im-online removal cleanup: remove off-chain storage

polkadot/runtime/rococo/src/lib.rs

@@ -1821,6 +1821,12 @@ sp_api::impl_runtime_apis! {
 
 	impl offchain_primitives::OffchainWorkerApi<Block> for Runtime {
 		fn offchain_worker(header: &<Block as BlockT>::Header) {
+			use sp_runtime::{traits::Header, DigestItem};
+
+			if header.digest().logs().iter().any(|di| di == &DigestItem::RuntimeEnvironmentUpdated) {
+				pallet_im_online::migration::clear_offchain_storage::<Runtime>()
+			}
+
 			Executive::offchain_worker(header)
 		}
 	}

prdoc/pr_2290.prdoc

@@ -0,0 +1,11 @@
+title: im-online pallet offcain storage cleanup
+
+doc:
+  - audience: Runtime Dev
+    description: |
+      This is a follow-up of #2265. It blindly removes all the offchain storage values added to
+      the database by now retired im-online pallet. In absence of such values, does nothing.
+
+crates:
+  - name: pallet-im-online
+  - name: rococo-runtime

substrate/frame/im-online/Cargo.toml

@@ -23,6 +23,7 @@ frame-benchmarking = { path = "../benchmarking", default-features = false, optio
 frame-support = { path = "../support", default-features = false }
 frame-system = { path = "../system", default-features = false }
 pallet-authorship = { path = "../authorship", default-features = false }
+pallet-session = { path = "../session", default-features = false }
 sp-application-crypto = { path = "../../primitives/application-crypto", default-features = false, features = ["serde"] }
 sp-core = { path = "../../primitives/core", default-features = false, features = ["serde"] }
 sp-io = { path = "../../primitives/io", default-features = false }

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

@@ -116,6 +116,18 @@ pub mod v1 {
 	}
 }
 
+pub fn clear_offchain_storage<T: pallet_session::Config>() {
+	let validator_set_size = pallet_session::Pallet::<T>::validators().len() as u32;
+	(0..validator_set_size).for_each(|idx| {
+		let key = {
+			let mut key = DB_PREFIX.to_vec();
+			key.extend(idx.encode());
+			key
+		};
+		sp_runtime::offchain::storage::StorageValueRef::persistent(&key).clear();
+	});
+}
+
 #[cfg(all(feature = "try-runtime", test))]
 mod test {
 	use super::*;