Fix statement distribution: forward statements to other peers. (#2146)

* add candidate hash statement circulation span

* add relay-parent to hash-span

* Some typos and misspellings in docs I found, during my studies. (#2144)

* Fix stale link to overseer docs

* Some typos and mispellings in docs/comments

I found during studying how Polkadot works.

* Rococo V1 (#2141)

* Update to latest master and use 30 minutes sessions

* add bootnodes to chainspec

* Update Substrate

* Update chain-spec

* Update Cargo.lock

* GENESIS

* Change session length to one hour

* Bump spec_version to not fuck anything up ;)

Co-authored-by: Erin Grasmick <erin@parity.io>

* avoid creating duplicate unbacked spans when we see extra statements (#2145)

* improve jaeger spans for statement distribution

* tweak and add failing test for repropagation

* make a change that gets the test passing

* guide: clarify

* remove semicolon

Co-authored-by: Robert Klotzner <eskimor@users.noreply.github.com>
Co-authored-by: Bastian Köcher <bkchr@users.noreply.github.com>
Co-authored-by: Erin Grasmick <erin@parity.io>

polkadot/node/subsystem/src/jaeger.rs

@@ -159,9 +159,13 @@ pub fn pov_span(pov: &PoV, span_name: impl Into<String>) -> JaegerSpan {
 
 /// Creates a `Span` referring to the given hash. All spans created with [`hash_span`] with the
 /// same hash (even from multiple different nodes) will be visible in the same view on Jaeger.
+///
+/// This span automatically has the `relay-parent` tag set.
 #[inline(always)]
 pub fn hash_span(hash: &Hash, span_name: impl Into<String>) -> JaegerSpan {
-	INSTANCE.read_recursive().span(|| { *hash }, span_name).into()
+	let mut span: JaegerSpan = INSTANCE.read_recursive().span(|| { *hash }, span_name).into();
+	span.add_string_tag("relay-parent", &format!("{:?}", hash));
+	span
 }
 
 /// Stateful convenience wrapper around [`mick_jaeger`].