[pbs-devel] [RFC v2 proxmox-backup 29/42] datastore: create/delete protected marker file on S3 storage backend

[Christian Ebner]

Commit 8292d3d2 ("api2/admin/datastore: add get/set_protection")
introduced the protected flag for backup snapshots, considering
snapshots as protected based on the presence/absence of the
`.protected` marker file in the corresponding snapshot directory.

To allow independent recovery of a datastore backed by an S3 bucket,
also create/delete the marker file on the object store backend. For
actual checks, still rely on the marker as encountered in the local
cache store.

Signed-off-by: Christian Ebner <c.ebner at proxmox.com>
---
 pbs-datastore/src/datastore.rs | 45 ++++++++++++++++++++++++++++++----
 1 file changed, 40 insertions(+), 5 deletions(-)

diff --git a/pbs-datastore/src/datastore.rs b/pbs-datastore/src/datastore.rs
index ab5c22501..5c8b49947 100644
--- a/pbs-datastore/src/datastore.rs
+++ b/pbs-datastore/src/datastore.rs
@@ -1539,12 +1539,47 @@ impl DataStore {
 
         let protected_path = backup_dir.protected_file();
         if protection {
-            std::fs::File::create(protected_path)
+            std::fs::File::create(&protected_path)
                 .map_err(|err| format_err!("could not create protection file: {}", err))?;
-        } else if let Err(err) = std::fs::remove_file(protected_path) {
-            // ignore error for non-existing file
-            if err.kind() != std::io::ErrorKind::NotFound {
-                bail!("could not remove protection file: {}", err);
+            if let DatastoreBackend::S3(s3_client) = self.backend()? {
+                let marker = backup_dir.relative_path().join(".protected");
+                let protected_marker = marker
+                    .to_str()
+                    .ok_or_else(|| format_err!("unexpected protected marker path"))?;
+                let response = proxmox_async::runtime::block_on(
+                    s3_client.put_object(protected_marker.into(), hyper::body::Body::empty()),
+                )?;
+                match response {
+                    PutObjectResponse::NeedsRetry => {
+                        let _ = std::fs::remove_file(protected_path);
+                        bail!("failed to mark snapshot as protected, needs retry")
+                    }
+                    PutObjectResponse::PreconditionFailed => {
+                        let _ = std::fs::remove_file(protected_path);
+                        bail!("failed to mark snapshot as protected, precondition failed")
+                    }
+                    PutObjectResponse::Success(_) => (),
+                }
+            }
+        } else {
+            if let Err(err) = std::fs::remove_file(&protected_path) {
+                // ignore error for non-existing file
+                if err.kind() != std::io::ErrorKind::NotFound {
+                    bail!("could not remove protection file: {err}");
+                }
+            }
+            if let DatastoreBackend::S3(s3_client) = self.backend()? {
+                let marker = backup_dir.relative_path().join(".protected");
+                let protected_marker = marker
+                    .to_str()
+                    .ok_or_else(|| format_err!("unexpected protected marker path"))?;
+                if let Err(err) = proxmox_async::runtime::block_on(
+                    s3_client.delete_object(protected_marker.into()),
+                ) {
+                    std::fs::File::create(&protected_path)
+                        .map_err(|err| format_err!("could not re-create protection file: {err}"))?;
+                    return Err(err);
+                }
             }
         }
 
-- 
2.39.5