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, 98 insertions, 0 deletions

diff --git a/src/garage/tests/k2v/poll.rs b/src/garage/tests/k2v/poll.rs
new file mode 100644
index 00000000..70dc0410
--- /dev/null
+++ b/src/garage/tests/k2v/poll.rs
@@ -0,0 +1,98 @@
+use hyper::Method;
+use std::time::Duration;
+
+use crate::common;
+
+#[tokio::test]
+async fn test_poll() {
+	let ctx = common::context();
+	let bucket = ctx.create_bucket("test-k2v-poll");
+
+	// Write initial value
+	let res = ctx
+		.k2v
+		.request
+		.builder(bucket.clone())
+		.method(Method::PUT)
+		.path("root")
+		.query_param("sort_key", Some("test1"))
+		.body(b"Initial value".to_vec())
+		.send()
+		.await
+		.unwrap();
+	assert_eq!(res.status(), 200);
+
+	// Retrieve initial value to get its causality token
+	let res2 = ctx
+		.k2v
+		.request
+		.builder(bucket.clone())
+		.path("root")
+		.query_param("sort_key", Some("test1"))
+		.signed_header("accept", "application/octet-stream")
+		.send()
+		.await
+		.unwrap();
+	assert_eq!(res2.status(), 200);
+	let ct = res2
+		.headers()
+		.get("x-garage-causality-token")
+		.unwrap()
+		.to_str()
+		.unwrap()
+		.to_string();
+
+	let res2_body = hyper::body::to_bytes(res2.into_body())
+		.await
+		.unwrap()
+		.to_vec();
+	assert_eq!(res2_body, b"Initial value");
+
+	// Start poll operation
+	let poll = {
+		let bucket = bucket.clone();
+		let ct = ct.clone();
+		tokio::spawn(async move {
+			let ctx = common::context();
+			ctx.k2v
+				.request
+				.builder(bucket.clone())
+				.path("root")
+				.query_param("sort_key", Some("test1"))
+				.query_param("causality_token", Some(ct))
+				.query_param("timeout", Some("10"))
+				.signed_header("accept", "application/octet-stream")
+				.send()
+				.await
+		})
+	};
+
+	// Write new value that supersedes initial one
+	let res = ctx
+		.k2v
+		.request
+		.builder(bucket.clone())
+		.method(Method::PUT)
+		.path("root")
+		.query_param("sort_key", Some("test1"))
+		.signed_header("x-garage-causality-token", ct)
+		.body(b"New value".to_vec())
+		.send()
+		.await
+		.unwrap();
+	assert_eq!(res.status(), 200);
+
+	// Check poll finishes with correct value
+	let poll_res = tokio::select! {
+		_ = tokio::time::sleep(Duration::from_secs(10)) => panic!("poll did not terminate in time"),
+		res = poll => res.unwrap().unwrap(),
+	};
+
+	assert_eq!(poll_res.status(), 200);
+
+	let poll_res_body = hyper::body::to_bytes(poll_res.into_body())
+		.await
+		.unwrap()
+		.to_vec();
+	assert_eq!(poll_res_body, b"New value");
+}