[pbs-devel] [RFC PATCH proxmox-backup 1/2] tape: media_catalog: commit as much as possible

[Dominik Csapak <d.csapak@proxmox.com>]

record when we finish an archive in the catalogs pending data,
and commit data until there. This way we can commit the catalog
even if we do not finish a chunk archive.

Signed-off-by: Dominik Csapak <d.csapak@proxmox.com>
---
sending as RFC, since i am not completely sure if i thought this
through completely, but in my tests it worked..

 src/tape/media_catalog.rs | 31 ++++++++++++++++++++++---------
 1 file changed, 22 insertions(+), 9 deletions(-)

diff --git a/src/tape/media_catalog.rs b/src/tape/media_catalog.rs
index 65b52a42..8dacf986 100644
--- a/src/tape/media_catalog.rs
+++ b/src/tape/media_catalog.rs
@@ -66,6 +66,7 @@ pub struct MediaCatalog  {
 
     content: HashMap<String, DatastoreContent>,
 
+    finished_archive_len: usize,
     pending: Vec<u8>,
 }
 
@@ -223,6 +224,7 @@ impl MediaCatalog {
                 current_archive: None,
                 last_entry: None,
                 content: HashMap::new(),
+                finished_archive_len: 0,
                 pending: Vec::new(),
             };
 
@@ -231,6 +233,7 @@ impl MediaCatalog {
             if !found_magic_number {
                 me.pending.extend(&Self::PROXMOX_BACKUP_MEDIA_CATALOG_MAGIC_1_1);
             }
+            me.finished_archive_len = me.pending.len();
 
             if write {
                 me.file = Some(file);
@@ -300,12 +303,15 @@ impl MediaCatalog {
                 current_archive: None,
                 last_entry: None,
                 content: HashMap::new(),
+                finished_archive_len: 0,
                 pending: Vec::new(),
             };
 
             me.log_to_stdout = log_to_stdout;
 
             me.pending.extend(&Self::PROXMOX_BACKUP_MEDIA_CATALOG_MAGIC_1_1);
+            me.finished_archive_len = me.pending.len();
+
 
             me.register_label(&media_id.label.uuid, 0, 0)?;
 
@@ -366,31 +372,34 @@ impl MediaCatalog {
     ///
     /// Fixme: this should be atomic ...
     pub fn commit(&mut self) -> Result<(), Error> {
-
-        if self.pending.is_empty() {
+        if self.finished_archive_len == 0 {
             return Ok(());
         }
 
         match self.file {
             Some(ref mut file) => {
-                file.write_all(&self.pending)?;
+                file.write_all(&self.pending[0..self.finished_archive_len])?;
                 file.flush()?;
                 file.sync_data()?;
             }
             None => bail!("media catalog not writable (opened read only)"),
         }
 
-        self.pending = Vec::new();
+        let pending = self.pending.len();
+        if self.finished_archive_len < pending {
+            self.pending
+                .copy_within(self.finished_archive_len..pending, 0);
+        }
+        self.pending
+            .truncate(self.pending.len() - self.finished_archive_len);
+        self.finished_archive_len = 0;
 
         Ok(())
     }
 
-    /// Conditionally commit if in pending data is large (> 1Mb)
+    /// Conditionally commit if finished archives in pending data is large (> 1MiB)
     pub fn commit_if_large(&mut self) -> Result<(), Error> {
-        if self.current_archive.is_some() {
-            bail!("can't commit catalog in the middle of an chunk archive");
-        }
-        if self.pending.len() > 1024*1024 {
+        if self.finished_archive_len > 1024*1024 {
             self.commit()?;
         }
         Ok(())
@@ -498,6 +507,7 @@ impl MediaCatalog {
 
         unsafe { self.pending.write_le_value(entry)?; }
 
+        self.finished_archive_len = self.pending.len();
         self.last_entry = Some((uuid.clone(), file_number));
 
         Ok(())
@@ -625,6 +635,7 @@ impl MediaCatalog {
 
                 unsafe { self.pending.write_le_value(entry)?; }
 
+                self.finished_archive_len = self.pending.len();
                 self.last_entry = Some((uuid, file_number));
             }
         }
@@ -688,6 +699,8 @@ impl MediaCatalog {
         self.pending.push(b':');
         self.pending.extend(snapshot.as_bytes());
 
+        self.finished_archive_len = self.pending.len();
+
         let content = self.content.entry(store.to_string())
             .or_insert(DatastoreContent::new());
 
-- 
2.30.2