diff --git a/secret_store/src/key_server_cluster/cluster_sessions.rs b/secret_store/src/key_server_cluster/cluster_sessions.rs
index 7b1a9cfe6..2c1081c3b 100644
--- a/secret_store/src/key_server_cluster/cluster_sessions.rs
+++ b/secret_store/src/key_server_cluster/cluster_sessions.rs
@@ -120,9 +120,9 @@ pub struct ClusterSessions {
 /// Active sessions container listener.
 pub trait ClusterSessionsListener<S: ClusterSession>: Send + Sync {
 	/// When new session is inserted to the container.
-	fn on_session_inserted(&self, session: Arc<S>);
+	fn on_session_inserted(&self, _session: Arc<S>) {}
 	/// When session is removed from the container.
-	fn on_session_removed(&self, session: Arc<S>);
+	fn on_session_removed(&self, _session: Arc<S>) {}
 }
 
 /// Active sessions container.
diff --git a/secret_store/src/listener/service_contract_listener.rs b/secret_store/src/listener/service_contract_listener.rs
index dcf615744..d53be7daa 100644
--- a/secret_store/src/listener/service_contract_listener.rs
+++ b/secret_store/src/listener/service_contract_listener.rs
@@ -117,6 +117,7 @@ enum ServiceTask {
 }
 
 impl ServiceContractListener {
+	/// Create new service contract listener.
 	pub fn new(client: &Arc<Client>, sync: &Arc<SyncProvider>, key_server: Arc<KeyServer>, cluster: Arc<ClusterClient>, self_key_pair: Arc<NodeKeyPair>, key_servers_set: Arc<KeyServerSet>) -> Arc<ServiceContractListener> {
 		let contract_addr = client.registry_address(SERVICE_CONTRACT_REGISTRY_NAME.to_owned())
 			.map(|a| {
@@ -154,6 +155,7 @@ impl ServiceContractListener {
 		contract
 	}
 
+	/// Process incoming events of service contract.
 	fn process_service_contract_events(&self, client: &Client, service_contract: Address, blocks: Vec<H256>) {
 		debug_assert!(!blocks.is_empty());
 
@@ -188,6 +190,7 @@ impl ServiceContractListener {
 			}));
 	}
 
+	/// Service thread procedure.
 	fn run_service_thread(data: Arc<ServiceContractListenerData>) {
 		loop {
 			let task = data.tasks_queue.wait();
@@ -203,6 +206,7 @@ impl ServiceContractListener {
 		}
 	}
 
+	/// Process single service task.
 	fn process_service_task(data: &Arc<ServiceContractListenerData>, task: ServiceTask) -> Result<(), String> {
 		match task {
 			ServiceTask::Retry =>
@@ -239,6 +243,7 @@ impl ServiceContractListener {
 		}
 	}
 
+	/// Retry processing pending requests.
 	fn retry_pending_requests(data: &Arc<ServiceContractListenerData>) -> Result<usize, String> {
 		let client = data.client.upgrade().ok_or("client is required".to_owned())?;
 		let retry_data = ::std::mem::replace(&mut *data.retry_data.lock(), Default::default());
@@ -298,6 +303,7 @@ impl ServiceContractListener {
 		Ok(processed_requests)
 	}
 
+	/// Generate server key.
 	fn generate_server_key(data: &Arc<ServiceContractListenerData>, server_key_id: &ServerKeyId, threshold: &H256) -> Result<Public, String> {
 		let threshold_num = threshold.low_u64();
 		if threshold != &threshold_num.into() || threshold_num >= ::std::usize::MAX as u64 {
@@ -313,6 +319,7 @@ impl ServiceContractListener {
 			.map_err(Into::into)
 	}
 
+	/// Publish server key.
 	fn publish_server_key(data: &Arc<ServiceContractListenerData>, server_key_id: &ServerKeyId, server_key: &Public) -> Result<(), String> {
 		let server_key_hash = keccak(server_key);
 		let signed_server_key = data.self_key_pair.sign(&server_key_hash).map_err(|e| format!("{}", e))?;
@@ -381,13 +388,14 @@ impl ChainNotify for ServiceContractListener {
 }
 
 impl ClusterSessionsListener<GenerationSession> for ServiceContractListener {
-	fn on_session_inserted(&self, _session: Arc<GenerationSession>) {
-	}
-
 	fn on_session_removed(&self, session: Arc<GenerationSession>) {
 		// TODO: only start if session started via the contract
+
 		// only publish when the session is started by another node
+		// when it is started by this node, it is published from process_service_task
 		if !is_processed_by_this_key_server(&*self.data.key_servers_set, &*self.data.self_key_pair, &session.id()) {
+			// by this time sesion must already be completed - either successfully, or not
+			debug_assert!(session.is_finished());
 			session.wait(Some(Default::default()))
 				.map_err(|e| format!("{}", e))
 				.and_then(|server_key| Self::publish_server_key(&self.data, &session.id(), &server_key))
@@ -406,6 +414,7 @@ impl ClusterSessionsListener<GenerationSession> for ServiceContractListener {
 }
 
 impl TasksQueue {
+	/// Create new tasks queue.
 	pub fn new() -> Self {
 		TasksQueue {
 			service_event: Condvar::new(),
@@ -413,12 +422,14 @@ impl TasksQueue {
 		}
 	}
 
+	/// Shutdown tasks queue.
 	pub fn shutdown(&self) {
 		let mut service_tasks = self.service_tasks.lock();
 		service_tasks.push_front(ServiceTask::Shutdown);
 		self.service_event.notify_all();
 	}
 
+	//// Push new tasks to the queue.
 	pub fn push<I>(&self, tasks: I) where I: Iterator<Item=ServiceTask> {
 		let mut service_tasks = self.service_tasks.lock();
 		service_tasks.extend(tasks);
@@ -427,6 +438,7 @@ impl TasksQueue {
 		}
 	}
 
+	/// Wait for new task.
 	pub fn wait(&self) -> ServiceTask {
 		let mut service_tasks = self.service_tasks.lock();
 		if service_tasks.is_empty() {