- [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>
**Specification:**
View spec at [this URL](https://git.deuxfleurs.fr/Deuxfleurs/garage/src/branch/k2v/doc/drafts/k2v-spec.md)
- [x] Specify the structure of K2V triples
- [x] Specify the DVVS format used for causality detection
- [x] Specify the K2V index (just a counter of number of values per partition key)
- [x] Specify single-item endpoints: ReadItem, InsertItem, DeleteItem
- [x] Specify index endpoint: ReadIndex
- [x] Specify multi-item endpoints: InsertBatch, ReadBatch, DeleteBatch
- [x] Move to JSON objects instead of tuples
- [x] Specify endpoints for polling for updates on single values (PollItem)
**Implementation:**
- [x] Table for K2V items, causal contexts
- [x] Indexing mechanism and table for K2V index
- [x] Make API handlers a bit more generic
- [x] K2V API endpoint
- [x] K2V API router
- [x] ReadItem
- [x] InsertItem
- [x] DeleteItem
- [x] PollItem
- [x] ReadIndex
- [x] InsertBatch
- [x] ReadBatch
- [x] DeleteBatch
**Testing:**
- [x] Just a simple Python script that does some requests to check visually that things are going right (does not contain parsing of results or assertions on returned values)
- [x] Actual tests:
- [x] Adapt testing framework
- [x] Simple test with InsertItem + ReadItem
- [x] Test with several Insert/Read/DeleteItem + ReadIndex
- [x] Test all combinations of return formats for ReadItem
- [x] Test with ReadBatch, InsertBatch, DeleteBatch
- [x] Test with PollItem
- [x] Test error codes
- [ ] Fix most broken stuff
- [x] test PollItem broken randomly
- [x] when invalid causality tokens are given, errors should be 4xx not 5xx
**Improvements:**
- [x] Descending range queries
- [x] Specify
- [x] Implement
- [x] Add test
- [x] Batch updates to index counter
- [x] Put K2V behind `k2v` feature flag
Co-authored-by: Alex Auvolat <alex@adnab.me>
Reviewed-on: Deuxfleurs/garage#293
Co-authored-by: Alex <alex@adnab.me>
Co-committed-by: Alex <alex@adnab.me>
Nodes would stabilize on different encoding formats for the values,
some having the pre-migration format and some having the post-migration
format. This would be reflected in the Merkle trees never converging
and thus having an infinite resync loop.
