memory leaks

common/params.cc

@@ -109,7 +109,10 @@ Params::~Params() {
   if (future.valid()) {
     future.wait();
   }
+  std::scoped_lock lk(pending_writes_lock);
   assert(queue.empty());
+  assert(pending_writes.empty());
+  assert(!writer_running);
 }
 
 std::vector<std::string> Params::allKeys() const {
@@ -245,19 +248,59 @@ void Params::clearAll(ParamKeyFlag key_flag) {
 }
 
 void Params::putNonBlocking(const std::string &key, const std::string &val) {
-   queue.push(std::make_pair(key, val));
-  // start thread on demand
-  if (!future.valid() || future.wait_for(std::chrono::milliseconds(0)) == std::future_status::ready) {
+  bool should_enqueue = false;
+  bool should_start_thread = false;
+
+  {
+    std::scoped_lock lk(pending_writes_lock);
+    auto it = pending_writes.find(key);
+    if (it == pending_writes.end()) {
+      pending_writes.emplace(key, val);
+      should_enqueue = true;
+    } else {
+      it->second = val;
+    }
+
+    if (!writer_running) {
+      writer_running = true;
+      should_start_thread = true;
+    }
+  }
+
+  if (should_enqueue) {
+    queue.push(key);
+  }
+
+  if (should_start_thread) {
     future = std::async(std::launch::async, &Params::asyncWriteThread, this);
   }
 }
 
 void Params::asyncWriteThread() {
-  // TODO: write the latest one if a key has multiple values in the queue.
-  std::pair<std::string, std::string> p;
-  while (queue.try_pop(p, 0)) {
+  std::string key;
+  while (true) {
+    if (!queue.try_pop(key, 0)) {
+      std::scoped_lock lk(pending_writes_lock);
+      if (queue.empty() && pending_writes.empty()) {
+        writer_running = false;
+        return;
+      }
+      continue;
+    }
+
+    std::string val;
+    {
+      std::scoped_lock lk(pending_writes_lock);
+      auto it = pending_writes.find(key);
+      if (it == pending_writes.end()) {
+        continue;
+      }
+      val = std::move(it->second);
+      pending_writes.erase(it);
+    }
+
     // Params::put is Thread-Safe
-    put(p.first, p.second);
+    put(key, val);
   }
 }
 

common/params.h

@@ -2,9 +2,11 @@
 
 #include <future>
 #include <map>
+#include <mutex>
 #include <optional>
 #include <string>
 #include <tuple>
+#include <unordered_map>
 #include <utility>
 #include <vector>
 
@@ -120,7 +122,10 @@ private:
 
   // for nonblocking write
   std::future<void> future;
-  SafeQueue<std::pair<std::string, std::string>> queue;
+  SafeQueue<std::string> queue;
+  std::mutex pending_writes_lock;
+  std::unordered_map<std::string, std::string> pending_writes;
+  bool writer_running = false;
 
   // StarPilot variables
   std::string cache_path;

common/tests/test_params.py

@@ -101,6 +101,16 @@ class TestParams:
     assert q.get("CarParams") is None
     assert q.get("CarParams", True) == b"1"
 
+  def test_put_nonblocking_latest_value_wins(self, tmp_path):
+    q = Params(str(tmp_path))
+    for i in range(100):
+      q.put_nonblocking("CarParams", f"value-{i}".encode())
+
+    del q
+
+    r = Params(str(tmp_path))
+    assert r.get("CarParams") == b"value-99"
+
   def test_params_all_keys(self):
     keys = Params().all_keys()