[pbs-devel] [PATCH proxmox-backup v2 2/7] tape: media_catalog: add fast_catalog beside normal catalog

[Dominik Csapak]

for some parts of the ui, we only need the snapshot list from the catalog,
and reading the whole catalog (can be multiple hundred MiB) is not
really necessary.

Instead, on every commit of the catalog, write the complete content list
into a seperate .index file, that can be read to get only the snapshot
list.

Signed-off-by: Dominik Csapak <d.csapak at proxmox.com>
---
 src/tape/media_catalog.rs | 114 +++++++++++++++++++++++++++++++++++++-
 1 file changed, 112 insertions(+), 2 deletions(-)

diff --git a/src/tape/media_catalog.rs b/src/tape/media_catalog.rs
index 086c8a7d..f7fcdd0a 100644
--- a/src/tape/media_catalog.rs
+++ b/src/tape/media_catalog.rs
@@ -1,8 +1,8 @@
 use std::convert::TryFrom;
 use std::fs::File;
-use std::io::{Write, Read, BufReader, Seek, SeekFrom};
+use std::io::{Write, Read, BufRead, BufReader, Seek, SeekFrom};
 use std::os::unix::io::AsRawFd;
-use std::path::Path;
+use std::path::{Path, PathBuf};
 use std::collections::{HashSet, HashMap};
 
 use anyhow::{bail, format_err, Error};
@@ -53,6 +53,7 @@ impl DatastoreContent {
 ///
 /// We use a simple binary format to store data on disk.
 pub struct MediaCatalog  {
+    base_path: PathBuf,
 
     uuid: Uuid, // BackupMedia uuid
 
@@ -108,7 +109,11 @@ impl MediaCatalog {
 
         let mut path = base_path.to_owned();
         path.push(uuid.to_string());
+        let mut fast_catalog = path.clone();
         path.set_extension("log");
+        fast_catalog.set_extension("index");
+
+        let _ = std::fs::remove_file(fast_catalog); // ignore errors
 
         match std::fs::remove_file(path) {
             Ok(()) => Ok(()),
@@ -217,6 +222,7 @@ impl MediaCatalog {
                 .map_err(|err| format_err!("fchown failed - {}", err))?;
 
             let mut me = Self {
+                base_path: base_path.to_path_buf(),
                 uuid: uuid.clone(),
                 file: None,
                 log_to_stdout: false,
@@ -294,6 +300,7 @@ impl MediaCatalog {
             let file = Self::create_temporary_database_file(base_path, uuid)?;
 
             let mut me = Self {
+                base_path: base_path.to_path_buf(),
                 uuid: uuid.clone(),
                 file: Some(file),
                 log_to_stdout: false,
@@ -360,6 +367,109 @@ impl MediaCatalog {
         &self.content
     }
 
+    fn load_fast_catalog(
+        file: &mut File,
+    ) -> Result<Vec<(String, String)>, Error> {
+        let mut list = Vec::new();
+        let file = BufReader::new(file);
+        for line in file.lines() {
+            let mut line = line?;
+
+            let idx = line
+                .find(':')
+                .ok_or_else(|| format_err!("invalid line format (no store found)"))?;
+
+            let snapshot = line.split_off(idx + 1);
+            line.truncate(idx);
+            list.push((line, snapshot));
+        }
+
+        Ok(list)
+    }
+
+    /// Returns a list of (store, snapshot) for a given MediaId
+    pub fn snapshot_list(
+        base_path: &Path,
+        media_id: &MediaId,
+    ) -> Result<Vec<(String, String)>, Error> {
+        let uuid = &media_id.label.uuid;
+
+        let mut path = base_path.to_owned();
+        path.push(uuid.to_string());
+        path.set_extension("index");
+
+
+        let list = proxmox::try_block!({
+
+            Self::create_basedir(base_path)?;
+
+            let mut file = match std::fs::OpenOptions::new().read(true).open(&path) {
+                Ok(file) => file,
+                Err(err) if err.kind() == std::io::ErrorKind::NotFound => {
+                    // open normal catalog and write fast index
+                    let catalog = Self::open(base_path, media_id, false, false)?;
+                    catalog.write_snapshot_list()?;
+                    let mut list = Vec::new();
+                    for (store, content) in catalog.content() {
+                        for snapshot in content.snapshot_index.keys() {
+                            list.push((store.to_string(), snapshot.to_string()));
+                        }
+                    }
+                    return Ok(list);
+                },
+                Err(err) => bail!(err),
+            };
+
+            Self::load_fast_catalog(&mut file)
+        }).map_err(|err: Error| {
+            format_err!("unable to open fast media catalog {:?} - {}", path, err)
+        })?;
+
+        Ok(list)
+    }
+
+    // writes the full snapshot list into <uuid>.index
+    fn write_snapshot_list(&self) -> Result<(), Error> {
+        let mut data = String::new();
+
+        for (store, content) in self.content() {
+            for snapshot in content.snapshot_index.keys() {
+                data.push_str(store);
+                data.push_str(":");
+                data.push_str(snapshot);
+                data.push_str("\n");
+            }
+        }
+
+        let mut path = self.base_path.clone();
+        path.push(self.uuid.to_string());
+        path.set_extension("index");
+
+        let backup_user = crate::backup::backup_user()?;
+        let options = if cfg!(test) {
+            // cannot chown the file in the test environment
+            CreateOptions::new()
+        } else {
+            CreateOptions::new().owner(backup_user.uid).group(backup_user.gid)
+        };
+
+        proxmox::tools::fs::replace_file(
+            path,
+            data.as_bytes(),
+            options,
+        )
+    }
+
+    /// Finishes the catalog by writing all pending data and a fast
+    /// index with only the snapshot list
+    pub fn finish(&mut self) -> Result<(), Error> {
+        self.commit()?;
+        self.write_snapshot_list().map_err(|err| {
+            format_err!("could not write fast catalog: {}", err)
+        })?;
+        Ok(())
+    }
+
     /// Commit pending changes
     ///
     /// This is necessary to store changes persistently.
-- 
2.30.2