be/src/service/impala-hs2-server.cc

// 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 "common/thread-debug-info.h"
#include "service/impala-server.h"
#include "service/impala-server.inline.h"

#include <algorithm>
#include <type_traits>

#include <boost/algorithm/string.hpp>
#include <boost/algorithm/string/join.hpp>
#include <boost/bind.hpp>
#include <boost/date_time/posix_time/posix_time_types.hpp>
#include <boost/unordered_set.hpp>
#include <jni.h>
#include <gperftools/heap-profiler.h>
#include <gperftools/malloc_extension.h>
#include <gtest/gtest.h>
#include <gutil/strings/substitute.h>
#include <rapidjson/stringbuffer.h>
#include <rapidjson/prettywriter.h>
#include <thrift/protocol/TDebugProtocol.h>

#include "common/logging.h"
#include "common/version.h"
#include "rpc/thrift-util.h"
#include "runtime/coordinator.h"
#include "runtime/exec-env.h"
#include "runtime/raw-value.h"
#include "scheduling/admission-controller.h"
#include "service/client-request-state.h"
#include "service/hs2-util.h"
#include "service/query-options.h"
#include "service/query-result-set.h"
#include "util/auth-util.h"
#include "util/debug-util.h"
#include "util/impalad-metrics.h"
#include "util/metrics.h"
#include "util/pretty-printer.h"
#include "util/runtime-profile-counters.h"
#include "util/string-parser.h"

#include "common/names.h"

using boost::adopt_lock_t;
using boost::algorithm::join;
using boost::algorithm::iequals;
using boost::uuids::uuid;
using namespace apache::hive::service::cli::thrift;
using namespace apache::hive::service::cli;
using namespace apache::thrift;
using namespace beeswax; // Converting QueryState
using namespace strings;

const TProtocolVersion::type MAX_SUPPORTED_HS2_VERSION =
    TProtocolVersion::HIVE_CLI_SERVICE_PROTOCOL_V6;

// HiveServer2 error returning macro
#define HS2_RETURN_ERROR(return_val, error_msg, error_state) \
  do { \
    return_val.status.__set_statusCode(thrift::TStatusCode::ERROR_STATUS); \
    return_val.status.__set_errorMessage((error_msg)); \
    return_val.status.__set_sqlState((error_state)); \
    return; \
  } while (false)

#define HS2_RETURN_IF_ERROR(return_val, status, error_state) \
  do { \
    const Status& _status = (status); \
    if (UNLIKELY(!_status.ok())) { \
      HS2_RETURN_ERROR(return_val, _status.GetDetail(), (error_state)); \
      return; \
    } \
  } while (false)

DECLARE_string(hostname);
DECLARE_int32(webserver_port);
DECLARE_int32(idle_session_timeout);
DECLARE_int32(disconnected_session_timeout);

namespace impala {

const string IMPALA_RESULT_CACHING_OPT = "impala.resultset.cache.size";

void ImpalaServer::ExecuteMetadataOp(const THandleIdentifier& session_handle,
    TMetadataOpRequest* request, TOperationHandle* handle, thrift::TStatus* status) {
  TUniqueId session_id;
  TUniqueId secret;
  Status unique_id_status =
      THandleIdentifierToTUniqueId(session_handle, &session_id, &secret);
  if (!unique_id_status.ok()) {
    status->__set_statusCode(thrift::TStatusCode::ERROR_STATUS);
    status->__set_errorMessage(unique_id_status.GetDetail());
    status->__set_sqlState(SQLSTATE_GENERAL_ERROR);
    return;
  }
  ScopedSessionState scoped_session(this);
  shared_ptr<SessionState> session;
  Status get_session_status =
      scoped_session.WithSession(session_id, SecretArg::Session(secret), &session);
  if (!get_session_status.ok()) {
    status->__set_statusCode(thrift::TStatusCode::ERROR_STATUS);
    status->__set_errorMessage(get_session_status.GetDetail());
    // TODO: (here and elsewhere) - differentiate between invalid session ID and timeout
    // when setting the error code.
    status->__set_sqlState(SQLSTATE_GENERAL_ERROR);
    return;
  }

  if (session == NULL) {
    status->__set_statusCode(thrift::TStatusCode::ERROR_STATUS);
    status->__set_errorMessage(Substitute("Invalid session id: $0",
        PrintId(session_id)));
    status->__set_sqlState(SQLSTATE_GENERAL_ERROR);
    return;
  }
  TQueryCtx query_ctx;
  PrepareQueryContext(&query_ctx);
  ScopedThreadContext tdi_context(GetThreadDebugInfo(), query_ctx.query_id);
  session->ToThrift(session_id, &query_ctx.session);
  request->__set_session(query_ctx.session);

  shared_ptr<ClientRequestState> request_state;
  // There is no user-supplied query text available because this metadata operation comes
  // from an RPC. As a best effort, we use the type of the operation.
  map<int, const char*>::const_iterator query_text_it =
      _TMetadataOpcode_VALUES_TO_NAMES.find(request->opcode);
  const string& query_text = query_text_it == _TMetadataOpcode_VALUES_TO_NAMES.end() ?
      "N/A" : query_text_it->second;
  query_ctx.client_request.stmt = query_text;
  request_state.reset(new ClientRequestState(query_ctx, exec_env_,
      exec_env_->frontend(), this, session));
  Status register_status = RegisterQuery(session, request_state);
  if (!register_status.ok()) {
    status->__set_statusCode(thrift::TStatusCode::ERROR_STATUS);
    status->__set_errorMessage(register_status.GetDetail());
    status->__set_sqlState(SQLSTATE_GENERAL_ERROR);
    return;
  }

