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fs: improve fs.watch ENOSPC error message
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Providing `No space left on device` is misleading in this case.
Replace it with something that describes it more accurately.

Refs: https://stackoverflow.com/questions/22475849/node-js-error-enospc/32600959

PR-URL: #21846
Reviewed-By: James M Snell <[email protected]>
Reviewed-By: Luigi Pinca <[email protected]>
Reviewed-By: Michaël Zasso <[email protected]>
Reviewed-By: Ruben Bridgewater <[email protected]>
Reviewed-By: Sakthipriyan Vairamani <[email protected]>
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addaleax authored and targos committed Sep 23, 2018
1 parent 9de6b26 commit c29734c
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Showing 3 changed files with 56 additions and 2 deletions.
2 changes: 1 addition & 1 deletion lib/internal/errors.js
Original file line number Diff line number Diff line change
Expand Up @@ -249,7 +249,7 @@ function getMessage(key, args) {
*/
function uvException(ctx) {
const [ code, uvmsg ] = errmap.get(ctx.errno);
let message = `${code}: ${uvmsg}, ${ctx.syscall}`;
let message = `${code}: ${ctx.message || uvmsg}, ${ctx.syscall}`;

let path;
let dest;
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5 changes: 4 additions & 1 deletion lib/internal/fs/watchers.js
Original file line number Diff line number Diff line change
Expand Up @@ -6,6 +6,7 @@ const {
StatWatcher: _StatWatcher
} = process.binding('fs');
const { FSEvent } = process.binding('fs_event_wrap');
const { UV_ENOSPC } = process.binding('uv');
const { EventEmitter } = require('events');
const {
getStatsFromBinding,
Expand Down Expand Up @@ -164,7 +165,9 @@ FSWatcher.prototype.start = function(filename,
const error = errors.uvException({
errno: err,
syscall: 'watch',
path: filename
path: filename,
message: err === UV_ENOSPC ?
'System limit for number of file watchers reached' : ''
});
error.filename = filename;
throw error;
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51 changes: 51 additions & 0 deletions test/sequential/test-fs-watch-system-limit.js
Original file line number Diff line number Diff line change
@@ -0,0 +1,51 @@
'use strict';
const common = require('../common');
const assert = require('assert');
const child_process = require('child_process');
const stream = require('stream');

if (!common.isLinux)
common.skip('The fs watch limit is OS-dependent');
if (!common.enoughTestCpu)
common.skip('This test is resource-intensive');

const processes = [];
const gatherStderr = new stream.PassThrough();
gatherStderr.setEncoding('utf8');
gatherStderr.setMaxListeners(Infinity);

let finished = false;
function spawnProcesses() {
for (let i = 0; i < 10; ++i) {
const proc = child_process.spawn(
process.execPath,
[ '-e',
`process.chdir(${JSON.stringify(__dirname)});
for (const file of fs.readdirSync('.'))
fs.watch(file, () => {});`
], { stdio: ['inherit', 'inherit', 'pipe'] });
proc.stderr.pipe(gatherStderr);
processes.push(proc);
}

setTimeout(() => {
if (!finished && processes.length < 200)
spawnProcesses();
}, 100);
}

spawnProcesses();

let accumulated = '';
gatherStderr.on('data', common.mustCallAtLeast((chunk) => {
accumulated += chunk;
if (accumulated.includes('Error:') && !finished) {
assert(
accumulated.includes('ENOSPC: System limit for number ' +
'of file watchers reached'),
accumulated);
console.log(`done after ${processes.length} processes, cleaning up`);
finished = true;
processes.forEach((proc) => proc.kill());
}
}, 1));

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