Update all imports to .js for esm support, use threads.js

threads.js has better support for modules - no need to give a
project-relative path to the worker file, which complicated the build.

Add rudimentary thread pooling w/ execution timeout.

src/graphql.ts

@@ -4,7 +4,7 @@ import {
   RouterContext,
   graphql,
   makeExecutableSchema,
-} from "./mods";
+} from "./mods.js";
 
 export interface ResolversProps {
   Query?: any;

src/graphql/index.ts

@@ -1,6 +1,7 @@
-import { mergeTypeDefs, mergeResolvers } from "../mods";
+import { mergeTypeDefs, mergeResolvers } from "../mods.js";
+import * as sudoku from "./sudoku.js";
 
-const modules = [require("./sudoku")];
+const modules = [sudoku];
 
 export const typeDefs = mergeTypeDefs(modules.map((mod) => mod.typeDefs));
 export const resolvers = mergeResolvers(modules.map((mod) => mod.resolvers));

src/graphql/sudoku.ts

@@ -1,5 +1,5 @@
-import { gql } from "../mods";
+import { gql } from "../mods.js";
-import { generate, GenerateArguments } from "../sudoku/index";
+import { generate, GenerateArguments } from "../sudoku/index.js";
 
 export const typeDefs = gql`
   """

src/main.ts

@@ -1,6 +1,6 @@
-import { Application, bodyParser } from "./mods";
+import { Application, bodyParser } from "./mods.js";
-import { applyGraphQL } from "./graphql";
+import { applyGraphQL } from "./graphql.js";
-import { typeDefs, resolvers } from "./graphql/index";
+import { typeDefs, resolvers } from "./graphql/index.js";
 import stoppable from "stoppable";
 
 import cors from "@koa/cors";

src/sudoku/index.ts

@@ -1,7 +1,8 @@
-import { StaticPool, isTimeoutError } from "node-worker-threads-pool";
+import { spawn, Thread, Worker } from "threads";
 
 import WORKERS from "physical-cpu-count";
-import { prettyPrint } from "./util";
+import { prettyPrint } from "./util.js";
+
 const TIMEOUT = 20000;
 
 export type Cell = number;
@@ -19,34 +20,52 @@ export type Sudoku = {
   cells: Cell[];
 };
 
-const pool = new StaticPool<GenerateArguments, Cell[]>({
+function getWorker() {
-  size: WORKERS,
+  return spawn(new Worker("./worker"));
-  task: "./src/sudoku/worker.js",
+}
-});
+
+const available: any = [];
+
+function initialize() {
+  for (let n = 0; n < WORKERS; n++) {
+    getWorker().then((worker) => available.push(worker));
+  }
+}
+initialize();
+
+function withTimeout<T>(promise: Promise<T>, ms: number, cb: () => Error) {
+  let timeout: NodeJS.Timeout;
+  return new Promise<T>((resolve, reject) => {
+    timeout = setTimeout(() => {
+      reject(cb());
+    }, ms);
+    promise.then(resolve).catch(reject);
+  }).finally(() => clearTimeout(timeout!));
+}
 
-let activeWorkers = 0;
 export async function generate(
   regionWidth: number,
   regionHeight: number,
   clues: number
 ): Promise<Sudoku> {
-  if (activeWorkers >= WORKERS) {
+  const proxy = available.shift();
-    throw new Error("No workers available. Please try again in a moment.");
+  if (!proxy) {
+    throw new Error("No workers available right now. Please try again.");
   }
 
   try {
-    activeWorkers++;
+    const puzzle: number[] = await withTimeout(
-    const puzzle = await pool.exec(
+      proxy.generate(regionWidth, regionHeight, clues),
-      {
+      TIMEOUT,
-        regionWidth,
+      () => {
-        regionHeight,
+        Thread.terminate(proxy);
-        clues,
+        getWorker().then((worker) => available.push(worker));
-      },
+        return new Error("Timed out. Try reducing the number of clues.");
-      TIMEOUT
+      }
     );
 
+    available.unshift(proxy);
     prettyPrint(regionWidth, regionHeight, puzzle);
-
     return {
       regionWidth,
       regionHeight,
@@ -54,11 +73,6 @@ export async function generate(
       cells: puzzle,
     };
   } catch (err) {
-    if (isTimeoutError(err)) {
-      throw new Error("Timed out. Try increasing the number of clues.");
-    }
     throw err;
-  } finally {
-    activeWorkers--;
   }
 }

src/sudoku/math.ts

@@ -6,9 +6,9 @@ import {
   addNodeToColumn,
   maskRow,
   unmaskRow,
-} from "./dlx";
+} from "./dlx.js";
-import { shuffle, range } from "./util";
+import { shuffle, range } from "./util.js";
-import { Cell } from "./index";
+import { Cell } from "./index.js";
 
 type NodeMeta = {
   index: number;

src/sudoku/util.ts

@@ -1,4 +1,4 @@
-import { Cell } from "./index";
+import { Cell } from "./index.js";
 
 export function randInt(lower: number, upper: number) {
   return Math.floor(Math.random() * (upper - lower)) + lower;

src/sudoku/worker.js

@@ -1,15 +1,16 @@
-const { SudokuMath } = require("./math");
+import { SudokuMath } from "./math.js";
-const { parentPort } = require("worker_threads");
+import { expose } from "threads/worker";
 
 const maths = {};
 
-parentPort.on("message", ({ regionWidth, regionHeight, clues }) => {
+expose({
+  generate(regionWidth, regionHeight, clues) {
     const math =
       maths[`${regionWidth}:${regionHeight}`] ||
       (maths[`${regionWidth}:${regionHeight}`] = new SudokuMath(
         regionWidth,
         regionHeight
       ));
-  const puzzle = math.generate(clues);
+    return math.generate(clues);
-  parentPort.postMessage(puzzle);
+  },
 });