Dynamically adjust PIP request costs based on gathered data (#5603)

* beginnings of load timer

* initial load timer implementation

* saturating adds

* create flow params from distribution

* update request credits and acknowledgement

* mark cumulative cost dead code

* fix compilation

* tests

* supply load share and other params to  lightprotocol params

* add file store

* fix ethsync compilation

* reshuffle constants

sync/src/api.rs

@@ -195,21 +195,33 @@ pub struct EthSync {
 impl EthSync {
 	/// Creates and register protocol with the network service
 	pub fn new(params: Params) -> Result<Arc<EthSync>, NetworkError> {
+		const MAX_LIGHTSERV_LOAD: f64 = 0.5;
+
 		let pruning_info = params.chain.pruning_info();
 		let light_proto = match params.config.serve_light {
 			false => None,
 			true => Some({
-				let light_params = LightParams {
+				let sample_store = params.network_config.net_config_path
+					.clone()
+					.map(::std::path::PathBuf::from)
+					.map(|mut p| { p.push("request_timings"); light_net::FileStore(p) })
+					.map(|store| Box::new(store) as Box<_>);
+
+				let mut light_params = LightParams {
 					network_id: params.config.network_id,
-					flow_params: Default::default(),
+					config: Default::default(),
 					capabilities: Capabilities {
 						serve_headers: true,
 						serve_chain_since: Some(pruning_info.earliest_chain),
 						serve_state_since: Some(pruning_info.earliest_state),
 						tx_relay: true,
 					},
+					sample_store: sample_store,
 				};
 
+				let max_peers = ::std::cmp::min(params.network_config.max_peers, 1);
+				light_params.config.load_share = MAX_LIGHTSERV_LOAD / max_peers as f64;
+
 				let mut light_proto = LightProtocol::new(params.provider, light_params);
 				light_proto.add_handler(Arc::new(TxRelay(params.chain.clone())));
 
@@ -686,13 +698,14 @@ impl LightSync {
 		let (sync, light_proto) = {
 			let light_params = LightParams {
 				network_id: params.network_id,
-				flow_params: Default::default(), // or `None`?
+				config: Default::default(),
 				capabilities: Capabilities {
 					serve_headers: false,
 					serve_chain_since: None,
 					serve_state_since: None,
 					tx_relay: false,
 				},
+				sample_store: None,
 			};
 
 			let mut light_proto = LightProtocol::new(params.client.clone(), light_params);