Allow modules to indicate full block. (#1687)

* Add transaction skipping.

* Update runtime.

substrate/srml/contract/src/gas.rs

@@ -16,6 +16,7 @@
 
 use crate::{GasSpent, Module, Trait};
 use balances;
+use runtime_primitives::BLOCK_FULL;
 use runtime_primitives::traits::{As, CheckedMul, CheckedSub, Zero};
 use runtime_support::StorageValue;
 
@@ -206,7 +207,8 @@ pub fn buy_gas<T: Trait>(
 	// This cannot underflow since `gas_spent` is never greater than `block_gas_limit`.
 	let gas_available = <Module<T>>::block_gas_limit() - <Module<T>>::gas_spent();
 	if gas_limit > gas_available {
-		return Err("block gas limit is reached");
+		// gas limit reached, revert the transaction and retry again in the future
+		return Err(BLOCK_FULL);
 	}
 
 	// Buy the specified amount of gas.

substrate/srml/executive/src/lib.rs

@@ -207,7 +207,10 @@ impl<
 		let r = f.dispatch(s.into());
 		<system::Module<System>>::note_applied_extrinsic(&r, encoded_len as u32);
 
-		r.map(|_| internal::ApplyOutcome::Success).or_else(|e| Ok(internal::ApplyOutcome::Fail(e)))
+		r.map(|_| internal::ApplyOutcome::Success).or_else(|e| match e {
+			primitives::BLOCK_FULL => Err(internal::ApplyError::FullBlock),
+			e => Ok(internal::ApplyOutcome::Fail(e))
+		})
 	}
 
 	fn final_checks(header: &System::Header) {

substrate/srml/support/src/lib.rs

@@ -56,8 +56,8 @@ mod double_map;
 pub use self::storage::{StorageVec, StorageList, StorageValue, StorageMap};
 pub use self::hashable::Hashable;
 pub use self::dispatch::{Parameter, Dispatchable, Callable, IsSubType};
+pub use self::double_map::StorageDoubleMap;
 pub use runtime_io::print;
-pub use double_map::StorageDoubleMap;
 
 #[doc(inline)]
 pub use srml_support_procedural::decl_storage;