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, 10 insertions, 1 deletions

diff --git a/src/garage/tests/common/mod.rs b/src/garage/tests/common/mod.rs
index 8f88c731..28874b02 100644
--- a/src/garage/tests/common/mod.rs
+++ b/src/garage/tests/common/mod.rs
@@ -17,18 +17,27 @@ pub struct Context {
 	pub garage: &'static garage::Instance,
 	pub client: Client,
 	pub custom_request: CustomRequester,
+	pub k2v: K2VContext,
+}
+
+pub struct K2VContext {
+	pub request: CustomRequester,
 }
 
 impl Context {
 	fn new() -> Self {
 		let garage = garage::instance();
 		let client = client::build_client(garage);
-		let custom_request = CustomRequester::new(garage);
+		let custom_request = CustomRequester::new_s3(garage);
+		let k2v_request = CustomRequester::new_k2v(garage);
 
 		Context {
 			garage,
 			client,
 			custom_request,
+			k2v: K2VContext {
+				request: k2v_request,
+			},
 		}
 	}