Log error in case consumer destructor throws (#61)

include/cppkafka/cppkafka.h

@@ -40,6 +40,7 @@
 #include <cppkafka/exceptions.h>
 #include <cppkafka/group_information.h>
 #include <cppkafka/kafka_handle_base.h>
+#include <cppkafka/logging.h>
 #include <cppkafka/macros.h>
 #include <cppkafka/message.h>
 #include <cppkafka/message_builder.h>

include/cppkafka/logging.h

@@ -0,0 +1,49 @@
+/*
+ * 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_LOGGING_H
+#define CPPKAFKA_LOGGING_H
+
+namespace cppkafka {
+
+// Based on syslog.h levels
+enum class LogLevel : int {
+    LOG_EMERG   = 0,    /* system is unusable */
+    LOG_ALERT   = 1,    /* action must be taken immediately */
+    LOG_CRIT    = 2,    /* critical conditions */
+    LOG_ERR     = 3,    /* error conditions */
+    LOG_WARNING = 4,    /* warning conditions */
+    LOG_NOTICE  = 5,    /* normal but significant condition */
+    LOG_INFO    = 6,    /* informational */
+    LOG_DEBUG   = 7     /* debug-level messages */
+};
+
+} //cppkafka
+
+#endif //CPPKAFKA_LOGGING_H

src/consumer.cpp

@@ -26,9 +26,10 @@
  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  *
  */
-
+#include <sstream>
 #include "consumer.h"
 #include "exceptions.h"
+#include "logging.h"
 #include "configuration.h"
 #include "topic_partition_list.h"
 
@@ -36,7 +37,7 @@ using std::vector;
 using std::string;
 using std::move;
 using std::make_tuple;
-
+using std::ostringstream;
 using std::chrono::milliseconds;
 
 namespace cppkafka {
@@ -73,9 +74,17 @@ Consumer::~Consumer() {
         rebalance_error_callback_ = nullptr;
         close();
     }
-    catch (const Exception&) {
-        // If close throws just silently ignore until there's some
-        // logging facility (if any)
+    catch (const Exception& ex) {
+        constexpr const char* library_name = "cppkafka";
+        ostringstream error_msg;
+        error_msg << "Failed to close consumer [" << get_name() << "]: " << ex.what();
+        const auto& callback = get_configuration().get_log_callback();
+        if (callback) {
+            callback(*this, static_cast<int>(LogLevel::LOG_ERR), library_name, error_msg.str());
+        }
+        else {
+            rd_kafka_log_print(get_handle(), static_cast<int>(LogLevel::LOG_ERR), library_name, error_msg.str().c_str());
+        }
     }
 }