diff --git a/opencensus/exporters/stats/prometheus/internal/prometheus_exporter.cc b/opencensus/exporters/stats/prometheus/internal/prometheus_exporter.cc
index 3bb5962..706b9b4 100644
--- a/opencensus/exporters/stats/prometheus/internal/prometheus_exporter.cc
+++ b/opencensus/exporters/stats/prometheus/internal/prometheus_exporter.cc
@@ -25,7 +25,7 @@ namespace opencensus {
 namespace exporters {
 namespace stats {

-std::vector<prometheus::MetricFamily> PrometheusExporter::Collect() const {
+std::vector<prometheus::MetricFamily> PrometheusExporter::Collect() {
   const auto data = opencensus::stats::StatsExporter::GetViewData();
   std::vector<prometheus::MetricFamily> output(data.size());
   for (int i = 0; i < data.size(); ++i) {
diff --git a/opencensus/exporters/stats/prometheus/prometheus_exporter.h b/opencensus/exporters/stats/prometheus/prometheus_exporter.h
index bbb285d..ab6471f 100644
--- a/opencensus/exporters/stats/prometheus/prometheus_exporter.h
+++ b/opencensus/exporters/stats/prometheus/prometheus_exporter.h
@@ -41,7 +41,7 @@ namespace stats {
 // PrometheusExporter is thread-safe.
 class PrometheusExporter final : public ::prometheus::Collectable {
  public:
-  std::vector<prometheus::MetricFamily> Collect() const override;
+  std::vector<prometheus::MetricFamily> Collect() override;
 };

 }  // namespace stats
diff --git a/opencensus/stats/internal/delta_producer.cc b/opencensus/stats/internal/delta_producer.cc
index 1d00504..7eb0d8a 100644
--- a/opencensus/stats/internal/delta_producer.cc
+++ b/opencensus/stats/internal/delta_producer.cc
@@ -75,6 +75,20 @@ DeltaProducer* DeltaProducer::Get() {
   return global_delta_producer;
 }

+void DeltaProducer::Shutdown() {
+  {
+    absl::MutexLock l(&mu_);
+    if (!thread_started_) {
+      return;
+    }
+    thread_started_ = false;
+  }
+  // Join loop thread when shutdown.
+  if (harvester_thread_.joinable()) {
+    harvester_thread_.join();
+  }
+}
+
 void DeltaProducer::AddMeasure() {
   delta_mu_.Lock();
   absl::MutexLock harvester_lock(&harvester_mu_);
@@ -115,7 +129,10 @@ void DeltaProducer::Flush() {
 }

 DeltaProducer::DeltaProducer()
-    : harvester_thread_(&DeltaProducer::RunHarvesterLoop, this) {}
+    : harvester_thread_(&DeltaProducer::RunHarvesterLoop, this) {
+  absl::MutexLock l(&mu_);
+  thread_started_ = true;
+}

 void DeltaProducer::SwapDeltas() {
   ABSL_ASSERT(last_delta_.delta().empty() && "Last delta was not consumed.");
@@ -131,11 +148,19 @@ void DeltaProducer::RunHarvesterLoop() {
   absl::Time next_harvest_time = absl::Now() + harvest_interval_;
   while (true) {
     const absl::Time now = absl::Now();
-    absl::SleepFor(next_harvest_time - now);
+    absl::SleepFor(absl::Seconds(0.1));
     // Account for the possibility that the last harvest took longer than
     // harvest_interval_ and we are already past next_harvest_time.
-    next_harvest_time = std::max(next_harvest_time, now) + harvest_interval_;
-    Flush();
+    if (absl::Now() > next_harvest_time) {
+      next_harvest_time = std::max(next_harvest_time, now) + harvest_interval_;
+      Flush();
+    }
+    {
+      absl::MutexLock l(&mu_);
+      if (!thread_started_) {
+        break;
+      }
+    }
   }
 }

diff --git a/opencensus/stats/internal/delta_producer.h b/opencensus/stats/internal/delta_producer.h
index e565f6a..453b4ef 100644
--- a/opencensus/stats/internal/delta_producer.h
+++ b/opencensus/stats/internal/delta_producer.h
@@ -71,6 +71,8 @@ class DeltaProducer final {
   // Returns a pointer to the singleton DeltaProducer.
   static DeltaProducer* Get();

