[pbs-devel] [PATCH v3 proxmox-backup 5/6] garbage collection: generate image list via datastore iterators

[Christian Ebner]

Instead of iterating over all images found in the datastore in an
unstructured manner, use the datastore iterators to logically iterate
over them as other datastore operations will.

This allows to better distinguish images in unexpected locations from
ones in their expected location, warning the user of unexpected ones
to allow to act on possible missconfigurations. Further, this will
allow to integrate marking of snapshots with missing chunks as
incomplete/corrupt more easily.

This now iterates twice over the images, as index files in unexpected
locations are still considered by generating a list of all images to
be found in the datastore and removing regular index files from that
list, leaving unexpected ones behind.

Signed-off-by: Christian Ebner <c.ebner at proxmox.com>
---
changes since version 2:
- split iterating from caching logic

 pbs-datastore/src/datastore.rs | 100 ++++++++++++++++++++++-----------
 1 file changed, 67 insertions(+), 33 deletions(-)

diff --git a/pbs-datastore/src/datastore.rs b/pbs-datastore/src/datastore.rs
index 7b5ea4272..c4123f2b7 100644
--- a/pbs-datastore/src/datastore.rs
+++ b/pbs-datastore/src/datastore.rs
@@ -25,7 +25,7 @@ use pbs_api_types::{
     MaintenanceMode, MaintenanceType, Operation, UPID,
 };
 
-use crate::backup_info::{BackupDir, BackupGroup};
+use crate::backup_info::{BackupDir, BackupGroup, BackupInfo};
 use crate::chunk_store::ChunkStore;
 use crate::dynamic_index::{DynamicIndexReader, DynamicIndexWriter};
 use crate::fixed_index::{FixedIndexReader, FixedIndexWriter};
@@ -970,10 +970,10 @@ impl DataStore {
         ListGroups::new(Arc::clone(self), ns)?.collect()
     }
 
-    fn list_images(&self) -> Result<Vec<PathBuf>, Error> {
+    fn list_images(&self) -> Result<HashSet<PathBuf>, Error> {
         let base = self.base_path();
 
-        let mut list = vec![];
+        let mut list = HashSet::new();
 
         use walkdir::WalkDir;
 
@@ -1021,7 +1021,7 @@ impl DataStore {
                 if archive_type == ArchiveType::FixedIndex
                     || archive_type == ArchiveType::DynamicIndex
                 {
-                    list.push(path);
+                    list.insert(path);
                 }
             }
         }
@@ -1117,43 +1117,77 @@ impl DataStore {
         status: &mut GarbageCollectionStatus,
         worker: &dyn WorkerTaskContext,
     ) -> Result<(), Error> {
-        let image_list = self.list_images()?;
-        let image_count = image_list.len();
-
+        // Iterate twice over the datastore to fetch images, even if this comes with an additional
+        // runtime cost:
+        // - First iteration to find all index files, no matter if they are in a location expected
+        //   by the datastore's hierarchy
+        // - Iterate using the datastore's helpers, so the namespaces, groups and snapshots are
+        //   looked up given the expected hierarchy and iterator logic
+        //
+        // By this it is assured that all index files are used, even if they would not have been
+        // seen by the regular logic and the user is informed by the garbage collection run about
+        // the detected index files not following the iterators logic.
+
+        let mut unprocessed_image_list = self.list_images()?;
+        let image_count = unprocessed_image_list.len();
+
+        let mut processed_images = 0;
         let mut last_percentage: usize = 0;
 
-        let mut strange_paths_count: u64 = 0;
-
-        for (i, img) in image_list.into_iter().enumerate() {
-            worker.check_abort()?;
-            worker.fail_on_shutdown()?;
-
-            if let Some(backup_dir_path) = img.parent() {
-                let backup_dir_path = backup_dir_path.strip_prefix(self.base_path())?;
-                if let Some(backup_dir_str) = backup_dir_path.to_str() {
-                    if pbs_api_types::parse_ns_and_snapshot(backup_dir_str).is_err() {
-                        strange_paths_count += 1;
+        let arc_self = Arc::new(self.clone());
+        for namespace in arc_self
+            .recursive_iter_backup_ns(BackupNamespace::root())
+            .context("creating namespace iterator failed")?
+        {
+            let namespace = namespace.context("iterating namespaces failed")?;
+            for group in arc_self.iter_backup_groups(namespace)? {
+                let group = group.context("iterating backup groups failed")?;
+                let mut snapshots = group.list_backups().context("listing snapshots failed")?;
+                // Sort by snapshot timestamp to iterate over consecutive snapshots for each image.
+                BackupInfo::sort_list(&mut snapshots, true);
+                for snapshot in snapshots {
+                    for file in snapshot.files {
+                        worker.check_abort()?;
+                        worker.fail_on_shutdown()?;
+
+                        let mut path = snapshot.backup_dir.full_path();
+                        path.push(file);
+
+                        let index = match self.open_index_reader(&path)? {
+                            Some(index) => index,
+                            None => continue,
+                        };
+                        self.index_mark_used_chunks(index, &path, status, worker)?;
+
+                        unprocessed_image_list.remove(&path);
+
+                        let percentage = (processed_images + 1) * 100 / image_count;
+                        if percentage > last_percentage {
+                            info!(
+                                "marked {percentage}% ({} of {image_count} index files)",
+                                processed_images + 1,
+                            );
+                            last_percentage = percentage;
+                        }
+                        processed_images += 1;
                     }
                 }
             }
-
-            if let Some(index) = self.open_index_reader(&img)? {
-                self.index_mark_used_chunks(index, &img, status, worker)?;
-            }
-
-            let percentage = (i + 1) * 100 / image_count;
-            if percentage > last_percentage {
-                info!(
-                    "marked {percentage}% ({} of {image_count} index files)",
-                    i + 1,
-                );
-                last_percentage = percentage;
-            }
         }
 
+        let strange_paths_count = unprocessed_image_list.len();
         if strange_paths_count > 0 {
-            info!(
-                "found (and marked) {strange_paths_count} index files outside of expected directory scheme"
+            warn!("found {strange_paths_count} index files outside of expected directory scheme");
+        }
+        for path in unprocessed_image_list {
+            let index = match self.open_index_reader(&path)? {
+                Some(index) => index,
+                None => continue,
+            };
+            self.index_mark_used_chunks(index, &path, status, worker)?;
+            warn!(
+                "Marked chunks for unexpected index file at '{}'",
+                path.to_string_lossy()
             );
         }
 
-- 
2.39.5