diff --git a/src/index.js b/src/index.js index 7e995e9..9c70324 100644 --- a/src/index.js +++ b/src/index.js @@ -4,7 +4,7 @@ const fs = require('fs') const glob = require('glob') const mkdirp = require('mkdirp') const promisify = require('util').promisify -const writeFile = promisify(require('fast-write-atomic')) +const writeAtomic = promisify(require('fast-write-atomic')) const path = require('path') const filter = require('interface-datastore').utils.filter @@ -22,6 +22,26 @@ const fsUnlink = promisify(fs.unlink || noop) const Key = IDatastore.Key const Errors = IDatastore.Errors +async function writeFile (path, contents) { + try { + await writeAtomic(path, contents) + } catch (err) { + if (err.code === 'EPERM' && err.syscall === 'rename') { + // fast-write-atomic writes a file to a temp location before renaming it. + // On Windows, if the final file already exists this error is thrown. + // No such error is thrown on Linux/Mac + // Make sure we can read & write to this file + await fsAccess(path, fs.constants.F_OK | fs.constants.W_OK) + + // The file was created by another context - this means there were + // attempts to write the same block by two different function calls + return + } + + throw err + } +} + /** * A datastore backed by the file system. * diff --git a/test/index.spec.js b/test/index.spec.js index 172d79e..125adbe 100644 --- a/test/index.spec.js +++ b/test/index.spec.js @@ -172,4 +172,19 @@ describe('FsDatastore', () => { } }) }) + + it('can survive concurrent writes', async () => { + const dir = utils.tmpdir() + const fstore = new FsStore(dir) + const key = new Key('CIQGFTQ7FSI2COUXWWLOQ45VUM2GUZCGAXLWCTOKKPGTUWPXHBNIVOY') + const value = Buffer.from('Hello world') + + await Promise.all( + new Array(100).fill(0).map(() => fstore.put(key, value)) + ) + + const res = await fstore.get(key) + + expect(res).to.deep.equal(value) + }) })