[pbs-devel] [PATCH proxmox-backup v8 35/45] api/datastore: implement refresh endpoint for stores with s3 backend

[Christian Ebner <c.ebner@proxmox.com>]

Allows to easily refresh the contents on the local cache store for
datastores backed by an S3 object store.

In order to guarantee that no read or write operations are ongoing,
the store is first set into the maintenance mode `S3Refresh`. Objects
are then fetched into a temporary directory to avoid loosing contents
and consistency in case of an error. Once all objects have been
fetched, clears out existing contents and moves the newly fetched
contents in place.

Signed-off-by: Christian Ebner <c.ebner@proxmox.com>
---
changes since version 7:
- add more error context
- fix clippy warning

 pbs-datastore/src/datastore.rs | 172 ++++++++++++++++++++++++++++++++-
 src/api2/admin/datastore.rs    |  34 +++++++
 2 files changed, 205 insertions(+), 1 deletion(-)

diff --git a/pbs-datastore/src/datastore.rs b/pbs-datastore/src/datastore.rs
index cab0f5b4d..c63759f9a 100644
--- a/pbs-datastore/src/datastore.rs
+++ b/pbs-datastore/src/datastore.rs
@@ -10,11 +10,13 @@ use anyhow::{bail, format_err, Context, Error};
 use http_body_util::BodyExt;
 use nix::unistd::{unlinkat, UnlinkatFlags};
 use pbs_tools::lru_cache::LruCache;
+use proxmox_lang::try_block;
+use tokio::io::AsyncWriteExt;
 use tracing::{info, warn};
 
 use proxmox_human_byte::HumanByte;
 use proxmox_s3_client::{
-    S3Client, S3ClientConfig, S3ClientOptions, S3ClientSecretsConfig, S3PathPrefix,
+    S3Client, S3ClientConfig, S3ClientOptions, S3ClientSecretsConfig, S3ObjectKey, S3PathPrefix,
 };
 use proxmox_schema::ApiType;
 
