Merge pull request #1185 from ethcore/ipc-fixes

Database service upgrade (from the ipc branch)

db/Cargo.toml

@@ -8,17 +8,19 @@ authors = ["Ethcore <admin@ethcore.io>"]
 build = "build.rs"
 
 [build-dependencies]
-syntex = "*"
+syntex = "0.32"
 ethcore-ipc-codegen = { path = "../ipc/codegen" }
 
 [dependencies]
-ethcore-util = { path = "../util" }
 clippy = { version = "0.0.67", optional = true}
 ethcore-devtools = { path = "../devtools" }
 ethcore-ipc = { path = "../ipc/rpc" }
 rocksdb = { git = "https://github.com/ethcore/rust-rocksdb" }
 semver = "0.2"
 ethcore-ipc-nano = { path = "../ipc/nano" }
+nanomsg = { git = "https://github.com/ethcore/nanomsg.rs.git" }
+crossbeam = "0.2"
+ethcore-util = { path = "../util" }
 
 [features]
 dev = ["clippy"]

db/src/database.rs

@@ -18,15 +18,13 @@
 
 use traits::*;
 use rocksdb::{DB, Writable, WriteBatch, IteratorMode, DBIterator,
-	IndexType, Options, DBCompactionStyle, BlockBasedOptions, Direction};
-use std::collections::BTreeMap;
-use std::sync::{RwLock};
+IndexType, Options, DBCompactionStyle, BlockBasedOptions, Direction};
+use std::sync::{RwLock, Arc};
 use std::convert::From;
 use ipc::IpcConfig;
-use std::ops::*;
 use std::mem;
 use ipc::binary::BinaryConvertError;
-use std::collections::VecDeque;
+use std::collections::{VecDeque, HashMap, BTreeMap};
 
 impl From<String> for Error {
 	fn from(s: String) -> Error {
@@ -34,20 +32,136 @@ impl From<String> for Error {
 	}
 }
 
+enum WriteCacheEntry {
+	Remove,
+	Write(Vec<u8>),
+}
+
+pub struct WriteCache {
+	entries: HashMap<Vec<u8>, WriteCacheEntry>,
+	preferred_len: usize,
+}
+
+const FLUSH_BATCH_SIZE: usize = 4096;
+
+impl WriteCache {
+	fn new(cache_len: usize) -> WriteCache {
+		WriteCache {
+			entries: HashMap::new(),
+			preferred_len: cache_len,
+		}
+	}
+
+	fn write(&mut self, key: Vec<u8>, val: Vec<u8>) {
+		self.entries.insert(key, WriteCacheEntry::Write(val));
+	}
+
+	fn remove(&mut self, key: Vec<u8>) {
+		self.entries.insert(key, WriteCacheEntry::Remove);
+	}
+
+	fn get(&self, key: &Vec<u8>) -> Option<Vec<u8>> {
+		self.entries.get(key).and_then(
+			|vec_ref| match vec_ref {
+				&WriteCacheEntry::Write(ref val) => Some(val.clone()),
+				&WriteCacheEntry::Remove => None
+			})
+	}
+
+	/// WriteCache should be locked for this
+	fn flush(&mut self, db: &DB, amount: usize) -> Result<(), Error> {
+		let batch = WriteBatch::new();
+		let mut removed_so_far = 0;
+		while removed_so_far < amount {
+			if self.entries.len() == 0 { break; }
+			let removed_key = {
+				let (key, cache_entry) = self.entries.iter().nth(0)
+				.expect("if entries.len == 0, we should have break in the loop, still we got here somehow");
+
+				match *cache_entry {
+					WriteCacheEntry::Write(ref val) => {
+						try!(batch.put(&key, val));
+					},
+					WriteCacheEntry::Remove => {
+						try!(batch.delete(&key));
+					},
+				}
+				key.clone()
+			};
+
+			self.entries.remove(&removed_key);
+
+			removed_so_far = removed_so_far + 1;
+		}
+		if removed_so_far > 0 {
+			try!(db.write(batch));
+		}
+		Ok(())
+	}
+
+	/// flushes until cache is empty
+	fn flush_all(&mut self, db: &DB) -> Result<(), Error> {
+		while !self.is_empty() { try!(self.flush(db, FLUSH_BATCH_SIZE)); }
+		Ok(())
+	}
+
+	fn is_empty(&self) -> bool {
+		self.entries.is_empty()
+	}
+
+	fn try_shrink(&mut self, db: &DB) -> Result<(), Error> {
+		if self.entries.len() > self.preferred_len {
+			try!(self.flush(db, FLUSH_BATCH_SIZE));
+		}
+		Ok(())
+	}
+}
+
 pub struct Database {
 	db: RwLock<Option<DB>>,
-	transactions: RwLock<BTreeMap<TransactionHandle, WriteBatch>>,
+	/// Iterators - dont't use between threads!
 	iterators: RwLock<BTreeMap<IteratorHandle, DBIterator>>,
+	write_cache: RwLock<WriteCache>,
 }
 
