lib/internal/linkedlist";
import { constants } from "nstdlib/stub/binding/tcp_wrap";

export default RoundRobinHandle;

function RoundRobinHandle(
  key,
  address,
  { port, fd, flags, backlog, readableAll, writableAll },
) {
  this.key = key;
  this.all = new Map();
  this.free = new Map();
  this.handles = init({ __proto__: null });
  this.handle = null;
  this.server = net.createServer(assert.fail);

  if (fd >= 0) this.server.listen({ fd, backlog });
  else if (port >= 0) {
    this.server.listen({
      port,
      host: address,
      // Currently, net module only supports `ipv6Only` option in `flags`.
      ipv6Only: Boolean(flags & constants.UV_TCP_IPV6ONLY),
      backlog,
    });
  } else
    this.server.listen({
      path: address,
      backlog,
      readableAll,
      writableAll,
    }); // UNIX socket path.
  this.server.once("listening", () => {
    this.handle = this.server._handle;
    this.handle.onconnection = (err, handle) => this.distribute(err, handle);
    this.server._handle = null;
    this.server = null;
  });
}

RoundRobinHandle.prototype.add = function (worker, send) {
  assert(this.all.has(worker.id) === false);
  this.all.set(worker.id, worker);

  const done = () => {
    if (this.handle.getsockname) {
      const out = {};
      this.handle.getsockname(out);
      // TODO(bnoordhuis) Check err.
      send(null, { sockname: out }, null);
    } else {
      send(null, null, null); // UNIX socket.
    }

    this.handoff(worker); // In case there are connections pending.
  };

  if (this.server === null) return done();

  // Still busy binding.
  this.server.once("listening", done);
  this.server.once("error", (err) => {
    send(err.errno, null);
  });
};

RoundRobinHandle.prototype.remove = function (worker) {
  const existed = this.all.delete(worker.id);

  if (!existed) return false;

  this.free.delete(worker.id);

  if (this.all.size !== 0) return false;

  while (!isEmpty(this.handles)) {
    const handle = peek(this.handles);
    handle.close();
    remove(handle);
  }

  this.handle.close();
  this.handle = null;
  return true;
};

RoundRobinHandle.prototype.distribute = function (err, handle) {
  // If `accept` fails just skip it (handle is undefined)
  if (err) {
    return;
  }
  append(this.handles, handle);
  // eslint-disable-next-line node-core/no-array-destructuring
  const [workerEntry] = this.free; // this.free is a SafeMap

  if (Array.isArray(workerEntry)) {
    const { 0: workerId, 1: worker } = workerEntry;
    this.free.delete(workerId);
    this.handoff(worker);
  }
};

RoundRobinHandle.prototype.handoff = function (worker) {
  if (!this.all.has(worker.id)) {
    return; // Worker is closing (or has closed) the server.
  }

  const handle = peek(this.handles);

  if (handle === null) {
    this.free.set(worker.id, worker); // Add to ready queue again.
    return;
  }

  remove(handle);

  const message = { act: "newconn", key: this.key };

  sendHelper(worker.process, message, handle, (reply) => {
    if (reply.accepted) handle.close();
    else this.distribute(0, handle); // Worker is shutting down. Send to another.

    this.handoff(worker);
  });
};