153 lines
3.4 KiB
JavaScript
153 lines
3.4 KiB
JavaScript
'use strict';
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/**
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* file-locking.js - file system locking (replaces fs-ext)
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*/
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const async = require('async');
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const locker = require('lockfile');
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const fs = require('fs');
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const path = require('path');
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// locks a file by creating a lock file
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const lockFile = function(name, next) {
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const lockFileName = `${name}.lock`;
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const lockOpts = {
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wait: 1000, // time (ms) to wait when checking for stale locks
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pollPeriod: 100, // how often (ms) to re-check stale locks
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stale: 5 * 60 * 1000, // locks are considered stale after 5 minutes
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retries: 100, // number of times to attempt to create a lock
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retryWait: 100, // time (ms) between tries
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};
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async.series({
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statdir: function(callback) {
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// test to see if the directory exists
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fs.stat(path.dirname(name), function(err, stats) {
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if (err) {
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callback(err);
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} else if (!stats.isDirectory()) {
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callback(new Error(path.dirname(name) + ' is not a directory'));
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} else {
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callback(null);
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}
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});
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},
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statfile: function(callback) {
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// test to see if the file to lock exists
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fs.stat(name, function(err, stats) {
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if (err) {
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callback(err);
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} else if (!stats.isFile()) {
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callback(new Error(path.dirname(name) + ' is not a file'));
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} else {
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callback(null);
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}
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});
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},
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lockfile: function(callback) {
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// try to lock the file
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locker.lock(lockFileName, lockOpts, callback);
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},
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}, function(err) {
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if (err) {
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// lock failed
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return next(err);
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}
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// lock succeeded
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return next(null);
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});
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};
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// unlocks file by removing existing lock file
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const unlockFile= function(name, next) {
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const lockFileName = `${name}.lock`;
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locker.unlock(lockFileName, function(err) {
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if (err) {
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return next(err);
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}
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return next(null);
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});
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};
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/**
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* Reads a local file, which involves
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* optionally taking a lock
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* reading the file contents
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* optionally parsing JSON contents
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* @param {*} name
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* @param {*} options
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* @param {*} next
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*/
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function readFile(name, options, next) {
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if (typeof options === 'function' && next === null) {
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next = options;
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options = {};
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}
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options = options || {};
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options.lock = options.lock || false;
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options.parse = options.parse || false;
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const lock = function(callback) {
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if (!options.lock) {
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return callback(null);
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}
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lockFile(name, function(err) {
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if (err) {
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return callback(err);
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}
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return callback(null);
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});
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};
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const read = function(callback) {
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fs.readFile(name, 'utf8', function(err, contents) {
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if (err) {
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return callback(err);
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}
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callback(null, contents);
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});
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};
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const parseJSON = function(contents, callback) {
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if (!options.parse) {
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return callback(null, contents);
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}
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try {
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contents = JSON.parse(contents);
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return callback(null, contents);
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} catch (err) {
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return callback(err);
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}
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};
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async.waterfall([
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lock,
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read,
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parseJSON,
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],
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function(err, result) {
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if (err) {
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return next(err);
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} else {
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return next(null, result);
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}
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});
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}
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exports.lockFile = lockFile;
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exports.unlockFile = unlockFile;
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exports.readFile = readFile;
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