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authorAlex <alex@adnab.me>2022-06-08 10:01:44 +0200
committerAlex <alex@adnab.me>2022-06-08 10:01:44 +0200
commitb44d3fc796484a50cd6854f20c9b46e5fddedc9d (patch)
tree29f6da0e8dc68485edf713aaa7331536f4ff4fde /src/db/sled_adapter.rs
parent7eed3ceda9cf964e3435f22fc1852e27f4f5a8ae (diff)
downloadgarage-b44d3fc796484a50cd6854f20c9b46e5fddedc9d.tar.gz
garage-b44d3fc796484a50cd6854f20c9b46e5fddedc9d.zip
Abstract database behind generic interface and implement alternative drivers (#322)
- [x] Design interface - [x] Implement Sled backend - [x] Re-implement the SledCountedTree hack ~~on Sled backend~~ on all backends (i.e. over the abstraction) - [x] Convert Garage code to use generic interface - [x] Proof-read converted Garage code - [ ] Test everything well - [x] Implement sqlite backend - [x] Implement LMDB backend - [ ] (Implement Persy backend?) - [ ] (Implement other backends? (like RocksDB, ...)) - [x] Implement backend choice in config file and garage server module - [x] Add CLI for converting between DB formats - Exploit the new interface to put more things in transactions - [x] `.updated()` trigger on Garage tables Fix #284 **Bugs** - [x] When exporting sqlite, trees iterate empty?? - [x] LMDB doesn't work **Known issues for various back-ends** - Sled: - Eats all my RAM and also all my disk space - `.len()` has to traverse the whole table - Is actually quite slow on some operations - And is actually pretty bad code... - Sqlite: - Requires a lock to be taken on all operations. The lock is also taken when iterating on a table with `.iter()`, and the lock isn't released until the iterator is dropped. This means that we must be VERY carefull to not do anything else inside a `.iter()` loop or else we will have a deadlock! Most such cases have been eliminated from the Garage codebase, but there might still be some that remain. If your Garage-over-Sqlite seems to hang/freeze, this is the reason. - (adapter uses a bunch of unsafe code) - Heed (LMDB): - Not suited for 32-bit machines as it has to map the whole DB in memory. - (adpater uses a tiny bit of unsafe code) **My recommendation:** avoid 32-bit machines and use LMDB as much as possible. **Converting databases** is actually quite easy. For example from Sled to LMDB: ```bash cd src/db cargo run --features cli --bin convert -- -i path/to/garage/meta/db -a sled -o path/to/garage/meta/db.lmdb -b lmdb ``` Then, just add this to your `config.toml`: ```toml db_engine = "lmdb" ``` Co-authored-by: Alex Auvolat <alex@adnab.me> Reviewed-on: https://git.deuxfleurs.fr/Deuxfleurs/garage/pulls/322 Co-authored-by: Alex <alex@adnab.me> Co-committed-by: Alex <alex@adnab.me>
Diffstat (limited to 'src/db/sled_adapter.rs')
-rw-r--r--src/db/sled_adapter.rs260
1 files changed, 260 insertions, 0 deletions
diff --git a/src/db/sled_adapter.rs b/src/db/sled_adapter.rs
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+use core::ops::Bound;
+
+use std::cell::Cell;
+use std::collections::HashMap;
+use std::sync::{Arc, RwLock};
+
+use sled::transaction::{
