Improve gossip use for drone and wallet

- Add utility function
  - Add thread sleep
  - Enable configurable timeout for gossip poll

src/thin_client.rs

@@ -5,12 +5,17 @@
 
 use bank::Account;
 use bincode::{deserialize, serialize};
+use crdt::{Crdt, CrdtError, NodeInfo, TestNode};
 use hash::Hash;
+use ncp::Ncp;
 use request::{Request, Response};
+use result::{Error, Result};
 use signature::{Keypair, Pubkey, Signature};
 use std::collections::HashMap;
 use std::io;
 use std::net::{SocketAddr, UdpSocket};
+use std::sync::atomic::AtomicBool;
+use std::sync::{Arc, RwLock};
 use std::thread::sleep;
 use std::time::Duration;
 use std::time::Instant;
@@ -320,6 +325,38 @@ impl Drop for ThinClient {
     }
 }
 
+pub fn poll_gossip_for_leader(leader_ncp: SocketAddr, timeout: Option<u64>) -> Result<NodeInfo> {
+    let exit = Arc::new(AtomicBool::new(false));
+    let testnode = TestNode::new_localhost();
+    let extra_data = testnode.data.clone();
+    let crdt = Arc::new(RwLock::new(Crdt::new(extra_data).expect("Crdt::new")));
+    let window = Arc::new(RwLock::new(vec![]));
+    let ncp = Ncp::new(
+        &crdt.clone(),
+        window,
+        None,
+        testnode.sockets.gossip,
+        testnode.sockets.gossip_send,
+        exit.clone(),
+    ).unwrap();
+    let leader_entry_point = NodeInfo::new_entry_point(leader_ncp);
+    crdt.write().unwrap().insert(&leader_entry_point);
+
+    sleep(Duration::from_millis(100));
+
+    let now = Instant::now();
+    // Block until leader's correct contact info is received
+    while crdt.read().unwrap().leader_data().is_none() {
+        if timeout.is_some() && now.elapsed() > Duration::new(timeout.unwrap(), 0) {
+            return Err(Error::CrdtError(CrdtError::NoLeader));
+        }
+    }
+
+    ncp.close()?;
+    let leader = crdt.read().unwrap().leader_data().unwrap().clone();
+    Ok(leader)
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;