+unsafe impl Send for Database {}
+unsafe impl Sync for Database {}
+
 impl Database {
 	pub fn new() -> Database {
 		Database {
 			db: RwLock::new(None),
-			transactions: RwLock::new(BTreeMap::new()),
 			iterators: RwLock::new(BTreeMap::new()),
+			write_cache: RwLock::new(WriteCache::new(DEFAULT_CACHE_LEN)),
 		}
 	}
+
+	pub fn flush(&self) -> Result<(), Error> {
+		let mut cache_lock = self.write_cache.write().unwrap();
+		let db_lock = self.db.read().unwrap();
+		if db_lock.is_none() { return Ok(()); }
+		let db = db_lock.as_ref().unwrap();
+
+		try!(cache_lock.try_shrink(&db));
+		Ok(())
+	}
+
+	pub fn flush_all(&self) -> Result<(), Error> {
+		let mut cache_lock = self.write_cache.write().unwrap();
+		let db_lock = self.db.read().unwrap();
+		if db_lock.is_none() { return Ok(()); }
+		let db = db_lock.as_ref().expect("we should have exited with Ok(()) on the previous step");
+
+		try!(cache_lock.flush_all(&db));
+		Ok(())
+
+	}
+}
+
+impl Drop for Database {
+	fn drop(&mut self) {
+		self.flush().unwrap();
+	}
 }
 
 #[derive(Ipc)]
@@ -72,51 +186,64 @@ impl DatabaseService for Database {
 		Ok(())
 	}
 
+	/// Opens database in the specified path with the default config
+	fn open_default(&self, path: String) -> Result<(), Error> {
+		self.open(DatabaseConfig::default(), path)
+	}
+
 	fn close(&self) -> Result<(), Error> {
+		try!(self.flush_all());
+
 		let mut db = self.db.write().unwrap();
 		if db.is_none() { return Err(Error::IsClosed); }
 
-		// TODO: wait for transactions to expire/close here?
-		if self.transactions.read().unwrap().len() > 0 { return Err(Error::UncommitedTransactions); }
-
 		*db = None;
 		Ok(())
 	}
 
 	fn put(&self, key: &[u8], value: &[u8]) -> Result<(), Error> {
-		let db_lock = self.db.read().unwrap();
-		let db = try!(db_lock.as_ref().ok_or(Error::IsClosed));
-
-		try!(db.put(key, value));
+		let mut cache_lock = self.write_cache.write().unwrap();
+		cache_lock.write(key.to_vec(), value.to_vec());
 		Ok(())
 	}
 
 	fn delete(&self, key: &[u8]) -> Result<(), Error> {
-		let db_lock = self.db.read().unwrap();
-		let db = try!(db_lock.as_ref().ok_or(Error::IsClosed));
-
-		try!(db.delete(key));
+		let mut cache_lock = self.write_cache.write().unwrap();
+		cache_lock.remove(key.to_vec());
 		Ok(())
 	}
 
-	fn write(&self, handle: TransactionHandle) -> Result<(), Error> {
-		let db_lock = self.db.read().unwrap();
-		let db = try!(db_lock.as_ref().ok_or(Error::IsClosed));
+	fn write(&self, transaction: DBTransaction) -> Result<(), Error> {
+		let mut cache_lock = self.write_cache.write().unwrap();
 
