feat: add collection locking

Author: peeeuzin

src/collection/mod.rs

@@ -6,6 +6,7 @@ use crate::btree::{BTree, ValueTrait};
 use crate::dustdata_config;
 use crate::error::{Error, Result};
 use crate::page::io::BlockIO;
+use std::fs;
 use std::sync::Mutex;
 use std::{fmt::Debug, sync::Arc};
 use xact::TransactionBuilder;
@@ -21,6 +22,8 @@ pub enum TransactionStatus {
     Aborted,
 }
 
+pub const COLLECTION_LOCK_FILE: &str = ".lock";
+
 #[derive(Clone)]
 pub struct Collection<T: ValueTrait> {
     btree: Arc<Mutex<BTree<String, T>>>,
@@ -31,9 +34,14 @@ pub struct Collection<T: ValueTrait> {
 impl<T: ValueTrait> Collection<T> {
     pub fn new(name: &str) -> Result<Self> {
         let dustdata_config = dustdata_config();
-
         let base_path = dustdata_config.data_path.join(name);
 
+        fs::create_dir_all(&base_path).ok();
+
+        // Create lock file
+        fs::File::create_new(base_path.join(COLLECTION_LOCK_FILE))
+            .map_err(|_| Error::DatabaseLocked)?;
+
         let xlog = Arc::new(Mutex::new(xlog::XLog::new(&base_path)?));
 
         let btree_block = BlockIO::new(base_path.join("Data.db")).map_err(Error::IoError)?;
@@ -99,3 +107,12 @@ impl<T: ValueTrait> Collection<T> {
         self.btree.lock().unwrap().get(&key.to_string())
     }
 }
+
+impl<T: ValueTrait> Drop for Collection<T> {
+    fn drop(&mut self) {
+        let dustdata_config = dustdata_config();
+        let base_path = dustdata_config.data_path.join(&self.name);
+
+        fs::remove_file(base_path.join(COLLECTION_LOCK_FILE)).unwrap();
+    }
+}

src/collection/xlog.rs

@@ -5,7 +5,7 @@ use crate::{
 };
 
 use serde::{Deserialize, Serialize};
-use std::{fs, ops::RangeBounds, path::Path};
+use std::{ops::RangeBounds, path::Path};
 
 pub const XLOG_FILENAME: &str = ".xlog";
 
@@ -26,7 +26,6 @@ impl<T: ValueTrait> XLog<T> {
     where
         P: AsRef<Path>,
     {
-        fs::create_dir_all(&path).ok();
         let log_path = path.as_ref().join(XLOG_FILENAME);
         let io = BlockIO::new(log_path).map_err(Error::IoError)?;
 

src/lib.rs

@@ -61,6 +61,7 @@ use error::Result;
 use serde::{de::DeserializeOwned, Serialize};
 use std::fmt::Debug;
 use std::fs;
+use std::sync::Arc;
 
 #[derive(Debug, PartialEq, Eq, PartialOrd, Ord, Clone)]
 pub enum Either<L, R> {
@@ -104,11 +105,11 @@ impl DustData {
         Ok(Self)
     }
 
-    pub fn collection<T>(&self, name: &str) -> Result<collection::Collection<T>>
+    pub fn collection<T>(&self, name: &str) -> Result<Arc<collection::Collection<T>>>
     where
         T: Sync + Send + Clone + Debug + Serialize + DeserializeOwned + 'static + Ord,
     {
-        collection::Collection::new(name)
+        Ok(Arc::new(collection::Collection::new(name)?))
     }
 
     pub fn drop_collection(&self, name: &str) -> Result<()> {

src/page/io.rs

@@ -1,3 +1,4 @@
+use fs2::FileExt;
 use serde::{de::DeserializeOwned, Deserialize, Serialize};
 use std::{
     fs::{self, File, OpenOptions},
@@ -171,5 +172,13 @@ pub fn open_file(path: &Path) -> io::Result<File> {
         .truncate(false)
         .open(path)?;
 
+    file.lock_exclusive()?;
+
     Ok(file)
 }
+
+impl Drop for BlockIO {
+    fn drop(&mut self) {
+        self.file.unlock().unwrap();
+    }
+}