@@ -2132,4 +2134,172 @@ impl DataStore {
     pub fn old_locking(&self) -> bool {
         *OLD_LOCKING
     }
+
+    /// Set the datastore's maintenance mode to `S3Refresh`, fetch from S3 object store, clear and
+    /// replace the local cache store contents. Once finished disable the maintenance mode again.
+    /// Returns with error for other datastore backends without setting the maintenance mode.
+    pub async fn s3_refresh(self: &Arc<Self>) -> Result<(), Error> {
+        match self.backend()? {
+            DatastoreBackend::Filesystem => bail!("store '{}' not backed by S3", self.name()),
+            DatastoreBackend::S3(s3_client) => {
+                try_block!({
+                    let _lock = pbs_config::datastore::lock_config()?;
+                    let (mut section_config, _digest) = pbs_config::datastore::config()?;
+                    let mut datastore: DataStoreConfig =
+                        section_config.lookup("datastore", self.name())?;
+                    datastore.set_maintenance_mode(Some(MaintenanceMode {
+                        ty: MaintenanceType::S3Refresh,
+                        message: None,
+                    }))?;
+                    section_config.set_data(self.name(), "datastore", &datastore)?;
+                    pbs_config::datastore::save_config(&section_config)?;
+                    drop(_lock);
+                    Ok::<(), Error>(())
+                })
+                .context("failed to set maintenance mode")?;
+
+                let store_base = self.base_path();
+
+                let tmp_base = proxmox_sys::fs::make_tmp_dir(&store_base, None)
+                    .context("failed to create temporary content folder in {store_base}")?;
+
+                let backup_user = pbs_config::backup_user().context("failed to get backup user")?;
+                let mode = nix::sys::stat::Mode::from_bits_truncate(0o0644);
+                let file_create_options = CreateOptions::new()
+                    .perm(mode)
+                    .owner(backup_user.uid)
+                    .group(backup_user.gid);
+                let mode = nix::sys::stat::Mode::from_bits_truncate(0o0755);
+                let dir_create_options = CreateOptions::new()
+                    .perm(mode)
+                    .owner(backup_user.uid)
+                    .group(backup_user.gid);
+
+                let list_prefix = S3PathPrefix::Some(S3_CONTENT_PREFIX.to_string());
+                let store_prefix = format!("{}/{S3_CONTENT_PREFIX}/", self.name());
+                let mut next_continuation_token: Option<String> = None;
+                loop {
+                    let list_objects_result = s3_client
+                        .list_objects_v2(&list_prefix, next_continuation_token.as_deref())
+                        .await
+                        .context("failed to list object")?;
+
+                    let objects_to_fetch: Vec<S3ObjectKey> = list_objects_result
+                        .contents
+                        .into_iter()
+                        .map(|item| item.key)
+                        .collect();
+
+                    for object_key in objects_to_fetch {
+                        let object_path = format!("{object_key}");
+                        let object_path = object_path.strip_prefix(&store_prefix).with_context(||
+                            format!("failed to strip store context prefix {store_prefix} for {object_key}")
+                        )?;
+                        if object_path.ends_with(NAMESPACE_MARKER_FILENAME) {
+                            continue;
+                        }
+
+                        info!("Fetching object {object_path}");
+
+                        let file_path = tmp_base.join(object_path);
+                        if let Some(parent) = file_path.parent() {
+                            proxmox_sys::fs::create_path(
+                                parent,
+                                Some(dir_create_options),
+                                Some(dir_create_options),
+                            )?;
+                        }
+
+                        let mut target_file = tokio::fs::OpenOptions::new()
+                            .write(true)
+                            .create(true)
+                            .truncate(true)
+                            .read(true)
+                            .open(&file_path)
+                            .await
+                            .with_context(|| {
+                                format!("failed to create target file {file_path:?}")
+                            })?;
+
+                        if let Some(response) = s3_client
+                            .get_object(object_key)
+                            .await
+                            .with_context(|| format!("failed to fetch object {object_path}"))?
+                        {
+                            let data = response
+                                .content
+                                .collect()
+                                .await
+                                .context("failed to collect object contents")?;
+                            target_file
+                                .write_all(&data.to_bytes())
+                                .await
+                                .context("failed to write to target file")?;
+                            file_create_options
+                                .apply_to(&mut target_file, &file_path)
+                                .context("failed to set target file create options")?;
+                            target_file
+                                .flush()
+                                .await
+                                .context("failed to flush target file")?;
+                        } else {
+                            bail!("failed to download {object_path}, not found");
+                        }
+                    }
+
+                    if list_objects_result.is_truncated {
+                        next_continuation_token = list_objects_result
+                            .next_continuation_token
+                            .as_ref()
+                            .cloned();
+                        continue;
+                    }
+                    break;
+                }
+
+                for ty in ["vm", "ct", "host", "ns"] {
+                    let store_base_clone = store_base.clone();
+                    let tmp_base_clone = tmp_base.clone();
+                    tokio::task::spawn_blocking(move || {
+                        let type_dir = store_base_clone.join(ty);
+                        if let Err(err) = std::fs::remove_dir_all(&type_dir) {
+                            if err.kind() != io::ErrorKind::NotFound {
+                                return Err(err).with_context(|| {
+                                    format!("failed to remove old contents in {type_dir:?}")
+                                });
+                            }
+                        }
+                        let tmp_type_dir = tmp_base_clone.join(ty);
+                        if let Err(err) = std::fs::rename(&tmp_type_dir, &type_dir) {
+                            if err.kind() != io::ErrorKind::NotFound {
+                                return Err(err)
+                                    .with_context(|| format!("failed to rename {tmp_type_dir:?}"));
+                            }
+                        }
+                        Ok::<(), Error>(())
+                    })
+                    .await?
+                    .with_context(|| format!("failed to refresh {store_base:?}"))?;
+                }
+
+                std::fs::remove_dir_all(&tmp_base).with_context(|| {
+                    format!("failed to cleanup temporary content in {tmp_base:?}")
+                })?;
+
+                try_block!({
+                    let _lock = pbs_config::datastore::lock_config()?;
+                    let (mut section_config, _digest) = pbs_config::datastore::config()?;
+                    let mut datastore: DataStoreConfig =
+                        section_config.lookup("datastore", self.name())?;
+                    datastore.set_maintenance_mode(None)?;
+                    section_config.set_data(self.name(), "datastore", &datastore)?;
+                    pbs_config::datastore::save_config(&section_config)?;
+                    drop(_lock);
+                    Ok::<(), Error>(())
+                })
+                .context("failed to clear maintenance mode")?;
+            }
+        }
+        Ok(())
+    }
 }
diff --git a/src/api2/admin/datastore.rs b/src/api2/admin/datastore.rs
index 80740e3fb..41cbee4de 100644
--- a/src/api2/admin/datastore.rs
+++ b/src/api2/admin/datastore.rs
@@ -2707,6 +2707,39 @@ pub async fn unmount(store: String, rpcenv: &mut dyn RpcEnvironment) -> Result<V
     Ok(json!(upid))
 }
 
+#[api(
+    protected: true,
+    input: {
+        properties: {
+            store: {
+                schema: DATASTORE_SCHEMA,
+            },
+        }
+    },
+    returns: {
+        schema: UPID_SCHEMA,
+    },
+    access: {
+        permission: &Permission::Privilege(&["datastore", "{store}"], PRIV_DATASTORE_MODIFY, false),
+    },
+)]
+/// Refresh datastore contents from S3 to local cache store.
+pub async fn s3_refresh(store: String, rpcenv: &mut dyn RpcEnvironment) -> Result<Value, Error> {
+    let datastore = DataStore::lookup_datastore(&store, Some(Operation::Lookup))?;
+    let auth_id: Authid = rpcenv.get_auth_id().unwrap().parse()?;
+    let to_stdout = rpcenv.env_type() == RpcEnvironmentType::CLI;
+
+    let upid = WorkerTask::spawn(
+        "s3-refresh",
+        Some(store),
+        auth_id.to_string(),
+        to_stdout,
+        move |_worker| async move { datastore.s3_refresh().await },
+    )?;
+
+    Ok(json!(upid))
+}
+
 #[sortable]
 const DATASTORE_INFO_SUBDIRS: SubdirMap = &[
     (
@@ -2773,6 +2806,7 @@ const DATASTORE_INFO_SUBDIRS: SubdirMap = &[
         &Router::new().download(&API_METHOD_PXAR_FILE_DOWNLOAD),
     ),
     ("rrd", &Router::new().get(&API_METHOD_GET_RRD_STATS)),
+    ("s3-refresh", &Router::new().put(&API_METHOD_S3_REFRESH)),
     (
         "snapshots",
         &Router::new()
-- 
2.47.2



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