partial fix #3701: sync job: pull: add transfer-last parameter

Specifying the transfer-last parameter limits the amount of backups
that get synced via the pull command/sync job. The parameter specifies
how many of the N latest backups should get pulled/synced. All other
backups will get skipped.

This is particularly useful in situations where the sync target has
less disk space than the source. Syncing all backups from the source
is not possible if there is not enough disk space on the target.
Additionally this can be used for limiting the amount of data
transferred, reducing load on the network.

The newest backup will always get re-synced, regardless of the setting
of the transfer-last parameter.

Signed-off-by: Stefan Hanreich <s.hanreich@proxmox.com>

pbs-api-types/src/jobs.rs

@@ -444,6 +444,11 @@ pub const GROUP_FILTER_SCHEMA: Schema = StringSchema::new(
 pub const GROUP_FILTER_LIST_SCHEMA: Schema =
     ArraySchema::new("List of group filters.", &GROUP_FILTER_SCHEMA).schema();
 
+pub const TRANSFER_LAST_SCHEMA: Schema =
+    IntegerSchema::new("Limit transfer to last N snapshots (per group), skipping others")
+        .minimum(1)
+        .schema();
+
 #[api(
     properties: {
         id: {
@@ -493,6 +498,10 @@ pub const GROUP_FILTER_LIST_SCHEMA: Schema =
             schema: GROUP_FILTER_LIST_SCHEMA,
             optional: true,
         },
+        "transfer-last": {
+            schema: TRANSFER_LAST_SCHEMA,
+            optional: true,
+        },
     }
 )]
 #[derive(Serialize, Deserialize, Clone, Updater, PartialEq)]
@@ -522,6 +531,8 @@ pub struct SyncJobConfig {
     pub group_filter: Option<Vec<GroupFilter>>,
     #[serde(flatten)]
     pub limit: RateLimitConfig,
+    #[serde(skip_serializing_if = "Option::is_none")]
+    pub transfer_last: Option<usize>,
 }
 
 impl SyncJobConfig {

src/api2/config/sync.rs

@@ -215,6 +215,8 @@ pub enum DeletableProperty {
     RemoteNs,
     /// Delete the max_depth property,
     MaxDepth,
+    /// Delete the transfer_last property,
+    TransferLast,
 }
 
 #[api(
@@ -309,6 +311,9 @@ pub fn update_sync_job(
                 DeletableProperty::MaxDepth => {
                     data.max_depth = None;
                 }
+                DeletableProperty::TransferLast => {
+                    data.transfer_last = None;
+                }
             }
         }
     }
@@ -343,6 +348,9 @@ pub fn update_sync_job(
     if let Some(group_filter) = update.group_filter {
         data.group_filter = Some(group_filter);
     }
+    if let Some(transfer_last) = update.transfer_last {
+        data.transfer_last = Some(transfer_last);
+    }
 
     if update.limit.rate_in.is_some() {
         data.limit.rate_in = update.limit.rate_in;
@@ -507,6 +515,7 @@ acl:1:/remote/remote1/remotestore1:write@pbs:RemoteSyncOperator
         group_filter: None,
         schedule: None,
         limit: pbs_api_types::RateLimitConfig::default(), // no limit
+        transfer_last: None,
     };
 
     // should work without ACLs

src/api2/pull.rs

@@ -10,6 +10,7 @@ use pbs_api_types::{
     Authid, BackupNamespace, GroupFilter, RateLimitConfig, SyncJobConfig, DATASTORE_SCHEMA,
     GROUP_FILTER_LIST_SCHEMA, NS_MAX_DEPTH_REDUCED_SCHEMA, PRIV_DATASTORE_BACKUP,
     PRIV_DATASTORE_PRUNE, PRIV_REMOTE_READ, REMOTE_ID_SCHEMA, REMOVE_VANISHED_BACKUPS_SCHEMA,
+    TRANSFER_LAST_SCHEMA,
 };
 use pbs_config::CachedUserInfo;
 use proxmox_rest_server::WorkerTask;
@@ -76,6 +77,7 @@ impl TryFrom<&SyncJobConfig> for PullParameters {
             sync_job.max_depth,
             sync_job.group_filter.clone(),
             sync_job.limit.clone(),
+            sync_job.transfer_last,
         )
     }
 }
@@ -201,7 +203,11 @@ pub fn do_sync_job(
             limit: {
                 type: RateLimitConfig,
                 flatten: true,
-            }
+            },
+            "transfer-last": {
+                schema: TRANSFER_LAST_SCHEMA,
+                optional: true,
+            },
         },
     },
     access: {
@@ -225,6 +231,7 @@ async fn pull(
     max_depth: Option<usize>,
     group_filter: Option<Vec<GroupFilter>>,
     limit: RateLimitConfig,
+    transfer_last: Option<usize>,
     rpcenv: &mut dyn RpcEnvironment,
 ) -> Result<String, Error> {
     let auth_id: Authid = rpcenv.get_auth_id().unwrap().parse()?;
@@ -257,6 +264,7 @@ async fn pull(
         max_depth,
         group_filter,
         limit,
+        transfer_last,
     )?;
     let client = pull_params.client().await?;
 

