[pbs-devel] [PATCH v3 proxmox-backup 42/58] client: implement prepare reference method

[Christian Ebner <c.ebner@proxmox.com>]

Implement a method that prepares the decoder instance to access a
previous snapshots metadata index and payload index in order to
pass it to the pxar archiver. The archiver than can utilize these
to compare the metadata for files to the previous state and gather
reusable chunks.

Signed-off-by: Christian Ebner <c.ebner@proxmox.com>
---
changes since version 2:
- moved checks for reader and mainifest to call side as suggested
- distinguish between previous manifest not having index and error state

 pbs-client/src/pxar/create.rs     | 14 +++++++-
 pbs-client/src/pxar/mod.rs        |  2 +-
 proxmox-backup-client/src/main.rs | 57 +++++++++++++++++++++++++++++--
 3 files changed, 69 insertions(+), 4 deletions(-)

diff --git a/pbs-client/src/pxar/create.rs b/pbs-client/src/pxar/create.rs
index 2c7867f22..335e3556f 100644
--- a/pbs-client/src/pxar/create.rs
+++ b/pbs-client/src/pxar/create.rs
@@ -19,6 +19,7 @@ use nix::sys::stat::{FileStat, Mode};
 use pathpatterns::{MatchEntry, MatchFlag, MatchList, MatchType, PatternFlag};
 use pbs_datastore::index::IndexFile;
 use proxmox_sys::error::SysError;
+use pxar::accessor::aio::Accessor;
 use pxar::encoder::{LinkOffset, SeqWrite};
 use pxar::Metadata;
 
@@ -26,8 +27,9 @@ use proxmox_io::vec;
 use proxmox_lang::c_str;
 use proxmox_sys::fs::{self, acl, xattr};
 
+use crate::RemoteChunkReader;
 use pbs_datastore::catalog::BackupCatalogWriter;
-use pbs_datastore::dynamic_index::DynamicIndexReader;
+use pbs_datastore::dynamic_index::{DynamicIndexReader, LocalDynamicReadAt};
 
 use crate::inject_reused_chunks::InjectChunks;
 use crate::pxar::metadata::errno_is_unsupported;
@@ -49,6 +51,16 @@ pub struct PxarCreateOptions {
     pub skip_e2big_xattr: bool,
 }
 
+/// Statefull information of previous backups snapshots for partial backups
+pub struct PxarPrevRef {
+    /// Reference accessor for metadata comparison
+    pub accessor: Accessor<LocalDynamicReadAt<RemoteChunkReader>>,
+    /// Reference index for reusing payload chunks
+    pub payload_index: DynamicIndexReader,
+    /// Reference archive name for partial backups
+    pub archive_name: String,
+}
+
 fn detect_fs_type(fd: RawFd) -> Result<i64, Error> {
     let mut fs_stat = std::mem::MaybeUninit::uninit();
     let res = unsafe { libc::fstatfs(fd, fs_stat.as_mut_ptr()) };
diff --git a/pbs-client/src/pxar/mod.rs b/pbs-client/src/pxar/mod.rs
index b7dcf8362..76652094e 100644
--- a/pbs-client/src/pxar/mod.rs
+++ b/pbs-client/src/pxar/mod.rs
@@ -56,7 +56,7 @@ pub(crate) mod tools;
 mod flags;
 pub use flags::Flags;
 
-pub use create::{create_archive, PxarCreateOptions, PxarWriters};
+pub use create::{create_archive, PxarCreateOptions, PxarPrevRef, PxarWriters};
 pub use extract::{
     create_tar, create_zip, extract_archive, extract_sub_dir, extract_sub_dir_seq, ErrorHandler,
     OverwriteFlags, PxarExtractContext, PxarExtractOptions,
diff --git a/proxmox-backup-client/src/main.rs b/proxmox-backup-client/src/main.rs
index 215095ee7..0b747453c 100644
--- a/proxmox-backup-client/src/main.rs
+++ b/proxmox-backup-client/src/main.rs
@@ -21,6 +21,7 @@ use proxmox_router::{cli::*, ApiMethod, RpcEnvironment};
 use proxmox_schema::api;
 use proxmox_sys::fs::{file_get_json, image_size, replace_file, CreateOptions};
 use proxmox_time::{epoch_i64, strftime_local};
+use pxar::accessor::aio::Accessor;
 use pxar::accessor::{MaybeReady, ReadAt, ReadAtOperation};
 
