JournalDB can now operate in "archive" mode.

util/src/journaldb.rs

@@ -25,7 +25,10 @@ use kvdb::{Database, DBTransaction, DatabaseConfig};
 use std::env;
 
 /// Implementation of the HashDB trait for a disk-backed database with a memory overlay
-/// and latent-removal semantics.
+/// and, possibly, latent-removal semantics.
+///
+/// If `counters` is `None`, then it behaves exactly like OverlayDB. If not it behaves
+/// differently:
 ///
 /// Like OverlayDB, there is a memory overlay; `commit()` must be called in order to 
 /// write operations out to disk. Unlike OverlayDB, `remove()` operations do not take effect
@@ -34,7 +37,7 @@ use std::env;
 pub struct JournalDB {
 	overlay: MemoryDB,
 	backing: Arc<Database>,
-	counters: Arc<RwLock<HashMap<H256, i32>>>,
+	counters: Option<Arc<RwLock<HashMap<H256, i32>>>>,
 }
 
 impl Clone for JournalDB {
@@ -48,10 +51,11 @@ impl Clone for JournalDB {
 }
 
 // all keys must be at least 12 bytes
-const LATEST_ERA_KEY : [u8; 12] = [ b'l', b'a', b's', b't', 0, 0, 0, 0, 0, 0, 0, 0 ]; 
-const VERSION_KEY : [u8; 12] = [ b'j', b'v', b'e', b'r', 0, 0, 0, 0, 0, 0, 0, 0 ]; 
+const LATEST_ERA_KEY : [u8; 12] = [ b'l', b'a', b's', b't', 0, 0, 0, 0, 0, 0, 0, 0 ];
+const VERSION_KEY : [u8; 12] = [ b'j', b'v', b'e', b'r', 0, 0, 0, 0, 0, 0, 0, 0 ];
 
-const DB_VERSION: u32 = 3;
+const DB_VERSION : u32 = 3;
+const DB_VERSION_NO_JOURNAL : u32 = 3 + 256;
 
 const PADDING : [u8; 10] = [ 0u8; 10 ];
 
@@ -59,25 +63,38 @@ impl JournalDB {
 
 	/// Create a new instance from file
 	pub fn new(path: &str) -> JournalDB {
+		Self::from_prefs(path, true)
+	}
+
+	/// Create a new instance from file
+	pub fn from_prefs(path: &str, prefer_journal: bool) -> JournalDB {
 		let opts = DatabaseConfig {
 			prefix_size: Some(12) //use 12 bytes as prefix, this must match account_db prefix
 		};
 		let backing = Database::open(&opts, path).unwrap_or_else(|e| {
 			panic!("Error opening state db: {}", e);
 		});
+		let with_journal;
 		if !backing.is_empty() {
 			match backing.get(&VERSION_KEY).map(|d| d.map(|v| decode::<u32>(&v))) {
-				Ok(Some(DB_VERSION)) => {},
+				Ok(Some(DB_VERSION)) => { with_journal = true; },
+				Ok(Some(DB_VERSION_NO_JOURNAL)) => { with_journal = false; },
 				v => panic!("Incompatible DB version, expected {}, got {:?}", DB_VERSION, v)
 			}
 		} else {
-			backing.put(&VERSION_KEY, &encode(&DB_VERSION)).expect("Error writing version to database");
+			backing.put(&VERSION_KEY, &encode(&(if prefer_journal { DB_VERSION } else { DB_VERSION_NO_JOURNAL }))).expect("Error writing version to database");
+			with_journal = prefer_journal;
 		}
-		let counters = JournalDB::read_counters(&backing);
+
+		let counters = if with_journal {
+			Some(Arc::new(RwLock::new(JournalDB::read_counters(&backing))))
+		} else {
+			None
+		};
 		JournalDB {
 			overlay: MemoryDB::new(),
 			backing: Arc::new(backing),
-			counters: Arc::new(RwLock::new(counters)),
+			counters: counters,
 		}
 	}
 
