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authorAlex Auvolat <alex@adnab.me>2022-02-10 12:33:29 +0100
committerGitea <gitea@fake.local>2022-02-10 17:38:27 +0100
commitaf261e17895d5d3b3bd0bdfd52b3d0db6a984a20 (patch)
treec4310d30eee36e32bb6df01196f177f787df43a8
parent4ae03aa774c72a67316853895de2b708f1db6cf4 (diff)
downloadgarage-af261e17895d5d3b3bd0bdfd52b3d0db6a984a20.tar.gz
garage-af261e17895d5d3b3bd0bdfd52b3d0db6a984a20.zip
Fix a bug when a migration is followed by a rebalance
Nodes would stabilize on different encoding formats for the values, some having the pre-migration format and some having the post-migration format. This would be reflected in the Merkle trees never converging and thus having an infinite resync loop.
-rw-r--r--src/table/data.rs27
1 files changed, 18 insertions, 9 deletions
diff --git a/src/table/data.rs b/src/table/data.rs
index 7af5f552..d7787b6b 100644
--- a/src/table/data.rs
+++ b/src/table/data.rs
@@ -130,22 +130,31 @@ where
let tree_key = self.tree_key(update.partition_key(), update.sort_key());
let changed = (&self.store, &self.merkle_todo).transaction(|(store, mkl_todo)| {
- let (old_entry, new_entry) = match store.get(&tree_key)? {
- Some(prev_bytes) => {
+ let (old_entry, old_bytes, new_entry) = match store.get(&tree_key)? {
+ Some(old_bytes) => {
let old_entry = self
- .decode_entry(&prev_bytes)
+ .decode_entry(&old_bytes)
.map_err(sled::transaction::ConflictableTransactionError::Abort)?;
let mut new_entry = old_entry.clone();
new_entry.merge(&update);
- (Some(old_entry), new_entry)
+ (Some(old_entry), Some(old_bytes), new_entry)
}
- None => (None, update.clone()),
+ None => (None, None, update.clone()),
};
- if Some(&new_entry) != old_entry.as_ref() {
- let new_bytes = rmp_to_vec_all_named(&new_entry)
- .map_err(Error::RmpEncode)
- .map_err(sled::transaction::ConflictableTransactionError::Abort)?;
+ // Scenario 1: the value changed, so of course there is a change
+ let value_changed = Some(&new_entry) != old_entry.as_ref();
+
+ // Scenario 2: the value didn't change but due to a migration in the
+ // data format, the messagepack encoding changed. In this case
+ // we have to write the migrated value in the table and update
+ // the associated Merkle tree entry.
+ let new_bytes = rmp_to_vec_all_named(&new_entry)
+ .map_err(Error::RmpEncode)
+ .map_err(sled::transaction::ConflictableTransactionError::Abort)?;
+ let encoding_changed = Some(&new_bytes[..]) != old_bytes.as_ref().map(|x| &x[..]);
+
+ if value_changed || encoding_changed {
let new_bytes_hash = blake2sum(&new_bytes[..]);
mkl_todo.insert(tree_key.clone(), new_bytes_hash.as_slice())?;
store.insert(tree_key.clone(), new_bytes)?;