Add make_rpc_request retry mechanism

src/rpc_request.rs

@@ -2,6 +2,7 @@ use reqwest;
 use reqwest::header::CONTENT_TYPE;
 use serde_json::{self, Value};
 use std::net::SocketAddr;
+use std::thread::sleep;
 use std::time::Duration;
 use std::{error, fmt};
 
@@ -64,23 +65,51 @@ impl RpcRequest {
         client: &RpcClient,
         id: u64,
         params: Option<Value>,
+    ) -> Result<Value, Box<dyn error::Error>> {
+        self.retry_make_rpc_request(client, id, params, 0)
+    }
+
+    pub fn retry_make_rpc_request(
+        &self,
+        client: &RpcClient,
+        id: u64,
+        params: Option<Value>,
+        mut retries: usize,
     ) -> Result<Value, Box<dyn error::Error>> {
         let request = self.build_request_json(id, params);
 
-        let mut response = client
-            .client
-            .post(&client.addr)
-            .header(CONTENT_TYPE, "application/json")
-            .body(request.to_string())
-            .send()?;
-        let json: Value = serde_json::from_str(&response.text()?)?;
-        if json["error"].is_object() {
-            Err(RpcError::RpcRequestError(format!(
-                "RPC Error response: {}",
-                serde_json::to_string(&json["error"]).unwrap()
-            )))?
+        loop {
+            match client
+                .client
+                .post(&client.addr)
+                .header(CONTENT_TYPE, "application/json")
+                .body(request.to_string())
+                .send()
+            {
+                Ok(mut response) => {
+                    let json: Value = serde_json::from_str(&response.text()?)?;
+                    if json["error"].is_object() {
+                        Err(RpcError::RpcRequestError(format!(
+                            "RPC Error response: {}",
+                            serde_json::to_string(&json["error"]).unwrap()
+                        )))?
+                    }
+                    return Ok(json["result"].clone());
+                }
+                Err(e) => {
+                    info!(
+                        "make_rpc_request() failed, {} retries left: {:?}",
+                        retries, e
+                    );
+                    if retries == 0 {
+                        Err(e)?;
+                    }
+                    retries -= 1;
+                    // TODO: Make the caller supply their desired retry frequency?
+                    sleep(Duration::from_millis(500));
+                }
+            }
         }
-        Ok(json["result"].clone())
     }
 
     fn build_request_json(&self, id: u64, params: Option<Value>) -> Value {
@@ -242,4 +271,44 @@ mod tests {
             RpcRequest::GetLastId.make_rpc_request(&rpc_client, 3, Some(json!("paramter")));
         assert_eq!(last_id.is_err(), true);
     }
+
+    #[test]
+    fn test_retry_make_rpc_request() {
+        solana_logger::setup();
+        let (sender, receiver) = channel();
+        thread::spawn(move || {
+            // 1. Pick a random port
+            // 2. Tell the client to start using it
+            // 3. Delay for 1.5 seconds before starting the server to ensure the client will fail
+            //    and need to retry
+            let rpc_addr = socketaddr!(0, 4242);
+            sender.send(rpc_addr.clone()).unwrap();
+            sleep(Duration::from_millis(1500));
+
+            let mut io = IoHandler::default();
+            io.add_method("getBalance", move |_params: Params| {
+                Ok(Value::Number(Number::from(5)))
+            });
+            let server = ServerBuilder::new(io)
+                .threads(1)
+                .cors(DomainsValidation::AllowOnly(vec![
+                    AccessControlAllowOrigin::Any,
+                ]))
+                .start_http(&rpc_addr)
+                .expect("Unable to start RPC server");
+            server.wait();
+        });
+
+        let rpc_addr = receiver.recv().unwrap();
+        let rpc_client = RpcClient::new_from_socket(rpc_addr);
+
+        let balance = RpcRequest::GetBalance.retry_make_rpc_request(
+            &rpc_client,
+            1,
+            Some(json!(["deadbeefXjn8o3yroDHxUtKsZZgoy4GPkPPXfouKNHhw"])),
+            10,
+        );
+        assert!(balance.is_ok());
+        assert_eq!(balance.unwrap().as_u64().unwrap(), 5);
+    }
 }