From 696097370eb7a7120151af5a4d323f0bb05ecbcb Mon Sep 17 00:00:00 2001
From: Antioch Peverell <30642645+antiochp@users.noreply.github.com>
Date: Tue, 27 Mar 2018 16:48:09 -0400
Subject: [PATCH] do not save header during header first sync (#891)

just use the header as a hint to go request the block
---
 chain/src/chain.rs   |  6 +-----
 chain/src/pipe.rs    | 18 ++++--------------
 grin/src/adapters.rs | 13 +++++++++++--
 3 files changed, 16 insertions(+), 21 deletions(-)

diff --git a/chain/src/chain.rs b/chain/src/chain.rs
index 16fcf285..026544a9 100644
--- a/chain/src/chain.rs
+++ b/chain/src/chain.rs
@@ -339,11 +339,7 @@ impl Chain {
 	}
 
 	/// Process a block header received during "header first" propagation.
-	pub fn process_block_header(
-		&self,
-		bh: &BlockHeader,
-		opts: Options,
-	) -> Result<Option<Tip>, Error> {
+	pub fn process_block_header(&self, bh: &BlockHeader, opts: Options) -> Result<(), Error> {
 		let header_head = self.get_header_head()?;
 		let ctx = self.ctx_from_head(header_head, opts);
 		pipe::process_block_header(bh, ctx)
diff --git a/chain/src/pipe.rs b/chain/src/pipe.rs
index e343f0e8..0ca8b2b0 100644
--- a/chain/src/pipe.rs
+++ b/chain/src/pipe.rs
@@ -164,7 +164,9 @@ pub fn sync_block_header(
 }
 
 /// Process block header as part of "header first" block propagation.
-pub fn process_block_header(bh: &BlockHeader, mut ctx: BlockContext) -> Result<Option<Tip>, Error> {
+/// We validate the header but we do not store it or update header head based on this.
+/// We will update these once we get the block back after requesting it.
+pub fn process_block_header(bh: &BlockHeader, mut ctx: BlockContext) -> Result<(), Error> {
 	debug!(
 		LOGGER,
 		"pipe: process_block_header: {} at {}",
@@ -173,19 +175,7 @@ pub fn process_block_header(bh: &BlockHeader, mut ctx: BlockContext) -> Result<O
 	);
 
 	check_header_known(bh.hash(), &mut ctx)?;
-	validate_header(&bh, &mut ctx)?;
-
-	debug!(
-		LOGGER,
-		"pipe: process_block_header: {} at {} is valid, saving.",
-		bh.hash(),
-		bh.height,
-	);
-
-	add_block_header(bh, &mut ctx)?;
-
-	// now update the header_head (if new header with most work)
-	update_header_head(bh, &mut ctx)
+	validate_header(&bh, &mut ctx)
 }
 
 /// Quick in-memory check to fast-reject any block header we've already handled
diff --git a/grin/src/adapters.rs b/grin/src/adapters.rs
index 0db19a5f..3303012c 100644
--- a/grin/src/adapters.rs
+++ b/grin/src/adapters.rs
@@ -542,6 +542,7 @@ impl ChainAdapter for ChainToPoolAndNetAdapter {
 		// If block contains txs then broadcast the compact block.
 		// If we received the block from another node then broadcast "header first"
 		// to minimize network traffic.
+
 		if opts.contains(Options::MINE) {
 			// propagate compact block out if we mined the block
 			// but broadcast full block if we have no txs
@@ -550,7 +551,6 @@ impl ChainAdapter for ChainToPoolAndNetAdapter {
 				// in the interest of testing all code paths
 				// randomly decide how we send an empty block out
 				// TODO - lock this down once we are comfortable it works...
-
 				let mut rng = rand::thread_rng();
 				if rng.gen() {
 					wo(&self.peers).broadcast_block(&b);
@@ -562,7 +562,16 @@ impl ChainAdapter for ChainToPoolAndNetAdapter {
 			}
 		} else {
 			// "header first" propagation if we are not the originator of this block
-			wo(&self.peers).broadcast_header(&b.header);
+			// again randomly chose between "header first" or "compact block" propagation
+			// to ensure we test a wide variety of code paths
+
+			let mut rng = rand::thread_rng();
+			if rng.gen() {
+				wo(&self.peers).broadcast_header(&b.header);
+			} else {
+				let cb = b.as_compact_block();
+				wo(&self.peers).broadcast_compact_block(&cb);
+			}
 		}
 	}
 }