Retry fs operations on EAGAIN error

graceful-fs.js

@@ -116,7 +116,7 @@ function patch (fs) {
 
     function go$readFile (path, options, cb, startTime) {
       return fs$readFile(path, options, function (err) {
-        if (err && (err.code === 'EMFILE' || err.code === 'ENFILE'))
+        if (err && (err.code === 'EMFILE' || err.code === 'ENFILE' || err.code === 'EAGAIN'))
           enqueue([go$readFile, [path, options, cb], err, startTime || Date.now(), Date.now()])
         else {
           if (typeof cb === 'function')
@@ -136,7 +136,7 @@ function patch (fs) {
 
     function go$writeFile (path, data, options, cb, startTime) {
       return fs$writeFile(path, data, options, function (err) {
-        if (err && (err.code === 'EMFILE' || err.code === 'ENFILE'))
+        if (err && (err.code === 'EMFILE' || err.code === 'ENFILE' || err.code === 'EAGAIN'))
           enqueue([go$writeFile, [path, data, options, cb], err, startTime || Date.now(), Date.now()])
         else {
           if (typeof cb === 'function')
@@ -157,7 +157,7 @@ function patch (fs) {
 
     function go$appendFile (path, data, options, cb, startTime) {
       return fs$appendFile(path, data, options, function (err) {
-        if (err && (err.code === 'EMFILE' || err.code === 'ENFILE'))
+        if (err && (err.code === 'EMFILE' || err.code === 'ENFILE' || err.code === 'EAGAIN'))
           enqueue([go$appendFile, [path, data, options, cb], err, startTime || Date.now(), Date.now()])
         else {
           if (typeof cb === 'function')
@@ -179,7 +179,7 @@ function patch (fs) {
 
     function go$copyFile (src, dest, flags, cb, startTime) {
       return fs$copyFile(src, dest, flags, function (err) {
-        if (err && (err.code === 'EMFILE' || err.code === 'ENFILE'))
+        if (err && (err.code === 'EMFILE' || err.code === 'ENFILE' || err.code === 'EAGAIN'))
           enqueue([go$copyFile, [src, dest, flags, cb], err, startTime || Date.now(), Date.now()])
         else {
           if (typeof cb === 'function')
@@ -212,7 +212,7 @@ function patch (fs) {
 
     function fs$readdirCallback (path, options, cb, startTime) {
       return function (err, files) {
-        if (err && (err.code === 'EMFILE' || err.code === 'ENFILE'))
+        if (err && (err.code === 'EMFILE' || err.code === 'ENFILE' || err.code === 'EAGAIN'))
           enqueue([
             go$readdir,
             [path, options, cb],
@@ -355,7 +355,7 @@ function patch (fs) {
 
     function go$open (path, flags, mode, cb, startTime) {
       return fs$open(path, flags, mode, function (err, fd) {
-        if (err && (err.code === 'EMFILE' || err.code === 'ENFILE'))
+        if (err && (err.code === 'EMFILE' || err.code === 'ENFILE' || err.code === 'EAGAIN'))
           enqueue([go$open, [path, flags, mode, cb], err, startTime || Date.now(), Date.now()])
         else {
           if (typeof cb === 'function')

test/eagain.js

@@ -0,0 +1,118 @@
+'use strict'
+
+var importFresh = require('import-fresh')
+var path = require('path')
+var realFs = require('fs')
+var test = require('tap').test
+
+var EAGAIN = Object.assign(new Error('FAKE EAGAIN'), { code: 'EAGAIN' })
+
+test('EAGAIN readFile is retried and eventually succeeds', function (t) {
+  var readFile = realFs.readFile
+  var eagainCount = 0
+
+  t.teardown(function () {
+    realFs.readFile = readFile
+  })
+
+  realFs.readFile = function (path, options, cb) {
+    process.nextTick(function () {
+      if (eagainCount < 3) {
+        eagainCount++
+        return cb(EAGAIN)
+      }
+      // succeed after 3 retries
+      cb(null, Buffer.from('test content'))
+    })
+  }
+
+  var fs = importFresh(path.dirname(__dirname))
+  fs.readFile('literally anything', function (err, data) {
+    t.notOk(err, 'should not get an error')
+    t.equal(eagainCount, 3, 'should have retried 3 times')
+    t.equal(data.toString(), 'test content', 'should get the content')
+    t.end()
+  })
+})
+
+test('EAGAIN eventually times out and returns error', function (t) {
+  var readFile = realFs.readFile
+  var realNow = Date.now
+
+  t.teardown(function () {
+    realFs.readFile = readFile
+    Date.now = realNow
+  })
+
+  realFs.readFile = function (path, options, cb) {
+    process.nextTick(function () {
+      cb(EAGAIN)
+      // hijack Date.now _after_ we call the callback, the callback will
+      // call it when adding the job to the queue, we want to capture it
+      // any time after that first call so we can pretend it's been 60s
+      Date.now = function () {
+        return realNow() + 60000
+      }
+    })
+  }
+
+  var fs = importFresh(path.dirname(__dirname))
+  fs.readFile('literally anything', function (err) {
+    t.equal(err.code, 'EAGAIN', 'eventually got the EAGAIN')
+    t.end()
+  })
+})
+
+test('EAGAIN open is retried and eventually succeeds', function (t) {
+  var open = realFs.open
+  var eagainCount = 0
+
+  t.teardown(function () {
+    realFs.open = open
+  })
+
+  realFs.open = function (path, flags, mode, cb) {
+    process.nextTick(function () {
+      if (eagainCount < 2) {
+        eagainCount++
+        return cb(EAGAIN)
+      }
+      // succeed after 2 retries with a fake fd
+      cb(null, 42)
+    })
+  }
+
+  var fs = importFresh(path.dirname(__dirname))
+  fs.open('literally anything', 'r', function (err, fd) {
+    t.notOk(err, 'should not get an error')
+    t.equal(eagainCount, 2, 'should have retried 2 times')
+    t.equal(fd, 42, 'should get the fd')
+    t.end()
+  })
+})
+
+test('EAGAIN writeFile is retried and eventually succeeds', function (t) {
+  var writeFile = realFs.writeFile
+  var eagainCount = 0
+
+  t.teardown(function () {
+    realFs.writeFile = writeFile
+  })
+
+  realFs.writeFile = function (path, data, options, cb) {
+    process.nextTick(function () {
+      if (eagainCount < 2) {
+        eagainCount++
+        return cb(EAGAIN)
+      }
+      cb(null)
+    })
+  }
+
+  var fs = importFresh(path.dirname(__dirname))
+  fs.writeFile('literally anything', 'data', function (err) {
+    t.notOk(err, 'should not get an error')
+    t.equal(eagainCount, 2, 'should have retried 2 times')
+    t.end()
+  })
+})