feat(xo-server/file restore): dedupe mount/unmount (#4961)

packages/xo-server/src/_dedupeUnmount.js

@@ -0,0 +1,45 @@
+import assert from 'assert'
+
+import ensureArray from './_ensureArray'
+import MultiKeyMap from './_MultiKeyMap'
+
+function State() {
+  this.i = 0
+  this.value = undefined
+}
+
+export const dedupeUnmount = (fn, keyFn) => {
+  const states = new MultiKeyMap()
+
+  return function() {
+    const keys = ensureArray(keyFn.apply(this, arguments))
+    let state = states.get(keys)
+    if (state === undefined) {
+      state = new State()
+      states.set(keys, state)
+
+      const mount = async () => {
+        try {
+          const value = await fn.apply(this, arguments)
+          return {
+            __proto__: value,
+            async unmount() {
+              assert(state.i > 0)
+              if (--state.i === 0) {
+                states.delete(keys)
+                await value.unmount()
+              }
+            },
+          }
+        } catch (error) {
+          states.delete(keys)
+          throw error
+        }
+      }
+
+      state.value = mount()
+    }
+    ++state.i
+    return state.value
+  }
+}

packages/xo-server/src/xo-mixins/file-restore-ng.js

@@ -6,9 +6,15 @@ import { normalize } from 'path'
 import { readdir, rmdir, stat } from 'fs-extra'
 import { ZipFile } from 'yazl'
 
+import { decorateWith } from '../_decorateWith'
+import { dedupeUnmount } from '../_dedupeUnmount'
 import { lvs, pvs } from '../lvm'
 import { resolveSubpath, tmpDir } from '../utils'
 
+const compose = (...fns) => value => fns.reduce((value, fn) => fn(value), value)
+
+const dedupeUnmountWithArgs = fn => dedupeUnmount(fn, (...args) => args)
+
 const IGNORED_PARTITION_TYPES = {
   // https://github.com/jhermsmeier/node-mbr/blob/master/lib/partition.js#L38
   0x05: true,
@@ -60,8 +66,10 @@ const parsePartxLine = createPairsParser({
       : value,
 })
 
-const listLvmLogicalVolumes = defer(
-  async ($defer, devicePath, partition, results = []) => {
+const listLvmLogicalVolumes = compose(
+  defer,
+  dedupeUnmountWithArgs
+)(async ($defer, devicePath, partition, results = []) => {
   const pv = await mountLvmPhysicalVolume(devicePath, partition)
   $defer(pv.unmount)
 
@@ -78,10 +86,10 @@ const listLvmLogicalVolumes = defer(
     }
   })
   return results
-  }
-)
+})
 
-async function mountLvmPhysicalVolume(devicePath, partition) {
+const mountLvmPhysicalVolume = dedupeUnmountWithArgs(
+  async (devicePath, partition) => {
     const args = []
     if (partition !== undefined) {
       args.push('-o', partition.start * 512)
@@ -101,9 +109,13 @@ async function mountLvmPhysicalVolume(devicePath, partition) {
         }
       },
     }
-}
+  }
+)
 
-const mountPartition = defer(async ($defer, devicePath, partition) => {
+const mountPartition = compose(
+  defer,
+  dedupeUnmountWithArgs
+)(async ($defer, devicePath, partition) => {
   const options = ['loop', 'ro']
 
   if (partition !== undefined) {
@@ -280,6 +292,7 @@ export default class BackupNgFileRestore {
     return partitions
   }
 
+  @decorateWith(dedupeUnmountWithArgs)
   @defer
   async _mountDisk($defer, remoteId, diskId) {
     const handler = await this._app.getRemoteHandler(remoteId)
@@ -321,6 +334,7 @@ export default class BackupNgFileRestore {
     }
   }
 
+  @decorateWith(dedupeUnmountWithArgs)
   @defer
   async _mountPartition($defer, devicePath, partitionId) {
     if (partitionId === undefined) {