Reserve the last read handler for ReadInteraction

Author: yunhanw-google

src/app/InteractionModelEngine.cpp

@@ -131,7 +131,6 @@ CHIP_ERROR InteractionModelEngine::NewReadClient(ReadClient ** const apReadClien
                                                  ReadClient::Callback * aCallback)
 {
     *apReadClient = nullptr;
-
     for (auto & readClient : mReadClients)
     {
         if (readClient.IsFree())
@@ -314,6 +313,15 @@ CHIP_ERROR InteractionModelEngine::OnReadInitialRequest(Messaging::ExchangeConte
         }
     }
 
+    // Reserve the last ReadHandler for ReadInteraction
+    if (aInteractionType == ReadHandler::InteractionType::Subscribe &&
+        ((CHIP_IM_MAX_NUM_READ_HANDLER - GetNumActiveReadHandlers()) == 1) && !HasActiveRead())
+    {
+        ChipLogProgress(InteractionModel, "Reserve the last ReadHandler for IM read Interaction");
+        aStatus = Protocols::InteractionModel::Status::ResourceExhausted;
+        return CHIP_NO_ERROR;
+    }
+
     for (auto & readHandler : mReadHandlers)
     {
         if (readHandler.IsFree())
@@ -728,5 +736,18 @@ void InteractionModelEngine::OnTimedWrite(TimedHandler * apTimedHandler, Messagi
     }
 }
 
+bool InteractionModelEngine::HasActiveRead()
+{
+    for (auto & readHandler : mReadHandlers)
+    {
+        if (!readHandler.IsFree() && readHandler.IsReadType())
+        {
+            return true;
+        }
+    }
+
+    return false;
+}
+
 } // namespace app
 } // namespace chip

src/app/InteractionModelEngine.h

@@ -275,6 +275,8 @@ class InteractionModelEngine : public Messaging::ExchangeDelegate, public Comman
                          TLV::TLVReader & apPayload) override;
     bool CommandExists(const ConcreteCommandPath & aCommandPath) override;
 
+    bool HasActiveRead();
+
     Messaging::ExchangeManager * mpExchangeMgr = nullptr;
     InteractionModelDelegate * mpDelegate      = nullptr;
 

src/app/tests/TestReadInteraction.cpp

@@ -1193,36 +1193,13 @@ void TestReadInteraction::TestSubscribeRoundtrip(nlTestSuite * apSuite, void * a
     readPrepareParams3.mMinIntervalFloorSeconds                  = 2;
     readPrepareParams3.mMaxIntervalCeilingSeconds                = 5;
 
-    printf("\nSend 4th subscribe request message to Node: %" PRIu64 "\n", chip::kTestDeviceNodeId);
+    printf("\nSend 4th subscribe request message to Node: %" PRIu64 ",  resource exhausted\n", chip::kTestDeviceNodeId);
 
     ReadClient readClient3;
     readClient3.Init(&ctx.GetExchangeManager(), &delegate, ReadClient::InteractionType::Subscribe);
     err = readClient3.SendSubscribeRequest(readPrepareParams3);
     NL_TEST_ASSERT(apSuite, err == CHIP_NO_ERROR);
     engine->GetReportingEngine().Run();
-    NL_TEST_ASSERT(apSuite, delegate.mGotReport);
-    NL_TEST_ASSERT(apSuite, delegate.mNumAttributeResponse == 1);
-    NL_TEST_ASSERT(apSuite, !delegate.mReadError);
-
-    delegate.mNumAttributeResponse = 0;
-    delegate.mGotReport            = false;
-    ReadPrepareParams readPrepareParams4(ctx.GetSessionBobToAlice());
-    chip::app::AttributePathParams attributePathParams4[1];
-    readPrepareParams4.mpAttributePathParamsList                 = attributePathParams4;
-    readPrepareParams4.mpAttributePathParamsList[0].mEndpointId  = kTestEndpointId;
-    readPrepareParams4.mpAttributePathParamsList[0].mClusterId   = kTestClusterId;
-    readPrepareParams4.mpAttributePathParamsList[0].mAttributeId = 1;
-    readPrepareParams4.mAttributePathParamsListSize              = 1;
-    readPrepareParams4.mMinIntervalFloorSeconds                  = 2;
-    readPrepareParams4.mMaxIntervalCeilingSeconds                = 5;
-
-    printf("\nSend 5th subscribe request message to Node: %" PRIu64 ",  resource exhausted\n", chip::kTestDeviceNodeId);
-
-    ReadClient readClient4;
-    readClient4.Init(&ctx.GetExchangeManager(), &delegate, ReadClient::InteractionType::Subscribe);
-    err = readClient4.SendSubscribeRequest(readPrepareParams4);
-    NL_TEST_ASSERT(apSuite, err == CHIP_NO_ERROR);
-    engine->GetReportingEngine().Run();
     NL_TEST_ASSERT(apSuite, !delegate.mGotReport);
     NL_TEST_ASSERT(apSuite, delegate.mNumAttributeResponse == 0);
     NL_TEST_ASSERT(apSuite, delegate.mReadError);