src/session.cpp - cassandra-cpp-driver - Git at Google

 /*
   Licensed to the Apache Software Foundation (ASF) under one
   or more contributor license agreements.  See the NOTICE file
   distributed with this work for additional information
   regarding copyright ownership.  The ASF licenses this file
   to you under the Apache License, Version 2.0 (the
   "License"); you may not use this file except in compliance
   with the License.  You may obtain a copy of the License at

       http://www.apache.org/licenses/LICENSE-2.0

   Unless required by applicable law or agreed to in writing, software
   distributed under the License is distributed on an "AS IS" BASIS,
   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   See the License for the specific language governing permissions and
   limitations under the License.
 */

 #include "session.hpp"

 #include "batch_request.hpp"
 #include "cluster_config.hpp"
 #include "constants.hpp"
 #include "execute_request.hpp"
 #include "external.hpp"
 #include "logger.hpp"
 #include "metrics.hpp"
 #include "monitor_reporting.hpp"
 #include "prepare_all_handler.hpp"
 #include "prepare_request.hpp"
 #include "request_processor_initializer.hpp"
 #include "scoped_lock.hpp"
 #include "statement.hpp"

 using namespace datastax;
 using namespace datastax::internal::core;

 extern "C" {

 CassSession* cass_session_new() {
   Session* session = new Session();
   return CassSession::to(session);
 }

 void cass_session_free(CassSession* session) {
   // This attempts to close the session because the joining will
   // hang indefinitely otherwise. This causes minimal delay
   // if the session is already closed.
   session->close()->wait();

   delete session->from();
 }

 CassFuture* cass_session_connect(CassSession* session, const CassCluster* cluster) {
   return cass_session_connect_keyspace(session, cluster, "");
 }

 CassFuture* cass_session_connect_keyspace(CassSession* session, const CassCluster* cluster,
                                           const char* keyspace) {
   return cass_session_connect_keyspace_n(session, cluster, keyspace, SAFE_STRLEN(keyspace));
 }

 CassFuture* cass_session_connect_keyspace_n(CassSession* session, const CassCluster* cluster,
                                             const char* keyspace, size_t keyspace_length) {
   Future::Ptr future(session->connect(cluster->config(), String(keyspace, keyspace_length)));
   future->inc_ref();
   return CassFuture::to(future.get());
 }

 CassFuture* cass_session_close(CassSession* session) {
   Future::Ptr future(session->close());
   future->inc_ref();
   return CassFuture::to(future.get());
 }

 CassFuture* cass_session_prepare(CassSession* session, const char* query) {
   return cass_session_prepare_n(session, query, SAFE_STRLEN(query));
 }

 CassFuture* cass_session_prepare_n(CassSession* session, const char* query, size_t query_length) {
   Future::Ptr future(session->prepare(query, query_length));
   future->inc_ref();
   return CassFuture::to(future.get());
 }

 CassFuture* cass_session_prepare_from_existing(CassSession* session, CassStatement* statement) {
   Future::Ptr future(session->prepare(statement));
   future->inc_ref();
   return CassFuture::to(future.get());
 }

 CassFuture* cass_session_execute(CassSession* session, const CassStatement* statement) {
   Future::Ptr future(session->execute(Request::ConstPtr(statement->from())));
   future->inc_ref();
   return CassFuture::to(future.get());
 }

 CassFuture* cass_session_execute_batch(CassSession* session, const CassBatch* batch) {
   Future::Ptr future(session->execute(Request::ConstPtr(batch->from())));
   future->inc_ref();
   return CassFuture::to(future.get());
 }

 const CassSchemaMeta* cass_session_get_schema_meta(const CassSession* session) {
   return CassSchemaMeta::to(new Metadata::SchemaSnapshot(session->cluster()->schema_snapshot()));
 }

 void cass_session_get_metrics(const CassSession* session, CassMetrics* metrics) {
   const Metrics* internal_metrics = session->metrics();

   if (internal_metrics == NULL) {
     LOG_WARN("Attempted to get metrics before connecting session object");
     memset(metrics, 0, sizeof(CassMetrics));
     return;
   }

   Metrics::Histogram::Snapshot requests_snapshot;
   internal_metrics->request_latencies.get_snapshot(&requests_snapshot);

   metrics->requests.min = requests_snapshot.min;
   metrics->requests.max = requests_snapshot.max;
   metrics->requests.mean = requests_snapshot.mean;
   metrics->requests.stddev = requests_snapshot.stddev;
   metrics->requests.median = requests_snapshot.median;
   metrics->requests.percentile_75th = requests_snapshot.percentile_75th;
   metrics->requests.percentile_95th = requests_snapshot.percentile_95th;
   metrics->requests.percentile_98th = requests_snapshot.percentile_98th;
   metrics->requests.percentile_99th = requests_snapshot.percentile_99th;
   metrics->requests.percentile_999th = requests_snapshot.percentile_999th;
   metrics->requests.one_minute_rate = internal_metrics->request_rates.one_minute_rate();
   metrics->requests.five_minute_rate = internal_metrics->request_rates.five_minute_rate();
   metrics->requests.fifteen_minute_rate = internal_metrics->request_rates.fifteen_minute_rate();
   metrics->requests.mean_rate = internal_metrics->request_rates.mean_rate();

