Fix #3167: avoid infinite wait on failure to init curl handle (#3200)

src/aws-cpp-sdk-core/include/aws/core/utils/ResourceManager.h

@@ -74,6 +74,34 @@ namespace Aws
                 return resource;
             }
 
+            /**
+             * Returns a resource with exclusive ownership or a nullptr.
+             * If resource is available within the wait timeout then the resource is returned.
+             * otherwise (if the timeout has expired or container is shutdown) the nullptr is returned.
+             * You must call Release on the resource when you are finished.
+             * This method is enabled only for pointer RESOURCE_TYPE type.
+             *
+             * @return instance of RESOURCE_TYPE, nullptr if the resource manager is being shutdown
+             */
+            template <typename std::enable_if<std::is_pointer<RESOURCE_TYPE>::value>::type* = nullptr>
+            RESOURCE_TYPE TryAcquire(const uint64_t timeoutMs) {
+              std::unique_lock<std::mutex> locker(m_queueLock);
+              bool hasResource = m_shutdown.load() || !m_resources.empty();
+              if (!hasResource) {
+                hasResource = m_semaphore.wait_for(locker, std::chrono::milliseconds(timeoutMs),
+                                                   [&]() { return m_shutdown.load() || !m_resources.empty(); });
+              }
+
+              if (m_shutdown || !hasResource) {
+                return nullptr;
+              }
+
+              RESOURCE_TYPE resource = m_resources.back();
+              m_resources.pop_back();
+
+              return resource;
+            }
+
             /**
              * Returns whether or not resources are currently available for acquisition
              *
@@ -122,6 +150,7 @@ namespace Aws
             {
                 std::unique_lock<std::mutex> locker(m_queueLock);
                 m_shutdown = true;
+                m_semaphore.notify_all();
 
                 //wait for all acquired resources to be released.
                 while (m_resources.size() < resourceCount)

src/aws-cpp-sdk-core/source/http/curl/CurlHandleContainer.cpp

@@ -32,6 +32,7 @@ CurlHandleContainer::~CurlHandleContainer()
         AWS_LOGSTREAM_DEBUG(CURL_HANDLE_CONTAINER_TAG, "Cleaning up " << handle);
         curl_easy_cleanup(handle);
     }
+    m_poolSize = 0;
 }
 
 CURL* CurlHandleContainer::AcquireCurlHandle()
@@ -44,7 +45,20 @@ CURL* CurlHandleContainer::AcquireCurlHandle()
         CheckAndGrowPool();
     }
 
-    CURL* handle = m_handleContainer.TryAcquire();
+    // TODO: 1.12: start to fail instead of infinite loop, possibly introduce another timeout config field
+    CURL* handle = nullptr;
+    bool errorLogged = false;  // avoid log explosion on legacy app behavior
+    while (!handle) {
+      constexpr unsigned long ACQUIRE_TIMEOUT = 1000l;  // some big enough arbitrary value, possibly need a user config or just fail ASAP.
+      handle = m_handleContainer.TryAcquire(ACQUIRE_TIMEOUT);
+      if (!handle && !errorLogged) {
+        AWS_LOGSTREAM_ERROR(CURL_HANDLE_CONTAINER_TAG,
+                            "Unable to Acquire a curl handle within 1 second. "
+                            "Waiting further, this method will start failing in 1.12.x. "
+                            "Please increase the pool size.");
+        errorLogged = true;
+      }
+    }
     AWS_LOGSTREAM_DEBUG(CURL_HANDLE_CONTAINER_TAG, "Connection has been released. Continuing.");
     AWS_LOGSTREAM_DEBUG(CURL_HANDLE_CONTAINER_TAG, "Returning connection handle " << handle);
     return handle;
@@ -80,10 +94,16 @@ void CurlHandleContainer::DestroyCurlHandle(CURL* handle)
         // If the handle is not released back to the pool, it could create a deadlock
         // Create a new handle and release that into the pool
         handle = CreateCurlHandleInPool();
+        if (!handle && m_poolSize) {
+          m_poolSize -= 1;
+        }
     }
     if (handle)
     {
         AWS_LOGSTREAM_DEBUG(CURL_HANDLE_CONTAINER_TAG, "Created replacement handle and released to pool: " << handle);
+    } else {
+      AWS_LOGSTREAM_ERROR(CURL_HANDLE_CONTAINER_TAG,
+                          "Failed to create a replacement handle. The handle pool size reduced to " << m_poolSize);
     }
 }
 