-		let mut transactions = self.transactions.write().unwrap();
-		let batch = try!(
-			transactions.remove(&handle).ok_or(Error::TransactionUnknown)
-		);
-		try!(db.write(batch));
+		let mut writes = transaction.writes.borrow_mut();
+		for kv in writes.drain(..) {
+			cache_lock.write(kv.key, kv.value);
+		}
+
+		let mut removes = transaction.removes.borrow_mut();
+		for k in removes.drain(..) {
+			cache_lock.remove(k);
+		}
 		Ok(())
 	}
 
 	fn get(&self, key: &[u8]) -> Result<Option<Vec<u8>>, Error> {
+		{
+			let key_vec = key.to_vec();
+			let cache_hit = self.write_cache.read().unwrap().get(&key_vec);
+
+			if cache_hit.is_some() {
+				return Ok(Some(cache_hit.expect("cache_hit.is_some() = true, still there is none somehow here")))
+			}
+		}
 		let db_lock = self.db.read().unwrap();
 		let db = try!(db_lock.as_ref().ok_or(Error::IsClosed));
 
 		match try!(db.get(key)) {
-			Some(db_vec) => Ok(Some(db_vec.to_vec())),
+			Some(db_vec) => {
+				Ok(Some(db_vec.to_vec()))
+			},
 			None => Ok(None),
 		}
 	}
@@ -166,37 +293,35 @@ impl DatabaseService for Database {
 		})
 	}
 
-	fn transaction_put(&self, transaction: TransactionHandle, key: &[u8], value: &[u8]) -> Result<(), Error>
-	{
-		let mut transactions = self.transactions.write().unwrap();
-		let batch = try!(
-			transactions.get_mut(&transaction).ok_or(Error::TransactionUnknown)
-		);
-		try!(batch.put(&key, &value));
+	fn dispose_iter(&self, handle: IteratorHandle) -> Result<(), Error> {
+		let mut iterators = self.iterators.write().unwrap();
+		iterators.remove(&handle);
 		Ok(())
 	}
-
-	fn transaction_delete(&self, transaction: TransactionHandle, key: &[u8]) -> Result<(), Error> {
-		let mut transactions = self.transactions.write().unwrap();
-		let batch = try!(
-			transactions.get_mut(&transaction).ok_or(Error::TransactionUnknown)
-		);
-		try!(batch.delete(&key));
-		Ok(())
-	}
-
-	fn new_transaction(&self) -> TransactionHandle {
-		let mut transactions = self.transactions.write().unwrap();
-		let next_transaction = transactions.keys().last().unwrap_or(&0) + 1;
-		transactions.insert(next_transaction, WriteBatch::new());
-
-		next_transaction
-	}
 }
 
 // TODO : put proper at compile-time
 impl IpcConfig for Database {}
 
+/// Database iterator
+pub struct DatabaseIterator {
+	client: Arc<DatabaseClient<::nanomsg::Socket>>,
+	handle: IteratorHandle,
+}
+
+impl Iterator for DatabaseIterator {
+	type Item = (Vec<u8>, Vec<u8>);
+
+	fn next(&mut self) -> Option<Self::Item> {
+		self.client.iter_next(self.handle).and_then(|kv| Some((kv.key, kv.value)))
+	}
+}
+
+impl Drop for DatabaseIterator {
+	fn drop(&mut self) {
+		self.client.dispose_iter(self.handle).unwrap();
+	}
+}
 
 #[cfg(test)]
 mod test {
@@ -215,7 +340,7 @@ mod test {
 	fn can_be_open_empty() {
 		let db = Database::new();
 		let path = RandomTempPath::create_dir();
-		db.open(DatabaseConfig { prefix_size: Some(8) }, path.as_str().to_owned()).unwrap();
+		db.open_default(path.as_str().to_owned()).unwrap();
 
 		assert!(db.is_empty().is_ok());
 	}
@@ -224,9 +349,10 @@ mod test {
 	fn can_store_key() {
 		let db = Database::new();
 		let path = RandomTempPath::create_dir();
-		db.open(DatabaseConfig { prefix_size: None }, path.as_str().to_owned()).unwrap();
+		db.open_default(path.as_str().to_owned()).unwrap();
 
 		db.put("xxx".as_bytes(), "1".as_bytes()).unwrap();
+		db.flush_all().unwrap();
 		assert!(!db.is_empty().unwrap());
 	}
 