   metrics->stats.total_connections = internal_metrics->total_connections.sum();
   metrics->stats.available_connections = metrics->stats.total_connections; // Deprecated
   metrics->stats.exceeded_write_bytes_water_mark = 0;                      // Deprecated
   metrics->stats.exceeded_pending_requests_water_mark = 0;                 // Deprecated

   metrics->errors.connection_timeouts = internal_metrics->connection_timeouts.sum();
   metrics->errors.pending_request_timeouts = 0; // Deprecated
   metrics->errors.request_timeouts = internal_metrics->request_timeouts.sum();
 }

 void cass_session_get_speculative_execution_metrics(const CassSession* session,
                                                     CassSpeculativeExecutionMetrics* metrics) {
   const Metrics* internal_metrics = session->metrics();

   if (internal_metrics == NULL) {
     LOG_WARN("Attempted to get speculative execution metrics before connecting session object");
     memset(metrics, 0, sizeof(CassSpeculativeExecutionMetrics));
     return;
   }

   Metrics::Histogram::Snapshot speculative_snapshot;
   internal_metrics->speculative_request_latencies.get_snapshot(&speculative_snapshot);

   metrics->min = speculative_snapshot.min;
   metrics->max = speculative_snapshot.max;
   metrics->mean = speculative_snapshot.mean;
   metrics->stddev = speculative_snapshot.stddev;
   metrics->median = speculative_snapshot.median;
   metrics->percentile_75th = speculative_snapshot.percentile_75th;
   metrics->percentile_95th = speculative_snapshot.percentile_95th;
   metrics->percentile_98th = speculative_snapshot.percentile_98th;
   metrics->percentile_99th = speculative_snapshot.percentile_99th;
   metrics->percentile_999th = speculative_snapshot.percentile_999th;
   metrics->count = internal_metrics->request_rates.speculative_request_count();
   metrics->percentage = internal_metrics->request_rates.speculative_request_percent();
 }

 CassUuid cass_session_get_client_id(CassSession* session) { return session->client_id(); }

 } // extern "C"

 static inline bool least_busy_comp(const RequestProcessor::Ptr& a, const RequestProcessor::Ptr& b) {
   return a->request_count() < b->request_count();
 }

 namespace datastax { namespace internal { namespace core {

 /**
  * An initialize helper class for `Session`. This keeps the initialization
  * logic and data out of the core class itself.
  */
 class SessionInitializer : public RefCounted<SessionInitializer> {
 public:
   typedef SharedRefPtr<SessionInitializer> Ptr;

   SessionInitializer(Session* session)
       : session_(session)
       , remaining_(0)
       , error_code_(CASS_OK) {
     uv_mutex_init(&mutex_);
   }

   SessionInitializer() { uv_mutex_destroy(&mutex_); }

   void initialize(const Host::Ptr& connected_host, ProtocolVersion protocol_version,
                   const HostMap& hosts, const TokenMap::Ptr& token_map, const String& local_dc) {
     inc_ref();

     const size_t thread_count_io = remaining_ = session_->config().thread_count_io();
     for (size_t i = 0; i < thread_count_io; ++i) {
       RequestProcessorInitializer::Ptr initializer(new RequestProcessorInitializer(
           connected_host, protocol_version, hosts, token_map, local_dc,
           bind_callback(&SessionInitializer::on_initialize, this)));

       RequestProcessorSettings settings(session_->config());
       settings.connection_pool_settings.connection_settings.client_id =
           to_string(session_->client_id());

       initializer->with_settings(RequestProcessorSettings(settings))
           ->with_listener(session_)
           ->with_keyspace(session_->connect_keyspace())
           ->with_metrics(session_->metrics())
           ->with_random(session_->random())
           ->initialize(session_->event_loop_group_->get(i));
     }
   }

 private:
   void on_initialize(RequestProcessorInitializer* initializer) {
     // A lock is required because request processors are initialized on
     // different threads .
     ScopedMutex l(&mutex_);

     if (initializer->is_ok()) {
       request_processors_.push_back(initializer->release_processor());
     } else {
       switch (initializer->error_code()) {
         case RequestProcessorInitializer::REQUEST_PROCESSOR_ERROR_KEYSPACE:
           error_code_ = CASS_ERROR_LIB_UNABLE_TO_SET_KEYSPACE;
           break;
         case RequestProcessorInitializer::REQUEST_PROCESSOR_ERROR_NO_HOSTS_AVAILABLE:
           error_code_ = CASS_ERROR_LIB_NO_HOSTS_AVAILABLE;
           break;
         case RequestProcessorInitializer::REQUEST_PROCESSOR_ERROR_UNABLE_TO_INIT:
           error_code_ = CASS_ERROR_LIB_UNABLE_TO_INIT;
           break;
         default:
           error_code_ = CASS_ERROR_LIB_INTERNAL_ERROR;
           break;
       }
       error_message_ = initializer->error_message();
     }

