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, 21 insertions, 5 deletions

diff --git a/src/garage/server.rs b/src/garage/server.rs
index 58c9e782..24bb25b3 100644
--- a/src/garage/server.rs
+++ b/src/garage/server.rs
@@ -8,10 +8,13 @@ use garage_util::error::Error;
 
 use garage_admin::metrics::*;
 use garage_admin::tracing_setup::*;
-use garage_api::run_api_server;
+use garage_api::s3::api_server::S3ApiServer;
 use garage_model::garage::Garage;
 use garage_web::run_web_server;
 
+#[cfg(feature = "k2v")]
+use garage_api::k2v::api_server::K2VApiServer;
+
 use crate::admin::*;
 
 async fn wait_from(mut chan: watch::Receiver<bool>) {
@@ -56,12 +59,21 @@ pub async fn run_server(config_file: PathBuf) -> Result<(), Error> {
 	info!("Create admin RPC handler...");
 	AdminRpcHandler::new(garage.clone());
 
-	info!("Initializing API server...");
-	let api_server = tokio::spawn(run_api_server(
+	info!("Initializing S3 API server...");
+	let s3_api_server = tokio::spawn(S3ApiServer::run(
 		garage.clone(),
 		wait_from(watch_cancel.clone()),
 	));
 
+	#[cfg(feature = "k2v")]
+	let k2v_api_server = {
+		info!("Initializing K2V API server...");
+		tokio::spawn(K2VApiServer::run(
+			garage.clone(),
+			wait_from(watch_cancel.clone()),
+		))
+	};
+
 	info!("Initializing web server...");
 	let web_server = tokio::spawn(run_web_server(
 		garage.clone(),
@@ -80,8 +92,12 @@ pub async fn run_server(config_file: PathBuf) -> Result<(), Error> {
 	// Stuff runs
 
 	// When a cancel signal is sent, stuff stops
-	if let Err(e) = api_server.await? {
-		warn!("API server exited with error: {}", e);
+	if let Err(e) = s3_api_server.await? {
+		warn!("S3 API server exited with error: {}", e);
+	}
+	#[cfg(feature = "k2v")]
+	if let Err(e) = k2v_api_server.await? {
+		warn!("K2V API server exited with error: {}", e);
 	}
 	if let Err(e) = web_server.await? {
 		warn!("Web server exited with error: {}", e);