  Status exec_status = request_state->Exec(*request);
  if (!exec_status.ok()) {
    discard_result(UnregisterQuery(request_state->query_id(), false, &exec_status));
    status->__set_statusCode(thrift::TStatusCode::ERROR_STATUS);
    status->__set_errorMessage(exec_status.GetDetail());
    status->__set_sqlState(SQLSTATE_GENERAL_ERROR);
    return;
  }

  request_state->UpdateNonErrorOperationState(TOperationState::FINISHED_STATE);

  Status inflight_status = SetQueryInflight(session, request_state);
  if (!inflight_status.ok()) {
    discard_result(UnregisterQuery(request_state->query_id(), false, &inflight_status));
    status->__set_statusCode(thrift::TStatusCode::ERROR_STATUS);
    status->__set_errorMessage(inflight_status.GetDetail());
    status->__set_sqlState(SQLSTATE_GENERAL_ERROR);
    return;
  }
  handle->__set_hasResultSet(true);
  // Secret is inherited from session.
  TUniqueId operation_id = request_state->query_id();
  TUniqueIdToTHandleIdentifier(operation_id, secret, &(handle->operationId));
  status->__set_statusCode(thrift::TStatusCode::SUCCESS_STATUS);
}

Status ImpalaServer::FetchInternal(ClientRequestState* request_state,
    SessionState* session, int32_t fetch_size, bool fetch_first,
    TFetchResultsResp* fetch_results) {
  // Make sure ClientRequestState::Wait() has completed before fetching rows. Wait()
  // ensures that rows are ready to be fetched (e.g., Wait() opens
  // ClientRequestState::output_exprs_, which are evaluated in
  // ClientRequestState::FetchRows() below).
  int64_t block_on_wait_time_us = 0;
  if (!request_state->BlockOnWait(
          request_state->fetch_rows_timeout_us(), &block_on_wait_time_us)) {
    fetch_results->status.__set_statusCode(thrift::TStatusCode::STILL_EXECUTING_STATUS);
    fetch_results->__set_hasMoreRows(true);
    fetch_results->__isset.results = false;
    return Status::OK();
  }

  lock_guard<mutex> frl(*request_state->fetch_rows_lock());
  lock_guard<mutex> l(*request_state->lock());

  // Check for cancellation or an error.
  RETURN_IF_ERROR(request_state->query_status());

  if (request_state->num_rows_fetched() == 0) {
    request_state->set_fetched_rows();
  }

  if (fetch_first) RETURN_IF_ERROR(request_state->RestartFetch());

  fetch_results->results.__set_startRowOffset(request_state->num_rows_fetched());

  // Child queries should always return their results in row-major format, rather than
  // inheriting the parent session's setting.
  bool is_child_query = request_state->parent_query_id() != TUniqueId();
  TProtocolVersion::type version = is_child_query ?
      TProtocolVersion::HIVE_CLI_SERVICE_PROTOCOL_V1 : session->hs2_version;
  scoped_ptr<QueryResultSet> result_set(QueryResultSet::CreateHS2ResultSet(
      version, *(request_state->result_metadata()), &(fetch_results->results)));
  RETURN_IF_ERROR(
      request_state->FetchRows(fetch_size, result_set.get(), block_on_wait_time_us));
  fetch_results->__isset.results = true;
  fetch_results->__set_hasMoreRows(!request_state->eos());
  return Status::OK();
}

Status ImpalaServer::TExecuteStatementReqToTQueryContext(
    const TExecuteStatementReq execute_request, TQueryCtx* query_ctx) {
  query_ctx->client_request.stmt = execute_request.statement;
  VLOG_QUERY << "TExecuteStatementReq: " << ThriftDebugString(execute_request);
  QueryOptionsMask set_query_options_mask;
  {
    shared_ptr<SessionState> session_state;
    TUniqueId session_id;
    TUniqueId secret;
    RETURN_IF_ERROR(THandleIdentifierToTUniqueId(execute_request.sessionHandle.sessionId,
        &session_id, &secret));

    RETURN_IF_ERROR(
        GetSessionState(session_id, SecretArg::Session(secret), &session_state));
    session_state->ToThrift(session_id, &query_ctx->session);
    lock_guard<mutex> l(session_state->lock);
    query_ctx->client_request.query_options = session_state->QueryOptions();
    set_query_options_mask = session_state->set_query_options_mask;
  }

  if (execute_request.__isset.confOverlay) {
    TQueryOptions overlay;
    QueryOptionsMask overlay_mask;
    map<string, string>::const_iterator conf_itr = execute_request.confOverlay.begin();
    for (; conf_itr != execute_request.confOverlay.end(); ++conf_itr) {
      if (conf_itr->first == IMPALA_RESULT_CACHING_OPT) continue;
      if (conf_itr->first == ChildQuery::PARENT_QUERY_OPT) {
        if (ParseId(conf_itr->second, &query_ctx->parent_query_id)) {
          query_ctx->__isset.parent_query_id = true;
        }
        continue;
      }
      RETURN_IF_ERROR(SetQueryOption(conf_itr->first, conf_itr->second,
          &overlay, &overlay_mask));
    }
    OverlayQueryOptions(overlay, overlay_mask, &query_ctx->client_request.query_options);
    set_query_options_mask |= overlay_mask;
  }
  // Only query options not set in the session or confOverlay can be overridden by the
  // pool options.
  AddPoolConfiguration(query_ctx, ~set_query_options_mask);
  VLOG_QUERY << "TClientRequest.queryOptions: "
             << ThriftDebugString(query_ctx->client_request.query_options);
  return Status::OK();
}

// HiveServer2 API
void ImpalaServer::OpenSession(TOpenSessionResp& return_val,
    const TOpenSessionReq& request) {
  HS2_RETURN_IF_ERROR(return_val, CheckNotShuttingDown(), SQLSTATE_GENERAL_ERROR);

