LB lagging health check

Author: finiteops

crates/rpc/rpc-eth-api/src/core.rs

@@ -47,10 +47,21 @@ impl<T> FullEthApiServer for T where
 {
 }
 
+/// Bitfinity lag API
+pub const LAG_STATUS_BAD: &str = "LAGGING";
+
+/// Bitfinity lag API
+pub const LAG_STATUS_OK: &str = "ACCEPTED_LAG";
+
 /// Eth rpc interface: <https://ethereum.github.io/execution-apis/api-documentation/>
 #[cfg_attr(not(feature = "client"), rpc(server, namespace = "eth"))]
 #[cfg_attr(feature = "client", rpc(server, client, namespace = "eth"))]
 pub trait EthApi<T: RpcObject, B: RpcObject, R: RpcObject, H: RpcObject> {
+    /// Bitfinity LB api extenstion
+    /// Handler for: `eth_lagging`
+    #[method(name = "lagging")]
+    async fn lagging(&self, accepted_lag: Option<U64>) -> RpcResult<String>;
+
     /// Returns the protocol version encoded as a string.
     #[method(name = "protocolVersion")]
     async fn protocol_version(&self) -> RpcResult<U64>;
@@ -386,6 +397,28 @@ where
     T: FullEthApi,
     jsonrpsee_types::error::ErrorObject<'static>: From<T::Error>,
 {
+    /// Handler for: `eth_lagging`
+    async fn lagging(&self, accepted_lag: Option<U64>) -> RpcResult<String> {
+        let accepted_lag = match accepted_lag {
+            Some(lag) => U256::from(lag),
+            // Assuming that lag behind for 3 block is ok
+            None => U256::from(3),
+        };
+
+        let network_block = BitfinityEvmRpc::network_block_number(self).await?;
+        let node_block = self.block_number()?;
+        let lag = network_block.saturating_sub(node_block);
+
+        let status =
+            if lag > accepted_lag { LAG_STATUS_BAD.to_owned() } else { LAG_STATUS_OK.to_owned() };
+
+        // Better to repond with string that add structure, import serde and stuff
+        let response =
+            format!("{}: lag: {} node: {} network: {}", status, lag, node_block, network_block);
+
+        Ok(response)
+    }
+
     /// Handler for: `eth_protocolVersion`
     async fn protocol_version(&self) -> RpcResult<U64> {
         trace!(target: "rpc::eth", "Serving eth_protocolVersion");

crates/rpc/rpc-eth-api/src/helpers/bitfinity_evm_rpc.rs

@@ -16,6 +16,23 @@ pub trait BitfinityEvmRpc {
     /// Returns the `ChainSpec`.
     fn chain_spec(&self) -> Arc<ChainSpec>;
 
+    /// Returns latest block number at the network/sync source.
+    fn network_block_number(&self) -> impl Future<Output = RpcResult<U256>> + Send {
+        let chain_spec = self.chain_spec();
+        async move {
+            let (rpc_url, client) = get_client(&chain_spec)?;
+
+            let block_number = client.get_block_number().await.map_err(|e| {
+                internal_rpc_err(format!(
+                    "failed to forward eth_blockNumber request to {}: {}",
+                    rpc_url, e
+                ))
+            })?;
+
+            Ok(U256::from(block_number))
+        }
+    }
+
     /// Forwards `eth_gasPrice` calls to the Bitfinity EVM.
     fn gas_price(&self) -> impl Future<Output = RpcResult<U256>> + Send {
         let chain_spec = self.chain_spec();