From b44d3fc796484a50cd6854f20c9b46e5fddedc9d Mon Sep 17 00:00:00 2001 From: Alex Date: Wed, 8 Jun 2022 10:01:44 +0200 Subject: 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 Reviewed-on: https://git.deuxfleurs.fr/Deuxfleurs/garage/pulls/322 Co-authored-by: Alex Co-committed-by: Alex --- src/table/schema.rs | 19 ++++++++++++++----- 1 file changed, 14 insertions(+), 5 deletions(-) (limited to 'src/table/schema.rs') diff --git a/src/table/schema.rs b/src/table/schema.rs index 37327037..74f57798 100644 --- a/src/table/schema.rs +++ b/src/table/schema.rs @@ -1,5 +1,6 @@ use serde::{Deserialize, Serialize}; +use garage_db as db; use garage_util::data::*; use crate::crdt::Crdt; @@ -82,11 +83,19 @@ pub trait TableSchema: Send + Sync { None } - // Updated triggers some stuff downstream, but it is not supposed to block or fail, - // as the update itself is an unchangeable fact that will never go back - // due to CRDT logic. Typically errors in propagation of info should be logged - // to stderr. - fn updated(&self, _old: Option<&Self::E>, _new: Option<&Self::E>) {} + /// Actions triggered by data changing in a table. If such actions + /// include updates to the local database that should be applied + /// atomically with the item update itself, a db transaction is + /// provided on which these changes should be done. + /// This function can return a DB error but that's all. + fn updated( + &self, + _tx: &mut db::Transaction, + _old: Option<&Self::E>, + _new: Option<&Self::E>, + ) -> db::TxOpResult<()> { + Ok(()) + } fn matches_filter(entry: &Self::E, filter: &Self::Filter) -> bool; } -- cgit v1.2.3