  // Generate session ID and the secret
  uuid secret_uuid;
  uuid session_uuid;
  {
    lock_guard<mutex> l(uuid_lock_);
    secret_uuid = crypto_uuid_generator_();
    session_uuid = crypto_uuid_generator_();
  }
  return_val.sessionHandle.sessionId.guid.assign(
      session_uuid.begin(), session_uuid.end());
  return_val.sessionHandle.sessionId.secret.assign(
      secret_uuid.begin(), secret_uuid.end());
  DCHECK_EQ(return_val.sessionHandle.sessionId.guid.size(), 16);
  DCHECK_EQ(return_val.sessionHandle.sessionId.secret.size(), 16);
  return_val.__isset.sessionHandle = true;
  TUniqueId session_id, secret;
  UUIDToTUniqueId(session_uuid, &session_id);
  UUIDToTUniqueId(secret_uuid, &secret);

  // DO NOT log this Thrift struct in its entirety, in case a bad client sets the
  // password.
  VLOG_QUERY << "Opening session: " << PrintId(session_id) << " username: "
             << request.username;

  // create a session state: initialize start time, session type, database and default
  // query options.
  // TODO: Fix duplication of code between here and ConnectionStart().
  shared_ptr<SessionState> state = make_shared<SessionState>(this, session_id, secret);
  state->closed = false;
  state->start_time_ms = UnixMillis();
  state->session_type = TSessionType::HIVESERVER2;
  state->network_address = ThriftServer::GetThreadConnectionContext()->network_address;
  state->last_accessed_ms = UnixMillis();
  // request.client_protocol is not guaranteed to be a valid TProtocolVersion::type, so
  // loading it can cause undefined behavior. Instead, we copy it to a value of the
  // "underlying type" of the enum, then copy it back to state->hs_version only once we
  // have clamped it to be at most MAX_SUPPORTED_HS2_VERSION.
  std::underlying_type_t<decltype(request.client_protocol)> protocol_integer;
  memcpy(&protocol_integer, &request.client_protocol, sizeof(request.client_protocol));
  state->hs2_version = static_cast<TProtocolVersion::type>(
      min<decltype(protocol_integer)>(MAX_SUPPORTED_HS2_VERSION, protocol_integer));
  state->kudu_latest_observed_ts = 0;

  // If the username was set by a lower-level transport, use it.
  const ThriftServer::ConnectionContext* connection_context =
      ThriftServer::GetThreadConnectionContext();
  if (!connection_context->username.empty()) {
    state->connected_user = connection_context->username;
    if (!connection_context->do_as_user.empty()) {
      state->do_as_user = connection_context->do_as_user;
      Status status = AuthorizeProxyUser(state->connected_user, state->do_as_user);
      HS2_RETURN_IF_ERROR(return_val, status, SQLSTATE_GENERAL_ERROR);
    }
  } else {
    state->connected_user = request.username;
  }

  // Process the supplied configuration map.
  state->database = "default";
  state->server_default_query_options = &default_query_options_;
  state->session_timeout = FLAGS_idle_session_timeout;
  if (request.__isset.configuration) {
    typedef map<string, string> ConfigurationMap;
    for (const ConfigurationMap::value_type& v: request.configuration) {
      if (iequals(v.first, "impala.doas.user")) {
        // If the current user is a valid proxy user, he/she can optionally perform
        // authorization requests on behalf of another user. This is done by setting
        // the 'impala.doas.user' Hive Server 2 configuration property.
        state->do_as_user = v.second;
        Status status = AuthorizeProxyUser(state->connected_user, state->do_as_user);
        HS2_RETURN_IF_ERROR(return_val, status, SQLSTATE_GENERAL_ERROR);
      } else if (iequals(v.first, "use:database")) {
        state->database = v.second;
      } else {
        // Normal configuration key. Use it to set session default query options.
        // Ignore failure (failures will be logged in SetQueryOption()).
        Status status = SetQueryOption(v.first, v.second, &state->set_query_options,
            &state->set_query_options_mask);
        if (status.ok() && iequals(v.first, "idle_session_timeout")) {
          state->session_timeout = state->set_query_options.idle_session_timeout;
          VLOG_QUERY << "OpenSession(): session: " << PrintId(session_id)
                     <<" idle_session_timeout="
                     << PrettyPrinter::Print(state->session_timeout, TUnit::TIME_S);
        }
      }
    }
  }
  RegisterSessionTimeout(state->session_timeout);
  TQueryOptionsToMap(state->QueryOptions(), &return_val.configuration);

  // OpenSession() should return the coordinator's HTTP server address.
  const string& http_addr = TNetworkAddressToString(MakeNetworkAddress(
      FLAGS_hostname, FLAGS_webserver_port));
  return_val.configuration.insert(make_pair("http_addr", http_addr));

  {
    lock_guard<mutex> l(connection_to_sessions_map_lock_);
    const TUniqueId& connection_id = ThriftServer::GetThreadConnectionId();
    connection_to_sessions_map_[connection_id].insert(session_id);
    state->connections.insert(connection_id);
  }

  // Put the session state in session_state_map_
  {
    lock_guard<mutex> l(session_state_map_lock_);
    session_state_map_.insert(make_pair(session_id, state));
  }

  ImpaladMetrics::IMPALA_SERVER_NUM_OPEN_HS2_SESSIONS->Increment(1);

  return_val.__isset.configuration = true;
  return_val.status.__set_statusCode(thrift::TStatusCode::SUCCESS_STATUS);
  return_val.serverProtocolVersion = state->hs2_version;
  VLOG_QUERY << "Opened session: " << PrintId(session_id) << " username: "
             << request.username;
}

void ImpalaServer::CloseSession(TCloseSessionResp& return_val,
    const TCloseSessionReq& request) {
  VLOG_QUERY << "CloseSession(): request=" << ThriftDebugString(request);