@@ -234,15 +360,37 @@ mod test {
 	fn can_retrieve() {
 		let db = Database::new();
 		let path = RandomTempPath::create_dir();
-		db.open(DatabaseConfig { prefix_size: None }, path.as_str().to_owned()).unwrap();
+		db.open_default(path.as_str().to_owned()).unwrap();
 		db.put("xxx".as_bytes(), "1".as_bytes()).unwrap();
 		db.close().unwrap();
 
-		db.open(DatabaseConfig { prefix_size: None }, path.as_str().to_owned()).unwrap();
+		db.open_default(path.as_str().to_owned()).unwrap();
 		assert_eq!(db.get("xxx".as_bytes()).unwrap().unwrap(), "1".as_bytes().to_vec());
 	}
 }
 
+#[cfg(test)]
+mod write_cache_tests {
+	use super::Database;
+	use traits::*;
+	use devtools::*;
+
+	#[test]
+	fn cache_write_flush() {
+		let db = Database::new();
+		let path = RandomTempPath::create_dir();
+
+		db.open_default(path.as_str().to_owned()).unwrap();
+		db.put("100500".as_bytes(), "1".as_bytes()).unwrap();
+		db.delete("100500".as_bytes()).unwrap();
+		db.flush_all().unwrap();
+
+		let val = db.get("100500".as_bytes()).unwrap();
+		assert!(val.is_none());
+	}
+
+}
+
 #[cfg(test)]
 mod client_tests {
 	use super::{DatabaseClient, Database};
@@ -251,6 +399,8 @@ mod client_tests {
 	use nanoipc;
 	use std::sync::Arc;
 	use std::sync::atomic::{Ordering, AtomicBool};
+	use crossbeam;
+	use run_worker;
 
 	fn init_worker(addr: &str) -> nanoipc::Worker<Database> {
 		let mut worker = nanoipc::Worker::<Database>::new(&Arc::new(Database::new()));
@@ -304,7 +454,7 @@ mod client_tests {
 		while !worker_is_ready.load(Ordering::Relaxed) { }
 		let client = nanoipc::init_duplex_client::<DatabaseClient<_>>(url).unwrap();
 
-		client.open(DatabaseConfig { prefix_size: Some(8) }, path.as_str().to_owned()).unwrap();
+		client.open_default(path.as_str().to_owned()).unwrap();
 		assert!(client.is_empty().unwrap());
 		worker_should_exit.store(true, Ordering::Relaxed);
 	}
@@ -314,27 +464,16 @@ mod client_tests {
 		let url = "ipc:///tmp/parity-db-ipc-test-30.ipc";
 		let path = RandomTempPath::create_dir();
 
-		let worker_should_exit = Arc::new(AtomicBool::new(false));
-		let worker_is_ready = Arc::new(AtomicBool::new(false));
-		let c_worker_should_exit = worker_should_exit.clone();
-		let c_worker_is_ready = worker_is_ready.clone();
-
-		::std::thread::spawn(move || {
-			let mut worker = init_worker(url);
-    		while !c_worker_should_exit.load(Ordering::Relaxed) {
-				worker.poll();
-				c_worker_is_ready.store(true, Ordering::Relaxed);
-			}
-		});
-
-		while !worker_is_ready.load(Ordering::Relaxed) { }
-		let client = nanoipc::init_duplex_client::<DatabaseClient<_>>(url).unwrap();
-
-		client.open(DatabaseConfig { prefix_size: Some(8) }, path.as_str().to_owned()).unwrap();
+		crossbeam::scope(move |scope| {
+			let stop = Arc::new(AtomicBool::new(false));
+			run_worker(scope, stop.clone(), url);
+			let client = nanoipc::init_client::<DatabaseClient<_>>(url).unwrap();
+			client.open_default(path.as_str().to_owned()).unwrap();
 			client.put("xxx".as_bytes(), "1".as_bytes()).unwrap();
 			client.close().unwrap();
 
-		worker_should_exit.store(true, Ordering::Relaxed);
+			stop.store(true, Ordering::Relaxed);
+		});
 	}
 
