Use max_expected_time_per_block value for the max_block_time (#3467)

* Use max_block_time queried from /genesis

* Clean solution

* Add unclog entry

* Remove serde-with dependency

.changelog/unreleased/improvements/ibc-relayer/3211-query-max-block-time.md

@@ -0,0 +1,3 @@
+- Query the /genesis RPC endpoint to retrieve the value of
+  `max_expected_time_per_block` and use it for `max_block_time`.
+  ([\#3211](https://github.com/informalsystems/hermes/issues/3211))

config.toml

@@ -285,9 +285,12 @@ max_tx_size = 2097152
 # can drift into the future. Default: 5s
 clock_drift = '5s'
 
-# Specify the maximum time per block for this chain.
+# Specify the fallback value for the maximum time per block for this chain.
 # The block time together with the clock drift are added to the source drift to estimate
 # the maximum clock drift when creating a client on this chain. Default: 30s
+# When validating the configuration, Hermes will query the /genesis RPC endpoint in order
+# to retrieve the `max_expected_time_per_block` and use it as the `max_block_time`.
+# If the query fails, the configured `max_block_time` is used instead.
 # For cosmos-SDK chains a good approximation is `timeout_propose` + `timeout_commit`
 # Note: This MUST be the same as the `max_expected_time_per_block` genesis parameter for Tendermint chains.
 max_block_time = '30s'

crates/relayer/src/chain/cosmos.rs

@@ -13,7 +13,7 @@ use std::{cmp::Ordering, thread};
 use tokio::runtime::Runtime as TokioRuntime;
 use tonic::codegen::http::Uri;
 use tonic::metadata::AsciiMetadataValue;
-use tracing::{error, instrument, trace, warn};
+use tracing::{error, info, instrument, trace, warn};
 
 use ibc_proto::cosmos::{
     base::node::v1beta1::ConfigResponse, staking::v1beta1::Params as StakingParams,
@@ -107,6 +107,8 @@ use crate::util::pretty::{
     PrettyIdentifiedChannel, PrettyIdentifiedClientState, PrettyIdentifiedConnection,
 };
 
+use self::types::app_state::GenesisAppState;
+
 pub mod batch;
 pub mod client;
 pub mod compatibility;
@@ -190,7 +192,7 @@ impl CosmosSdkChain {
     ///
     /// Emits a log warning in case any error is encountered and
     /// exits early without doing subsequent validations.
-    pub fn validate_params(&self) -> Result<(), Error> {
+    pub fn validate_params(&mut self) -> Result<(), Error> {
         let unbonding_period = self.unbonding_period()?;
         let trusting_period = self.trusting_period(unbonding_period);
 
@@ -283,6 +285,28 @@ impl CosmosSdkChain {
             ));
         }
 
+        // Query /genesis RPC endpoint to retrieve the `max_expected_time_per_block` value
+        // to use as `max_block_time`.
+        // If it is not found, keep the configured `max_block_time`.
+        match self.block_on(self.rpc_client.genesis::<GenesisAppState>()) {
+            Ok(genesis_reponse) => {
+                let old_max_block_time = self.config.max_block_time;
+                self.config.max_block_time =
+                    Duration::from_nanos(genesis_reponse.app_state.max_expected_time_per_block());
+                info!(
+                    "Updated `max_block_time` using /genesis endpoint. Old value: `{}s`, new value: `{}s`",
+                    old_max_block_time.as_secs(),
+                    self.config.max_block_time.as_secs()
+                );
+            }
+            Err(e) => {
+                warn!(
+                    "Will use fallback value for max_block_time: `{}s`. Error: {e}",
+                    self.config.max_block_time.as_secs()
+                );
+            }
+        }
+
         Ok(())
     }
 
@@ -965,7 +989,7 @@ impl ChainEndpoint for CosmosSdkChain {
     /// Emits a log warning in case anything is amiss.
     /// Exits early if any health check fails, without doing any
     /// further checks.
-    fn health_check(&self) -> Result<HealthCheck, Error> {
+    fn health_check(&mut self) -> Result<HealthCheck, Error> {
         if let Err(e) = do_health_check(self) {
             warn!("Health checkup for chain '{}' failed", self.id());
             warn!("    Reason: {}", e.detail());

crates/relayer/src/chain/cosmos/types/app_state.rs

@@ -0,0 +1,47 @@
+//! Structure used to parse queried Genesis state using
+//! /genesis RPC endpoint.
+
+use serde::Deserialize as SerdeDeserialize;
+use serde_derive::Deserialize;
+use serde_derive::Serialize;
+
+#[derive(Debug, Deserialize, Serialize)]
+pub struct GenesisAppState {
+    ibc: IbcConfig,
+}
+
+impl GenesisAppState {
+    pub fn max_expected_time_per_block(&self) -> u64 {
+        self.ibc
+            .connection_genesis
+            .params
+            .max_expected_time_per_block
+    }
+}
+
+#[derive(Debug, Deserialize, Serialize)]
+struct IbcConfig {
+    connection_genesis: ConnectionGenesisConfig,
+}
+
+#[derive(Debug, Deserialize, Serialize)]
+struct ConnectionGenesisConfig {
+    params: ConnectionGenesisParams,
+}
+
+#[derive(Debug, Deserialize, Serialize)]
+struct ConnectionGenesisParams {
+    #[serde(deserialize_with = "deserialize_max_expected_per_block")]
+    max_expected_time_per_block: u64,
+}
+
+fn deserialize_max_expected_per_block<'de, T, D>(de: D) -> Result<T, D::Error>
+where
+    D: serde::Deserializer<'de>,
+    T: std::str::FromStr,
+    <T as std::str::FromStr>::Err: std::fmt::Display,
+{
+    String::deserialize(de)?
+        .parse()
+        .map_err(serde::de::Error::custom)
+}

crates/relayer/src/chain/cosmos/types/mod.rs

@@ -1,4 +1,5 @@
 pub mod account;
+pub mod app_state;
 pub mod config;
 pub mod events;
 pub mod gas;

crates/relayer/src/chain/endpoint.rs

@@ -98,7 +98,7 @@ pub trait ChainEndpoint: Sized {
     fn shutdown(self) -> Result<(), Error>;
 
     /// Perform a health check
-    fn health_check(&self) -> Result<HealthCheck, Error>;
+    fn health_check(&mut self) -> Result<HealthCheck, Error>;
 
     // Events
     fn subscribe(&mut self) -> Result<Subscription, Error>;