address some comments

Author: BewareMyPower

include/pulsar/AutoClusterFailover.h

@@ -23,6 +23,9 @@
 
 #include <chrono>
 #include <cstdint>
+#include <functional>
+#include <memory>
+#include <vector>
 
 namespace pulsar {
 
@@ -61,7 +64,9 @@ class PULSAR_PUBLIC AutoClusterFailover final : public ServiceInfoProvider {
      * - failoverThreshold: the number of consecutive failed probes required before switching away from
      *   the current cluster.
      * - switchBackThreshold: the number of consecutive successful probes to the primary required before
-     *   switching back from a secondary.
+     *   switching back from a secondary while that secondary remains available. If the active secondary
+     *   becomes unavailable and the primary is available, the implementation may switch back to the
+     *   primary immediately, regardless of this threshold.
      */
     class Builder {
        public:
@@ -80,7 +85,9 @@ class PULSAR_PUBLIC AutoClusterFailover final : public ServiceInfoProvider {
             return *this;
         }
 
-        // Set the number of consecutive successful primary probes required before switching back. Default: 1.
+        // Set the number of consecutive successful primary probes required before switching back from a
+        // healthy secondary. If the active secondary becomes unavailable and the primary is available,
+        // the implementation may switch back immediately regardless of this threshold. Default: 1.
         Builder& withSwitchBackThreshold(uint32_t threshold) {
             config_.switchBackThreshold = threshold;
             return *this;

lib/AutoClusterFailover.cc

@@ -60,20 +60,18 @@ class AutoClusterFailoverImpl : public std::enable_shared_from_this<AutoClusterF
 
     ~AutoClusterFailoverImpl() {
         using namespace std::chrono_literals;
-        if (!thread_.joinable() || !future_.valid()) {
+        if (!thread_.joinable()) {
             return;
         }
 
         cancelTimer(*timer_);
         workGuard_.reset();
         ioContext_.stop();
 
-        if (future_.wait_for(1s) != std::future_status::ready) {
-            LOG_WARN("AutoClusterFailoverImpl is not stopped within 3 seconds, skip it");
-            thread_.detach();
-        } else {
-            thread_.join();
+        if (future_.wait_for(3s) != std::future_status::ready) {
+            LOG_WARN("AutoClusterFailoverImpl is not stopped within 3 seconds, waiting for it to finish");
         }
+        thread_.join();
     }
 
     auto primary() const noexcept { return config_.primary; }
@@ -367,7 +365,7 @@ class AutoClusterFailoverImpl : public std::enable_shared_from_this<AutoClusterF
                         return;
                     }
 
-                    LOG_DEBUG("Detected primary after secondary is available "
+                    LOG_DEBUG("Detected primary while secondary is unavailable "
                               << self->config_.primary.serviceUrl() << " availability: " << primaryAvailable);
                     if (primaryAvailable) {
                         self->switchTo(&self->config_.primary);