@@ -94,9 +111,48 @@ impl JournalDB {
 		self.backing.get(&LATEST_ERA_KEY).expect("Low level database error").is_none()
 	}
 
+	/// Commit all recent insert operations.
+	pub fn commit(&mut self, now: u64, id: &H256, end: Option<(u64, H256)>) -> Result<u32, UtilError> {
+		let have_counters = self.counters.is_some();
+		if have_counters {
+			self.commit_with_counters(now, id, end)
+		} else {
+			self.commit_without_counters()
+		}
+	}
+
+	/// Drain the overlay and place it into a batch for the DB.
+	fn batch_overlay_insertions(overlay: &mut MemoryDB, batch: &DBTransaction) -> (usize, usize) {
+		let mut ret = 0usize;
+		let mut deletes = 0usize;
+		for i in overlay.drain().into_iter() {
+			let (key, (value, rc)) = i;
+			if rc > 0 {
+				assert!(rc == 1);
+				batch.put(&key.bytes(), &value).expect("Low-level database error. Some issue with your hard disk?");
+				ret += 1;
+			}
+			if rc < 0 {
+				assert!(rc == -1);
+				ret += 1;
+				deletes += 1;
+			}
+		}
+		(ret, deletes)
+	}
+
+	/// Just commit the overlay into the backing DB.
+	fn commit_without_counters(&mut self) -> Result<u32, UtilError> {
+		let batch = DBTransaction::new();
+		let (ret, _) = Self::batch_overlay_insertions(&mut self.overlay, &batch);
+		try!(self.backing.write(batch));
+		Ok(ret as u32)
+
+	}
+
 	/// Commit all recent insert operations and historical removals from the old era
 	/// to the backing database.
-	pub fn commit(&mut self, now: u64, id: &H256, end: Option<(u64, H256)>) -> Result<u32, UtilError> {
+	fn commit_with_counters(&mut self, now: u64, id: &H256, end: Option<(u64, H256)>) -> Result<u32, UtilError> {
 		// journal format: 
 		// [era, 0] => [ id, [insert_0, ...], [remove_0, ...] ]
 		// [era, 1] => [ id, [insert_0, ...], [remove_0, ...] ]
@@ -122,8 +178,8 @@ impl JournalDB {
 
 		// record new commit's details.
 		debug!("commit: #{} ({}), end era: {:?}", now, id, end);
+		let mut counters = self.counters.as_ref().unwrap().write().unwrap();
 		let batch = DBTransaction::new();
-		let mut counters = self.counters.write().unwrap();
 		{
 			let mut index = 0usize;
 			let mut last;
@@ -196,25 +252,11 @@ impl JournalDB {
 		}
 
 		// Commit overlay insertions
-		let mut ret = 0u32;
-		let mut deletes = 0usize;
-		for i in self.overlay.drain().into_iter() {
-			let (key, (value, rc)) = i;
-			if rc > 0 {
-				assert!(rc == 1);
-				batch.put(&key.bytes(), &value).expect("Low-level database error. Some issue with your hard disk?");
-				ret += 1;
-			}
-			if rc < 0 {
-				assert!(rc == -1);
-				ret += 1;
-				deletes += 1;
-			}
-		}
+		let (ret, deletes) = Self::batch_overlay_insertions(&mut self.overlay, &batch);
 
 		try!(self.backing.write(batch));
 		debug!("commit: Deleted {} nodes", deletes);
-		Ok(ret)
+		Ok(ret as u32)
 	}
 
 

util/src/overlaydb.rs

@@ -146,7 +146,7 @@ impl OverlayDB {
 			})
 	}
 
-	/// Get the refs and value of the given key.
+	/// Put the refs and value of the given key, possibly deleting it from the db.
 	fn put_payload(&self, key: &H256, payload: (Bytes, u32)) -> bool {
 		if payload.1 > 0 {
 			let mut s = RlpStream::new_list(2);