+  void Shutdown();
+
   // Adds a new Measure.
   void AddMeasure();

@@ -124,6 +126,9 @@ class DeltaProducer final {
   // thread when calling a flush during harvesting.
   Delta last_delta_ ABSL_GUARDED_BY(harvester_mu_);
   std::thread harvester_thread_ ABSL_GUARDED_BY(harvester_mu_);
+
+  mutable absl::Mutex mu_;
+  bool thread_started_ ABSL_GUARDED_BY(mu_) = false;
 };

 }  // namespace stats
diff --git a/opencensus/stats/internal/stats_exporter.cc b/opencensus/stats/internal/stats_exporter.cc
index 7de96d6..f9cac57 100644
--- a/opencensus/stats/internal/stats_exporter.cc
+++ b/opencensus/stats/internal/stats_exporter.cc
@@ -95,25 +95,57 @@ void StatsExporterImpl::ClearHandlersForTesting() {
 }

 void StatsExporterImpl::StartExportThread() ABSL_EXCLUSIVE_LOCKS_REQUIRED(mu_) {
-  t_ = std::thread(&StatsExporterImpl::RunWorkerLoop, this);
   thread_started_ = true;
+  t_ = std::thread(&StatsExporterImpl::RunWorkerLoop, this);
+}
+
+void StatsExporterImpl::Shutdown() {
+  {
+    absl::MutexLock l(&mu_);
+    if (!thread_started_) {
+      return;
+    }
+    thread_started_ = false;
+  }
+  // Join loop thread when shutdown.
+  if (t_.joinable()) {
+    t_.join();
+  }
 }

 void StatsExporterImpl::RunWorkerLoop() {
   absl::Time next_export_time = GetNextExportTime();
   while (true) {
     // SleepFor() returns immediately when given a negative duration.
-    absl::SleepFor(next_export_time - absl::Now());
+    absl::SleepFor(absl::Seconds(0.1));
     // In case the last export took longer than the export interval, we
     // calculate the next time from now.
-    next_export_time = GetNextExportTime();
-    Export();
+    if (absl::Now() > next_export_time) {
+      next_export_time = GetNextExportTime();
+      Export();
+    }
+    {
+      absl::MutexLock l(&mu_);
+      if (!thread_started_) {
+        break;
+      }
+    }
   }
 }

 // StatsExporter
 // -------------

+void StatsExporter::Shutdown() {
+  StatsExporterImpl::Get()->Shutdown();
+  StatsExporterImpl::Get()->ClearHandlersForTesting();
+}
+
+void StatsExporter::ExportNow() {
+  DeltaProducer::Get()->Flush();
+  StatsExporterImpl::Get()->Export();
+}
+
 // static
 void StatsExporter::SetInterval(absl::Duration interval) {
   StatsExporterImpl::Get()->SetInterval(interval);
diff --git a/opencensus/stats/internal/stats_exporter_impl.h b/opencensus/stats/internal/stats_exporter_impl.h
index abbd13e..823471e 100644
--- a/opencensus/stats/internal/stats_exporter_impl.h
+++ b/opencensus/stats/internal/stats_exporter_impl.h
@@ -34,6 +34,7 @@ class StatsExporterImpl {
  public:
   static StatsExporterImpl* Get();
   void SetInterval(absl::Duration interval);
+  void Shutdown();
   absl::Time GetNextExportTime() const;
   void AddView(const ViewDescriptor& view);
   void RemoveView(absl::string_view name);
diff --git a/opencensus/stats/stats_exporter.h b/opencensus/stats/stats_exporter.h
index 6756858..228069b 100644
--- a/opencensus/stats/stats_exporter.h
+++ b/opencensus/stats/stats_exporter.h
@@ -44,6 +44,8 @@ class StatsExporter final {

   // Removes the view with 'name' from the registry, if one is registered.
   static void RemoveView(absl::string_view name);
+  static void Shutdown();
+  static void ExportNow();

   // StatsExporter::Handler is the interface for push exporters that export
   // recorded data for registered views. The exporter should provide a static