From ea71fb91752cb12d563f7b83f55e159c86d04579 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Bastian=20K=C3=B6cher?= <git@kchr.de>
Date: Fri, 19 Jun 2020 11:55:10 +0200
Subject: [PATCH] Track last blocks in informant display

This implements tracking of the last seen blocks in informant display
to prevent printing the import message twice. In Cumulus we first import
blocks as part of the block building with `new_best == false` and set
the best block after we know which one was included by the relay chain.
This leads to printing the import messages two times. This pr solves the
problem by track the latest seen blocks to not print the message twice.
---
 client/informant/src/lib.rs | 59 ++++++++++++++++++++++++++-----------
 1 file changed, 41 insertions(+), 18 deletions(-)

diff --git a/client/informant/src/lib.rs b/client/informant/src/lib.rs
index 720f5d6a1bfbc..6a8acbadc36be 100644
--- a/client/informant/src/lib.rs
+++ b/client/informant/src/lib.rs
@@ -28,9 +28,7 @@ use sp_blockchain::HeaderMetadata;
 use sp_runtime::traits::{Block as BlockT, Header};
 use sp_transaction_pool::TransactionPool;
 use sp_utils::{status_sinks, mpsc::tracing_unbounded};
-use std::fmt::Display;
-use std::sync::Arc;
-use std::time::Duration;
+use std::{fmt::Display, sync::Arc, time::Duration, collections::VecDeque};
 use parking_lot::Mutex;
 
 mod display;
@@ -96,12 +94,30 @@ where
 			future::ready(())
 		});
 
+	future::join(
+		display_notifications,
+		display_block_import(client, format.prefix),
+	).map(|_| ())
+}
+
+fn display_block_import<B: BlockT, C>(
+	client: Arc<C>,
+	prefix: String,
+) -> impl Future<Output = ()>
+where
+	C: UsageProvider<B> + HeaderMetadata<B> + BlockchainEvents<B>,
+	<C as HeaderMetadata<B>>::Error: Display,
+{
 	let mut last_best = {
 		let info = client.usage_info();
 		Some((info.chain.best_number, info.chain.best_hash))
 	};
 
-	let display_block_import = client.import_notification_stream().for_each(move |n| {
+	// Hashes of the last blocks we have seen at import.
+	let mut last_blocks = VecDeque::new();
+	let max_blocks_to_track = 100;
+
+	client.import_notification_stream().for_each(move |n| {
 		// detect and log reorganizations.
 		if let Some((ref last_num, ref last_hash)) = last_best {
 			if n.header.parent_hash() != last_hash && n.is_new_best  {
@@ -114,7 +130,7 @@ where
 				match maybe_ancestor {
 					Ok(ref ancestor) if ancestor.hash != *last_hash => info!(
 						"♻️  {}Reorg on #{},{} to #{},{}, common ancestor #{},{}",
-						format.prefix,
+						prefix,
 						Colour::Red.bold().paint(format!("{}", last_num)), last_hash,
 						Colour::Green.bold().paint(format!("{}", n.header.number())), n.hash,
 						Colour::White.bold().paint(format!("{}", ancestor.number)), ancestor.hash,
@@ -129,18 +145,25 @@ where
 			last_best = Some((n.header.number().clone(), n.hash.clone()));
 		}
 
-		info!(
-			target: "substrate",
-			"✨ {}Imported #{} ({})",
-			format.prefix,
-			Colour::White.bold().paint(format!("{}", n.header.number())), 
-			n.hash,
-		);
-		future::ready(())
-	});
 
-	future::join(
-		display_notifications,
-		display_block_import
-	).map(|_| ())
+		// If we already printed a message for a given block recently,
+		// we should not print it again.
+		if !last_blocks.contains(&n.hash) {
+			last_blocks.push_back(n.hash.clone());
+
+			if last_blocks.len() > max_blocks_to_track {
+				last_blocks.pop_front();
+			}
+
+			info!(
+				target: "substrate",
+				"✨ {}Imported #{} ({})",
+				prefix,
+				Colour::White.bold().paint(format!("{}", n.header.number())),
+				n.hash,
+			);
+		}
+
+		future::ready(())
+	})
 }