+ ConflictableTransactionError, TransactionError, Transactional, TransactionalTree,
+ UnabortableTransactionError,
+};
+
+use crate::{
+ Db, Error, IDb, ITx, ITxFn, Result, TxError, TxFnResult, TxOpError, TxOpResult, TxResult,
+ TxValueIter, Value, ValueIter,
+};
+
+pub use sled;
+
+// -- err
+
+impl From<sled::Error> for Error {
+ fn from(e: sled::Error) -> Error {
+ Error(format!("Sled: {}", e).into())
+ }
+}
+
+impl From<sled::Error> for TxOpError {
+ fn from(e: sled::Error) -> TxOpError {
+ TxOpError(e.into())
+ }
+}
+
+// -- db
+
+pub struct SledDb {
+ db: sled::Db,
+ trees: RwLock<(Vec<sled::Tree>, HashMap<String, usize>)>,
+}
+
+impl SledDb {
+ pub fn init(db: sled::Db) -> Db {
+ let s = Self {
+ db,
+ trees: RwLock::new((Vec::new(), HashMap::new())),
+ };
+ Db(Arc::new(s))
+ }
+
+ fn get_tree(&self, i: usize) -> Result<sled::Tree> {
+ self.trees
+ .read()
+ .unwrap()
+ .0
+ .get(i)
+ .cloned()
+ .ok_or_else(|| Error("invalid tree id".into()))
+ }
+}
+
+impl IDb for SledDb {
+ fn engine(&self) -> String {
+ "Sled".into()
+ }
+
+ fn open_tree(&self, name: &str) -> Result<usize> {
+ let mut trees = self.trees.write().unwrap();
+ if let Some(i) = trees.1.get(name) {
+ Ok(*i)
+ } else {
+ let tree = self.db.open_tree(name)?;
+ let i = trees.0.len();
+ trees.0.push(tree);
+ trees.1.insert(name.to_string(), i);
+ Ok(i)
+ }
+ }
+
+ fn list_trees(&self) -> Result<Vec<String>> {
+ let mut trees = vec![];
+ for name in self.db.tree_names() {
+ let name = std::str::from_utf8(&name)
+ .map_err(|e| Error(format!("{}", e).into()))?
+ .to_string();
+ if name != "__sled__default" {
+ trees.push(name);
+ }
+ }
+ Ok(trees)
+ }
+
+ // ----
+
+ fn get(&self, tree: usize, key: &[u8]) -> Result<Option<Value>> {
+ let tree = self.get_tree(tree)?;
+ let val = tree.get(key)?;
+ Ok(val.map(|x| x.to_vec()))
+ }
+
+ fn len(&self, tree: usize) -> Result<usize> {
+ let tree = self.get_tree(tree)?;
+ Ok(tree.len())
+ }
+
+ fn insert(&self, tree: usize, key: &[u8], value: &[u8]) -> Result<Option<Value>> {
+ let tree = self.get_tree(tree)?;
+ let old_val = tree.insert(key, value)?;
+ Ok(old_val.map(|x| x.to_vec()))
+ }
+
+ fn remove(&self, tree: usize, key: &[u8]) -> Result<Option<Value>> {
+ let tree = self.get_tree(tree)?;
+ let old_val = tree.remove(key)?;
+ Ok(old_val.map(|x| x.to_vec()))
+ }
+
+ fn iter(&self, tree: usize) -> Result<ValueIter<'_>> {
+ let tree = self.get_tree(tree)?;
+ Ok(Box::new(tree.iter().map(|v| {
+ v.map(|(x, y)| (x.to_vec(), y.to_vec())).map_err(Into::into)
+ })))
+ }
+
+ fn iter_rev(&self, tree: usize) -> Result<ValueIter<'_>> {
+ let tree = self.get_tree(tree)?;
+ Ok(Box::new(tree.iter().rev().map(|v| {
+ v.map(|(x, y)| (x.to_vec(), y.to_vec())).map_err(Into::into)
+ })))
+ }
+
+ fn range<'r>(
+ &self,
+ tree: usize,
+ low: Bound<&'r [u8]>,
+ high: Bound<&'r [u8]>,
+ ) -> Result<ValueIter<'_>> {
+ let tree = self.get_tree(tree)?;
+ Ok(Box::new(tree.range::<&'r [u8], _>((low, high)).map(|v| {
+ v.map(|(x, y)| (x.to_vec(), y.to_vec())).map_err(Into::into)
+ })))
+ }
+ fn range_rev<'r>(
+ &self,
+ tree: usize,
+ low: Bound<&'r [u8]>,
+ high: Bound<&'r [u8]>,
