fix(backups/IncrementalRemote): ensure chaining is ok and mutualize code with IncrementalXapi

@xen-orchestra/backups/_runners/_vmRunners/IncrementalRemote.mjs

@@ -2,6 +2,7 @@ import { asyncEach } from '@vates/async-each'
 import { decorateMethodsWith } from '@vates/decorate-with'
 import { defer } from 'golike-defer'
 import assert from 'node:assert'
+import * as UUID from 'uuid'
 import isVhdDifferencingDisk from 'vhd-lib/isVhdDifferencingDisk.js'
 import mapValues from 'lodash/mapValues.js'
 
@@ -9,11 +10,48 @@ import { AbstractRemote } from './_AbstractRemote.mjs'
 import { forkDeltaExport } from './_forkDeltaExport.mjs'
 import { IncrementalRemoteWriter } from '../_writers/IncrementalRemoteWriter.mjs'
 import { Task } from '../../Task.mjs'
+import { Disposable } from 'promise-toolbox'
+import { openVhd } from 'vhd-lib'
+import { getVmBackupDir } from '../../_getVmBackupDir.mjs'
 
 class IncrementalRemoteVmBackupRunner extends AbstractRemote {
   _getRemoteWriter() {
     return IncrementalRemoteWriter
   }
+  async _selectBaseVm(metadata) {
+    // for each disk , get the parent
+    const baseUuidToSrcVdi = new Map()
+
+    // no previous backup for a base( =key) backup
+    if (metadata.isBase) {
+      return
+    }
+    await asyncEach(Object.entries(metadata.vdis), async ([id, vdi]) => {
+      const isDifferencing = metadata.isVhdDifferencing[`${id}.vhd`]
+      if (isDifferencing) {
+        const vmDir = getVmBackupDir(metadata.vm.uuid)
+        const path = `${vmDir}/${metadata.vhds[id]}`
+        // don't catch error : we can't recover if the source vhd are missing
+        await Disposable.use(openVhd(this._sourceRemoteAdapter._handler, path), vhd => {
+          baseUuidToSrcVdi.set(UUID.stringify(vhd.header.parentUuid), vdi.$snapshot_of$uuid)
+        })
+      }
+    })
+
+    const presentBaseVdis = new Map(baseUuidToSrcVdi)
+    await this._callWriters(
+      writer => presentBaseVdis.size !== 0 && writer.checkBaseVdis(presentBaseVdis),
+      'writer.checkBaseVdis()',
+      false
+    )
+    // check if the parent vdi are present in all the remotes
+    baseUuidToSrcVdi.forEach((srcVdiUuid, baseUuid) => {
+      if (!presentBaseVdis.has(baseUuid)) {
+        throw new Error(`Missing vdi ${baseUuid} which is a base for a delta`)
+      }
+    })
+    // yeah , let's go
+  }
   async _run($defer) {
     const transferList = await this._computeTransferList(({ mode }) => mode === 'delta')
     await this._callWriters(async writer => {
@@ -26,7 +64,7 @@ class IncrementalRemoteVmBackupRunner extends AbstractRemote {
     if (transferList.length > 0) {
       for (const metadata of transferList) {
         assert.strictEqual(metadata.mode, 'delta')
-
+        await this._selectBaseVm(metadata)
         await this._callWriters(writer => writer.prepare({ isBase: metadata.isBase }), 'writer.prepare()')
         const incrementalExport = await this._sourceRemoteAdapter.readIncrementalVmBackup(metadata, undefined, {
           useChain: false,
@@ -50,6 +88,17 @@ class IncrementalRemoteVmBackupRunner extends AbstractRemote {
             }),
           'writer.transfer()'
         )
+        // this will update parent name with the needed alias
+        await this._callWriters(
+          writer =>
+            writer.updateUuidAndChain({
+              isVhdDifferencing,
+              timestamp: metadata.timestamp,
+              vdis: incrementalExport.vdis,
+            }),
+          'writer.updateUuidAndChain()'
+        )
+
         await this._callWriters(writer => writer.cleanup(), 'writer.cleanup()')
         // for healthcheck
         this._tags = metadata.vm.tags