     if (remaining_ > 0 && --remaining_ == 0) {
       { // This requires locking because cluster events can happen during
         // initialization.
         ScopedMutex l(&session_->mutex_);
         session_->request_processor_count_ = request_processors_.size();
         session_->request_processors_ = request_processors_;
       }
       if (error_code_ != CASS_OK) {
         session_->notify_connect_failed(error_code_, error_message_);
       } else {
         session_->notify_connected();
         session_->cluster()->start_monitor_reporting(to_string(session_->client_id()),
                                                      to_string(session_->session_id()),
                                                      session_->config());
       }
       l.unlock(); // Unlock before destroying the object
       dec_ref();
     }
   }

 private:
   uv_mutex_t mutex_;
   Session* session_;
   size_t remaining_;
   CassError error_code_;
   String error_message_;
   RequestProcessor::Vec request_processors_;
 };

 }}} // namespace datastax::internal::core

 Session::Session()
     : request_processor_count_(0)
     , is_closing_(false) {
   uv_mutex_init(&mutex_);
 }

 Session::~Session() {
   join();
   uv_mutex_destroy(&mutex_);
 }

 Future::Ptr Session::prepare(const char* statement, size_t length) {
   PrepareRequest::Ptr prepare(new PrepareRequest(String(statement, length)));

   ResponseFuture::Ptr future(new ResponseFuture(cluster()->schema_snapshot()));
   future->prepare_request = PrepareRequest::ConstPtr(prepare);

   execute(RequestHandler::Ptr(new RequestHandler(prepare, future, metrics())));

   return future;
 }

 Future::Ptr Session::prepare(const Statement* statement) {
   String query;

   if (statement->opcode() == CQL_OPCODE_QUERY) { // Simple statement
     query = statement->query();
   } else { // Bound statement
     query = static_cast<const ExecuteRequest*>(statement)->prepared()->query();
   }

   PrepareRequest::Ptr prepare(new PrepareRequest(query));

   // Inherit the settings of the existing statement. These will in turn be
   // inherited by bound statements.
   prepare->set_settings(statement->settings());

   ResponseFuture::Ptr future(new ResponseFuture(cluster()->schema_snapshot()));
   future->prepare_request = PrepareRequest::ConstPtr(prepare);

   execute(RequestHandler::Ptr(new RequestHandler(prepare, future, metrics())));

   return future;
 }

 Future::Ptr Session::execute(const Request::ConstPtr& request) {
   ResponseFuture::Ptr future(new ResponseFuture());

   RequestHandler::Ptr request_handler(new RequestHandler(request, future, metrics()));

   if (request_handler->request()->opcode() == CQL_OPCODE_EXECUTE) {
     const ExecuteRequest* execute = static_cast<const ExecuteRequest*>(request_handler->request());
     request_handler->set_prepared_metadata(cluster()->prepared(execute->prepared()->id()));
   }

   execute(request_handler);

   return future;
 }

 void Session::execute(const RequestHandler::Ptr& request_handler) {
   if (state() != SESSION_STATE_CONNECTED) {
     request_handler->set_error(CASS_ERROR_LIB_NO_HOSTS_AVAILABLE, "Session is not connected");
     return;
   }

   // This intentionally doesn't lock the request processors. The processors will
   // be populated before the connect future returns and calling execute during
   // the connection process is undefined behavior. Locking would cause unnecessary
   // overhead for something that's constant once the session is connected.
   const RequestProcessor::Ptr& request_processor =
       *std::min_element(request_processors_.begin(), request_processors_.end(), least_busy_comp);
   request_processor->process_request(request_handler);
 }

 void Session::join() {
   if (event_loop_group_) {
     event_loop_group_->close_handles();
     event_loop_group_->join();
     event_loop_group_.reset();
   }
 }

 void Session::on_connect(const Host::Ptr& connected_host, ProtocolVersion protocol_version,
                          const HostMap& hosts, const TokenMap::Ptr& token_map,
                          const String& local_dc) {
   int rc = 0;

   if (hosts.empty()) {
     notify_connect_failed(CASS_ERROR_LIB_NO_HOSTS_AVAILABLE,
                           "No hosts provided or no hosts resolved");
     return;
   }

   join();
   event_loop_group_.reset(new RoundRobinEventLoopGroup(config().thread_count_io()));
   rc = event_loop_group_->init("Request Processor");
   if (rc != 0) {
     notify_connect_failed(CASS_ERROR_LIB_UNABLE_TO_INIT, "Unable to initialize event loop group");
     return;
   }

