fix a bug where reader could hang when there is no attributes

source/adios2/toolkit/format/dataman/DataManSerializer.cpp

@@ -345,6 +345,7 @@ void DataManSerializer::PutAttributes(core::IO &io)
 {
     TAU_SCOPED_TIMER_FUNC();
     const auto &attributesDataMap = io.GetAttributesDataMap();
+    bool attributePut = false;
     for (const auto &attributePair : attributesDataMap)
     {
         const std::string name(attributePair.first);
@@ -360,6 +361,23 @@ void DataManSerializer::PutAttributes(core::IO &io)
     }
         ADIOS2_FOREACH_ATTRIBUTE_STDTYPE_1ARG(declare_type)
 #undef declare_type
+        attributePut = true;
+    }
+
+    if (not m_StaticDataFinished)
+    {
+        if (not attributePut)
+        {
+            nlohmann::json staticVar;
+            staticVar["N"] = "NoAttributes";
+            staticVar["Y"] = "bool";
+            staticVar["V"] = true;
+            staticVar["G"] = true;
+            m_StaticDataJsonMutex.lock();
+            m_StaticDataJson["S"].emplace_back(std::move(staticVar));
+            m_StaticDataJsonMutex.unlock();
+        }
+        m_StaticDataFinished = true;
     }
 }
 

source/adios2/toolkit/format/dataman/DataManSerializer.h

@@ -222,6 +222,7 @@ class DataManSerializer
     // for global variables and attributes, needs mutex
     nlohmann::json m_StaticDataJson;
     std::mutex m_StaticDataJsonMutex;
+    bool m_StaticDataFinished = false;
 
     // for generating deferred requests, only accessed from reader app thread,
     // does not need mutex

testing/adios2/engine/wdm/CMakeLists.txt

@@ -10,5 +10,10 @@ if(ADIOS2_HAVE_MPI AND ADIOS2_HAVE_ZeroMQ)
     add_test(NAME WdmTest COMMAND "mpirun" "-n" "8" $<TARGET_FILE:WdmTest>)
 endif()
 
+if(ADIOS2_HAVE_MPI AND ADIOS2_HAVE_ZeroMQ)
+    add_executable(WdmTestNoAttributes WdmTestNoAttributes.cpp)
+    target_link_libraries(WdmTestNoAttributes adios2 gtest MPI::MPI_C)
+    add_test(NAME WdmTestNoAttributes COMMAND "mpirun" "-n" "8" $<TARGET_FILE:WdmTestNoAttributes>)
+endif()
 
 

testing/adios2/engine/wdm/WdmTest.cpp

@@ -114,7 +114,8 @@ void VerifyData(const T *data, size_t step, const Dims &start,
 }
 
 void Writer(const Dims &shape, const Dims &start, const Dims &count,
-            const size_t steps, const adios2::Params &engineParams)
+            const size_t steps, const adios2::Params &engineParams,
+            const std::string &name)
 {
     size_t datasize = std::accumulate(count.begin(), count.end(), 1,
                                       std::multiplies<size_t>());
@@ -152,8 +153,7 @@ void Writer(const Dims &shape, const Dims &start, const Dims &count,
     auto bpDComplexes = dataManIO.DefineVariable<std::complex<double>>(
         "bpDComplexes", shape, start, count);
     dataManIO.DefineAttribute<int>("AttInt", 110);
-    adios2::Engine dataManWriter =
-        dataManIO.Open("stream", adios2::Mode::Write);
+    adios2::Engine dataManWriter = dataManIO.Open(name, adios2::Mode::Write);
     for (int i = 0; i < steps; ++i)
     {
         dataManWriter.BeginStep();
@@ -184,13 +184,14 @@ void Writer(const Dims &shape, const Dims &start, const Dims &count,
 }
 
 void Reader(const Dims &shape, const Dims &start, const Dims &count,
-            const size_t steps, const adios2::Params &engineParams)
+            const size_t steps, const adios2::Params &engineParams,
+            const std::string &name)
 {
     adios2::ADIOS adios(mpiComm, adios2::DebugON);
     adios2::IO dataManIO = adios.DeclareIO("Test");
     dataManIO.SetEngine("wdm");
     dataManIO.SetParameters(engineParams);
-    adios2::Engine dataManReader = dataManIO.Open("stream", adios2::Mode::Read);
+    adios2::Engine dataManReader = dataManIO.Open(name, adios2::Mode::Read);
 
     size_t datasize = std::accumulate(count.begin(), count.end(), 1,
                                       std::multiplies<size_t>());
@@ -332,16 +333,19 @@ TEST_F(WdmEngineTest, BaseTest)
     Dims start = {2, (size_t)mpiRank * 2};
     Dims count = {5, 2};
 
+    adios2::Params engineParams = {{"Port", "12306"}, {"Verbose", "0"}};
+    std::string filename = "BaseTest";
+
     if (mpiGroup == 0)
     {
-        Writer(shape, start, count, 1000, adios2::Params());
+        Writer(shape, start, count, 1000, engineParams, filename);
     }
 
-    std::this_thread::sleep_for(std::chrono::milliseconds(1));
+    std::this_thread::sleep_for(std::chrono::milliseconds(100));
 
     if (mpiGroup == 1)
     {
-        Reader(shape, start, count, 10, adios2::Params());
+        Reader(shape, start, count, 10, engineParams, filename);
     }
 
     MPI_Barrier(MPI_COMM_WORLD);