  TUniqueId session_id;
  TUniqueId secret;
  HS2_RETURN_IF_ERROR(return_val, THandleIdentifierToTUniqueId(
      request.sessionHandle.sessionId, &session_id, &secret), SQLSTATE_GENERAL_ERROR);
  HS2_RETURN_IF_ERROR(return_val,
      CloseSessionInternal(
          session_id, SecretArg::Session(secret), /* ignore_if_absent= */ false),
      SQLSTATE_GENERAL_ERROR);
  return_val.status.__set_statusCode(thrift::TStatusCode::SUCCESS_STATUS);
}

void ImpalaServer::GetInfo(TGetInfoResp& return_val,
    const TGetInfoReq& request) {
  VLOG_QUERY << "GetInfo(): request=" << ThriftDebugString(request);
  HS2_RETURN_IF_ERROR(return_val, CheckNotShuttingDown(), SQLSTATE_GENERAL_ERROR);

  TUniqueId session_id;
  TUniqueId secret;
  HS2_RETURN_IF_ERROR(return_val, THandleIdentifierToTUniqueId(
      request.sessionHandle.sessionId, &session_id, &secret), SQLSTATE_GENERAL_ERROR);
  ScopedSessionState session_handle(this);
  shared_ptr<SessionState> session;
  HS2_RETURN_IF_ERROR(return_val,
      session_handle.WithSession(session_id, SecretArg::Session(secret), &session),
      SQLSTATE_GENERAL_ERROR);

  switch (request.infoType) {
    case TGetInfoType::CLI_SERVER_NAME:
    case TGetInfoType::CLI_DBMS_NAME:
      return_val.infoValue.__set_stringValue("Impala");
      break;
    case TGetInfoType::CLI_DBMS_VER:
      return_val.infoValue.__set_stringValue(GetDaemonBuildVersion());
      break;
    default:
      HS2_RETURN_ERROR(return_val, "Unsupported operation",
          SQLSTATE_OPTIONAL_FEATURE_NOT_IMPLEMENTED);
  }
  return_val.status.__set_statusCode(thrift::TStatusCode::SUCCESS_STATUS);
}

void ImpalaServer::ExecuteStatement(TExecuteStatementResp& return_val,
    const TExecuteStatementReq& request) {
  VLOG_QUERY << "ExecuteStatement(): request=" << ThriftDebugString(request);
  HS2_RETURN_IF_ERROR(return_val, CheckNotShuttingDown(), SQLSTATE_GENERAL_ERROR);
  // We ignore the runAsync flag here: Impala's queries will always run asynchronously,
  // and will block on fetch. To the client, this looks like Hive's synchronous mode; the
  // difference is that rows are not available when ExecuteStatement() returns.
  TQueryCtx query_ctx;
  Status status = TExecuteStatementReqToTQueryContext(request, &query_ctx);
  HS2_RETURN_IF_ERROR(return_val, status, SQLSTATE_GENERAL_ERROR);

  TUniqueId session_id;
  TUniqueId secret;
  HS2_RETURN_IF_ERROR(return_val, THandleIdentifierToTUniqueId(
      request.sessionHandle.sessionId, &session_id, &secret), SQLSTATE_GENERAL_ERROR);
  ScopedSessionState session_handle(this);
  shared_ptr<SessionState> session;
  HS2_RETURN_IF_ERROR(return_val,
      session_handle.WithSession(session_id, SecretArg::Session(secret), &session),
      SQLSTATE_GENERAL_ERROR);
  if (session == NULL) {
    string err_msg = Substitute("Invalid session id: $0", PrintId(session_id));
    VLOG(1) << err_msg;
    HS2_RETURN_IF_ERROR(return_val, Status::Expected(err_msg), SQLSTATE_GENERAL_ERROR);
  }

  // Optionally enable result caching to allow restarting fetches.
  int64_t cache_num_rows = -1;
  if (request.__isset.confOverlay) {
    map<string, string>::const_iterator iter =
        request.confOverlay.find(IMPALA_RESULT_CACHING_OPT);
    if (iter != request.confOverlay.end()) {
      StringParser::ParseResult parse_result;
      cache_num_rows = StringParser::StringToInt<int64_t>(
          iter->second.c_str(), iter->second.size(), &parse_result);
      if (parse_result != StringParser::PARSE_SUCCESS) {
        HS2_RETURN_IF_ERROR(
            return_val, Status::Expected(Substitute("Invalid value '$0' for '$1' option.",
                iter->second, IMPALA_RESULT_CACHING_OPT)), SQLSTATE_GENERAL_ERROR);
      }
    }
  }

  shared_ptr<ClientRequestState> request_state;
  status = Execute(&query_ctx, session, &request_state);
  HS2_RETURN_IF_ERROR(return_val, status, SQLSTATE_GENERAL_ERROR);

  // Start thread to wait for results to become available.
  status = request_state->WaitAsync();
  if (!status.ok()) goto return_error;

  // Optionally enable result caching on the ClientRequestState.
  if (cache_num_rows > 0) {
    status = request_state->SetResultCache(
        QueryResultSet::CreateHS2ResultSet(
            session->hs2_version, *request_state->result_metadata(), nullptr),
        cache_num_rows);
    if (!status.ok()) goto return_error;
  }
  // Once the query is running do a final check for session closure and add it to the
  // set of in-flight queries.
  status = SetQueryInflight(session, request_state);
  if (!status.ok()) goto return_error;
  return_val.__isset.operationHandle = true;
  return_val.operationHandle.__set_operationType(TOperationType::EXECUTE_STATEMENT);
  return_val.operationHandle.__set_hasResultSet(request_state->returns_result_set());
  // Secret is inherited from session.
  TUniqueIdToTHandleIdentifier(request_state->query_id(), secret,
                               &return_val.operationHandle.operationId);
  return_val.status.__set_statusCode(
      apache::hive::service::cli::thrift::TStatusCode::SUCCESS_STATUS);