   rc = event_loop_group_->run();
   if (rc != 0) {
     notify_connect_failed(CASS_ERROR_LIB_UNABLE_TO_INIT, "Unable to run event loop group");
     return;
   }

   for (HostMap::const_iterator it = hosts.begin(), end = hosts.end(); it != end; ++it) {
     const Host::Ptr& host = it->second;
     config().host_listener()->on_host_added(host);
     config().host_listener()->on_host_up(
         host); // If host is down it will be marked down later in the connection process
   }

   request_processors_.clear();
   request_processor_count_ = 0;
   is_closing_ = false;
   SessionInitializer::Ptr initializer(new SessionInitializer(this));
   initializer->initialize(connected_host, protocol_version, hosts, token_map, local_dc);
 }

 void Session::on_close() {
   // If there are request processors still connected those need to be closed
   // first before sending the close notification.
   ScopedMutex l(&mutex_);
   is_closing_ = true;
   if (request_processor_count_ > 0) {
     for (RequestProcessor::Vec::const_iterator it = request_processors_.begin(),
                                                end = request_processors_.end();
          it != end; ++it) {
       (*it)->close();
     }
   } else {
     notify_closed();
   }
 }

 void Session::on_host_up(const Host::Ptr& host) {
   // Ignore up events from the control connection; however external host
   // listeners should still be notified. The connection pools will reconnect
   // themselves when the host becomes available.
   config().host_listener()->on_host_up(host);
 }

 void Session::on_host_down(const Host::Ptr& host) {
   // Ignore down events from the control connection; however external host
   // listeners should still be notified. The connection pools can determine if a
   // host is down themselves. The control connection host can become partitioned
   // from the rest of the cluster and in that scenario a down event from the
   // down event from the control connection would be invalid.
   ScopedMutex l(&mutex_);
   if (!is_closing_) { // Refrain from host down events while session is closing
     l.unlock();
     config().host_listener()->on_host_down(host);
   }
 }

 void Session::on_host_added(const Host::Ptr& host) {
   { // Lock for request processor
     ScopedMutex l(&mutex_);
     for (RequestProcessor::Vec::const_iterator it = request_processors_.begin(),
                                                end = request_processors_.end();
          it != end; ++it) {
       (*it)->notify_host_added(host);
     }
   }
   config().host_listener()->on_host_added(host);
 }

 void Session::on_host_removed(const Host::Ptr& host) {
   { // Lock for request processor
     ScopedMutex l(&mutex_);
     for (RequestProcessor::Vec::const_iterator it = request_processors_.begin(),
                                                end = request_processors_.end();
          it != end; ++it) {
       (*it)->notify_host_removed(host);
     }
   }
   config().host_listener()->on_host_removed(host);
 }

 void Session::on_token_map_updated(const TokenMap::Ptr& token_map) {
   ScopedMutex l(&mutex_);
   for (RequestProcessor::Vec::const_iterator it = request_processors_.begin(),
                                              end = request_processors_.end();
        it != end; ++it) {
     (*it)->notify_token_map_updated(token_map);
   }
 }

 void Session::on_host_maybe_up(const Host::Ptr& host) {
   ScopedMutex l(&mutex_);
   for (RequestProcessor::Vec::const_iterator it = request_processors_.begin(),
                                              end = request_processors_.end();
        it != end; ++it) {
     (*it)->notify_host_maybe_up(host->address());
   }
 }

 void Session::on_host_ready(const Host::Ptr& host) {
   ScopedMutex l(&mutex_);
   for (RequestProcessor::Vec::const_iterator it = request_processors_.begin(),
                                              end = request_processors_.end();
        it != end; ++it) {
     (*it)->notify_host_ready(host);
   }
 }

 void Session::on_pool_up(const Address& address) { cluster()->notify_host_up(address); }

 void Session::on_pool_down(const Address& address) { cluster()->notify_host_down(address); }

 void Session::on_pool_critical_error(const Address& address, Connector::ConnectionError code,
                                      const String& message) {
   cluster()->notify_host_down(address);
 }

 void Session::on_keyspace_changed(const String& keyspace,
                                   const KeyspaceChangedHandler::Ptr& handler) {
   ScopedMutex l(&mutex_);
   for (RequestProcessor::Vec::const_iterator it = request_processors_.begin(),
                                              end = request_processors_.end();
        it != end; ++it) {
     (*it)->set_keyspace(keyspace, handler);
   }
 }

 void Session::on_prepared_metadata_changed(const String& id,
                                            const PreparedMetadata::Entry::Ptr& entry) {
   cluster()->prepared(id, entry);
 }

 void Session::on_close(RequestProcessor* processor) {
   // Requires a lock because the close callback is called from several
   // different request processor threads.
   ScopedMutex l(&mutex_);
   if (request_processor_count_ > 0 && --request_processor_count_ == 0) {
     notify_closed();
   }
 }
	/*
	Licensed to the Apache Software Foundation (ASF) under one
	or more contributor license agreements. See the NOTICE file
	distributed with this work for additional information
	regarding copyright ownership. The ASF licenses this file
	to you under the Apache License, Version 2.0 (the
	"License"); you may not use this file except in compliance
	with the License. You may obtain a copy of the License at

	http://www.apache.org/licenses/LICENSE-2.0

	Unless required by applicable law or agreed to in writing, software
	distributed under the License is distributed on an "AS IS" BASIS,
	WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
	See the License for the specific language governing permissions and
	limitations under the License.
	*/