src/bin/proxmox-backup-manager.rs

@@ -13,7 +13,7 @@ use pbs_api_types::percent_encoding::percent_encode_component;
 use pbs_api_types::{
     BackupNamespace, GroupFilter, RateLimitConfig, SyncJobConfig, DATASTORE_SCHEMA,
     GROUP_FILTER_LIST_SCHEMA, IGNORE_VERIFIED_BACKUPS_SCHEMA, NS_MAX_DEPTH_SCHEMA,
-    REMOTE_ID_SCHEMA, REMOVE_VANISHED_BACKUPS_SCHEMA, UPID_SCHEMA,
+    REMOTE_ID_SCHEMA, REMOVE_VANISHED_BACKUPS_SCHEMA, TRANSFER_LAST_SCHEMA, UPID_SCHEMA,
     VERIFICATION_OUTDATED_AFTER_SCHEMA,
 };
 use pbs_client::{display_task_log, view_task_result};
@@ -272,6 +272,10 @@ fn task_mgmt_cli() -> CommandLineInterface {
                 schema: OUTPUT_FORMAT,
                 optional: true,
             },
+            "transfer-last": {
+                schema: TRANSFER_LAST_SCHEMA,
+                optional: true,
+            },
         }
    }
 )]
@@ -287,6 +291,7 @@ async fn pull_datastore(
     max_depth: Option<usize>,
     group_filter: Option<Vec<GroupFilter>>,
     limit: RateLimitConfig,
+    transfer_last: Option<usize>,
     param: Value,
 ) -> Result<Value, Error> {
     let output_format = get_output_format(&param);
@@ -319,6 +324,10 @@ async fn pull_datastore(
         args["remove-vanished"] = Value::from(remove_vanished);
     }
 
+    if transfer_last.is_some() {
+        args["transfer-last"] = json!(transfer_last)
+    }
+
     let mut limit_json = json!(limit);
     let limit_map = limit_json
         .as_object_mut()

src/server/pull.rs

@@ -59,6 +59,8 @@ pub(crate) struct PullParameters {
     group_filter: Option<Vec<GroupFilter>>,
     /// Rate limits for all transfers from `remote`
     limit: RateLimitConfig,
+    /// How many snapshots should be transferred at most (taking the newest N snapshots)
+    transfer_last: Option<usize>,
 }
 
 impl PullParameters {
@@ -78,6 +80,7 @@ impl PullParameters {
         max_depth: Option<usize>,
         group_filter: Option<Vec<GroupFilter>>,
         limit: RateLimitConfig,
+        transfer_last: Option<usize>,
     ) -> Result<Self, Error> {
         let store = DataStore::lookup_datastore(store, Some(Operation::Write))?;
 
@@ -109,6 +112,7 @@ impl PullParameters {
             max_depth,
             group_filter,
             limit,
+            transfer_last,
         })
     }
 
@@ -632,6 +636,7 @@ async fn pull_group(
     let fingerprint = client.fingerprint();
 
     let last_sync = params.store.last_successful_backup(&target_ns, group)?;
+    let last_sync_time = last_sync.unwrap_or(i64::MIN);
 
     let mut remote_snapshots = std::collections::HashSet::new();
 
@@ -646,6 +651,13 @@ async fn pull_group(
         count: 0,
     };
 
+    let total_amount = list.len();
+
+    let cutoff = params
+        .transfer_last
+        .map(|count| total_amount.saturating_sub(count))
+        .unwrap_or_default();
+
     for (pos, item) in list.into_iter().enumerate() {
         let snapshot = item.backup;
 
@@ -661,11 +673,13 @@ async fn pull_group(
 
         remote_snapshots.insert(snapshot.time);
 
-        if let Some(last_sync_time) = last_sync {
-            if last_sync_time > snapshot.time {
-                skip_info.update(snapshot.time);
-                continue;
-            }
+        if last_sync_time > snapshot.time {
+            skip_info.update(snapshot.time);
+            continue;
+        }
+
+        if pos < cutoff && last_sync_time != snapshot.time {
+            continue;
         }
 
         // get updated auth_info (new tickets)