First implementation of K2V (#293)

**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: https://git.deuxfleurs.fr/Deuxfleurs/garage/pulls/293
Co-authored-by: Alex <alex@adnab.me>
Co-committed-by: Alex <alex@adnab.me>

1 files changed, 16 insertions, 3 deletions

diff --git a/src/garage/admin.rs b/src/garage/admin.rs
index 0b20bb20..af0c3f22 100644
--- a/src/garage/admin.rs
+++ b/src/garage/admin.rs
@@ -21,8 +21,8 @@ use garage_model::garage::Garage;
 use garage_model::helper::error::{Error, OkOrBadRequest};
 use garage_model::key_table::*;
 use garage_model::migrate::Migrate;
-use garage_model::object_table::ObjectFilter;
 use garage_model::permission::*;
+use garage_model::s3::object_table::ObjectFilter;
 
 use crate::cli::*;
 use crate::repair::Repair;
@@ -80,7 +80,13 @@ impl AdminRpcHandler {
 		let buckets = self
 			.garage
 			.bucket_table
-			.get_range(&EmptyKey, None, Some(DeletedFilter::NotDeleted), 10000)
+			.get_range(
+				&EmptyKey,
+				None,
+				Some(DeletedFilter::NotDeleted),
+				10000,
+				EnumerationOrder::Forward,
+			)
 			.await?;
 		Ok(AdminRpc::BucketList(buckets))
 	}
@@ -210,7 +216,13 @@ impl AdminRpcHandler {
 		let objects = self
 			.garage
 			.object_table
-			.get_range(&bucket_id, None, Some(ObjectFilter::IsData), 10)
+			.get_range(
+				&bucket_id,
+				None,
+				Some(ObjectFilter::IsData),
+				10,
+				EnumerationOrder::Forward,
+			)
 			.await?;
 		if !objects.is_empty() {
 			return Err(Error::BadRequest(format!(
@@ -445,6 +457,7 @@ impl AdminRpcHandler {
 				None,
 				Some(KeyFilter::Deleted(DeletedFilter::NotDeleted)),
 				10000,
+				EnumerationOrder::Forward,
 			)
 			.await?
 			.iter()