  VLOG_QUERY << "ExecuteStatement(): return_val=" << ThriftDebugString(return_val);
  return;

 return_error:
  discard_result(UnregisterQuery(request_state->query_id(), false, &status));
  HS2_RETURN_ERROR(return_val, status.GetDetail(), SQLSTATE_GENERAL_ERROR);
}

void ImpalaServer::GetTypeInfo(TGetTypeInfoResp& return_val,
    const TGetTypeInfoReq& request) {
  VLOG_QUERY << "GetTypeInfo(): request=" << ThriftDebugString(request);
  HS2_RETURN_IF_ERROR(return_val, CheckNotShuttingDown(), SQLSTATE_GENERAL_ERROR);

  TMetadataOpRequest req;
  req.__set_opcode(TMetadataOpcode::GET_TYPE_INFO);
  req.__set_get_type_info_req(request);

  TOperationHandle handle;
  thrift::TStatus status;
  ExecuteMetadataOp(request.sessionHandle.sessionId, &req, &handle, &status);
  handle.__set_operationType(TOperationType::GET_TYPE_INFO);
  return_val.__set_operationHandle(handle);
  return_val.__set_status(status);

  VLOG_QUERY << "GetTypeInfo(): return_val=" << ThriftDebugString(return_val);
}

void ImpalaServer::GetCatalogs(TGetCatalogsResp& return_val,
    const TGetCatalogsReq& request) {
  VLOG_QUERY << "GetCatalogs(): request=" << ThriftDebugString(request);
  HS2_RETURN_IF_ERROR(return_val, CheckNotShuttingDown(), SQLSTATE_GENERAL_ERROR);

  TMetadataOpRequest req;
  req.__set_opcode(TMetadataOpcode::GET_CATALOGS);
  req.__set_get_catalogs_req(request);

  TOperationHandle handle;
  thrift::TStatus status;
  ExecuteMetadataOp(request.sessionHandle.sessionId, &req, &handle, &status);
  handle.__set_operationType(TOperationType::GET_CATALOGS);
  return_val.__set_operationHandle(handle);
  return_val.__set_status(status);

  VLOG_QUERY << "GetCatalogs(): return_val=" << ThriftDebugString(return_val);
}

void ImpalaServer::GetSchemas(TGetSchemasResp& return_val,
    const TGetSchemasReq& request) {
  VLOG_QUERY << "GetSchemas(): request=" << ThriftDebugString(request);
  HS2_RETURN_IF_ERROR(return_val, CheckNotShuttingDown(), SQLSTATE_GENERAL_ERROR);

  TMetadataOpRequest req;
  req.__set_opcode(TMetadataOpcode::GET_SCHEMAS);
  req.__set_get_schemas_req(request);

  TOperationHandle handle;
  thrift::TStatus status;
  ExecuteMetadataOp(request.sessionHandle.sessionId, &req, &handle, &status);
  handle.__set_operationType(TOperationType::GET_SCHEMAS);
  return_val.__set_operationHandle(handle);
  return_val.__set_status(status);

  VLOG_QUERY << "GetSchemas(): return_val=" << ThriftDebugString(return_val);
}

void ImpalaServer::GetTables(TGetTablesResp& return_val,
    const TGetTablesReq& request) {
  VLOG_QUERY << "GetTables(): request=" << ThriftDebugString(request);
  HS2_RETURN_IF_ERROR(return_val, CheckNotShuttingDown(), SQLSTATE_GENERAL_ERROR);

  TMetadataOpRequest req;
  req.__set_opcode(TMetadataOpcode::GET_TABLES);
  req.__set_get_tables_req(request);

  TOperationHandle handle;
  thrift::TStatus status;
  ExecuteMetadataOp(request.sessionHandle.sessionId, &req, &handle, &status);
  handle.__set_operationType(TOperationType::GET_TABLES);
  return_val.__set_operationHandle(handle);
  return_val.__set_status(status);

  VLOG_QUERY << "GetTables(): return_val=" << ThriftDebugString(return_val);
}

void ImpalaServer::GetTableTypes(TGetTableTypesResp& return_val,
    const TGetTableTypesReq& request) {
  VLOG_QUERY << "GetTableTypes(): request=" << ThriftDebugString(request);
  HS2_RETURN_IF_ERROR(return_val, CheckNotShuttingDown(), SQLSTATE_GENERAL_ERROR);

  TMetadataOpRequest req;
  req.__set_opcode(TMetadataOpcode::GET_TABLE_TYPES);
  req.__set_get_table_types_req(request);

  TOperationHandle handle;
  thrift::TStatus status;
  ExecuteMetadataOp(request.sessionHandle.sessionId, &req, &handle, &status);
  handle.__set_operationType(TOperationType::GET_TABLE_TYPES);
  return_val.__set_operationHandle(handle);
  return_val.__set_status(status);

  VLOG_QUERY << "GetTableTypes(): return_val=" << ThriftDebugString(return_val);

}

void ImpalaServer::GetColumns(TGetColumnsResp& return_val,
    const TGetColumnsReq& request) {
  VLOG_QUERY << "GetColumns(): request=" << ThriftDebugString(request);
  HS2_RETURN_IF_ERROR(return_val, CheckNotShuttingDown(), SQLSTATE_GENERAL_ERROR);

  TMetadataOpRequest req;
  req.__set_opcode(TMetadataOpcode::GET_COLUMNS);
  req.__set_get_columns_req(request);

  TOperationHandle handle;
  thrift::TStatus status;
  ExecuteMetadataOp(request.sessionHandle.sessionId, &req, &handle, &status);
  handle.__set_operationType(TOperationType::GET_COLUMNS);
  return_val.__set_operationHandle(handle);
  return_val.__set_status(status);

