Do not save parents after all

In particular this means that this doesn't change the API, so only patch
version bump needed.

README.md

@@ -60,7 +60,7 @@ More details are available [in the book][reference-link-implementation-details].
 - Import AlephBFT in your crate
   ```toml
   [dependencies]
-  aleph-bft = "^0.37"
+  aleph-bft = "^0.36"
   ```
 - The main entry point is the `run_session` function, which returns a Future that runs the
   consensus algorithm.

consensus/Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "aleph-bft"
-version = "0.37.0"
+version = "0.36.4"
 edition = "2021"
 authors = ["Cardinal Cryptography"]
 categories = ["algorithms", "data-structures", "cryptography", "database"]

consensus/src/backup/loader.rs

@@ -11,7 +11,7 @@ use log::{error, info, warn};
 
 use crate::{
     units::{UncheckedSignedUnit, Unit, UnitCoord},
-    Data, Hasher, NodeIndex, NodeMap, Round, SessionId, Signature,
+    Data, Hasher, NodeIndex, Round, SessionId, Signature,
 };
 
 const LOG_TARGET: &str = "AlephBFT-backup-loader";
@@ -91,8 +91,7 @@ impl<H: Hasher, D: Data, S: Signature, R: AsyncRead> BackupLoader<H, D, S, R> {
         let input = &mut &buf[..];
         let mut result = Vec::new();
         while !input.is_empty() {
-            // TODO(A0-4234): We should use the parents information to respond to reconstruction failures.
-            result.push(<(UncheckedSignedUnit<H, D, S>, NodeMap<H::Hash>)>::decode(input)?.0);
+            result.push(<UncheckedSignedUnit<H, D, S>>::decode(input)?);
         }
         Ok(result)
     }
@@ -242,15 +241,15 @@ mod tests {
     use codec::Encode;
     use futures::channel::oneshot;
 
-    use aleph_bft_mock::{Data, Hash64, Hasher64, Keychain, Loader, Signature};
+    use aleph_bft_mock::{Data, Hasher64, Keychain, Loader, Signature};
 
     use crate::{
         backup::BackupLoader,
         units::{
             create_preunits, creator_set, preunit_to_full_unit, preunit_to_unchecked_signed_unit,
-            UncheckedSignedUnit as GenericUncheckedSignedUnit, Unit,
+            UncheckedSignedUnit as GenericUncheckedSignedUnit,
         },
-        NodeCount, NodeIndex, NodeMap, Round, SessionId,
+        NodeCount, NodeIndex, Round, SessionId,
     };
 
     type UncheckedSignedUnit = GenericUncheckedSignedUnit<Hasher64, Data, Signature>;
@@ -309,17 +308,7 @@ mod tests {
     }
 
     fn encode_all(items: Vec<UncheckedSignedUnit>) -> Vec<Vec<u8>> {
-        items
-            .iter()
-            .map(|u| {
-                (
-                    u,
-                    // for now encode empty parents as we ignore them anyway
-                    NodeMap::<Hash64>::with_size(u.as_signable().control_hash().n_members()),
-                )
-                    .encode()
-            })
-            .collect()
+        items.iter().map(|u| u.encode()).collect()
     }
 
     fn prepare_test(encoded_items: Vec<u8>) -> PrepareTestResponse<impl futures::Future> {

consensus/src/backup/saver.rs

@@ -34,9 +34,8 @@ impl<H: Hasher, D: Data, MK: MultiKeychain, W: AsyncWrite> BackupSaver<H, D, MK,
     }
 
     pub async fn save_unit(&mut self, unit: &DagUnit<H, D, MK>) -> Result<(), std::io::Error> {
-        let parents = unit.parents().clone();
         let unit: UncheckedSignedUnit<_, _, _> = unit.clone().unpack().into();
-        self.backup.write_all(&(unit, parents).encode()).await?;
+        self.backup.write_all(&unit.encode()).await?;
         self.backup.flush().await
     }
 

consensus/src/testing/crash_recovery.rs

@@ -1,9 +1,9 @@
 use crate::{
     testing::{init_log, spawn_honest_member, HonestMember, Network, ReconnectSender},
     units::{UncheckedSignedUnit, Unit, UnitCoord},
-    NodeCount, NodeIndex, NodeMap, SpawnHandle, TaskHandle,
+    NodeCount, NodeIndex, SpawnHandle, TaskHandle,
 };
-use aleph_bft_mock::{Data, Hash64, Hasher64, Router, Signature, Spawner};
+use aleph_bft_mock::{Data, Hasher64, Router, Signature, Spawner};
 use codec::Decode;
 use futures::{
     channel::{mpsc, oneshot},
@@ -129,12 +129,7 @@ fn verify_backup(buf: &mut &[u8]) -> HashSet<UnitCoord> {
     let mut already_saved = HashSet::new();
 
     while !buf.is_empty() {
-        let unit = <(
-            UncheckedSignedUnit<Hasher64, Data, Signature>,
-            NodeMap<Hash64>,
-        )>::decode(buf)
-        .unwrap()
-        .0;
+        let unit = <UncheckedSignedUnit<Hasher64, Data, Signature>>::decode(buf).unwrap();
         let full_unit = unit.as_signable();
         let coord = full_unit.coord();
         let parent_ids = &full_unit.as_pre_unit().control_hash().parents_mask;