+ ) -> Result<ValueIter<'_>> {
+ let tree = self.get_tree(tree)?;
+ Ok(Box::new(tree.range::<&'r [u8], _>((low, high)).rev().map(
+ |v| v.map(|(x, y)| (x.to_vec(), y.to_vec())).map_err(Into::into),
+ )))
+ }
+
+ // ----
+
+ fn transaction(&self, f: &dyn ITxFn) -> TxResult<(), ()> {
+ let trees = self.trees.read().unwrap();
+ let res = trees.0.transaction(|txtrees| {
+ let mut tx = SledTx {
+ trees: txtrees,
+ err: Cell::new(None),
+ };
+ match f.try_on(&mut tx) {
+ TxFnResult::Ok => {
+ assert!(tx.err.into_inner().is_none());
+ Ok(())
+ }
+ TxFnResult::Abort => {
+ assert!(tx.err.into_inner().is_none());
+ Err(ConflictableTransactionError::Abort(()))
+ }
+ TxFnResult::DbErr => {
+ let e = tx.err.into_inner().expect("No DB error");
+ Err(e.into())
+ }
+ }
+ });
+ match res {
+ Ok(()) => Ok(()),
+ Err(TransactionError::Abort(())) => Err(TxError::Abort(())),
+ Err(TransactionError::Storage(s)) => Err(TxError::Db(s.into())),
+ }
+ }
+}
+
+// ----
+
+struct SledTx<'a> {
+ trees: &'a [TransactionalTree],
+ err: Cell<Option<UnabortableTransactionError>>,
+}
+
+impl<'a> SledTx<'a> {
+ fn get_tree(&self, i: usize) -> TxOpResult<&TransactionalTree> {
+ self.trees.get(i).ok_or_else(|| {
+ TxOpError(Error(
+ "invalid tree id (it might have been openned after the transaction started)".into(),
+ ))
+ })
+ }
+
+ fn save_error<R>(
+ &self,
+ v: std::result::Result<R, UnabortableTransactionError>,
+ ) -> TxOpResult<R> {
+ match v {
+ Ok(x) => Ok(x),
+ Err(e) => {
+ let txt = format!("{}", e);
+ self.err.set(Some(e));
+ Err(TxOpError(Error(txt.into())))
+ }
+ }
+ }
+}
+
+impl<'a> ITx for SledTx<'a> {
+ fn get(&self, tree: usize, key: &[u8]) -> TxOpResult<Option<Value>> {
+ let tree = self.get_tree(tree)?;
+ let tmp = self.save_error(tree.get(key))?;
+ Ok(tmp.map(|x| x.to_vec()))
+ }
+ fn len(&self, _tree: usize) -> TxOpResult<usize> {
+ unimplemented!(".len() in transaction not supported with Sled backend")
+ }
+
+ fn insert(&mut self, tree: usize, key: &[u8], value: &[u8]) -> TxOpResult<Option<Value>> {
+ let tree = self.get_tree(tree)?;
+ let old_val = self.save_error(tree.insert(key, value))?;
+ Ok(old_val.map(|x| x.to_vec()))
+ }
+ fn remove(&mut self, tree: usize, key: &[u8]) -> TxOpResult<Option<Value>> {
+ let tree = self.get_tree(tree)?;
+ let old_val = self.save_error(tree.remove(key))?;
+ Ok(old_val.map(|x| x.to_vec()))
+ }
+
+ fn iter(&self, _tree: usize) -> TxOpResult<TxValueIter<'_>> {
+ unimplemented!("Iterators in transactions not supported with Sled backend");
+ }
+ fn iter_rev(&self, _tree: usize) -> TxOpResult<TxValueIter<'_>> {
+ unimplemented!("Iterators in transactions not supported with Sled backend");
+ }
+
+ fn range<'r>(
+ &self,
+ _tree: usize,
+ _low: Bound<&'r [u8]>,
+ _high: Bound<&'r [u8]>,
+ ) -> TxOpResult<TxValueIter<'_>> {
+ unimplemented!("Iterators in transactions not supported with Sled backend");
+ }
+ fn range_rev<'r>(
+ &self,
+ _tree: usize,
+ _low: Bound<&'r [u8]>,
+ _high: Bound<&'r [u8]>,
+ ) -> TxOpResult<TxValueIter<'_>> {
+ unimplemented!("Iterators in transactions not supported with Sled backend");
+ }
+}