Unify maximum supported PoV size a bit. (#2691)

* Unify maximum supported PoV size a bit.

* Use MAX_POV_SIZE also in `HostConfiguration`.

* Fix types.

polkadot/node/network/protocol/src/request_response/mod.rs

@@ -36,6 +36,7 @@ use std::borrow::Cow;
 use std::time::Duration;
 
 use futures::channel::mpsc;
+use polkadot_primitives::v1::MAX_COMPRESSED_POV_SIZE;
 use strum::EnumIter;
 
 pub use sc_network::config as network;
@@ -99,10 +100,7 @@ impl Protocol {
 			Protocol::CollationFetching => RequestResponseConfig {
 				name: p_name,
 				max_request_size: 10_000,
-				/// Collations are expected to be around 10Meg, probably much smaller with
-				/// compression. So 30Meg should be well sufficient, we might be able to reduce
-				/// this further, if needed.
-				max_response_size: 30_000_000,
+				max_response_size: MAX_COMPRESSED_POV_SIZE as u64,
 				// Taken from initial implementation in collator protocol:
 				request_timeout: DEFAULT_REQUEST_TIMEOUT_CONNECTED,
 				inbound_queue: Some(tx),

polkadot/node/service/src/chain_spec.rs

@@ -25,7 +25,7 @@ use kusama_runtime as kusama;
 use pallet_im_online::sr25519::AuthorityId as ImOnlineId;
 use pallet_staking::Forcing;
 use polkadot::constants::currency::DOTS;
-use polkadot_primitives::v1::{AccountId, AccountPublic, ValidatorId, AssignmentId};
+use polkadot_primitives::v1::{AccountId, AccountPublic, AssignmentId, MAX_POV_SIZE, ValidatorId};
 use polkadot_runtime as polkadot;
 use rococo_runtime as rococo;
 use rococo_runtime::constants::currency::DOTS as ROC;
@@ -877,7 +877,7 @@ fn rococo_staging_testnet_config_genesis(wasm_binary: &[u8]) -> rococo_runtime::
 				validation_upgrade_delay: 300,
 				acceptance_period: 1200,
 				max_code_size: 5 * 1024 * 1024,
-				max_pov_size: 50 * 1024 * 1024,
+				max_pov_size: MAX_POV_SIZE,
 				max_head_data_size: 32 * 1024,
 				group_rotation_frequency: 20,
 				chain_availability_period: 4,

polkadot/primitives/src/v1.rs

@@ -458,6 +458,17 @@ impl PoV {
 #[derive(Clone, Encode, Decode, PartialEq, Eq)]
 pub struct CompressedPoV(Vec<u8>);
 
+/// Maximum PoV size we support right now.
+pub const MAX_POV_SIZE: u32 = 50 * 1024 * 1024;
+
+/// Very conservative (compression ratio of 1).
+///
+/// Experiments showed that we have a typical compression ratio of 3.4.
+/// https://github.com/ordian/bench-compression-algorithms/
+///
+/// So this could be reduced if deemed necessary.
+pub const MAX_COMPRESSED_POV_SIZE: u32 = MAX_POV_SIZE;
+
 #[derive(Debug, Clone, Copy, PartialEq, Eq, thiserror::Error)]
 #[cfg(feature = "std")]
 #[allow(missing_docs)]
@@ -490,13 +501,12 @@ impl CompressedPoV {
 	#[cfg(not(target_os = "unknown"))]
 	pub fn decompress(&self) -> Result<PoV, CompressedPoVError> {
 		use std::io::Read;
-		const MAX_POV_BLOCK_SIZE: usize = 32 * 1024 * 1024;
 
 		struct InputDecoder<'a, T: std::io::BufRead>(&'a mut zstd::Decoder<T>, usize);
 		impl<'a, T: std::io::BufRead> parity_scale_codec::Input for InputDecoder<'a, T> {
 			fn read(&mut self, into: &mut [u8]) -> Result<(), parity_scale_codec::Error> {
 				self.1 = self.1.saturating_add(into.len());
-				if self.1 > MAX_POV_BLOCK_SIZE {
+				if self.1 > MAX_POV_SIZE as usize {
 					return Err("pov block too big".into())
 				}
 				self.0.read_exact(into).map_err(Into::into)