fix: avoid synchronous calls where possible

Signed-off-by: Aarni Koskela <akx@iki.fi>

src/main.js

@@ -3,6 +3,7 @@
 'use strict';
 
 import fs from 'node:fs';
+import fsp from 'node:fs/promises';
 import path from 'path';
 import { fileURLToPath } from 'url';
 import axios from 'axios';
@@ -23,6 +24,7 @@ if (args.length >= 3 && args[2][0] !== '-') {
 }
 
 import { program } from 'commander';
+import { existsP } from './promises.js';
 program
   .description('tileserver-gl startup options')
   .usage('tileserver-gl [mbtiles] [options]')
@@ -95,7 +97,7 @@ const startWithInputFile = async (inputFile) => {
     inputFile = path.resolve(process.cwd(), inputFile);
     inputFilePath = path.dirname(inputFile);
 
-    const inputFileStats = fs.statSync(inputFile);
+    const inputFileStats = await fsp.stat(inputFile);
     if (!inputFileStats.isFile() || inputFileStats.size === 0) {
       console.log(`ERROR: Not a valid input file: `);
       process.exit(1);
@@ -140,11 +142,11 @@ const startWithInputFile = async (inputFile) => {
         };
       }
 
-      const styles = fs.readdirSync(path.resolve(styleDir, 'styles'));
+      const styles = await fsp.readdir(path.resolve(styleDir, 'styles'));
       for (const styleName of styles) {
         const styleFileRel = styleName + '/style.json';
         const styleFile = path.resolve(styleDir, 'styles', styleFileRel);
-        if (fs.existsSync(styleFile)) {
+        if (await existsP(styleFile)) {
           config['styles'][styleName] = {
             style: styleFileRel,
             tilejson: {
@@ -189,7 +191,7 @@ const startWithInputFile = async (inputFile) => {
         process.exit(1);
       }
 
-      instance.getInfo((err, info) => {
+      instance.getInfo(async (err, info) => {
         if (err || !info) {
           console.log('ERROR: Metadata missing in the MBTiles.');
           console.log(
@@ -207,11 +209,11 @@ const startWithInputFile = async (inputFile) => {
             mbtiles: path.basename(inputFile),
           };
 
-          const styles = fs.readdirSync(path.resolve(styleDir, 'styles'));
+          const styles = await fsp.readdir(path.resolve(styleDir, 'styles'));
           for (const styleName of styles) {
             const styleFileRel = styleName + '/style.json';
             const styleFile = path.resolve(styleDir, 'styles', styleFileRel);
-            if (fs.existsSync(styleFile)) {
+            if (await existsP(styleFile)) {
               config['styles'][styleName] = {
                 style: styleFileRel,
                 tilejson: {
@@ -254,10 +256,10 @@ fs.stat(path.resolve(opts.config), async (err, stats) => {
       return startWithInputFile(inputFile);
     } else {
       // try to find in the cwd
-      const files = fs.readdirSync(process.cwd());
+      const files = await fsp.readdir(process.cwd());
       for (const filename of files) {
         if (filename.endsWith('.mbtiles') || filename.endsWith('.pmtiles')) {
-          const inputFilesStats = fs.statSync(filename);
+          const inputFilesStats = await fsp.stat(filename);
           if (inputFilesStats.isFile() && inputFilesStats.size > 0) {
             inputFile = filename;
             break;

src/promises.js

@@ -0,0 +1,14 @@
+import util from 'node:util';
+import fsp from 'node:fs/promises';
+import zlib from 'zlib';
+
+export const gzipP = util.promisify(zlib.gzip);
+export const gunzipP = util.promisify(zlib.gunzip);
+export const existsP = async (path) => {
+  try {
+    await fsp.access(path); // Defaults to F_OK: indicating that the file is visible to the calling process
+    return true;
+  } catch (err) {
+    return false;
+  }
+};

src/serve_data.js

@@ -1,8 +1,7 @@
 'use strict';
 
-import fs from 'node:fs';
+import fsp from 'node:fs/promises';
 import path from 'path';
-import zlib from 'zlib';
 
 import clone from 'clone';
 import express from 'express';
@@ -10,12 +9,13 @@ import MBTiles from '@mapbox/mbtiles';
 import Pbf from 'pbf';
 import { VectorTile } from '@mapbox/vector-tile';
 
-import { getTileUrls, isValidHttpUrl, fixTileJSONCenter } from './utils.js';
+import { fixTileJSONCenter, getTileUrls, isValidHttpUrl } from './utils.js';
 import {
-  openPMtiles,
   getPMtilesInfo,
   getPMtilesTile,
+  openPMtiles,
 } from './pmtiles_adapter.js';
+import { gunzipP, gzipP } from './promises.js';
 
 export const serve_data = {
   init: (options, repo) => {
@@ -89,12 +89,12 @@ export const serve_data = {
             headers['Content-Encoding'] = 'gzip';
             res.set(headers);
 