  VLOG_QUERY << "GetColumns(): return_val=" << ThriftDebugString(return_val);
}

void ImpalaServer::GetFunctions(TGetFunctionsResp& return_val,
    const TGetFunctionsReq& request) {
  VLOG_QUERY << "GetFunctions(): request=" << ThriftDebugString(request);
  HS2_RETURN_IF_ERROR(return_val, CheckNotShuttingDown(), SQLSTATE_GENERAL_ERROR);

  TMetadataOpRequest req;
  req.__set_opcode(TMetadataOpcode::GET_FUNCTIONS);
  req.__set_get_functions_req(request);

  TOperationHandle handle;
  thrift::TStatus status;
  ExecuteMetadataOp(request.sessionHandle.sessionId, &req, &handle, &status);
  handle.__set_operationType(TOperationType::GET_FUNCTIONS);
  return_val.__set_operationHandle(handle);
  return_val.__set_status(status);

  VLOG_QUERY << "GetFunctions(): return_val=" << ThriftDebugString(return_val);
}

void ImpalaServer::GetPrimaryKeys(TGetPrimaryKeysResp& return_val,
    const TGetPrimaryKeysReq& request) {
  VLOG_QUERY << "GetPrimaryKeys(): request=" << ThriftDebugString(request);
  HS2_RETURN_IF_ERROR(return_val, CheckNotShuttingDown(), SQLSTATE_GENERAL_ERROR);

  TMetadataOpRequest req;
  req.__set_opcode(TMetadataOpcode::GET_PRIMARY_KEYS);
  req.__set_get_primary_keys_req(request);

  TOperationHandle handle;
  thrift::TStatus status;
  ExecuteMetadataOp(request.sessionHandle.sessionId, &req, &handle, &status);
  return_val.__set_operationHandle(handle);
  return_val.__set_status(status);

  VLOG_QUERY << "GetPrimaryKeys(): return_val=" << ThriftDebugString(return_val);
}

void ImpalaServer::GetCrossReference(TGetCrossReferenceResp& return_val,
    const TGetCrossReferenceReq& request) {
  VLOG_QUERY << "GetCrossReference(): request=" << ThriftDebugString(request);
  HS2_RETURN_IF_ERROR(return_val, CheckNotShuttingDown(), SQLSTATE_GENERAL_ERROR);

  TMetadataOpRequest req;
  req.__set_opcode(TMetadataOpcode::GET_CROSS_REFERENCE);
  req.__set_get_cross_reference_req(request);

  TOperationHandle handle;
  thrift::TStatus status;
  ExecuteMetadataOp(request.sessionHandle.sessionId, &req, &handle, &status);
  return_val.__set_operationHandle(handle);
  return_val.__set_status(status);

  VLOG_QUERY << "GetCrossReference(): return_val=" << ThriftDebugString(return_val);
}

void ImpalaServer::GetOperationStatus(TGetOperationStatusResp& return_val,
    const TGetOperationStatusReq& request) {
  if (request.operationHandle.operationId.guid.size() == 0) {
    // An empty operation handle identifier means no execution and no result for this
    // query (USE <database>).
    VLOG_ROW << "GetOperationStatus(): guid size 0";
    return_val.operationState = TOperationState::FINISHED_STATE;
    return_val.status.__set_statusCode(thrift::TStatusCode::SUCCESS_STATUS);
    return;
  }

  // Secret is inherited from session.
  TUniqueId query_id;
  TUniqueId op_secret;
  HS2_RETURN_IF_ERROR(return_val, THandleIdentifierToTUniqueId(
      request.operationHandle.operationId, &query_id, &op_secret),
      SQLSTATE_GENERAL_ERROR);
  VLOG_ROW << "GetOperationStatus(): query_id=" << PrintId(query_id);

  shared_ptr<ClientRequestState> request_state = GetClientRequestState(query_id);
  if (UNLIKELY(request_state.get() == nullptr)) {
    // No handle was found
    HS2_RETURN_ERROR(return_val,
      Substitute("Invalid query handle: $0", PrintId(query_id)), SQLSTATE_GENERAL_ERROR);
  }

  ScopedSessionState session_handle(this);
  const TUniqueId session_id = request_state->session_id();
  shared_ptr<SessionState> session;
  HS2_RETURN_IF_ERROR(return_val,
      session_handle.WithSession(
          session_id, SecretArg::Operation(op_secret, query_id), &session),
      SQLSTATE_GENERAL_ERROR);

  {
    lock_guard<mutex> l(*request_state->lock());
    TOperationState::type operation_state = request_state->operation_state();
    return_val.__set_operationState(operation_state);
    if (operation_state == TOperationState::ERROR_STATE) {
      DCHECK(!request_state->query_status().ok());
      return_val.__set_errorMessage(request_state->query_status().GetDetail());
      return_val.__set_sqlState(SQLSTATE_GENERAL_ERROR);
    } else {
      DCHECK(request_state->query_status().ok());
    }
  }
}

void ImpalaServer::CancelOperation(TCancelOperationResp& return_val,
    const TCancelOperationReq& request) {
  TUniqueId query_id;
  TUniqueId op_secret;
  HS2_RETURN_IF_ERROR(return_val, THandleIdentifierToTUniqueId(
      request.operationHandle.operationId, &query_id, &op_secret),
      SQLSTATE_GENERAL_ERROR);
  VLOG_QUERY << "CancelOperation(): query_id=" << PrintId(query_id);

  shared_ptr<ClientRequestState> request_state = GetClientRequestState(query_id);
  if (UNLIKELY(request_state.get() == nullptr)) {
    // No handle was found
    HS2_RETURN_ERROR(return_val,
      Substitute("Invalid query handle: $0", PrintId(query_id)), SQLSTATE_GENERAL_ERROR);
  }
  ScopedSessionState session_handle(this);
  const TUniqueId session_id = request_state->session_id();
  HS2_RETURN_IF_ERROR(return_val,
      session_handle.WithSession(session_id, SecretArg::Operation(op_secret, query_id)),
      SQLSTATE_GENERAL_ERROR);
  HS2_RETURN_IF_ERROR(return_val, CancelInternal(query_id, true), SQLSTATE_GENERAL_ERROR);
  return_val.status.__set_statusCode(thrift::TStatusCode::SUCCESS_STATUS);
}

