Only maintain a repo scheduler when a Repo instance is present.

The Repo scheduler is crashing in it's destructor on shutdown in some
environments so make the scheduler lifetime dependent upon the
Repo object lifetime.  This also reduces resource usage when no
Database instances are present.

PiperOrigin-RevId: 255657460

Author: smiles

database/src/desktop/core/repo.cc

@@ -15,6 +15,7 @@
 #include "database/src/desktop/core/repo.h"
 
 #include "app/src/callback.h"
+#include "app/src/mutex.h"
 #include "app/src/log.h"
 #include "app/src/scheduler.h"
 #include "app/src/variant_util.h"
@@ -40,7 +41,9 @@ using callback::NewCallback;
 namespace database {
 namespace internal {
 
-scheduler::Scheduler Repo::s_scheduler_;
+static Mutex g_scheduler_mutex;  // NOLINT
+static int g_scheduler_ref_count = 0;
+scheduler::Scheduler* Repo::s_scheduler_;
 
 // Transaction Response class to pass to PersistentConnection.
 // This is used to capture all the data to use when ResponseCallback is
@@ -86,10 +89,16 @@ Repo::Repo(App* app, DatabaseInternal* database, const char* url)
                                     parser.secure);
   url_ = host_info_.ToString();
 
+  {
+    MutexLock lock(g_scheduler_mutex);
+    g_scheduler_ref_count++;
+    if (s_scheduler_ == nullptr) s_scheduler_ = new scheduler::Scheduler();
+  }
+
   connection_.reset(new connection::PersistentConnection(app, host_info_, this,
-                                                         &s_scheduler_));
+                                                         s_scheduler_));
   // Kick off any expensive additional initialization
-  s_scheduler_.Schedule(NewCallback(
+  s_scheduler_->Schedule(NewCallback(
       [](ThisRef ref) {
         ThisRefLock lock(&ref);
         if (lock.GetReference() != nullptr) {
@@ -107,6 +116,14 @@ Repo::~Repo() {
   // while the SyncTree is being torn down.
   safe_this_.ClearReference();
   connection_.reset(nullptr);
+  {
+    MutexLock lock(g_scheduler_mutex);
+    if (g_scheduler_ref_count) g_scheduler_ref_count--;
+    if (g_scheduler_ref_count == 0) {
+      delete s_scheduler_;
+      s_scheduler_ = nullptr;
+    }
+  }
 }
 
 void Repo::AddEventCallback(UniquePtr<EventRegistration> event_registration) {

database/src/desktop/core/repo.h

@@ -105,7 +105,7 @@ class Repo : public connection::PersistentConnectionEventHandler {
 
   const std::string& url() const { return url_; }
 
-  static scheduler::Scheduler& scheduler() { return s_scheduler_; }
+  static scheduler::Scheduler& scheduler() { return *s_scheduler_; }
 
   ThisRef& this_ref() { return safe_this_; }
 
@@ -158,7 +158,7 @@ class Repo : public connection::PersistentConnectionEventHandler {
   // The scheduler shared with every DatabaseInternal. It is designed to
   // out-live any class which is using it, so that it is safe to use even in
   // destructor.
-  static scheduler::Scheduler s_scheduler_;
+  static scheduler::Scheduler* s_scheduler_;
 
   // Caches information about the connection to the host.
   connection::HostInfo host_info_;