Fix Docker state drift: add 5s background state poller and make mutating operations idempotent (404/304 as success)

src/docker_state_poller.cpp

@@ -0,0 +1,59 @@
+#include "docker_state_poller.hpp"
+
+DockerStatePoller::~DockerStatePoller() {
+    stop();
+}
+
+void DockerStatePoller::start(const DockerManager& docker,
+                              PostFunction post,
+                              ResultCallback callback) {
+    stop();
+    docker_ = &docker;
+    post_ = std::move(post);
+    callback_ = std::move(callback);
+    {
+        std::lock_guard<std::mutex> lock(mutex_);
+        stop_ = false;
+        immediate_ = false;
+    }
+    thread_ = std::thread(&DockerStatePoller::loop, this);
+}
+
+void DockerStatePoller::stop() {
+    {
+        std::lock_guard<std::mutex> lock(mutex_);
+        stop_ = true;
+    }
+    cv_.notify_all();
+    if (thread_.joinable()) thread_.join();
+}
+
+void DockerStatePoller::trigger_now() {
+    {
+        std::lock_guard<std::mutex> lock(mutex_);
+        immediate_ = true;
+    }
+    cv_.notify_all();
+}
+
+void DockerStatePoller::loop() {
+    while (true) {
+        {
+            std::unique_lock<std::mutex> lock(mutex_);
+            cv_.wait_for(lock, kInterval, [this] { return stop_ || immediate_; });
+            if (stop_) break;
+            immediate_ = false;
+        }
+
+        if (!docker_ || !post_ || !callback_) continue;
+
+        auto containers = docker_->getContainerList();
+        auto images = docker_->getImageList();
+
+        post_([callback = callback_,
+               containers = std::move(containers),
+               images = std::move(images)]() mutable {
+            callback(std::move(containers), std::move(images));
+        });
+    }
+}