	#include "session.hpp"

	#include "batch_request.hpp"
	#include "cluster_config.hpp"
	#include "constants.hpp"
	#include "execute_request.hpp"
	#include "external.hpp"
	#include "logger.hpp"
	#include "metrics.hpp"
	#include "monitor_reporting.hpp"
	#include "prepare_all_handler.hpp"
	#include "prepare_request.hpp"
	#include "request_processor_initializer.hpp"
	#include "scoped_lock.hpp"
	#include "statement.hpp"

	using namespace datastax;
	using namespace datastax::internal::core;

	extern "C" {

	CassSession* cass_session_new() {
	Session* session = new Session();
	return CassSession::to(session);
	}

	void cass_session_free(CassSession* session) {
	// This attempts to close the session because the joining will
	// hang indefinitely otherwise. This causes minimal delay
	// if the session is already closed.
	session->close()->wait();

	delete session->from();
	}

	CassFuture* cass_session_connect(CassSession* session, const CassCluster* cluster) {
	return cass_session_connect_keyspace(session, cluster, "");
	}

	CassFuture* cass_session_connect_keyspace(CassSession* session, const CassCluster* cluster,
	const char* keyspace) {
	return cass_session_connect_keyspace_n(session, cluster, keyspace, SAFE_STRLEN(keyspace));
	}

	CassFuture* cass_session_connect_keyspace_n(CassSession* session, const CassCluster* cluster,
	const char* keyspace, size_t keyspace_length) {
	Future::Ptr future(session->connect(cluster->config(), String(keyspace, keyspace_length)));
	future->inc_ref();
	return CassFuture::to(future.get());
	}

	CassFuture* cass_session_close(CassSession* session) {
	Future::Ptr future(session->close());
	future->inc_ref();
	return CassFuture::to(future.get());
	}

	CassFuture* cass_session_prepare(CassSession* session, const char* query) {
	return cass_session_prepare_n(session, query, SAFE_STRLEN(query));
	}

	CassFuture* cass_session_prepare_n(CassSession* session, const char* query, size_t query_length) {
	Future::Ptr future(session->prepare(query, query_length));
	future->inc_ref();
	return CassFuture::to(future.get());
	}

	CassFuture* cass_session_prepare_from_existing(CassSession* session, CassStatement* statement) {
	Future::Ptr future(session->prepare(statement));
	future->inc_ref();
	return CassFuture::to(future.get());
	}

	CassFuture* cass_session_execute(CassSession* session, const CassStatement* statement) {
	Future::Ptr future(session->execute(Request::ConstPtr(statement->from())));
	future->inc_ref();
	return CassFuture::to(future.get());
	}

	CassFuture* cass_session_execute_batch(CassSession* session, const CassBatch* batch) {
	Future::Ptr future(session->execute(Request::ConstPtr(batch->from())));
	future->inc_ref();
	return CassFuture::to(future.get());
	}

	const CassSchemaMeta* cass_session_get_schema_meta(const CassSession* session) {
	return CassSchemaMeta::to(new Metadata::SchemaSnapshot(session->cluster()->schema_snapshot()));
	}

	void cass_session_get_metrics(const CassSession* session, CassMetrics* metrics) {
	const Metrics* internal_metrics = session->metrics();

	if (internal_metrics == NULL) {
	LOG_WARN("Attempted to get metrics before connecting session object");
	memset(metrics, 0, sizeof(CassMetrics));
	return;
	}

	Metrics::Histogram::Snapshot requests_snapshot;
	internal_metrics->request_latencies.get_snapshot(&requests_snapshot);

	metrics->requests.min = requests_snapshot.min;
	metrics->requests.max = requests_snapshot.max;
	metrics->requests.mean = requests_snapshot.mean;
	metrics->requests.stddev = requests_snapshot.stddev;
	metrics->requests.median = requests_snapshot.median;
	metrics->requests.percentile_75th = requests_snapshot.percentile_75th;
	metrics->requests.percentile_95th = requests_snapshot.percentile_95th;
	metrics->requests.percentile_98th = requests_snapshot.percentile_98th;
	metrics->requests.percentile_99th = requests_snapshot.percentile_99th;
	metrics->requests.percentile_999th = requests_snapshot.percentile_999th;
	metrics->requests.one_minute_rate = internal_metrics->request_rates.one_minute_rate();
	metrics->requests.five_minute_rate = internal_metrics->request_rates.five_minute_rate();
	metrics->requests.fifteen_minute_rate = internal_metrics->request_rates.fifteen_minute_rate();
	metrics->requests.mean_rate = internal_metrics->request_rates.mean_rate();