 	#[test]
@@ -342,29 +481,93 @@ mod client_tests {
 		let url = "ipc:///tmp/parity-db-ipc-test-40.ipc";
 		let path = RandomTempPath::create_dir();
 
-		let worker_should_exit = Arc::new(AtomicBool::new(false));
-		let worker_is_ready = Arc::new(AtomicBool::new(false));
-		let c_worker_should_exit = worker_should_exit.clone();
-		let c_worker_is_ready = worker_is_ready.clone();
+		crossbeam::scope(move |scope| {
+			let stop = Arc::new(AtomicBool::new(false));
+			run_worker(scope, stop.clone(), url);
+			let client = nanoipc::init_client::<DatabaseClient<_>>(url).unwrap();
 
-		::std::thread::spawn(move || {
-			let mut worker = init_worker(url);
-    		while !c_worker_should_exit.load(Ordering::Relaxed) {
-				worker.poll();
-				c_worker_is_ready.store(true, Ordering::Relaxed);
-			}
-		});
-
-		while !worker_is_ready.load(Ordering::Relaxed) { }
-		let client = nanoipc::init_duplex_client::<DatabaseClient<_>>(url).unwrap();
-
-		client.open(DatabaseConfig { prefix_size: Some(8) }, path.as_str().to_owned()).unwrap();
+			client.open_default(path.as_str().to_owned()).unwrap();
 			client.put("xxx".as_bytes(), "1".as_bytes()).unwrap();
 			client.close().unwrap();
 
-		client.open(DatabaseConfig { prefix_size: Some(8) }, path.as_str().to_owned()).unwrap();
+			client.open_default(path.as_str().to_owned()).unwrap();
 			assert_eq!(client.get("xxx".as_bytes()).unwrap().unwrap(), "1".as_bytes().to_vec());
 
-		worker_should_exit.store(true, Ordering::Relaxed);
+			stop.store(true, Ordering::Relaxed);
+		});
+	}
+
+	#[test]
+	fn can_read_empty() {
+		let url = "ipc:///tmp/parity-db-ipc-test-45.ipc";
+		let path = RandomTempPath::create_dir();
+
+		crossbeam::scope(move |scope| {
+			let stop = Arc::new(AtomicBool::new(false));
+			run_worker(scope, stop.clone(), url);
+			let client = nanoipc::init_client::<DatabaseClient<_>>(url).unwrap();
+
+			client.open_default(path.as_str().to_owned()).unwrap();
+			assert!(client.get("xxx".as_bytes()).unwrap().is_none());
+
+			stop.store(true, Ordering::Relaxed);
+		});
+	}
+
+
+	#[test]
+	fn can_commit_client_transaction() {
+		let url = "ipc:///tmp/parity-db-ipc-test-60.ipc";
+		let path = RandomTempPath::create_dir();
+
+		crossbeam::scope(move |scope| {
+			let stop = Arc::new(AtomicBool::new(false));
+			run_worker(scope, stop.clone(), url);
+			let client = nanoipc::init_client::<DatabaseClient<_>>(url).unwrap();
+			client.open_default(path.as_str().to_owned()).unwrap();
+
+			let transaction = DBTransaction::new();
+			transaction.put("xxx".as_bytes(), "1".as_bytes());
+			client.write(transaction).unwrap();
+
+			client.close().unwrap();
+
+			client.open_default(path.as_str().to_owned()).unwrap();
+			assert_eq!(client.get("xxx".as_bytes()).unwrap().unwrap(), "1".as_bytes().to_vec());
+
+			stop.store(true, Ordering::Relaxed);
+		});
+	}
+
+	#[test]
+	fn key_write_read_ipc() {
+		let url = "ipc:///tmp/parity-db-ipc-test-70.ipc";
+		let path = RandomTempPath::create_dir();
+
+		crossbeam::scope(|scope| {
+			let stop = StopGuard::new();
+			run_worker(&scope, stop.share(), url);
+
+			let client = nanoipc::init_client::<DatabaseClient<_>>(url).unwrap();
+
+			client.open_default(path.as_str().to_owned()).unwrap();
+			let mut batch = Vec::new();
+			for _ in 0..100 {
+				batch.push((random_str(256).as_bytes().to_vec(), random_str(256).as_bytes().to_vec()));
+				batch.push((random_str(256).as_bytes().to_vec(), random_str(2048).as_bytes().to_vec()));
+				batch.push((random_str(2048).as_bytes().to_vec(), random_str(2048).as_bytes().to_vec()));
+				batch.push((random_str(2048).as_bytes().to_vec(), random_str(256).as_bytes().to_vec()));
+			}
+
+			for &(ref k, ref v) in batch.iter() {
+				client.put(k, v).unwrap();
+			}
+			client.close().unwrap();
+
+			client.open_default(path.as_str().to_owned()).unwrap();
+			for &(ref k, ref v) in batch.iter() {
+				assert_eq!(v, &client.get(k).unwrap().unwrap());
+			}
+		});
 	}
 }

