tape: implement backup using latest-only flag

src/api2/tape/backup.rs

@@ -143,9 +143,6 @@ pub fn do_tape_backup_job(
             set_tape_device_state(&tape_job.drive, &worker.upid().to_string())?;
             job.start(&worker.upid().to_string())?;
 
-            let eject_media = false;
-            let export_media_set = false;
-
             task_log!(worker,"Starting tape backup job '{}'", job_id);
             if let Some(event_str) = schedule {
                 task_log!(worker,"task triggered by schedule '{}'", event_str);
@@ -156,8 +153,9 @@ pub fn do_tape_backup_job(
                 datastore,
                 &tape_job.drive,
                 &pool_config,
-                eject_media,
-                export_media_set,
+                tape_job.eject_media.unwrap_or(false),
+                tape_job.export_media_set.unwrap_or(false),
+                tape_job.latest_only.unwrap_or(false),
             );
 
             let status = worker.create_state(&job_result);
@@ -233,6 +231,11 @@ pub fn run_tape_backup_job(
                 type: bool,
                 optional: true,
             },
+            "latest-only": {
+                description: "Backup latest snapshots only.",
+                type: bool,
+                optional: true,
+            },
         },
     },
     returns: {
@@ -246,6 +249,7 @@ pub fn backup(
     drive: String,
     eject_media: Option<bool>,
     export_media_set: Option<bool>,
+    latest_only: Option<bool>,
     rpcenv: &mut dyn RpcEnvironment,
 ) -> Result<Value, Error> {
 
@@ -265,6 +269,7 @@ pub fn backup(
 
     let eject_media = eject_media.unwrap_or(false);
     let export_media_set = export_media_set.unwrap_or(false);
+    let latest_only = latest_only.unwrap_or(false);
 
     let job_id = format!("{}:{}:{}", store, pool, drive);
 
@@ -276,7 +281,16 @@ pub fn backup(
         move |worker| {
             let _drive_lock = drive_lock; // keep lock guard
             set_tape_device_state(&drive, &worker.upid().to_string())?;
-            backup_worker(&worker, datastore, &drive, &pool_config, eject_media, export_media_set)?;
+            backup_worker(
+                &worker,
+                datastore,
+                &drive,
+                &pool_config,
+                eject_media,
+                export_media_set,
+                latest_only,
+            )?;
+
             // ignore errors
             let _ = set_tape_device_state(&drive, "");
             Ok(())
@@ -293,6 +307,7 @@ fn backup_worker(
     pool_config: &MediaPoolConfig,
     eject_media: bool,
     export_media_set: bool,
+    latest_only: bool,
 ) -> Result<(), Error> {
 
     let status_path = Path::new(TAPE_STATUS_DIR);
@@ -310,10 +325,24 @@ fn backup_worker(
 
     group_list.sort_unstable();
 
+    if latest_only {
+        task_log!(worker, "latest-only: true (only considering latest snapshots)");
+    }
+    
     for group in group_list {
         let mut snapshot_list = group.list_backups(&datastore.base_path())?;
+
         BackupInfo::sort_list(&mut snapshot_list, true); // oldest first
 
+        if latest_only {
+            if let Some(info) = snapshot_list.pop() {
+                if pool_writer.contains_snapshot(&info.backup_dir.to_string()) {
+                    continue;
+                }
+                task_log!(worker, "backup snapshot {}", info.backup_dir);
+                backup_snapshot(worker, &mut pool_writer, datastore.clone(), info.backup_dir)?;
+            }
+        } else {
             for info in snapshot_list {
                 if pool_writer.contains_snapshot(&info.backup_dir.to_string()) {
                     continue;
@@ -322,6 +351,7 @@ fn backup_worker(
                 backup_snapshot(worker, &mut pool_writer, datastore.clone(), info.backup_dir)?;
             }
         }
+    }
 
     pool_writer.commit()?;
 

src/config/tape_job.rs

@@ -78,11 +78,11 @@ pub struct TapeBackupJobConfig {
     pub pool: String,
     pub drive: String,
     #[serde(skip_serializing_if="Option::is_none")]
-    eject_media: Option<bool>,
+    pub eject_media: Option<bool>,
     #[serde(skip_serializing_if="Option::is_none")]
-    export_media_set: Option<bool>,
+    pub export_media_set: Option<bool>,
     #[serde(skip_serializing_if="Option::is_none")]
-    latest_only: Option<bool>,
+    pub latest_only: Option<bool>,
     #[serde(skip_serializing_if="Option::is_none")]
     pub comment: Option<String>,
     #[serde(skip_serializing_if="Option::is_none")]