	metrics->stats.total_connections = internal_metrics->total_connections.sum();
	metrics->stats.available_connections = metrics->stats.total_connections; // Deprecated
	metrics->stats.exceeded_write_bytes_water_mark = 0; // Deprecated
	metrics->stats.exceeded_pending_requests_water_mark = 0; // Deprecated

	metrics->errors.connection_timeouts = internal_metrics->connection_timeouts.sum();
	metrics->errors.pending_request_timeouts = 0; // Deprecated
	metrics->errors.request_timeouts = internal_metrics->request_timeouts.sum();
	}

	void cass_session_get_speculative_execution_metrics(const CassSession* session,
	CassSpeculativeExecutionMetrics* metrics) {
	const Metrics* internal_metrics = session->metrics();

	if (internal_metrics == NULL) {
	LOG_WARN("Attempted to get speculative execution metrics before connecting session object");
	memset(metrics, 0, sizeof(CassSpeculativeExecutionMetrics));
	return;
	}

	Metrics::Histogram::Snapshot speculative_snapshot;
	internal_metrics->speculative_request_latencies.get_snapshot(&speculative_snapshot);

	metrics->min = speculative_snapshot.min;
	metrics->max = speculative_snapshot.max;
	metrics->mean = speculative_snapshot.mean;
	metrics->stddev = speculative_snapshot.stddev;
	metrics->median = speculative_snapshot.median;
	metrics->percentile_75th = speculative_snapshot.percentile_75th;
	metrics->percentile_95th = speculative_snapshot.percentile_95th;
	metrics->percentile_98th = speculative_snapshot.percentile_98th;
	metrics->percentile_99th = speculative_snapshot.percentile_99th;
	metrics->percentile_999th = speculative_snapshot.percentile_999th;
	metrics->count = internal_metrics->request_rates.speculative_request_count();
	metrics->percentage = internal_metrics->request_rates.speculative_request_percent();
	}

	CassUuid cass_session_get_client_id(CassSession* session) { return session->client_id(); }

	} // extern "C"

	static inline bool least_busy_comp(const RequestProcessor::Ptr& a, const RequestProcessor::Ptr& b) {
	return a->request_count() < b->request_count();
	}

	namespace datastax { namespace internal { namespace core {

	/**
	* An initialize helper class for `Session`. This keeps the initialization
	* logic and data out of the core class itself.
	*/
	class SessionInitializer : public RefCounted<SessionInitializer> {
	public:
	typedef SharedRefPtr<SessionInitializer> Ptr;

	SessionInitializer(Session* session)
	: session_(session)
	, remaining_(0)
	, error_code_(CASS_OK) {
	uv_mutex_init(&mutex_);
	}

	SessionInitializer() { uv_mutex_destroy(&mutex_); }

	void initialize(const Host::Ptr& connected_host, ProtocolVersion protocol_version,
	const HostMap& hosts, const TokenMap::Ptr& token_map, const String& local_dc) {
	inc_ref();

	const size_t thread_count_io = remaining_ = session_->config().thread_count_io();
	for (size_t i = 0; i < thread_count_io; ++i) {
	RequestProcessorInitializer::Ptr initializer(new RequestProcessorInitializer(
	connected_host, protocol_version, hosts, token_map, local_dc,
	bind_callback(&SessionInitializer::on_initialize, this)));

	RequestProcessorSettings settings(session_->config());
	settings.connection_pool_settings.connection_settings.client_id =
	to_string(session_->client_id());

	initializer->with_settings(RequestProcessorSettings(settings))
	->with_listener(session_)
	->with_keyspace(session_->connect_keyspace())
	->with_metrics(session_->metrics())
	->with_random(session_->random())
	->initialize(session_->event_loop_group_->get(i));
	}
	}

	private:
	void on_initialize(RequestProcessorInitializer* initializer) {
	// A lock is required because request processors are initialized on
	// different threads .
	ScopedMutex l(&mutex_);

	if (initializer->is_ok()) {
	request_processors_.push_back(initializer->release_processor());
	} else {
	switch (initializer->error_code()) {
	case RequestProcessorInitializer::REQUEST_PROCESSOR_ERROR_KEYSPACE:
	error_code_ = CASS_ERROR_LIB_UNABLE_TO_SET_KEYSPACE;
	break;
	case RequestProcessorInitializer::REQUEST_PROCESSOR_ERROR_NO_HOSTS_AVAILABLE:
	error_code_ = CASS_ERROR_LIB_NO_HOSTS_AVAILABLE;
	break;
	case RequestProcessorInitializer::REQUEST_PROCESSOR_ERROR_UNABLE_TO_INIT:
	error_code_ = CASS_ERROR_LIB_UNABLE_TO_INIT;
	break;
	default:
	error_code_ = CASS_ERROR_LIB_INTERNAL_ERROR;
	break;
	}
	error_message_ = initializer->error_message();
	}

