Callback invoker to sink all thrown exceptions (#74)

include/cppkafka/detail/callback_invoker.h

@@ -0,0 +1,127 @@
+/*
+ * Copyright (c) 2017, Matias Fontanini
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ *
+ * * Redistributions of source code must retain the above copyright
+ *   notice, this list of conditions and the following disclaimer.
+ * * Redistributions in binary form must reproduce the above
+ *   copyright notice, this list of conditions and the following disclaimer
+ *   in the documentation and/or other materials provided with the
+ *   distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ */
+
+#ifndef CPPKAFKA_CALLBACK_INVOKER_H
+#define CPPKAFKA_CALLBACK_INVOKER_H
+
+#include <sstream>
+#include <assert.h>
+#include "../logging.h"
+#include "../kafka_handle_base.h"
+
+namespace cppkafka {
+
+// Error values
+template <typename T>
+T error_value() { return T{}; }
+
+template<> inline
+void error_value<void>() {};
+
+template<> inline
+bool error_value<bool>() { return false; }
+
+template<> inline
+int error_value<int>() { return -1; }
+
+/**
+ * \brief Wraps an std::function object and runs it while preventing all exceptions from escaping
+ * \tparam Func An std::function object
+ */
+template <typename Func>
+class CallbackInvoker
+{
+public:
+    using RetType = typename Func::result_type;
+    using LogCallback = std::function<void(KafkaHandleBase& handle,
+                                           int level,
+                                           const std::string& facility,
+                                           const std::string& message)>;
+    CallbackInvoker(const char* callback_name,
+                    const Func& callback,
+                    KafkaHandleBase* handle)
+    : callback_name_(callback_name),
+      callback_(callback),
+      handle_(handle) {
+    }
+    
+    explicit operator bool() const {
+        return (bool)callback_;
+    }
+    
+    template <typename ...Args>
+    RetType operator()(Args&&... args) const {
+        static const char* library_name = "cppkafka";
+        std::ostringstream error_msg;
+        try {
+            if (callback_) {
+                return callback_(std::forward<Args>(args)...);
+            }
+            return error_value<RetType>();
+        }
+        catch (const std::exception& ex) {
+            if (handle_) {
+                error_msg << "Caught exception in " << callback_name_ << " callback: " << ex.what();
+            }
+        }
+        catch (...) {
+            if (handle_) {
+                error_msg << "Caught unknown exception in " << callback_name_ << " callback";
+            }
+        }
+        // Log error
+        if (handle_) {
+            if (handle_->get_configuration().get_log_callback()) {
+                try {
+                    // Log it
+                    handle_->get_configuration().get_log_callback()(*handle_,
+                                                                    static_cast<int>(LogLevel::LOG_ERR),
+                                                                    library_name,
+                                                                    error_msg.str());
+                }
+                catch (...) {} // sink everything
+            }
+            else {
+                rd_kafka_log_print(handle_->get_handle(),
+                                   static_cast<int>(LogLevel::LOG_ERR),
+                                   library_name,
+                                   error_msg.str().c_str());
+            }
+        }
+        return error_value<RetType>();
+    }
+private:
+    const char* callback_name_;
+    const Func& callback_;
+    KafkaHandleBase* handle_;
+};
+
+}
+
+#endif