void ImpalaServer::CloseOperation(TCloseOperationResp& return_val,
    const TCloseOperationReq& request) {
  TCloseImpalaOperationReq request2;
  request2.operationHandle = request.operationHandle;
  TCloseImpalaOperationResp tmp_resp;
  CloseImpalaOperation(tmp_resp, request2);
  return_val.status = tmp_resp.status;
}

void ImpalaServer::CloseImpalaOperation(TCloseImpalaOperationResp& return_val,
    const TCloseImpalaOperationReq& request) {
  TUniqueId query_id;
  TUniqueId op_secret;
  HS2_RETURN_IF_ERROR(return_val, THandleIdentifierToTUniqueId(
      request.operationHandle.operationId, &query_id, &op_secret),
      SQLSTATE_GENERAL_ERROR);
  VLOG_QUERY << "CloseOperation(): query_id=" << PrintId(query_id);

  shared_ptr<ClientRequestState> request_state = GetClientRequestState(query_id);
  if (UNLIKELY(request_state.get() == nullptr)) {
    // No handle was found
    HS2_RETURN_ERROR(return_val,
      Substitute("Invalid query handle: $0", PrintId(query_id)), SQLSTATE_GENERAL_ERROR);
  }
  ScopedSessionState session_handle(this);
  const TUniqueId session_id = request_state->session_id();
  HS2_RETURN_IF_ERROR(return_val,
      session_handle.WithSession(session_id, SecretArg::Operation(op_secret, query_id)),
      SQLSTATE_GENERAL_ERROR);
  if (request_state->stmt_type() == TStmtType::DML) {
    Status query_status;
    if (request_state->GetDmlStats(&return_val.dml_result, &query_status)) {
      return_val.__isset.dml_result = true;
    }
  }

  // TODO: use timeout to get rid of unwanted request_state.
  HS2_RETURN_IF_ERROR(return_val, UnregisterQuery(query_id, true),
      SQLSTATE_GENERAL_ERROR);
  return_val.status.__set_statusCode(thrift::TStatusCode::SUCCESS_STATUS);
}

void ImpalaServer::GetResultSetMetadata(TGetResultSetMetadataResp& return_val,
    const TGetResultSetMetadataReq& request) {
  // Convert Operation id to TUniqueId and get the query exec state.
  TUniqueId query_id;
  TUniqueId op_secret;
  HS2_RETURN_IF_ERROR(return_val, THandleIdentifierToTUniqueId(
      request.operationHandle.operationId, &query_id, &op_secret),
      SQLSTATE_GENERAL_ERROR);
  VLOG_QUERY << "GetResultSetMetadata(): query_id=" << PrintId(query_id);

  shared_ptr<ClientRequestState> request_state = GetClientRequestState(query_id);
  if (UNLIKELY(request_state.get() == nullptr)) {
    VLOG_QUERY << "GetResultSetMetadata(): invalid query handle";
    // No handle was found
    HS2_RETURN_ERROR(return_val,
      Substitute("Invalid query handle: $0", PrintId(query_id)), SQLSTATE_GENERAL_ERROR);
  }
  ScopedSessionState session_handle(this);
  const TUniqueId session_id = request_state->session_id();
  HS2_RETURN_IF_ERROR(return_val,
      session_handle.WithSession(session_id, SecretArg::Operation(op_secret, query_id)),
      SQLSTATE_GENERAL_ERROR);
  {
    lock_guard<mutex> l(*request_state->lock());

    // Convert TResultSetMetadata to TGetResultSetMetadataResp
    const TResultSetMetadata* result_set_md = request_state->result_metadata();
    DCHECK(result_set_md != NULL);
    if (result_set_md->columns.size() > 0) {
      return_val.__isset.schema = true;
      return_val.schema.columns.resize(result_set_md->columns.size());
      for (int i = 0; i < result_set_md->columns.size(); ++i) {
        return_val.schema.columns[i].__set_columnName(
            result_set_md->columns[i].columnName);
        return_val.schema.columns[i].position = i;
        return_val.schema.columns[i].typeDesc.types.resize(1);
        ColumnType t = ColumnType::FromThrift(result_set_md->columns[i].columnType);
        return_val.schema.columns[i].typeDesc.types[0] = t.ToHs2Type();
      }
    }
  }

  return_val.status.__set_statusCode(thrift::TStatusCode::SUCCESS_STATUS);
  VLOG_QUERY << "GetResultSetMetadata(): return_val=" << ThriftDebugString(return_val);
}

void ImpalaServer::FetchResults(TFetchResultsResp& return_val,
    const TFetchResultsReq& request) {
  if (request.orientation != TFetchOrientation::FETCH_NEXT
      && request.orientation != TFetchOrientation::FETCH_FIRST) {
    HS2_RETURN_ERROR(return_val, "Unsupported operation",
        SQLSTATE_OPTIONAL_FEATURE_NOT_IMPLEMENTED);
  }
  bool fetch_first = request.orientation == TFetchOrientation::FETCH_FIRST;

  // Convert Operation id to TUniqueId and get the query exec state.
  TUniqueId query_id;
  TUniqueId op_secret;
  HS2_RETURN_IF_ERROR(return_val, THandleIdentifierToTUniqueId(
      request.operationHandle.operationId, &query_id, &op_secret),
      SQLSTATE_GENERAL_ERROR);
  VLOG_ROW << "FetchResults(): query_id=" << PrintId(query_id)
           << " fetch_size=" << request.maxRows;

  shared_ptr<ClientRequestState> request_state = GetClientRequestState(query_id);
  if (UNLIKELY(request_state == nullptr)) {
    string err_msg = Substitute("Invalid query handle: $0", PrintId(query_id));
    VLOG(1) << err_msg;
    HS2_RETURN_ERROR(return_val, err_msg, SQLSTATE_GENERAL_ERROR);
  }

