[stable2503] Backport #9325

prdoc/pr_9325.prdoc

@@ -0,0 +1,16 @@
+# Schema: Polkadot SDK PRDoc Schema (prdoc) v1.0.0
+# See doc at https://raw.githubusercontent.com/paritytech/polkadot-sdk/master/prdoc/schema_user.json
+
+title: Fix pallet-im-online benchmarking for runtimes with MaxKeys < 1000
+
+doc:
+  - audience: Runtime Dev
+    description: |
+      Fixes benchmarking for pallet-im-online when runtime configuration has MaxKeys < 1000.
+      Previously, the benchmark code used a hardcoded constant MAX_KEYS = 1000 which would
+      cause benchmark failures for runtimes configured with fewer maximum keys. This change
+      updates the benchmark to dynamically use the MaxKeys value from the pallet's Config trait.
+
+crates:
+- name: pallet-im-online
+  bump: patch

substrate/frame/im-online/src/benchmarking.rs

@@ -29,8 +29,6 @@ use sp_runtime::{
 
 use crate::*;
 
-const MAX_KEYS: u32 = 1000;
-
 pub fn create_heartbeat<T: Config>(
 	k: u32,
 ) -> Result<
@@ -67,7 +65,7 @@ mod benchmarks {
 	use super::*;
 
 	#[benchmark(extra)]
-	fn heartbeat(k: Linear<1, MAX_KEYS>) -> Result<(), BenchmarkError> {
+	fn heartbeat(k: Linear<1, { <T as Config>::MaxKeys::get() }>) -> Result<(), BenchmarkError> {
 		let (input_heartbeat, signature) = create_heartbeat::<T>(k)?;
 
 		#[extrinsic_call]
@@ -77,7 +75,9 @@ mod benchmarks {
 	}
 
 	#[benchmark(extra)]
-	fn validate_unsigned(k: Linear<1, MAX_KEYS>) -> Result<(), BenchmarkError> {
+	fn validate_unsigned(
+		k: Linear<1, { <T as Config>::MaxKeys::get() }>,
+	) -> Result<(), BenchmarkError> {
 		let (input_heartbeat, signature) = create_heartbeat::<T>(k)?;
 		let call = Call::heartbeat { heartbeat: input_heartbeat, signature };
 
@@ -91,7 +91,9 @@ mod benchmarks {
 	}
 
 	#[benchmark]
-	fn validate_unsigned_and_then_heartbeat(k: Linear<1, MAX_KEYS>) -> Result<(), BenchmarkError> {
+	fn validate_unsigned_and_then_heartbeat(
+		k: Linear<1, { <T as Config>::MaxKeys::get() }>,
+	) -> Result<(), BenchmarkError> {
 		let (input_heartbeat, signature) = create_heartbeat::<T>(k)?;
 		let call = Call::heartbeat { heartbeat: input_heartbeat, signature };
 		let call_enc = call.encode();