fix: fix batch ordering issue

Fixes issue #75
Raw client waiting map was using the same channel
for every request/response. When items were put
back into the channel inside of _reader_thread
the waiting receiver in recv would just take the
next response without validating it on request id
request.
This fixes this by using unique channels for each
request response inside of the waiting map.

Author: marshallyale

src/raw_client.rs

@@ -3,7 +3,7 @@
 //! This module contains the definition of the raw client that wraps the transport method
 
 use std::borrow::Borrow;
-use std::collections::{BTreeMap, BTreeSet, HashMap, VecDeque};
+use std::collections::{BTreeMap, HashMap, VecDeque};
 use std::io::{BufRead, BufReader, Read, Write};
 use std::mem::drop;
 use std::net::{TcpStream, ToSocketAddrs};
@@ -762,22 +762,23 @@ impl<T: Read + Write> ElectrumApi for RawClient<T> {
     fn batch_call(&self, batch: &Batch) -> Result<Vec<serde_json::Value>, Error> {
         let mut raw = Vec::new();
 
-        let mut missing_responses = BTreeSet::new();
+        let mut missing_responses = Vec::new();
         let mut answers = BTreeMap::new();
 
-        // Add our listener to the map before we send the request, Here we will clone the sender
-        // for every request id, so that we only have to monitor one receiver.
-        let (sender, receiver) = channel();
+        // Add our listener to the map before we send the request
 
         for (method, params) in batch.iter() {
             let req = Request::new_id(
                 self.last_id.fetch_add(1, Ordering::SeqCst),
                 method,
                 params.to_vec(),
             );
-            missing_responses.insert(req.id);
+            // Add distinct channel to each request so when we remove our request id (and sender) from the waiting_map
+            // we can be sure that the response gets sent to the correct channel in self.recv
+            let (sender, receiver) = channel();
+            missing_responses.push((req.id, receiver));
 
-            self.waiting_map.lock()?.insert(req.id, sender.clone());
+            self.waiting_map.lock()?.insert(req.id, sender);
 
             raw.append(&mut serde_json::to_vec(&req)?);
             raw.extend_from_slice(b"\n");
@@ -796,7 +797,7 @@ impl<T: Read + Write> ElectrumApi for RawClient<T> {
 
         self.increment_calls();
 
-        for req_id in missing_responses.iter() {
+        for (req_id, receiver) in missing_responses.iter() {
             match self.recv(&receiver, *req_id) {
                 Ok(mut resp) => answers.insert(req_id, resp["result"].take()),
                 Err(e) => {
@@ -805,7 +806,7 @@ impl<T: Read + Write> ElectrumApi for RawClient<T> {
                     warn!("got error for req_id {}: {:?}", req_id, e);
                     warn!("removing all waiting req of this batch");
                     let mut guard = self.waiting_map.lock()?;
-                    for req_id in missing_responses.iter() {
+                    for (req_id, _) in missing_responses.iter() {
                         guard.remove(req_id);
                     }
                     return Err(e);