tests/aws-cpp-sdk-core-tests/utils/ResourceManagerTest.cpp

@@ -0,0 +1,107 @@
+/**
+ * Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
+ * SPDX-License-Identifier: Apache-2.0.
+ */
+
+#include <aws/core/utils/ResourceManager.h>
+#include <aws/testing/AwsCppSdkGTestSuite.h>
+
+#include <future>
+#include <random>
+
+using namespace Aws::Utils;
+
+class ExclusiveOwnershipResourceManagerTest : public Aws::Testing::AwsCppSdkGTestSuite {};
+
+TEST_F(ExclusiveOwnershipResourceManagerTest, TestAcquire) {
+  class TestResource {
+   public:
+    TestResource(int startVal) : m_value(startVal) {}
+
+    int GetValue() { return m_value; }
+
+    void DoSomething() {
+      std::unique_lock<std::mutex> lock(m_lock, std::defer_lock);
+
+      if (!lock.try_lock()) {
+        m_fail = true;  // concurrent access detected
+      }
+      m_value += 1;
+    }
+
+    bool Fail() { return m_fail; }
+
+   protected:
+    int m_value = 0;
+    std::mutex m_lock;
+    bool m_fail = false;
+  };
+
+  ExclusiveOwnershipResourceManager<TestResource*> resourceManagerInTest;
+
+  ASSERT_FALSE(resourceManagerInTest.HasResourcesAvailable());
+  ASSERT_EQ(nullptr, resourceManagerInTest.TryAcquire(1l));
+
+  static const size_t RESOURCES = 6;
+  TestResource* resources[RESOURCES] = {};
+  for (int i = 0; i < (int)RESOURCES; ++i) {
+    resources[i] = new TestResource(i);
+    resourceManagerInTest.Release(resources[i]);
+  }
+
+  static const size_t THREADS = 8;
+  Aws::Vector<std::future<bool>> futures(THREADS);
+
+  auto useResourceFn = [](ExclusiveOwnershipResourceManager<TestResource*>& resourceManager) -> bool {
+    std::random_device rd;
+    std::mt19937_64 randGen(rd());
+    std::uniform_int_distribution<int64_t> randDist(0, 100);
+
+    for (size_t j = 0; j < 50; ++j) {
+      TestResource* resource = nullptr;
+      while (!resource) {
+        resource = resourceManager.TryAcquire(randDist(randGen));
+      }
+      // "do something" for rand ms
+      int64_t sleepFor = randDist(randGen);
+      std::this_thread::sleep_for(std::chrono::milliseconds(sleepFor));
+      const int before = resource->GetValue();
+      resource->DoSomething();
+      EXPECT_NE(before, resource->GetValue());
+      resourceManager.Release(resource);
+    }
+    return true;
+  };
+
+  for (size_t i = 0; i < THREADS; ++i) {
+    futures[i] = std::async([&resourceManagerInTest, &useResourceFn]() -> bool { return useResourceFn(resourceManagerInTest); });
+  }
+
+  for (size_t i = 0; i < THREADS; ++i) {
+    bool batchResult = futures[i].get();
+    ASSERT_TRUE(batchResult);
+  }
+
+  // single thread test
+  Aws::Vector<TestResource*> inUse;
+  for (int i = 0; i < (int)RESOURCES; ++i) {
+    TestResource* resource = resourceManagerInTest.TryAcquire(0l);
+    ASSERT_TRUE(resource);
+    const int before = resource->GetValue();
+    resource->DoSomething();
+    EXPECT_NE(before, resource->GetValue());
+    inUse.push_back(resource);
+  }
+  for (auto resource : inUse) {
+    resourceManagerInTest.Release(resource);
+  }
+
+  Aws::Vector<TestResource*> released = resourceManagerInTest.ShutdownAndWait(RESOURCES);
+  ASSERT_EQ(RESOURCES, released.size());
+
+  for (int i = 0; i < (int)RESOURCES; ++i) {
+    ASSERT_FALSE(resources[i]->Fail());
+    ASSERT_NE(i, resources[i]->GetValue());
+    delete resources[i];
+  }
+}