[pbs-devel] [PATCH proxmox-backup] Revert "fix #5710: api: backup: stat known chunks on backup finish"

[Christian Ebner]

Commit da11d226 ("fix #5710: api: backup: stat known chunks on backup
finish") introduced a seemingly cheap server side check to verify
existence of known chunks in the chunk store by stating. This check
however does not scale for large backup snapshots which might contain
millions of known chunks, as reported in the community forum [0].
Revert the changes for now instead of making this opt-in/opt-out, a
more general approach has to be thought out to mark backup snapshots
which fail verification.

Link to the report in the forum:
[0] https://forum.proxmox.com/threads/158812/

Fixes: da11d226 ("fix #5710: api: backup: stat known chunks on backup finish")
Signed-off-by: Christian Ebner <c.ebner at proxmox.com>
---
 src/api2/backup/environment.rs | 54 +++++-----------------------------
 src/api2/backup/mod.rs         | 22 +-------------
 2 files changed, 8 insertions(+), 68 deletions(-)

diff --git a/src/api2/backup/environment.rs b/src/api2/backup/environment.rs
index 19624fae3..99d885e2e 100644
--- a/src/api2/backup/environment.rs
+++ b/src/api2/backup/environment.rs
@@ -1,4 +1,4 @@
-use anyhow::{bail, format_err, Context, Error};
+use anyhow::{bail, format_err, Error};
 use nix::dir::Dir;
 use std::collections::HashMap;
 use std::sync::{Arc, Mutex};
@@ -72,14 +72,8 @@ struct FixedWriterState {
     incremental: bool,
 }
 
-#[derive(Copy, Clone)]
-struct KnownChunkInfo {
-    uploaded: bool,
-    length: u32,
-}
-
-// key=digest, value=KnownChunkInfo
-type KnownChunksMap = HashMap<[u8; 32], KnownChunkInfo>;
+// key=digest, value=length
+type KnownChunksMap = HashMap<[u8; 32], u32>;
 
 struct SharedBackupState {
     finished: bool,
@@ -165,13 +159,7 @@ impl BackupEnvironment {
 
         state.ensure_unfinished()?;
 
-        state.known_chunks.insert(
-            digest,
-            KnownChunkInfo {
-                uploaded: false,
-                length,
-            },
-        );
+        state.known_chunks.insert(digest, length);
 
         Ok(())
     }
@@ -225,13 +213,7 @@ impl BackupEnvironment {
         }
 
         // register chunk
-        state.known_chunks.insert(
-            digest,
-            KnownChunkInfo {
-                uploaded: true,
-                length: size,
-            },
-        );
+        state.known_chunks.insert(digest, size);
 
         Ok(())
     }
@@ -266,13 +248,7 @@ impl BackupEnvironment {
         }
 
         // register chunk
-        state.known_chunks.insert(
-            digest,
-            KnownChunkInfo {
-                uploaded: true,
-                length: size,
-            },
-        );
+        state.known_chunks.insert(digest, size);
 
         Ok(())
     }
@@ -280,23 +256,7 @@ impl BackupEnvironment {
     pub fn lookup_chunk(&self, digest: &[u8; 32]) -> Option<u32> {
         let state = self.state.lock().unwrap();
 
-        state
-            .known_chunks
-            .get(digest)
-            .map(|known_chunk_info| known_chunk_info.length)
-    }
-
-    /// stat known chunks from previous backup, so excluding newly uploaded ones
-    pub fn stat_prev_known_chunks(&self) -> Result<(), Error> {
-        let state = self.state.lock().unwrap();
-        for (digest, known_chunk_info) in &state.known_chunks {
-            if !known_chunk_info.uploaded {
-                self.datastore
-                    .stat_chunk(digest)
-                    .with_context(|| format!("stat failed on {}", hex::encode(digest)))?;
-            }
-        }
-        Ok(())
+        state.known_chunks.get(digest).copied()
     }
 
     /// Store the writer with an unique ID
diff --git a/src/api2/backup/mod.rs b/src/api2/backup/mod.rs
index 31334b59c..0373d135b 100644
--- a/src/api2/backup/mod.rs
+++ b/src/api2/backup/mod.rs
@@ -1,6 +1,6 @@
 //! Backup protocol (HTTP2 upgrade)
 
-use anyhow::{bail, format_err, Context, Error};
+use anyhow::{bail, format_err, Error};
 use futures::*;
 use hex::FromHex;
 use hyper::header::{HeaderValue, CONNECTION, UPGRADE};
@@ -788,26 +788,6 @@ fn finish_backup(
 ) -> Result<Value, Error> {
     let env: &BackupEnvironment = rpcenv.as_ref();
 
-    if let Err(err) = env.stat_prev_known_chunks() {
-        env.debug(format!("stat registered chunks failed - {err:?}"));
-
-        if let Some(last) = env.last_backup.as_ref() {
-            // No need to acquire snapshot lock, already locked when starting the backup
-            let verify_state = SnapshotVerifyState {
-                state: VerifyState::Failed,
-                upid: env.worker.upid().clone(), // backup writer UPID
-            };
-            let verify_state = serde_json::to_value(verify_state)?;
-            last.backup_dir
-                .update_manifest(|manifest| {
-                    manifest.unprotected["verify_state"] = verify_state;
-                })
-                .with_context(|| "manifest update failed")?;
-        }
-
-        bail!("stat known chunks failed - {err:?}");
-    }
-
     env.finish_backup()?;
     env.log("successfully finished backup");
 
-- 
2.39.5