-            data = zlib.gzipSync(data);
+            data = await gzipP(data);
 
             return res.status(200).send(data);
           }
         } else if (item.sourceType === 'mbtiles') {
-          item.source.getTile(z, x, y, (err, data, headers) => {
+          item.source.getTile(z, x, y, async (err, data, headers) => {
             let isGzipped;
             if (err) {
               if (/does not exist/.test(err.message)) {
@@ -114,7 +114,7 @@ export const serve_data = {
                     data.slice(0, 2).indexOf(Buffer.from([0x1f, 0x8b])) === 0;
                   if (options.dataDecoratorFunc) {
                     if (isGzipped) {
-                      data = zlib.unzipSync(data);
+                      data = await gunzipP(data);
                       isGzipped = false;
                     }
                     data = options.dataDecoratorFunc(id, 'data', data, z, x, y);
@@ -126,7 +126,7 @@ export const serve_data = {
                   headers['Content-Type'] = 'application/json';
 
                   if (isGzipped) {
-                    data = zlib.unzipSync(data);
+                    data = await gunzipP(data);
                     isGzipped = false;
                   }
 
@@ -151,7 +151,7 @@ export const serve_data = {
                 res.set(headers);
 
                 if (!isGzipped) {
-                  data = zlib.gzipSync(data);
+                  data = await gzipP(data);
                 }
 
                 return res.status(200).send(data);
@@ -212,7 +212,7 @@ export const serve_data = {
     };
 
     if (!isValidHttpUrl(inputFile)) {
-      const inputFileStats = fs.statSync(inputFile);
+      const inputFileStats = await fsp.stat(inputFile);
       if (!inputFileStats.isFile() || inputFileStats.size === 0) {
         throw Error(`Not valid input file: "${inputFile}"`);
       }

src/serve_rendered.js

@@ -17,7 +17,6 @@ import fs from 'node:fs';
 import path from 'path';
 import url from 'url';
 import util from 'util';
-import zlib from 'zlib';
 import sharp from 'sharp';
 import clone from 'clone';
 import Color from 'color';
@@ -42,6 +41,8 @@ import {
   getPMtilesTile,
 } from './pmtiles_adapter.js';
 import { renderOverlay, renderWatermark, renderAttribution } from './render.js';
+import fsp from 'node:fs/promises';
+import { gunzipP } from './promises.js';
 
 const FLOAT_PATTERN = '[+-]?(?:\\d+|\\d+.?\\d+)';
 const PATH_PATTERN =
@@ -943,7 +944,7 @@ export const serve_rendered = {
                   callback(null, response);
                 }
               } else if (sourceType === 'mbtiles') {
-                source.getTile(z, x, y, (err, data, headers) => {
+                source.getTile(z, x, y, async (err, data, headers) => {
                   if (err) {
                     if (options.verbose)
                       console.log('MBTiles error, serving empty', err);
@@ -962,7 +963,7 @@ export const serve_rendered = {
 
                   if (format === 'pbf') {
                     try {
-                      response.data = zlib.unzipSync(data);
+                      response.data = await gunzipP(data);
                     } catch (err) {
                       console.log(
                         'Skipping incorrect header for tile mbtiles://%s/%s/%s/%s.pbf',
@@ -1039,7 +1040,7 @@ export const serve_rendered = {
     const styleFile = params.style;
     const styleJSONPath = path.resolve(options.paths.styles, styleFile);
     try {
-      styleJSON = JSON.parse(fs.readFileSync(styleJSONPath));
+      styleJSON = JSON.parse(await fsp.readFile(styleJSONPath));
     } catch (e) {
       console.log('Error parsing style file');
       return false;
@@ -1145,7 +1146,7 @@ export const serve_rendered = {
         }
 
         if (!isValidHttpUrl(inputFile)) {
-          const inputFileStats = fs.statSync(inputFile);
+          const inputFileStats = await fsp.stat(inputFile);
           if (!inputFileStats.isFile() || inputFileStats.size === 0) {
             throw Error(`Not valid PMTiles file: "${inputFile}"`);
           }
@@ -1187,9 +1188,9 @@ export const serve_rendered = {
           }
         } else {
           queue.push(
-            new Promise((resolve, reject) => {
+            new Promise(async (resolve, reject) => {
               inputFile = path.resolve(options.paths.mbtiles, inputFile);
-              const inputFileStats = fs.statSync(inputFile);
+              const inputFileStats = await fsp.stat(inputFile);
               if (!inputFileStats.isFile() || inputFileStats.size === 0) {
                 throw Error(`Not valid MBTiles file: "${inputFile}"`);
               }

src/serve_style.js

@@ -87,7 +87,7 @@ export const serve_style = {
 
     let styleFileData;
     try {
-      styleFileData = fs.readFileSync(styleFile);
+      styleFileData = fs.readFileSync(styleFile); // TODO: could be made async if this function was
     } catch (e) {
       console.log('Error reading style file');
       return false;

src/utils.js

@@ -2,9 +2,10 @@
 
 import path from 'path';
 import fsPromises from 'fs/promises';
-import fs, { existsSync } from 'node:fs';
+import fs from 'node:fs';
 import clone from 'clone';
 import { combine } from '@jsse/pbfont';
+import { existsP } from './promises.js';
 
 /**
  * Restrict user input to an allowed set of options.
@@ -225,7 +226,7 @@ export const listFonts = async (fontPath) => {
     const stats = await fsPromises.stat(path.join(fontPath, file));
     if (
       stats.isDirectory() &&
-      existsSync(path.join(fontPath, file, '0-255.pbf'))
+      (await existsP(path.join(fontPath, file, '0-255.pbf')))
     ) {
       existingFonts[path.basename(file)] = true;
     }