[pbs-devel] [PATCH proxmox-backup] client: catalog: improve error message for missing catalog

[Christian Ebner]

Commit c0302805c "client: backup: conditionally write catalog for
file level backups" drops encoding of the dedicated catalog when
archives are encoded as split metadata/data archives with the
`change-detection-mode` set to `data` or `metadata`.

Since the catalog is not present anymore, accessing these snapshots
via the `proxmox-backup-client catalog` command is obsolete for these
cases, one should opt for the `proxmox-backup-client mount` command
to inspect these archives instead.

Improve the error message one gets when trying to access such
snapshots by checking if the catalog is present in the manifest and if
not, check if it contains a split pxar archive.

A caller now gets the following error message:

```
no catalog for split pxar archives, use `mount` instead to inspect content
```

instead of the rather generic

```
Unable to open dynamic index "/<snapshot-path>/catalog.pcat1.didx"
- No such file or directory (os error 2)
```

Reported in the community forum:
https://forum.proxmox.com/threads/150713/

Signed-off-by: Christian Ebner <c.ebner at proxmox.com>
---
 proxmox-backup-client/src/catalog.rs | 25 +++++++++++++++++++++++--
 1 file changed, 23 insertions(+), 2 deletions(-)

diff --git a/proxmox-backup-client/src/catalog.rs b/proxmox-backup-client/src/catalog.rs
index 276457c1d..7e3bdd4e9 100644
--- a/proxmox-backup-client/src/catalog.rs
+++ b/proxmox-backup-client/src/catalog.rs
@@ -14,6 +14,7 @@ use pbs_client::tools::key_source::get_encryption_key_password;
 use pbs_client::{BackupReader, RemoteChunkReader};
 use pbs_tools::crypt_config::CryptConfig;
 use pbs_tools::json::required_string_param;
+use pbs_datastore::manifest::{BackupManifest, FileInfo};
 
 use crate::helper;
 use crate::{
@@ -24,6 +25,24 @@ use crate::{
     IndexFile, Shell, CATALOG_NAME, KEYFD_SCHEMA, REPO_URL_SCHEMA,
 };
 
+fn lookup_catalog_file_info(manifest: &BackupManifest) -> Result<&FileInfo, Error> {
+    let file_info = match manifest.lookup_file_info(CATALOG_NAME) {
+        Ok(file_info) => file_info,
+        Err(err) => {
+            for file_info in manifest.files() {
+                if file_info.filename.ends_with(".mpxar.didx") {
+                    bail!(
+                        "no catalog for split pxar archives, use `mount` instead to inspect content"
+                    );
+                }
+            }
+            return Err(err);
+        }
+    };
+
+    Ok(file_info)
+}
+
 #[api(
    input: {
         properties: {
@@ -89,14 +108,14 @@ async fn dump_catalog(param: Value) -> Result<Value, Error> {
     let (manifest, _) = client.download_manifest().await?;
     manifest.check_fingerprint(crypt_config.as_ref().map(Arc::as_ref))?;
 
+    let file_info = lookup_catalog_file_info(&manifest)?;
+
     let index = client
         .download_dynamic_index(&manifest, CATALOG_NAME)
         .await?;
 
     let most_used = index.find_most_used_chunks(8);
 
-    let file_info = manifest.lookup_file_info(CATALOG_NAME)?;
-
     let chunk_reader = RemoteChunkReader::new(
         client.clone(),
         crypt_config,
@@ -207,6 +226,8 @@ async fn catalog_shell(param: Value) -> Result<(), Error> {
     let (manifest, _) = client.download_manifest().await?;
     manifest.check_fingerprint(crypt_config.as_ref().map(Arc::as_ref))?;
 
+    lookup_catalog_file_info(&manifest)?;
+
     let decoder = helper::get_pxar_fuse_accessor(
         &server_archive_name,
         client.clone(),
-- 
2.39.2