feat(storage): add IsOpen API for zonal read operation

google/cloud/storage/async/object_descriptor.cc

@@ -52,6 +52,8 @@ std::pair<AsyncReader, AsyncToken> ObjectDescriptor::ReadLast(
   return {AsyncReader(std::move(reader)), std::move(token)};
 }
 
+bool ObjectDescriptor::IsOpen() const { return impl_->IsOpen(); }
+
 GOOGLE_CLOUD_CPP_INLINE_NAMESPACE_END
 }  // namespace storage
 }  // namespace cloud

google/cloud/storage/async/object_descriptor.h

@@ -76,6 +76,14 @@ class ObjectDescriptor {
    */
   std::pair<AsyncReader, AsyncToken> ReadLast(std::int64_t limit);
 
+  /**
+   * Returns true if the descriptor is open.
+   *
+   * A descriptor is open if it has not been cancelled and has not hit a
+   * permanent failure.
+   */
+  bool IsOpen() const;
+
  private:
   std::shared_ptr<ObjectDescriptorConnection> impl_;
 };

google/cloud/storage/async/object_descriptor_connection.h

@@ -61,6 +61,14 @@ class ObjectDescriptorConnection {
   virtual std::unique_ptr<AsyncReaderConnection> Read(ReadParams p) = 0;
 
   virtual void MakeSubsequentStream() = 0;
+
+  /**
+   * Returns true if the descriptor is open.
+   *
+   * A descriptor is open if it has not been cancelled and has not hit a
+   * permanent failure.
+   */
+  virtual bool IsOpen() const { return true; }
 };
 
 GOOGLE_CLOUD_CPP_INLINE_NAMESPACE_END

google/cloud/storage/async/object_descriptor_test.cc

@@ -186,6 +186,15 @@ TEST(ObjectDescriptor, ReadExceedsMaxRange) {
   EXPECT_FALSE(token.valid());
 }
 
+TEST(ObjectDescriptor, IsOpen) {
+  auto mock = std::make_shared<MockAsyncObjectDescriptorConnection>();
+  EXPECT_CALL(*mock, IsOpen).WillOnce(Return(true)).WillOnce(Return(false));
+
+  auto tested = ObjectDescriptor(mock);
+  EXPECT_TRUE(tested.IsOpen());
+  EXPECT_FALSE(tested.IsOpen());
+}
+
 }  // namespace
 GOOGLE_CLOUD_CPP_INLINE_NAMESPACE_END
 }  // namespace storage

google/cloud/storage/internal/async/connection_impl.cc

@@ -55,6 +55,7 @@
 #include "google/cloud/internal/async_streaming_read_rpc_timeout.h"
 #include "google/cloud/internal/async_streaming_write_rpc_timeout.h"
 #include "google/cloud/internal/make_status.h"
+#include <grpcpp/grpcpp.h>
 #include <memory>
 #include <utility>
 
@@ -231,19 +232,33 @@ AsyncConnectionImpl::Open(OpenParams p) {
 
   auto pending = factory(std::move(initial_request));
   using ReturnType = std::shared_ptr<storage::ObjectDescriptorConnection>;
-  return pending.then(
-      [rp = std::move(resume_policy), fa = std::move(factory),
-       rs = std::move(p.read_spec),
-       options = std::move(p.options)](auto f) mutable -> StatusOr<ReturnType> {
-        auto result = f.get();
-        if (!result) return std::move(result).status();
-
-        auto impl = std::make_shared<ObjectDescriptorImpl>(
-            std::move(rp), std::move(fa), std::move(rs),
-            std::move(result->stream), std::move(options));
-        impl->Start(std::move(result->first_response));
-        return ReturnType(impl);
-      });
+  return pending.then([rp = std::move(resume_policy), fa = std::move(factory),
+                       rs = std::move(p.read_spec),
+                       options = std::move(p.options), refresh = refresh_](
+                          auto f) mutable -> StatusOr<ReturnType> {
+    auto result = f.get();
+    if (!result) return std::move(result).status();
+
+    // The descriptor remains open if at least one gRPC channel is in a
+    // functional state. We consider READY, IDLE, and CONNECTING to be
+    // functional. TRANSIENT_FAILURE and SHUTDOWN are not included because they
+    // indicate a definitive loss of connectivity or terminal closure.
+    auto transport_ok = [refresh] {
+      if (!refresh) return true;
+      auto const& channels = refresh->channels();
+      return std::any_of(
+          channels.begin(), channels.end(), [](auto const& channel) {
+            auto state = channel->GetState(false);
+            return state == GRPC_CHANNEL_READY || state == GRPC_CHANNEL_IDLE ||
+                   state == GRPC_CHANNEL_CONNECTING;
+          });
+    };
+    auto impl = std::make_shared<ObjectDescriptorImpl>(
+        std::move(rp), std::move(fa), std::move(rs), std::move(result->stream),
+        std::move(options), std::move(transport_ok));
+    impl->Start(std::move(result->first_response));
+    return ReturnType(impl);
+  });
 }
 