db/src/lib.rs.in

@@ -19,7 +19,71 @@ extern crate rocksdb;
 extern crate ethcore_devtools as devtools;
 extern crate semver;
 extern crate ethcore_ipc_nano as nanoipc;
+extern crate nanomsg;
+extern crate crossbeam;
 extern crate ethcore_util as util;
 
 pub mod database;
 pub mod traits;
+
+pub use traits::{DatabaseService, DBTransaction, Error};
+pub use database::{Database, DatabaseClient, DatabaseIterator};
+
+use std::sync::Arc;
+use std::sync::atomic::*;
+use std::path::PathBuf;
+
+pub type DatabaseNanoClient = DatabaseClient<::nanomsg::Socket>;
+pub type DatabaseConnection = nanoipc::GuardedSocket<DatabaseNanoClient>;
+
+#[derive(Debug)]
+pub enum ServiceError {
+	Io(std::io::Error),
+	Socket(nanoipc::SocketError),
+}
+
+impl std::convert::From<std::io::Error> for ServiceError {
+	fn from(io_error: std::io::Error) -> ServiceError { ServiceError::Io(io_error) }
+}
+
+impl std::convert::From<nanoipc::SocketError> for ServiceError {
+	fn from(socket_error: nanoipc::SocketError) -> ServiceError { ServiceError::Socket(socket_error) }
+}
+
+pub fn blocks_service_url(db_path: &str) -> Result<String, std::io::Error> {
+	let mut path = PathBuf::from(db_path);
+	try!(::std::fs::create_dir_all(db_path));
+	path.push("blocks.ipc");
+	Ok(format!("ipc://{}", path.to_str().unwrap()))
+}
+
+pub fn extras_service_url(db_path: &str) -> Result<String, ::std::io::Error> {
+	let mut path = PathBuf::from(db_path);
+	try!(::std::fs::create_dir_all(db_path));
+	path.push("extras.ipc");
+	Ok(format!("ipc://{}", path.to_str().unwrap()))
+}
+
+pub fn blocks_client(db_path: &str) -> Result<DatabaseConnection, ServiceError> {
+	let url = try!(blocks_service_url(db_path));
+	let client = try!(nanoipc::init_client::<DatabaseClient<_>>(&url));
+	Ok(client)
+}
+
+pub fn extras_client(db_path: &str) -> Result<DatabaseConnection, ServiceError> {
+	let url = try!(extras_service_url(db_path));
+	let client = try!(nanoipc::init_client::<DatabaseClient<_>>(&url));
+	Ok(client)
+}
+
+// for tests
+pub fn run_worker(scope: &crossbeam::Scope, stop: Arc<AtomicBool>, socket_path: &str) {
+	let socket_path = socket_path.to_owned();
+	scope.spawn(move || {
+		let mut worker = nanoipc::Worker::new(&Arc::new(Database::new()));
+		worker.add_reqrep(&socket_path).unwrap();
+		while !stop.load(Ordering::Relaxed) {
+			worker.poll();
+		}
+	});
+}

db/src/traits.rs

@@ -1,21 +1,38 @@
+// Copyright 2015, 2016 Ethcore (UK) Ltd.
+// This file is part of Parity.
+
+// Parity is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+
+// Parity is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+
+// You should have received a copy of the GNU General Public License
+// along with Parity.  If not, see <http://www.gnu.org/licenses/>.
+
 //! Ethcore database trait
 
