Re: [pbs-devel] [RFC v2 proxmox-backup 27/36] client: implement prepare reference method

["Fabian Grünbichler" <f.gruenbichler@proxmox.com>]

On March 5, 2024 10:26 am, Christian Ebner wrote:
> 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 1:
> - no changes
> 
>  pbs-client/src/pxar/create.rs     | 13 ++++++
>  pbs-client/src/pxar/mod.rs        |  2 +-
>  proxmox-backup-client/src/main.rs | 71 ++++++++++++++++++++++++++++++-
>  3 files changed, 83 insertions(+), 3 deletions(-)
> 
> diff --git a/pbs-client/src/pxar/create.rs b/pbs-client/src/pxar/create.rs
> index 9ae84d37..cb0af29e 100644
> --- a/pbs-client/src/pxar/create.rs
> +++ b/pbs-client/src/pxar/create.rs
> @@ -17,6 +17,7 @@ use nix::sys::stat::{FileStat, Mode};
>  
>  use pathpatterns::{MatchEntry, MatchFlag, MatchList, MatchType, PatternFlag};
>  use proxmox_sys::error::SysError;
> +use pxar::accessor::aio::Accessor;
>  use pxar::encoder::{LinkOffset, SeqWrite};
>  use pxar::Metadata;
>  
> @@ -24,7 +25,9 @@ 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, LocalDynamicReadAt};
>  
>  use crate::inject_reused_chunks::InjectChunks;
>  use crate::pxar::metadata::errno_is_unsupported;
> @@ -46,6 +49,16 @@ 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 14674b9b..24315f5f 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};
> +pub use create::{create_archive, PxarCreateOptions, PxarPrevRef};
>  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 f077ddf6..8d657c15 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::{
> @@ -1181,6 +1182,72 @@ async fn create_backup(
>      Ok(Value::Null)
>  }
>  
> +async fn prepare_reference(
> +    target_base: &str,
> +    extension: &str,
> +    manifest: Option<Arc<BackupManifest>>,
> +    backup_writer: &BackupWriter,
> +    backup_reader: Option<Arc<BackupReader>>,
> +    crypt_config: Option<Arc<CryptConfig>>,
> +) -> Result<Option<PxarPrevRef>, Error> {
> +    let target = format!("{target_base}.meta.{extension}");
> +    let payload_target = format!("{target_base}.pld.{extension}");
> +
> +    let manifest = if let Some(ref manifest) = manifest {
> +        manifest
> +    } else {
> +        return Ok(None);
> +    };
> +
> +    let backup_reader = if let Some(ref reader) = backup_reader {
> +        reader
> +    } else {
> +        return Ok(None);
> +    };

couldn't these checks be done before/at the call site and this fn take
the manifest and reader without Option? see comments for the patch where
this is used..

> +
> +    let metadata_ref_index = if let Ok(index) = backup_reader
> +        .download_dynamic_index(&manifest, &target)
> +        .await
> +    {
> +        index
> +    } else {
> +        log::info!("No previous metadata index, fallback to regular encoding");
> +        return Ok(None);
> +    };
> +
> +    let known_payload_chunks = Arc::new(Mutex::new(HashSet::new()));
> +    let payload_ref_index = if let Ok(index) = backup_writer
> +        .download_previous_dynamic_index(&payload_target, &manifest, known_payload_chunks)
> +        .await
> +    {
> +        index
> +    } else {
> +        log::info!("No previous payload index, fallback to regular encoding");
> +        return Ok(None);
> +    };

for these two, it might make sense to differentiate between:
- previous manifest doesn't have that index -> no need to try download,
  we can just skip
- previous manifest has that index -> we try to download -> we need to
  handle the error (and tell the user about the error message - it might
  indicate a problem after all!)

> +
> +    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).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
> 
> 
> 
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