fix(xo-server/worker): forget remote after use (#4079)

Fixes xoa-support#1378
Fixes xoa-support#1384
Fixes xoa-support#1399

CHANGELOG.unreleased.md

@@ -2,7 +2,7 @@
 
 ### Enhancements
 
-- [Remote] Benchmarks (read and write rate speed) added when remote is tested [#3991](https://github.com/vatesfr/xen-orchestra/issues/3991) (PR [#4015](https://github.com/vatesfr/xen-orchestra/pull/4015))
+- [Remotes] Benchmarks (read and write rate speed) added when remote is tested [#3991](https://github.com/vatesfr/xen-orchestra/issues/3991) (PR [#4015](https://github.com/vatesfr/xen-orchestra/pull/4015))
 - [Cloud Config] Support both NoCloud and Config Drive 2 datasources for maximum compatibility (PR [#4053](https://github.com/vatesfr/xen-orchestra/pull/4053))
 - [Advanced] Configurable cookie validity (PR [#4059](https://github.com/vatesfr/xen-orchestra/pull/4059))
 - [Plugins] Display number of installed plugins [#4008](https://github.com/vatesfr/xen-orchestra/issues/4008) (PR [#4050](https://github.com/vatesfr/xen-orchestra/pull/4050))
@@ -10,6 +10,7 @@
 ### Bug fixes
 
 - [Home] Always sort the items by their names as a secondary sort criteria [#3983](https://github.com/vatesfr/xen-orchestra/issues/3983) (PR [#4047](https://github.com/vatesfr/xen-orchestra/pull/4047))
+- [Remotes] Fixes `spawn mount EMFILE` error during backup
 - Properly redirect to sign in page instead of being stuck in a refresh loop
 
 ### Released packages

packages/xo-server/src/xo-mixins/workers/worker.js

@@ -1,5 +1,6 @@
 // @flow
 
+import defer from 'golike-defer'
 import { type Remote, getHandler } from '@xen-orchestra/fs'
 import { mergeVhd as mergeVhd_ } from 'vhd-lib'
 
@@ -12,7 +13,8 @@ global.Promise = require('bluebird')
 // $FlowFixMe
 const config: Object = JSON.parse(process.env.XO_CONFIG)
 
-export async function mergeVhd(
+export const mergeVhd = defer(async function(
+  $defer: any,
   parentRemote: Remote,
   parentPath: string,
   childRemote: Remote,
@@ -21,9 +23,11 @@ export async function mergeVhd(
   const parentHandler = getHandler(parentRemote, config.remoteOptions)
   const childHandler = getHandler(childRemote, config.remoteOptions)
 
-  // DO NOT forget the handlers as it they are still in use in the main process
   await parentHandler.sync()
+  $defer.call(parentHandler, 'forget')
+
   await childHandler.sync()
+  $defer.call(childHandler, 'forget')
 
   return mergeVhd_(parentHandler, parentPath, childHandler, childPath)
-}
+})