impl approval distribution (#2160)

* initial impl approval distribution

* initial tests and fixes

* batching seems difficult: different peers have different needs

* bridge: fix test after merge

* some guide updates

* only send assignments to peers who know about the block

* fix a test, add approvals test

* simplify

* do not send assignment to peers for finalized blocks

* guide: protocol input and output

* one more test

* more comments, logs, initial metrics

* fix a typo

* one more thing: early return when reimporting a thing locally

Author: Andronik Ordian

Cargo.lock

@@ -52,6 +52,7 @@ members = [
 	"node/core/proposer",
 	"node/core/provisioner",
 	"node/core/runtime-api",
+	"node/network/approval-distribution",
 	"node/network/bridge",
 	"node/network/pov-distribution",
 	"node/network/protocol",

Cargo.toml

@@ -0,0 +1,28 @@
+[package]
+name = "polkadot-approval-distribution"
+version = "0.1.0"
+authors = ["Parity Technologies <[email protected]>"]
+edition = "2018"
+
+[dependencies]
+polkadot-node-primitives = { path = "../../primitives" }
+polkadot-node-network-protocol = { path = "../protocol" }
+polkadot-node-subsystem = { path = "../../subsystem" }
+polkadot-node-subsystem-util = { path = "../../subsystem-util" }
+polkadot-primitives = { path = "../../../primitives" }
+
+futures = "0.3.8"
+tracing = "0.1.22"
+tracing-futures = "0.2.4"
+
+[dev-dependencies]
+sp-core = { git = "https://github.com/paritytech/substrate", branch = "master", features = ["std"] }
+
+polkadot-node-subsystem-util = { path = "../../subsystem-util" }
+polkadot-node-subsystem-test-helpers = { path = "../../subsystem-test-helpers" }
+
+assert_matches = "1.4.0"
+schnorrkel = { version = "0.9.1", default-features = false }
+rand_core = "0.5.1" # should match schnorrkel
+env_logger = "0.8.2"
+log = "0.4.13"