rotate endpoints on each offchain worker exection

Signed-off-by: Uncle Stinky <uncle.stinky@ghostchain.io>

pallets/slow-clap/Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "ghost-slow-clap"
-version = "0.3.33"
+version = "0.3.34"
 description = "Applause protocol for the EVM bridge"
 license.workspace = true
 authors.workspace = true

pallets/slow-clap/src/lib.rs

@@ -28,7 +28,7 @@ use sp_runtime::{
         storage_lock::{StorageLock, Time},
         HttpError,
     },
-    traits::{BlockNumberProvider, Convert, Saturating},
+    traits::{BlockNumberProvider, Convert, Saturating, TrailingZeroInput},
     Perbill, RuntimeAppPublic, RuntimeDebug, SaturatedConversion,
 };
 use sp_staking::{
@@ -692,14 +692,35 @@ impl<T: Config> Pallet<T> {
         let block_distance_key = Self::create_storage_key(b"block-distance-", &network_id_encoded);
         let endpoint_key = Self::create_storage_key(b"endpoint-", &network_id_encoded);
 
-        let rpc_endpoint = Self::read_persistent_offchain_storage(
-            &endpoint_key,
-            network_data.default_endpoint.clone(),
-        );
         let max_block_distance = Self::read_persistent_offchain_storage(
             &block_distance_key,
             network_data.block_distance,
         );
+        let stored_endpoints = Self::read_persistent_offchain_storage(
+            &endpoint_key,
+            network_data.default_endpoints.clone(),
+        );
+
+        let random_seed = sp_io::offchain::random_seed();
+        let random_number = <u32>::decode(
+            &mut TrailingZeroInput::new(random_seed.as_ref())
+        ).expect("input is padded with zeroes; qed");
+
+        let rpc_endpoint = if stored_endpoints.len() > 0 {
+            stored_endpoints
+                .iter()
+                .nth((random_number as usize)
+                    .checked_rem(stored_endpoints.len())
+                    .unwrap_or_default())
+                .expect("stored endpoint should be non empty; qed")
+        } else {
+            network_data.default_endpoints
+                .iter()
+                .nth((random_number as usize)
+                    .checked_rem(network_data.default_endpoints.len())
+                    .unwrap_or_default())
+                .expect("default endpoint should be non empty; qed")
+        };
 
         StorageValueRef::persistent(&block_number_key)
             .mutate(

pallets/slow-clap/src/tests.rs

@@ -22,7 +22,7 @@ fn prepare_evm_network(
 ) -> NetworkData {
     let network_data = NetworkData {
         chain_name: "Ethereum".into(),
-        default_endpoint: get_rpc_endpoint(),
+        default_endpoints: get_rpc_endpoints(),
         finality_delay: 69,
         rate_limit_delay: 69,
         block_distance: 69,
@@ -1041,6 +1041,13 @@ fn get_rpc_endpoint() -> Vec<u8> {
     b"https://rpc.endpoint.network.com".to_vec()
 }
 
+fn get_rpc_endpoints() -> Vec<Vec<u8>> {
+    vec![
+        get_rpc_endpoint(),
+        b"https://other.endpoint.network.com".to_vec(),
+    ]
+}
+
 fn get_gatekeeper() -> Vec<u8> {
     b"0x4d224452801ACEd8B2F0aebE155379bb5D594381".to_vec()
 }