fix(xapi): respect the config file setting for preferNbd (#8780)

* fix(nbd-client): handle unreachable VM through nbd

when the user select nbd but don't have any way to reach
the storage/host of the VM (for example no NBD enabled network,
or a NBD enabled network unreachable by xo/proxy it was timing out
and blocking the start of the backup
This error was blocking the fallback to export stream mechanism

* fix(xapi): respect the config file setting for preferNbd

* fix(xapi): don't close export stream if nbd failed to connect

* fix(xapi):respect vhd/qcow2 when faling back to a full if delta exports fails

@vates/nbd-client/multi.mjs

@@ -70,7 +70,9 @@ export default class MultiNbdClient {
       await _connect()
     }
     if (this.#clients.length === 0) {
-      throw new Error(`Fail to connect to any Nbd client`)
+      const error = new Error(`Fail to connect to any Nbd client`, { nbdInfos: this.#settings })
+      error.code = 'NO_NBD_AVAILABLE'
+      throw error
     }
     if (this.#clients.length < this.#nbdConcurrency) {
       warn(

@xen-orchestra/xapi/disks/Xapi.mjs

@@ -52,7 +52,7 @@ export class XapiDiskSource extends DiskPassthrough {
    * @param {number} [params.nbdConcurrency=2]
    * @param {number} [params.blockSize=2*1024*1024]
    */
-  constructor({ xapi, vdiRef, baseRef, preferNbd = true, nbdConcurrency = 2, blockSize = 2 * 1024 * 1024 }) {
+  constructor({ xapi, vdiRef, baseRef, preferNbd = xapi._preferNbd, nbdConcurrency = 2, blockSize = 2 * 1024 * 1024 }) {
     super(undefined)
     this.#baseRef = baseRef
     this.#blockSize = blockSize
@@ -89,17 +89,15 @@ export class XapiDiskSource extends DiskPassthrough {
         source = new DiskLargerBlock(source, this.#blockSize)
       }
     } catch (err) {
-      await source?.close()
       if (err.code === 'NO_NBD_AVAILABLE') {
         warn(`can't connect through NBD, fallback to stream export`)
         if (streamSource === undefined) {
           throw new Error(`Can't open stream source`)
         }
         return streamSource
-      } else {
-        await streamSource?.close()
-        throw err
       }
+      await source?.close() // this will close source and stream source
+      throw err
     }
     this.#useNbd = true
     const readAhead = new ReadAhead(source)
@@ -128,15 +126,14 @@ export class XapiDiskSource extends DiskPassthrough {
         source = new XapiQcow2StreamSource({ vdiRef, baseRef, xapi })
       }
       await source.init()
-    } catch (err) {
+    } catch (error) {
       await source?.close()
-      if (err.code === 'VDI_CANT_DO_DELTA') {
-        warn(`can't compute delta of XapiVhdStreamSource ${vdiRef} from ${baseRef}, fallBack to a full`)
-        // @todo : should clear CBT status since it probably a little broken
-        source = new XapiVhdStreamSource({ vdiRef, baseRef: undefined, xapi })
-        await source.init()
+      if (baseRef !== undefined) {
+        warn(`can't compute delta ${vdiRef} from ${baseRef}, fallBack to a full`, { error })
+        this.#baseRef = undefined
+        return this.#openExportStream()
       } else {
-        throw err
+        throw error
       }
     }
     return source

CHANGELOG.unreleased.md

@@ -25,6 +25,7 @@
   - [Charts] Fix tooltip overflow when too close to the edge [Forum#11012](https://xcp-ng.org/forum/topic/11012/graph-in-v0.12.0-48bf9/2) (PR [#8779](https://github.com/vatesfr/xen-orchestra/pull/8779))
 
 - [VM/New] Fix `Cannot read properties of undefined (reading '$ref')` when creating VM configured to PXE boot (PR [#8782](https://github.com/vatesfr/xen-orchestra/pull/8782))
+- [Backups] fix backup job getting stuck without NBD (PR [#8780](https://github.com/vatesfr/xen-orchestra/pull/8780))
 
 ### Packages to release
 
@@ -42,6 +43,7 @@
 
 <!--packages-start-->
 
+- @vates/nbd-client patch
 - @vates/types minor
 - @xen-orchestra/rest-api minor
 - @xen-orchestra/web-core minor