Generate txhashset archives on 720 block intervals. (#2813)

* generate txhashset archives on 250 block intervals.

* moved txhashset_archive_interval to global and added a simple test.

* cleaning up the tests and adding license.

* increasing cleanup duration to 24 hours to prevent premature deletion of the current txhashset archive

* bug fixes and changing request_state to request height using archive_interval.

* removing stopstate from chain_test_helper to fix compile issue

servers/src/common/adapters.rs

@@ -372,6 +372,10 @@ impl p2p::ChainAdapter for NetToChainAdapter {
 		}
 	}
 
+	fn txhashset_archive_header(&self) -> Result<core::BlockHeader, chain::Error> {
+		self.chain().txhashset_archive_header()
+	}
+
 	fn txhashset_receive_ready(&self) -> bool {
 		match self.sync_state.status() {
 			SyncStatus::TxHashsetDownload { .. } => true,

servers/src/grin/sync/state_sync.rs

@@ -160,6 +160,9 @@ impl StateSync {
 
 	fn request_state(&self, header_head: &chain::Tip) -> Result<Arc<Peer>, p2p::Error> {
 		let threshold = global::state_sync_threshold() as u64;
+		let archive_interval = global::txhashset_archive_interval();
+		let mut txhashset_height = header_head.height.saturating_sub(threshold);
+		txhashset_height = txhashset_height.saturating_sub(txhashset_height % archive_interval);
 
 		if let Some(peer) = self.peers.most_work_peer() {
 			// ask for txhashset at state_sync_threshold
@@ -168,18 +171,18 @@ impl StateSync {
 				.get_block_header(&header_head.prev_block_h)
 				.map_err(|e| {
 					error!(
-						"chain error dirung getting a block header {}: {:?}",
+						"chain error during getting a block header {}: {:?}",
 						&header_head.prev_block_h, e
 					);
 					p2p::Error::Internal
 				})?;
-			for _ in 0..threshold {
+			while txhashset_head.height > txhashset_height {
 				txhashset_head = self
 					.chain
 					.get_previous_header(&txhashset_head)
 					.map_err(|e| {
 						error!(
-							"chain error dirung getting a previous block header {}: {:?}",
+							"chain error during getting a previous block header {}: {:?}",
 							txhashset_head.hash(),
 							e
 						);