[pbs-devel] [PATCH proxmox-backup v9 43/46] datastore: mark store as in-use by setting marker on s3 backend

[Christian Ebner]

Adds an in-use marker on the S3 store to protect from accidental reuse
of the same datastore by multiple Proxmox Backup Server instances. Set
the marker file on store creation.

The local cache folder is however always assumed to be empty and needs
creation on datastore creation to guarantee consistency.

Signed-off-by: Christian Ebner <c.ebner at proxmox.com>
---
changes since version 8:
- no changes

 src/api2/config/datastore.rs | 44 +++++++++++++++++++++++++++++++++++-
 1 file changed, 43 insertions(+), 1 deletion(-)

diff --git a/src/api2/config/datastore.rs b/src/api2/config/datastore.rs
index 9b87e01f2..67ce6505b 100644
--- a/src/api2/config/datastore.rs
+++ b/src/api2/config/datastore.rs
@@ -4,6 +4,7 @@ use std::sync::Arc;
 use ::serde::{Deserialize, Serialize};
 use anyhow::{bail, format_err, Context, Error};
 use hex::FromHex;
+use http_body_util::BodyExt;
 use serde_json::Value;
 use tracing::{info, warn};
 
@@ -35,10 +36,20 @@ use pbs_config::CachedUserInfo;
 
 use pbs_datastore::get_datastore_mount_status;
 use proxmox_rest_server::WorkerTask;
+use proxmox_s3_client::S3ObjectKey;
 
 use crate::server::jobstate;
 use crate::tools::disks::unmount_by_mountpoint;
 
+const S3_DATASTORE_IN_USE_MARKER: &str = ".in-use";
+
+#[derive(Default, serde::Deserialize, serde::Serialize)]
+#[serde(rename_all = "kebab-case")]
+struct InUseContent {
+    #[serde(skip_serializing_if = "Option::is_none")]
+    hostname: Option<String>,
+}
+
 #[api(
     input: {
         properties: {},
@@ -153,6 +164,23 @@ pub(crate) fn do_create_datastore(
                 // Fine to block since this runs in worker task
                 proxmox_async::runtime::block_on(s3_client.head_bucket())
                     .context("failed to access bucket")?;
+
+                let object_key = S3ObjectKey::from(S3_DATASTORE_IN_USE_MARKER);
+                if let Some(response) =
+                    proxmox_async::runtime::block_on(s3_client.get_object(object_key.clone()))
+                        .context("failed to get in-use marker from bucket")?
+                {
+                    let content = proxmox_async::runtime::block_on(response.content.collect())
+                        .unwrap_or_default();
+                    let content =
+                        String::from_utf8(content.to_bytes().to_vec()).unwrap_or_default();
+                    let in_use: InUseContent = serde_json::from_str(&content).unwrap_or_default();
+                    if let Some(hostname) = in_use.hostname {
+                        bail!("Bucket already contains datastore in use by host {hostname}");
+                    } else {
+                        bail!("Bucket already contains datastore in use");
+                    }
+                }
                 backend_s3_client = Some(Arc::new(s3_client));
             }
         }
@@ -165,7 +193,7 @@ pub(crate) fn do_create_datastore(
         UnmountGuard::new(None)
     };
 
-    let chunk_store = if reuse_datastore {
+    let chunk_store = if reuse_datastore && backend_s3_client.is_none() {
         ChunkStore::verify_chunkstore(&path).and_then(|_| {
             // Must be the only instance accessing and locking the chunk store,
             // dropping will close all other locks from this process on the lockfile as well.
@@ -195,6 +223,20 @@ pub(crate) fn do_create_datastore(
         )?
     };
 
+    if let Some(ref s3_client) = backend_s3_client {
+        let object_key = S3ObjectKey::from(S3_DATASTORE_IN_USE_MARKER);
+        let content = serde_json::to_string(&InUseContent {
+            hostname: Some(proxmox_sys::nodename().to_string()),
+        })
+        .context("failed to encode hostname")?;
+        proxmox_async::runtime::block_on(s3_client.put_object(
+            object_key,
+            hyper::body::Bytes::from(content).into(),
+            true,
+        ))
+        .context("failed to upload in-use marker for datastore")?;
+    }
+
     if tuning.gc_atime_safety_check.unwrap_or(true) {
         chunk_store
             .check_fs_atime_updates(true, backend_s3_client)
-- 
2.47.2