	if (remaining_ > 0 && --remaining_ == 0) {
	{ // This requires locking because cluster events can happen during
	// initialization.
	ScopedMutex l(&session_->mutex_);
	session_->request_processor_count_ = request_processors_.size();
	session_->request_processors_ = request_processors_;
	}
	if (error_code_ != CASS_OK) {
	session_->notify_connect_failed(error_code_, error_message_);
	} else {
	session_->notify_connected();
	session_->cluster()->start_monitor_reporting(to_string(session_->client_id()),
	to_string(session_->session_id()),
	session_->config());
	}
	l.unlock(); // Unlock before destroying the object
	dec_ref();
	}
	}

	private:
	uv_mutex_t mutex_;
	Session* session_;
	size_t remaining_;
	CassError error_code_;
	String error_message_;
	RequestProcessor::Vec request_processors_;
	};

	}}} // namespace datastax::internal::core

	Session::Session()
	: request_processor_count_(0)
	, is_closing_(false) {
	uv_mutex_init(&mutex_);
	}

	Session::~Session() {
	join();
	uv_mutex_destroy(&mutex_);
	}

	Future::Ptr Session::prepare(const char* statement, size_t length) {
	PrepareRequest::Ptr prepare(new PrepareRequest(String(statement, length)));

	ResponseFuture::Ptr future(new ResponseFuture(cluster()->schema_snapshot()));
	future->prepare_request = PrepareRequest::ConstPtr(prepare);

	execute(RequestHandler::Ptr(new RequestHandler(prepare, future, metrics())));

	return future;
	}

	Future::Ptr Session::prepare(const Statement* statement) {
	String query;

	if (statement->opcode() == CQL_OPCODE_QUERY) { // Simple statement
	query = statement->query();
	} else { // Bound statement
	query = static_cast<const ExecuteRequest*>(statement)->prepared()->query();
	}

	PrepareRequest::Ptr prepare(new PrepareRequest(query));

	// Inherit the settings of the existing statement. These will in turn be
	// inherited by bound statements.
	prepare->set_settings(statement->settings());

	ResponseFuture::Ptr future(new ResponseFuture(cluster()->schema_snapshot()));
	future->prepare_request = PrepareRequest::ConstPtr(prepare);

	execute(RequestHandler::Ptr(new RequestHandler(prepare, future, metrics())));

	return future;
	}

	Future::Ptr Session::execute(const Request::ConstPtr& request) {
	ResponseFuture::Ptr future(new ResponseFuture());

	RequestHandler::Ptr request_handler(new RequestHandler(request, future, metrics()));

	if (request_handler->request()->opcode() == CQL_OPCODE_EXECUTE) {
	const ExecuteRequest* execute = static_cast<const ExecuteRequest*>(request_handler->request());
	request_handler->set_prepared_metadata(cluster()->prepared(execute->prepared()->id()));
	}

	execute(request_handler);

	return future;
	}

	void Session::execute(const RequestHandler::Ptr& request_handler) {
	if (state() != SESSION_STATE_CONNECTED) {
	request_handler->set_error(CASS_ERROR_LIB_NO_HOSTS_AVAILABLE, "Session is not connected");
	return;
	}

	// This intentionally doesn't lock the request processors. The processors will
	// be populated before the connect future returns and calling execute during
	// the connection process is undefined behavior. Locking would cause unnecessary
	// overhead for something that's constant once the session is connected.
	const RequestProcessor::Ptr& request_processor =
	*std::min_element(request_processors_.begin(), request_processors_.end(), least_busy_comp);
	request_processor->process_request(request_handler);
	}

	void Session::join() {
	if (event_loop_group_) {
	event_loop_group_->close_handles();
	event_loop_group_->join();
	event_loop_group_.reset();
	}
	}

	void Session::on_connect(const Host::Ptr& connected_host, ProtocolVersion protocol_version,
	const HostMap& hosts, const TokenMap::Ptr& token_map,
	const String& local_dc) {
	int rc = 0;

	if (hosts.empty()) {
	notify_connect_failed(CASS_ERROR_LIB_NO_HOSTS_AVAILABLE,
	"No hosts provided or no hosts resolved");
	return;
	}

	join();
	event_loop_group_.reset(new RoundRobinEventLoopGroup(config().thread_count_io()));
	rc = event_loop_group_->init("Request Processor");
	if (rc != 0) {
	notify_connect_failed(CASS_ERROR_LIB_UNABLE_TO_INIT, "Unable to initialize event loop group");
	return;
	}