 use pbs_api_types::{
@@ -30,7 +31,7 @@ use pbs_api_types::{
     BACKUP_TYPE_SCHEMA, TRAFFIC_CONTROL_BURST_SCHEMA, TRAFFIC_CONTROL_RATE_SCHEMA,
 };
 use pbs_client::catalog_shell::Shell;
-use pbs_client::pxar::ErrorHandler as PxarErrorHandler;
+use pbs_client::pxar::{ErrorHandler as PxarErrorHandler, PxarPrevRef};
 use pbs_client::tools::{
     complete_archive_name, complete_auth_id, complete_backup_group, complete_backup_snapshot,
     complete_backup_source, complete_chunk_size, complete_group_or_snapshot,
@@ -50,7 +51,7 @@ use pbs_client::{
 };
 use pbs_datastore::catalog::{BackupCatalogWriter, CatalogReader, CatalogWriter};
 use pbs_datastore::chunk_store::verify_chunk_size;
-use pbs_datastore::dynamic_index::{BufferedDynamicReader, DynamicIndexReader};
+use pbs_datastore::dynamic_index::{BufferedDynamicReader, DynamicIndexReader, LocalDynamicReadAt};
 use pbs_datastore::fixed_index::FixedIndexReader;
 use pbs_datastore::index::IndexFile;
 use pbs_datastore::manifest::{
@@ -1177,6 +1178,58 @@ async fn create_backup(
     Ok(Value::Null)
 }
 
+async fn prepare_reference(
+    target: &str,
+    manifest: Arc<BackupManifest>,
+    backup_writer: &BackupWriter,
+    backup_reader: Arc<BackupReader>,
+    crypt_config: Option<Arc<CryptConfig>>,
+) -> Result<Option<PxarPrevRef>, Error> {
+    let (target, payload_target) = helper::get_pxar_archive_names(target);
+    let payload_target = payload_target.unwrap_or_default();
+
+    let metadata_ref_index = if let Ok(index) = backup_reader
+        .download_dynamic_index(&manifest, &target)
+        .await
+    {
+        index
+    } else {
+        log::info!("No previous metadata index, continue without reference");
+        return Ok(None);
+    };
+
+    if let Err(_err) = manifest.lookup_file_info(&payload_target) {
+        log::info!("No previous payload index found in manifest, continue without reference");
+        return Ok(None);
+    }
+
+    let known_payload_chunks = Arc::new(Mutex::new(HashSet::new()));
+    let payload_ref_index = backup_writer
+        .download_previous_dynamic_index(&payload_target, &manifest, known_payload_chunks)
+        .await?;
+
+    log::info!("Using previous index as metadata reference for '{target}'");
+
+    let most_used = metadata_ref_index.find_most_used_chunks(8);
+    let file_info = manifest.lookup_file_info(&target)?;
+    let chunk_reader = RemoteChunkReader::new(
+        backup_reader.clone(),
+        crypt_config.clone(),
+        file_info.chunk_crypt_mode(),
+        most_used,
+    );
+    let reader = BufferedDynamicReader::new(metadata_ref_index, chunk_reader);
+    let archive_size = reader.archive_size();
+    let reader = LocalDynamicReadAt::new(reader);
+    let accessor = Accessor::new(reader, archive_size, None).await?;
+
+    Ok(Some(pbs_client::pxar::PxarPrevRef {
+        accessor,
+        payload_index: payload_ref_index,
+        archive_name: target,
+    }))
+}
+
 async fn dump_image<W: Write>(
     client: Arc<BackupReader>,
     crypt_config: Option<Arc<CryptConfig>>,
-- 
2.39.2