Modify gas price statistics (#2947)

* gas price distribution + median + tests

* put histogram in util

* use the util histogram

* remove the default gas price implementation

* histogram rpc

* fix empty corpus

* Add JS ethcore_gasPriceHistogram

* Fix typo (s/types/type/) & subsequent failing test

* Fix return type & formatting

* bucketBounds

* Add jsapi e2e test verification

rpc/src/v1/helpers/dispatch.rs

@@ -92,8 +92,5 @@ fn prepare_transaction<C, M>(client: &C, miner: &M, request: TransactionRequest)
 }
 
 pub fn default_gas_price<C, M>(client: &C, miner: &M) -> U256 where C: MiningBlockChainClient, M: MinerService {
-	client
-		.gas_price_statistics(100, 8)
-		.map(|x| x[4])
-		.unwrap_or_else(|_| miner.sensible_gas_price())
+	client.gas_price_median(100).unwrap_or_else(|| miner.sensible_gas_price())
 }

rpc/src/v1/helpers/errors.rs

@@ -32,6 +32,7 @@ mod codes {
 	pub const NO_WORK: i64 = -32001;
 	pub const NO_AUTHOR: i64 = -32002;
 	pub const NO_NEW_WORK: i64 = -32003;
+	pub const NOT_ENOUGH_DATA: i64 = -32006;
 	pub const UNKNOWN_ERROR: i64 = -32009;
 	pub const TRANSACTION_ERROR: i64 = -32010;
 	pub const EXECUTION_ERROR: i64 = -32015;
@@ -152,6 +153,14 @@ pub fn no_author() -> Error {
 	}
 }
 
+pub fn not_enough_data() -> Error {
+	Error {
+		code: ErrorCode::ServerError(codes::NOT_ENOUGH_DATA),
+		message: "The node does not have enough data to compute the given statistic.".into(),
+		data: None
+	}
+}
+
 pub fn token(e: String) -> Error {
 	Error {
 		code: ErrorCode::ServerError(codes::UNKNOWN_ERROR),

rpc/src/v1/impls/ethcore.rs

@@ -33,7 +33,7 @@ use ethcore::ids::BlockID;
 
 use jsonrpc_core::Error;
 use v1::traits::Ethcore;
-use v1::types::{Bytes, U256, H160, H256, H512, Peers, Transaction, RpcSettings};
+use v1::types::{Bytes, U256, H160, H256, H512, Peers, Transaction, RpcSettings, Histogram};
 use v1::helpers::{errors, SigningQueue, SignerService, NetworkSettings};
 use v1::helpers::dispatch::DEFAULT_MAC;
 use v1::helpers::auto_args::Ready;
@@ -222,13 +222,9 @@ impl<C, M, S: ?Sized, F> Ethcore for EthcoreClient<C, M, S, F> where
 		Ok(Bytes::new(version_data()))
 	}
 
-	fn gas_price_statistics(&self) -> Result<Vec<U256>, Error> {
+	fn gas_price_histogram(&self) -> Result<Histogram, Error> {
 		try!(self.active());
-
-		match take_weak!(self.client).gas_price_statistics(100, 8) {
-			Ok(stats) => Ok(stats.into_iter().map(Into::into).collect()),
-			_ => Err(Error::internal_error()),
-		}
+		take_weak!(self.client).gas_price_histogram(100, 10).ok_or_else(errors::not_enough_data).map(Into::into)
 	}
 
 	fn unsigned_transactions_count(&self) -> Result<usize, Error> {

rpc/src/v1/tests/helpers/miner_service.rs

@@ -253,4 +253,7 @@ impl MinerService for TestMinerService {
 		self.latest_closed_block.lock().as_ref().map_or(None, |b| b.block().fields().state.code(address).map(|c| (*c).clone()))
 	}
 
+	fn sensible_gas_price(&self) -> U256 {
+		20000000000u64.into()
+	}
 }

rpc/src/v1/traits/ethcore.rs

@@ -18,7 +18,7 @@
 use jsonrpc_core::Error;
 
 use v1::helpers::auto_args::{Wrap, WrapAsync, Ready};
-use v1::types::{H160, H256, H512, U256, Bytes, Peers, Transaction, RpcSettings};
+use v1::types::{H160, H256, H512, U256, Bytes, Peers, Transaction, RpcSettings, Histogram};
 
 build_rpc_trait! {
 	/// Ethcore-specific rpc interface.
@@ -76,8 +76,8 @@ build_rpc_trait! {
 		fn default_extra_data(&self) -> Result<Bytes, Error>;
 
 		/// Returns distribution of gas price in latest blocks.
-		#[rpc(name = "ethcore_gasPriceStatistics")]
-		fn gas_price_statistics(&self) -> Result<Vec<U256>, Error>;
+		#[rpc(name = "ethcore_gasPriceHistogram")]
+		fn gas_price_histogram(&self) -> Result<Histogram, Error>;
 
 		/// Returns number of unsigned transactions waiting in the signer queue (if signer enabled)
 		/// Returns error when signer is disabled

rpc/src/v1/types/histogram.rs

@@ -0,0 +1,39 @@
+// Copyright 2015, 2016 Ethcore (UK) Ltd.
+// This file is part of Parity.
+
+// Parity is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+
+// Parity is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+
+// You should have received a copy of the GNU General Public License
+// along with Parity. If not, see <http://www.gnu.org/licenses/>.
+
+//! Gas prices histogram.
+
+use v1::types::U256;
+use util::stats;
+
+/// Values of RPC settings.
+#[derive(Serialize, Deserialize)]
+pub struct Histogram {
+	/// Gas prices for bucket edges.
+	#[serde(rename="bucketBounds")]
+	pub bucket_bounds: Vec<U256>,
+	/// Transacion counts for each bucket.
+	pub counts: Vec<u64>,
+}
+
+impl From<stats::Histogram> for Histogram {
+	fn from(h: stats::Histogram) -> Self {
+		Histogram {
+			bucket_bounds: h.bucket_bounds.into_iter().map(Into::into).collect(),
+			counts: h.counts
+		}
+	}
+}

rpc/src/v1/types/mod.rs.in

@@ -32,6 +32,7 @@ mod trace;
 mod trace_filter;
 mod uint;
 mod work;
+mod histogram;
 
 pub use self::bytes::Bytes;
 pub use self::block::{Block, BlockTransactions};
@@ -51,3 +52,4 @@ pub use self::trace::{LocalizedTrace, TraceResults};
 pub use self::trace_filter::TraceFilter;
 pub use self::uint::U256;
 pub use self::work::Work;
+pub use self::histogram::Histogram;