	rc = event_loop_group_->run();
	if (rc != 0) {
	notify_connect_failed(CASS_ERROR_LIB_UNABLE_TO_INIT, "Unable to run event loop group");
	return;
	}

	for (HostMap::const_iterator it = hosts.begin(), end = hosts.end(); it != end; ++it) {
	const Host::Ptr& host = it->second;
	config().host_listener()->on_host_added(host);
	config().host_listener()->on_host_up(
	host); // If host is down it will be marked down later in the connection process
	}

	request_processors_.clear();
	request_processor_count_ = 0;
	is_closing_ = false;
	SessionInitializer::Ptr initializer(new SessionInitializer(this));
	initializer->initialize(connected_host, protocol_version, hosts, token_map, local_dc);
	}

	void Session::on_close() {
	// If there are request processors still connected those need to be closed
	// first before sending the close notification.
	ScopedMutex l(&mutex_);
	is_closing_ = true;
	if (request_processor_count_ > 0) {
	for (RequestProcessor::Vec::const_iterator it = request_processors_.begin(),
	end = request_processors_.end();
	it != end; ++it) {
	(*it)->close();
	}
	} else {
	notify_closed();
	}
	}

	void Session::on_host_up(const Host::Ptr& host) {
	// Ignore up events from the control connection; however external host
	// listeners should still be notified. The connection pools will reconnect
	// themselves when the host becomes available.
	config().host_listener()->on_host_up(host);
	}

	void Session::on_host_down(const Host::Ptr& host) {
	// Ignore down events from the control connection; however external host
	// listeners should still be notified. The connection pools can determine if a
	// host is down themselves. The control connection host can become partitioned
	// from the rest of the cluster and in that scenario a down event from the
	// down event from the control connection would be invalid.
	ScopedMutex l(&mutex_);
	if (!is_closing_) { // Refrain from host down events while session is closing
	l.unlock();
	config().host_listener()->on_host_down(host);
	}
	}

	void Session::on_host_added(const Host::Ptr& host) {
	{ // Lock for request processor
	ScopedMutex l(&mutex_);
	for (RequestProcessor::Vec::const_iterator it = request_processors_.begin(),
	end = request_processors_.end();
	it != end; ++it) {
	(*it)->notify_host_added(host);
	}
	}
	config().host_listener()->on_host_added(host);
	}

	void Session::on_host_removed(const Host::Ptr& host) {
	{ // Lock for request processor
	ScopedMutex l(&mutex_);
	for (RequestProcessor::Vec::const_iterator it = request_processors_.begin(),
	end = request_processors_.end();
	it != end; ++it) {
	(*it)->notify_host_removed(host);
	}
	}
	config().host_listener()->on_host_removed(host);
	}

	void Session::on_token_map_updated(const TokenMap::Ptr& token_map) {
	ScopedMutex l(&mutex_);
	for (RequestProcessor::Vec::const_iterator it = request_processors_.begin(),
	end = request_processors_.end();
	it != end; ++it) {
	(*it)->notify_token_map_updated(token_map);
	}
	}

	void Session::on_host_maybe_up(const Host::Ptr& host) {
	ScopedMutex l(&mutex_);
	for (RequestProcessor::Vec::const_iterator it = request_processors_.begin(),
	end = request_processors_.end();
	it != end; ++it) {
	(*it)->notify_host_maybe_up(host->address());
	}
	}

	void Session::on_host_ready(const Host::Ptr& host) {
	ScopedMutex l(&mutex_);
	for (RequestProcessor::Vec::const_iterator it = request_processors_.begin(),
	end = request_processors_.end();
	it != end; ++it) {
	(*it)->notify_host_ready(host);
	}
	}

	void Session::on_pool_up(const Address& address) { cluster()->notify_host_up(address); }

	void Session::on_pool_down(const Address& address) { cluster()->notify_host_down(address); }

	void Session::on_pool_critical_error(const Address& address, Connector::ConnectionError code,
	const String& message) {
	cluster()->notify_host_down(address);
	}

	void Session::on_keyspace_changed(const String& keyspace,
	const KeyspaceChangedHandler::Ptr& handler) {
	ScopedMutex l(&mutex_);
	for (RequestProcessor::Vec::const_iterator it = request_processors_.begin(),
	end = request_processors_.end();
	it != end; ++it) {
	(*it)->set_keyspace(keyspace, handler);
	}
	}

	void Session::on_prepared_metadata_changed(const String& id,
	const PreparedMetadata::Entry::Ptr& entry) {
	cluster()->prepared(id, entry);
	}

	void Session::on_close(RequestProcessor* processor) {
	// Requires a lock because the close callback is called from several
	// different request processor threads.
	ScopedMutex l(&mutex_);
	if (request_processor_count_ > 0 && --request_processor_count_ == 0) {
	notify_closed();
	}
	}