Add getHealth RPC method

client/src/http_sender.rs

@@ -85,6 +85,14 @@ impl RpcSender for HttpSender {
                                             }
                                         }
                                     },
+                                    rpc_custom_error::JSON_RPC_SERVER_ERROR_NODE_UNHEALTHLY => {
+                                        match serde_json::from_value::<rpc_custom_error::RpcNodeUnhealthyErrorData>(json["error"]["data"].clone()) {
+                                            Ok(rpc_custom_error::RpcNodeUnhealthyErrorData { num_slots_behind}) => RpcResponseErrorData::NodeUnhealthy {num_slots_behind},
+                                            Err(_err) => {
+                                                RpcResponseErrorData::Empty
+                                            }
+                                        }
+                                    },
                                     _ => RpcResponseErrorData::Empty
                                 };
 

client/src/rpc_client.rs

@@ -928,6 +928,11 @@ impl RpcClient {
         Ok(hash)
     }
 
+    pub fn get_health(&self) -> ClientResult<()> {
+        self.send::<String>(RpcRequest::GetHealth, Value::Null)
+            .map(|_| ())
+    }
+
     pub fn get_token_account(&self, pubkey: &Pubkey) -> ClientResult<Option<UiTokenAccount>> {
         Ok(self
             .get_token_account_with_commitment(pubkey, self.commitment_config)?

client/src/rpc_custom_error.rs

@@ -25,13 +25,21 @@ pub enum RpcCustomError {
     BlockNotAvailable {
         slot: Slot,
     },
-    RpcNodeUnhealthy,
+    RpcNodeUnhealthy {
+        num_slots_behind: Slot,
+    },
     TransactionPrecompileVerificationFailure(solana_sdk::transaction::TransactionError),
     SlotSkipped {
         slot: Slot,
     },
 }
 
+#[derive(Debug, Serialize, Deserialize)]
+#[serde(rename_all = "camelCase")]
+pub struct RpcNodeUnhealthyErrorData {
+    pub num_slots_behind: Slot,
+}
+
 impl From<RpcCustomError> for Error {
     fn from(e: RpcCustomError) -> Self {
         match e {
@@ -65,10 +73,12 @@ impl From<RpcCustomError> for Error {
                 message: format!("Block not available for slot {}", slot),
                 data: None,
             },
-            RpcCustomError::RpcNodeUnhealthy => Self {
+            RpcCustomError::RpcNodeUnhealthy { num_slots_behind } => Self {
                 code: ErrorCode::ServerError(JSON_RPC_SERVER_ERROR_NODE_UNHEALTHLY),
-                message: "RPC node is unhealthy".to_string(),
-                data: None,
+                message: format!("RPC node is behind by {} slots", num_slots_behind),
+                data: Some(serde_json::json!(RpcNodeUnhealthyErrorData {
+                    num_slots_behind
+                })),
             },
             RpcCustomError::TransactionPrecompileVerificationFailure(e) => Self {
                 code: ErrorCode::ServerError(

client/src/rpc_request.rs

@@ -1,6 +1,6 @@
 use crate::rpc_response::RpcSimulateTransactionResult;
 use serde_json::{json, Value};
-use solana_sdk::pubkey::Pubkey;
+use solana_sdk::{clock::Slot, pubkey::Pubkey};
 use std::fmt;
 use thiserror::Error;
 
@@ -25,6 +25,7 @@ pub enum RpcRequest {
     GetFees,
     GetFirstAvailableBlock,
     GetGenesisHash,
+    GetHealth,
     GetIdentity,
     GetInflationGovernor,
     GetInflationRate,
@@ -80,6 +81,7 @@ impl fmt::Display for RpcRequest {
             RpcRequest::GetFees => "getFees",
             RpcRequest::GetFirstAvailableBlock => "getFirstAvailableBlock",
             RpcRequest::GetGenesisHash => "getGenesisHash",
+            RpcRequest::GetHealth => "getHealth",
             RpcRequest::GetIdentity => "getIdentity",
             RpcRequest::GetInflationGovernor => "getInflationGovernor",
             RpcRequest::GetInflationRate => "getInflationRate",
@@ -143,6 +145,7 @@ impl RpcRequest {
 pub enum RpcResponseErrorData {
     Empty,
     SendTransactionPreflightFailure(RpcSimulateTransactionResult),
+    NodeUnhealthy { num_slots_behind: Slot },
 }
 
 impl fmt::Display for RpcResponseErrorData {