From 29b871841a90b5ddf06b56b99cf489dab1926ceb Mon Sep 17 00:00:00 2001
From: Joseph Goulden <joegoulden@protonmail.com>
Date: Fri, 15 Nov 2019 07:21:42 +0000
Subject: [PATCH] =?UTF-8?q?fix:=20for=20TUI=20status=20try=20to=20acquire?=
 =?UTF-8?q?=20read=20lock=20on=20pmmr=5Fheader=20but=20if=20no=E2=80=A6=20?=
 =?UTF-8?q?(#3119)?=
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fix: for TUI status try to acquire read lock on pmmr_header but if not available just leave the header stats alone
---
 chain/src/chain.rs          | 12 ++++++++++++
 servers/src/common/stats.rs |  2 +-
 servers/src/grin/server.rs  | 18 +++++++++++-------
 src/bin/tui/status.rs       | 26 ++++++++++++++------------
 4 files changed, 38 insertions(+), 20 deletions(-)

diff --git a/chain/src/chain.rs b/chain/src/chain.rs
index 5d09d564d..d8c7713d8 100644
--- a/chain/src/chain.rs
+++ b/chain/src/chain.rs
@@ -1216,6 +1216,18 @@ impl Chain {
 			.map_err(|e| ErrorKind::StoreErr(e, "chain tail".to_owned()).into())
 	}
 
+	/// Tip (head) of the header chain if read lock can be acquired right now.
+	pub fn try_header_head(&self) -> Result<Option<Tip>, Error> {
+		match self.header_pmmr.try_read() {
+			Some(lock) => {
+				let hash = lock.head_hash()?;
+				let header = self.store.get_block_header(&hash)?;
+				Ok(Some(Tip::from_header(&header)))
+			}
+			None => Ok(None),
+		}
+	}
+
 	/// Tip (head) of the header chain.
 	pub fn header_head(&self) -> Result<Tip, Error> {
 		let hash = self.header_pmmr.read().head_hash()?;
diff --git a/servers/src/common/stats.rs b/servers/src/common/stats.rs
index 8ada81749..ba44e04fb 100644
--- a/servers/src/common/stats.rs
+++ b/servers/src/common/stats.rs
@@ -53,7 +53,7 @@ pub struct ServerStats {
 	/// Chain head
 	pub chain_stats: ChainStats,
 	/// sync header head
-	pub header_stats: ChainStats,
+	pub header_stats: Option<ChainStats>,
 	/// Whether we're currently syncing
 	pub sync_status: SyncStatus,
 	/// Handle to current stratum server stats
diff --git a/servers/src/grin/server.rs b/servers/src/grin/server.rs
index 539ca270b..c623a76fd 100644
--- a/servers/src/grin/server.rs
+++ b/servers/src/grin/server.rs
@@ -506,13 +506,17 @@ impl Server {
 			total_difficulty: head.total_difficulty(),
 		};
 
-		let header_tip = self.chain.header_head()?;
-		let header = self.chain.get_block_header(&header_tip.hash())?;
-		let header_stats = ChainStats {
-			latest_timestamp: header.timestamp,
-			height: header.height,
-			last_block_h: header.prev_hash,
-			total_difficulty: header.total_difficulty(),
+		let header_stats = match self.chain.try_header_head()? {
+			Some(tip) => {
+				let header = self.chain.get_block_header(&tip.hash())?;
+				Some(ChainStats {
+					latest_timestamp: header.timestamp,
+					height: header.height,
+					last_block_h: header.prev_hash,
+					total_difficulty: header.total_difficulty(),
+				})
+			}
+			_ => None,
 		};
 
 		let disk_usage_bytes = WalkDir::new(&self.config.db_root)
diff --git a/src/bin/tui/status.rs b/src/bin/tui/status.rs
index 2f15cd623..27596fe63 100644
--- a/src/bin/tui/status.rs
+++ b/src/bin/tui/status.rs
@@ -295,18 +295,20 @@ impl TUIStatusListener for TUIStatusView {
 		c.call_on_id("chain_timestamp", |t: &mut TextView| {
 			t.set_content(stats.chain_stats.latest_timestamp.to_string());
 		});
-		c.call_on_id("basic_header_tip_hash", |t: &mut TextView| {
-			t.set_content(stats.header_stats.last_block_h.to_string() + "...");
-		});
-		c.call_on_id("basic_header_chain_height", |t: &mut TextView| {
-			t.set_content(stats.header_stats.height.to_string());
-		});
-		c.call_on_id("basic_header_total_difficulty", |t: &mut TextView| {
-			t.set_content(stats.header_stats.total_difficulty.to_string());
-		});
-		c.call_on_id("basic_header_timestamp", |t: &mut TextView| {
-			t.set_content(stats.header_stats.latest_timestamp.to_string());
-		});
+		if let Some(header_stats) = &stats.header_stats {
+			c.call_on_id("basic_header_tip_hash", |t: &mut TextView| {
+				t.set_content(header_stats.last_block_h.to_string() + "...");
+			});
+			c.call_on_id("basic_header_chain_height", |t: &mut TextView| {
+				t.set_content(header_stats.height.to_string());
+			});
+			c.call_on_id("basic_header_total_difficulty", |t: &mut TextView| {
+				t.set_content(header_stats.total_difficulty.to_string());
+			});
+			c.call_on_id("basic_header_timestamp", |t: &mut TextView| {
+				t.set_content(header_stats.latest_timestamp.to_string());
+			});
+		}
 		c.call_on_id("tx_pool_size", |t: &mut TextView| {
 			t.set_content(stats.tx_stats.tx_pool_size.to_string());
 		});