-use ipc::BinaryConvertable;
 use std::mem;
 use ipc::binary::BinaryConvertError;
 use std::collections::VecDeque;
+use std::cell::RefCell;
 
-pub type TransactionHandle = u32;
 pub type IteratorHandle = u32;
 
+pub const DEFAULT_CACHE_LEN: usize = 12288;
+
 #[derive(Binary)]
 pub struct KeyValue {
 	pub key: Vec<u8>,
 	pub value: Vec<u8>,
 }
 
-#[derive(Debug, Binary)]
-pub enum Error {
+	#[derive(Debug, Binary)]
+	pub enum Error {
 	AlreadyOpen,
 	IsClosed,
 	RocksDb(String),
@@ -28,13 +45,36 @@ pub enum Error {
 #[derive(Binary)]
 pub struct DatabaseConfig {
 	/// Optional prefix size in bytes. Allows lookup by partial key.
-	pub prefix_size: Option<usize>
+	pub prefix_size: Option<usize>,
+	/// write cache length
+	pub cache: usize,
 }
 
-pub trait DatabaseService {
+impl Default for DatabaseConfig {
+	fn default() -> DatabaseConfig {
+		DatabaseConfig {
+			prefix_size: None,
+			cache: DEFAULT_CACHE_LEN,
+		}
+	}
+}
+
+impl DatabaseConfig {
+	fn with_prefix(prefix: usize) -> DatabaseConfig {
+		DatabaseConfig {
+			prefix_size: Some(prefix),
+			cache: DEFAULT_CACHE_LEN,
+		}
+	}
+}
+
+	pub trait DatabaseService : Sized {
 	/// Opens database in the specified path
 	fn open(&self, config: DatabaseConfig, path: String) -> Result<(), Error>;
 
+	/// Opens database in the specified path with the default config
+	fn open_default(&self, path: String) -> Result<(), Error>;
+
 	/// Closes database
 	fn close(&self) -> Result<(), Error>;
 
@@ -44,18 +84,6 @@ pub trait DatabaseService {
 	/// Delete value by key.
 	fn delete(&self, key: &[u8]) -> Result<(), Error>;
 
-	/// Insert a key-value pair in the transaction. Any existing value value will be overwritten.
-	fn transaction_put(&self, transaction: TransactionHandle, key: &[u8], value: &[u8]) -> Result<(), Error>;
-
-	/// Delete value by key using transaction
-	fn transaction_delete(&self, transaction: TransactionHandle, key: &[u8]) -> Result<(), Error>;
-
-	/// Commit transaction to database.
-	fn write(&self, tr: TransactionHandle) -> Result<(), Error>;
-
-	/// Initiate new transaction on database
-	fn new_transaction(&self) -> TransactionHandle;
-
 	/// Get value by key.
 	fn get(&self, key: &[u8]) -> Result<Option<Vec<u8>>, Error>;
 
@@ -70,4 +98,35 @@ pub trait DatabaseService {
 
 	/// Next key-value for the the given iterator
 	fn iter_next(&self, iterator: IteratorHandle) -> Option<KeyValue>;
+
+	/// Dispose iteration that is no longer needed
+	fn dispose_iter(&self, handle: IteratorHandle) -> Result<(), Error>;
+
+	/// Write client transaction
+	fn write(&self, transaction: DBTransaction) -> Result<(), Error>;
+}
+
+#[derive(Binary)]
+pub struct DBTransaction {
+	pub writes: RefCell<Vec<KeyValue>>,
+	pub removes: RefCell<Vec<Vec<u8>>>,
+}
+
+impl DBTransaction {
+	pub fn new() -> DBTransaction {
+		DBTransaction {
+			writes: RefCell::new(Vec::new()),
+			removes: RefCell::new(Vec::new()),
+		}
+	}
+
+	pub fn put(&self, key: &[u8], value: &[u8]) {
+		let mut brw = self.writes.borrow_mut();
+		brw.push(KeyValue { key: key.to_vec(), value: value.to_vec() });
+	}
+
+	pub fn delete(&self, key: &[u8]) {
+		let mut brw = self.removes.borrow_mut();
+		brw.push(key.to_vec());
+	}
 }