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/metrics.rs | 21 ++++++++++----------- 1 file changed, 10 insertions(+), 11 deletions(-) (limited to 'src/table/metrics.rs') diff --git a/src/table/metrics.rs b/src/table/metrics.rs index 752a2a6d..3a1783e0 100644 --- a/src/table/metrics.rs +++ b/src/table/metrics.rs @@ -1,6 +1,7 @@ use opentelemetry::{global, metrics::*, KeyValue}; -use garage_util::sled_counter::SledCountedTree; +use garage_db as db; +use garage_db::counted_tree_hack::CountedTree; /// TableMetrics reference all counter used for metrics pub struct TableMetrics { @@ -19,21 +20,19 @@ pub struct TableMetrics { pub(crate) sync_items_received: Counter, } impl TableMetrics { - pub fn new( - table_name: &'static str, - merkle_todo: sled::Tree, - gc_todo: SledCountedTree, - ) -> Self { + pub fn new(table_name: &'static str, merkle_todo: db::Tree, gc_todo: CountedTree) -> Self { let meter = global::meter(table_name); TableMetrics { _merkle_todo_len: meter .u64_value_observer( "table.merkle_updater_todo_queue_length", move |observer| { - observer.observe( - merkle_todo.len() as u64, - &[KeyValue::new("table_name", table_name)], - ) + if let Ok(v) = merkle_todo.len() { + observer.observe( + v as u64, + &[KeyValue::new("table_name", table_name)], + ); + } }, ) .with_description("Merkle tree updater TODO queue length") @@ -45,7 +44,7 @@ impl TableMetrics { observer.observe( gc_todo.len() as u64, &[KeyValue::new("table_name", table_name)], - ) + ); }, ) .with_description("Table garbage collector TODO queue length") -- cgit v1.2.3