Add GetGuaranteedReadRequestsPerFabric

src/app/InteractionModelEngine.cpp

@@ -785,7 +785,7 @@ bool InteractionModelEngine::EnsureResourceForSubscription(FabricIndex aFabricIn
 
 bool InteractionModelEngine::TrimFabricForRead(FabricIndex aFabricIndex)
 {
-    constexpr size_t minSupportedPathsPerFabricForRead = kMinSupportedReadRequestsPerFabric * kMinSupportedPathsPerReadRequest;
+    const size_t minSupportedPathsPerFabricForRead = GetGuaranteedReadRequestsPerFabric() * kMinSupportedPathsPerReadRequest;
 
     size_t attributePathsUsedByCurrentFabric = 0;
     size_t eventPathsUsedByCurrentFabric     = 0;
@@ -841,7 +841,7 @@ bool InteractionModelEngine::TrimFabricForRead(FabricIndex aFabricIndex)
     if (candidate != nullptr &&
         ((attributePathsUsedByCurrentFabric > minSupportedPathsPerFabricForRead ||
           eventPathsUsedByCurrentFabric > minSupportedPathsPerFabricForRead ||
-          readTransactionsOnCurrentFabric > kMinSupportedReadRequestsPerFabric) ||
+          readTransactionsOnCurrentFabric > GetGuaranteedReadRequestsPerFabric()) ||
          // Always evict the transactions on PASE sessions if the fabric table is full.
          (aFabricIndex == kUndefinedFabricIndex && mpFabricTable->FabricCount() == GetConfigMaxFabrics())))
     {
@@ -931,13 +931,10 @@ Protocols::InteractionModel::Status InteractionModelEngine::EnsureResourceForRea
 
     // Resources exhausted, since there is already some read requests ongoing on this fabric, please retry later.
     if (usedAttributePathsInFabric + aRequestedAttributePathCount >
-            kMinSupportedPathsPerReadRequest * kMinSupportedReadRequestsPerFabric ||
-        usedEventPathsInFabric + aRequestedEventPathCount > kMinSupportedPathsPerReadRequest * kMinSupportedReadRequestsPerFabric)
-    {
-        return Protocols::InteractionModel::Status::Busy;
-    }
-
-    if (usedReadHandlersInFabric >= kMinSupportedReadRequestsPerFabric)
+            kMinSupportedPathsPerReadRequest * GetGuaranteedReadRequestsPerFabric() ||
+        usedEventPathsInFabric + aRequestedEventPathCount >
+            kMinSupportedPathsPerReadRequest * GetGuaranteedReadRequestsPerFabric() ||
+        usedReadHandlersInFabric >= GetGuaranteedReadRequestsPerFabric())
     {
         return Protocols::InteractionModel::Status::Busy;
     }

src/app/InteractionModelEngine.h

@@ -277,7 +277,8 @@ class InteractionModelEngine : public Messaging::UnsolicitedMessageHandler,
 
     //
     // Override the maximal capacity of the underlying read handler pool to mimic
-    // out of memory scenarios in unit-tests.
+    // out of memory scenarios in unit-tests. You need to SetConfigMaxFabrics to make GetGuaranteedReadRequestsPerFabric
+    // working correctly.
     //
     // If -1 is passed in, no override is instituted and default behavior resumes.
     //
@@ -441,6 +442,11 @@ class InteractionModelEngine : public Messaging::UnsolicitedMessageHandler,
 #endif
     }
 
+    inline size_t GetGuaranteedReadRequestsPerFabric() const
+    {
+        return GetReadHandlerPoolCapacityForReads() / GetConfigMaxFabrics();
+    }
+
     /**
      * Verify and ensure (by killing oldest read handlers that make the resources used by the current fabric exceed the fabric
      * quota)

src/controller/tests/data_model/TestRead.cpp

@@ -2436,6 +2436,7 @@ void TestReadInteraction::TestReadHandler_ParallelReads(nlTestSuite * apSuite, v
 
     app::InteractionModelEngine::GetInstance()->SetForceHandlerQuota(true);
     app::InteractionModelEngine::GetInstance()->SetHandlerCapacityForReads(2);
+    app::InteractionModelEngine::GetInstance()->SetConfigMaxFabrics(2);
     app::InteractionModelEngine::GetInstance()->SetPathPoolCapacityForReads(
         2 * app::InteractionModelEngine::kMinSupportedPathsPerReadRequest);
 
@@ -2597,7 +2598,7 @@ void TestReadInteraction::TestReadHandler_ParallelReads(nlTestSuite * apSuite, v
     // Case 5: The device's fabric table is not full, PASE sessions are counted as a valid fabric and can evict existing read
     // transactions.
     {
-        app::InteractionModelEngine::GetInstance()->SetConfigMaxFabrics(-1);
+        app::InteractionModelEngine::GetInstance()->SetConfigMaxFabrics(3);
 
         TestReadCallback readCallback;
         TestPerpetualListReadCallback backgroundReadCallback1;