 future<StatusOr<std::unique_ptr<storage::AsyncReaderConnection>>>

google/cloud/storage/internal/async/object_descriptor_connection_tracing.cc

@@ -46,6 +46,7 @@ class AsyncObjectDescriptorConnectionTracing
   absl::optional<google::storage::v2::Object> metadata() const override {
     return impl_->metadata();
   }
+  bool IsOpen() const override { return impl_->IsOpen(); }
 
   std::unique_ptr<storage::AsyncReaderConnection> Read(ReadParams p) override {
     internal::OTelScope scope(span_);

google/cloud/storage/internal/async/object_descriptor_impl.cc

@@ -34,11 +34,13 @@ ObjectDescriptorImpl::ObjectDescriptorImpl(
     std::unique_ptr<storage::ResumePolicy> resume_policy,
     OpenStreamFactory make_stream,
     google::storage::v2::BidiReadObjectSpec read_object_spec,
-    std::shared_ptr<OpenStream> stream, Options options)
+    std::shared_ptr<OpenStream> stream, Options options,
+    std::function<bool()> transport_ok)
     : resume_policy_prototype_(std::move(resume_policy)),
       make_stream_(std::move(make_stream)),
       read_object_spec_(std::move(read_object_spec)),
-      options_(std::move(options)) {
+      options_(std::move(options)),
+      transport_ok_(std::move(transport_ok)) {
   stream_manager_ = std::make_unique<StreamManager>(
       []() -> std::shared_ptr<ReadStream> { return nullptr; },  // NOLINT
       std::make_shared<ReadStream>(std::move(stream),
@@ -62,8 +64,18 @@ void ObjectDescriptorImpl::Start(
   }
 }
 
+bool ObjectDescriptorImpl::IsOpen() const {
+  {
+    std::unique_lock<std::mutex> lk(mu_);
+    if (cancelled_) return false;
+    if (stream_manager_->Empty()) return false;
+  }
+  return !transport_ok_ || transport_ok_();
+}
+
 void ObjectDescriptorImpl::Cancel() {
   std::unique_lock<std::mutex> lk(mu_);
+  if (cancelled_) return;
   cancelled_ = true;
   if (stream_manager_) stream_manager_->CancelAll();
   if (pending_stream_.valid()) pending_stream_.cancel();

google/cloud/storage/internal/async/object_descriptor_impl.h

@@ -27,6 +27,7 @@
 #include "absl/types/optional.h"
 #include "google/storage/v2/storage.pb.h"
 #include <cstdint>
+#include <functional>
 #include <memory>
 #include <mutex>
 #include <unordered_map>
@@ -59,8 +60,8 @@ class ObjectDescriptorImpl
   ObjectDescriptorImpl(std::unique_ptr<storage::ResumePolicy> resume_policy,
                        OpenStreamFactory make_stream,
                        google::storage::v2::BidiReadObjectSpec read_object_spec,
-                       std::shared_ptr<OpenStream> stream,
-                       Options options = {});
+                       std::shared_ptr<OpenStream> stream, Options options = {},
+                       std::function<bool()> transport_ok = {});
   ~ObjectDescriptorImpl() override;
 
   // Start the read loop.
@@ -82,6 +83,8 @@ class ObjectDescriptorImpl
 
   std::size_t StreamSize() const;
 
+  bool IsOpen() const override;
+
  private:
   using StreamManager = MultiStreamManager<ReadStream, ReadRange>;
   using StreamIterator =
@@ -123,6 +126,7 @@ class ObjectDescriptorImpl
       google::cloud::StatusOr<storage_internal::OpenStreamResult>>
       pending_stream_;
   bool cancelled_ = false;
+  std::function<bool()> transport_ok_;
 };
 
 GOOGLE_CLOUD_CPP_INLINE_NAMESPACE_END

google/cloud/storage/internal/async/object_descriptor_impl_test.cc

@@ -67,15 +67,18 @@ auto constexpr kMetadataText = R"pb(
 
 auto NoResume() { return storage::LimitedErrorCountResumePolicy(0)(); }
 
-auto MakeTested(std::unique_ptr<storage::ResumePolicy> resume_policy,
-                OpenStreamFactory make_stream,
-                google::storage::v2::BidiReadObjectSpec read_object_spec,
-                std::shared_ptr<OpenStream> stream) {
+auto MakeTested(
+    std::unique_ptr<storage::ResumePolicy> resume_policy,
+    OpenStreamFactory make_stream,
+    google::storage::v2::BidiReadObjectSpec read_object_spec,
+    std::shared_ptr<OpenStream> stream,
+    std::function<bool()> transport_ok = [] { return true; }) {
   Options options;
   options.set<storage::EnableMultiStreamOptimizationOption>(true);
   return std::make_shared<ObjectDescriptorImpl>(
       std::move(resume_policy), std::move(make_stream),
-      std::move(read_object_spec), std::move(stream), std::move(options));
+      std::move(read_object_spec), std::move(stream), std::move(options),
+      std::move(transport_ok));
 }
 
