Having all Engine enum variants conditional causes compilation errors
when *none* of the DB engine features is enabled. This is not an issue
for full garage build, but affects crates that use garage_db as
dependency.
Change all variants to be present at all times. It solves compilation
errors and also allows us to better differentiate between invalid DB
engine name and engine with support not compiled in current binary.
Use optional DB open overrides for both input and output database.
Duplicating the same override flag for input/output would result in too
many, too long flags. It would be too costly for very rare edge-case
where converting between same DB engine, just with different flags.
Because overrides flags for different engines are disjoint and we are
preventing conversion between same input/ouput DB engine, we can have
only one set.
The override flag will be passed either to input or output, based on
engine type it belongs to. It will never be passed to both of them and
cause unwelcome surprise to user.
- [x] Refactoring of internal counting API
- [x] Repair procedure for counters (it's an offline procedure!!!)
- [x] New counter for objects in buckets
- [x] Add quotas to buckets struct
- [x] Add CLI to manage bucket quotas
- [x] Add admin API to manage bucket quotas
- [x] Apply quotas by adding checks on put operations
- [x] Proof-read
Co-authored-by: Alex Auvolat <alex@adnab.me>
Reviewed-on: Deuxfleurs/garage#326
Co-authored-by: Alex <alex@adnab.me>
Co-committed-by: Alex <alex@adnab.me>
- [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: Deuxfleurs/garage#322
Co-authored-by: Alex <alex@adnab.me>
Co-committed-by: Alex <alex@adnab.me>