 MATCHER_P(IsProtoEqualModuloRepeatedFieldOrdering, value,
@@ -1784,6 +1787,83 @@ TEST(ObjectDescriptorImpl, MultiStreamOptimizationDisabled) {
   tested.reset();
 }
 
+/// @test Verify that IsOpen() is true by default.
+TEST(ObjectDescriptorImpl, IsOpenTrueByDefault) {
+  MockFactory factory;
+  auto stream = std::make_unique<MockStream>();
+  EXPECT_CALL(*stream, Finish).WillOnce(Return(make_ready_future(Status{})));
+  EXPECT_CALL(*stream, Cancel).Times(AtMost(1));
+  auto tested = MakeTested(NoResume(), factory.AsStdFunction(),
+                           google::storage::v2::BidiReadObjectSpec{},
+                           std::make_shared<OpenStream>(std::move(stream)));
+  EXPECT_TRUE(tested->IsOpen());
+}
+
+/// @test Verify that IsOpen() is false after Cancel().
+TEST(ObjectDescriptorImpl, IsOpenFalseOnCancel) {
+  MockFactory factory;
+  auto stream = std::make_unique<MockStream>();
+  EXPECT_CALL(*stream, Finish).WillOnce(Return(make_ready_future(Status{})));
+  EXPECT_CALL(*stream, Cancel).Times(AtMost(2));
+  auto tested = MakeTested(NoResume(), factory.AsStdFunction(),
+                           google::storage::v2::BidiReadObjectSpec{},
+                           std::make_shared<OpenStream>(std::move(stream)));
+  EXPECT_TRUE(tested->IsOpen());
+  tested->Cancel();
+  EXPECT_FALSE(tested->IsOpen());
+}
+
+/// @test Verify that IsOpen() is false if transport health check fails.
+TEST(ObjectDescriptorImpl, IsOpenFalseOnPermanentError) {
+  MockFactory factory;
+  auto stream = std::make_unique<MockStream>();
+  EXPECT_CALL(*stream, Finish).WillOnce(Return(make_ready_future(Status{})));
+  EXPECT_CALL(*stream, Cancel).Times(AtMost(1));
+  bool transport_ok = true;
+  auto transport_ok_callback = [&transport_ok] { return transport_ok; };
+
+  auto tested = MakeTested(NoResume(), factory.AsStdFunction(),
+                           google::storage::v2::BidiReadObjectSpec{},
+                           std::make_shared<OpenStream>(std::move(stream)),
+                           transport_ok_callback);
+
+  EXPECT_TRUE(tested->IsOpen());
+  transport_ok = false;
+  EXPECT_FALSE(tested->IsOpen());
+}
+
+TEST(ObjectDescriptorImpl, IsOpenFalseOnTransportFailure) {
+  auto stream = std::make_unique<MockStream>();
+  EXPECT_CALL(*stream, Cancel).Times(1);
+  EXPECT_CALL(*stream, Finish).WillOnce([] {
+    return make_ready_future(Status{});
+  });
+  MockFactory factory;
+  auto transport_ok = [] { return false; };
+  auto tested = std::make_shared<ObjectDescriptorImpl>(
+      NoResume(), factory.AsStdFunction(),
+      google::storage::v2::BidiReadObjectSpec{},
+      std::make_shared<OpenStream>(std::move(stream)), Options{},
+      std::move(transport_ok));
+  EXPECT_FALSE(tested->IsOpen());
+}
+
+TEST(ObjectDescriptorImpl, IsOpenTrueOnTransportSuccess) {
+  auto stream = std::make_unique<MockStream>();
+  EXPECT_CALL(*stream, Cancel).Times(1);
+  EXPECT_CALL(*stream, Finish).WillOnce([] {
+    return make_ready_future(Status{});
+  });
+  MockFactory factory;
+  auto transport_ok = [] { return true; };
+  auto tested = std::make_shared<ObjectDescriptorImpl>(
+      NoResume(), factory.AsStdFunction(),
+      google::storage::v2::BidiReadObjectSpec{},
+      std::make_shared<OpenStream>(std::move(stream)), Options{},
+      std::move(transport_ok));
+  EXPECT_TRUE(tested->IsOpen());
+}
+
 }  // namespace
 GOOGLE_CLOUD_CPP_INLINE_NAMESPACE_END
 }  // namespace storage_internal

google/cloud/storage/mocks/mock_async_object_descriptor_connection.h

@@ -33,6 +33,7 @@ class MockAsyncObjectDescriptorConnection
               (ReadParams), (override));
   MOCK_METHOD(void, MakeSubsequentStream, (), (override));
   MOCK_METHOD(Options, options, (), (const, override));
+  MOCK_METHOD(bool, IsOpen, (), (const, override));
 };
 
 GOOGLE_CLOUD_CPP_INLINE_NAMESPACE_END