  // Validate the secret and keep the session that originated the query alive.
  ScopedSessionState session_handle(this);
  const TUniqueId session_id = request_state->session_id();
  shared_ptr<SessionState> session;
  HS2_RETURN_IF_ERROR(return_val,
      session_handle.WithSession(
          session_id, SecretArg::Operation(op_secret, query_id), &session),
      SQLSTATE_GENERAL_ERROR);

  Status status = FetchInternal(
      request_state.get(), session.get(), request.maxRows, fetch_first, &return_val);
  VLOG_ROW << "FetchResults(): #results=" << return_val.results.rows.size()
           << " has_more=" << (return_val.hasMoreRows ? "true" : "false");
  if (!status.ok()) {
    // Only unregister the query if the underlying error is unrecoverable.
    // Clients are expected to understand that a failed FETCH_FIRST is recoverable,
    // and hence, the query must eventually be closed by the client.
    // It is important to ensure FETCH_NEXT does not return recoverable errors to
    // preserve compatibility with clients written against Impala versions < 1.3.
    if (status.IsRecoverableError()) {
      DCHECK(fetch_first);
    } else {
      discard_result(UnregisterQuery(query_id, false, &status));
    }
    HS2_RETURN_ERROR(return_val, status.GetDetail(), SQLSTATE_GENERAL_ERROR);
    return_val.status.__set_statusCode(thrift::TStatusCode::SUCCESS_STATUS);
  }
}

void ImpalaServer::GetLog(TGetLogResp& return_val, const TGetLogReq& request) {
  TUniqueId query_id;
  TUniqueId op_secret;
  HS2_RETURN_IF_ERROR(return_val, THandleIdentifierToTUniqueId(
      request.operationHandle.operationId, &query_id, &op_secret),
      SQLSTATE_GENERAL_ERROR);

  shared_ptr<ClientRequestState> request_state = GetClientRequestState(query_id);
  if (UNLIKELY(request_state.get() == nullptr)) {
    // No handle was found
    HS2_RETURN_ERROR(return_val,
      Substitute("Invalid query handle: $0", PrintId(query_id)), SQLSTATE_GENERAL_ERROR);
  }

  // GetLog doesn't have an associated session handle, so we presume that this request
  // should keep alive the same session that orignated the query.
  ScopedSessionState session_handle(this);
  const TUniqueId session_id = request_state->session_id();
  HS2_RETURN_IF_ERROR(return_val,
      session_handle.WithSession(session_id, SecretArg::Operation(op_secret, query_id)),
      SQLSTATE_GENERAL_ERROR);

  stringstream ss;
  Coordinator* coord = request_state->GetCoordinator();
  if (coord != nullptr) {
    // Report progress
    ss << coord->progress().ToString() << "\n";
  }
  // Report the query status, if the query failed.
  {
    // Take the lock to ensure that if the client sees a query_state == EXCEPTION, it is
    // guaranteed to see the error query_status.
    lock_guard<mutex> l(*request_state->lock());
    Status query_status = request_state->query_status();
    DCHECK_EQ(request_state->operation_state() == TOperationState::ERROR_STATE,
        !query_status.ok());
    // If the query status is !ok, include the status error message at the top of the log.
    if (!query_status.ok()) ss << query_status.GetDetail();
  }

  // Report analysis errors
  ss << join(request_state->GetAnalysisWarnings(), "\n");
  // Report queuing reason if the admission controller queued the query.
  const string* admission_result = request_state->summary_profile()->GetInfoString(
      AdmissionController::PROFILE_INFO_KEY_ADMISSION_RESULT);
  if (admission_result != nullptr) {
    if (*admission_result == AdmissionController::PROFILE_INFO_VAL_QUEUED) {
      ss << AdmissionController::PROFILE_INFO_KEY_ADMISSION_RESULT << " : "
         << *admission_result << "\n";
      const string* queued_reason = request_state->summary_profile()->GetInfoString(
          AdmissionController::PROFILE_INFO_KEY_LAST_QUEUED_REASON);
      if (queued_reason != nullptr) {
        ss << AdmissionController::PROFILE_INFO_KEY_LAST_QUEUED_REASON << " : "
           << *queued_reason << "\n";
      }
    }
  }
  if (coord != nullptr) {
    // Report execution errors
    ss << coord->GetErrorLog();
  }
  return_val.log = ss.str();
  return_val.status.__set_statusCode(thrift::TStatusCode::SUCCESS_STATUS);
}

void ImpalaServer::GetExecSummary(TGetExecSummaryResp& return_val,
    const TGetExecSummaryReq& request) {
  TUniqueId session_id;
  TUniqueId secret;
  HS2_RETURN_IF_ERROR(return_val, THandleIdentifierToTUniqueId(
      request.sessionHandle.sessionId, &session_id, &secret),
      SQLSTATE_GENERAL_ERROR);
  ScopedSessionState session_handle(this);
  shared_ptr<SessionState> session;
  HS2_RETURN_IF_ERROR(return_val,
      session_handle.WithSession(
          session_id, SecretArg::Session(secret), &session),
      SQLSTATE_GENERAL_ERROR);
  if (session == NULL) {
    HS2_RETURN_ERROR(return_val, Substitute("Invalid session id: $0",
        PrintId(session_id)), SQLSTATE_GENERAL_ERROR);
  }

  TUniqueId query_id, op_secret;
  HS2_RETURN_IF_ERROR(return_val,
      THandleIdentifierToTUniqueId(
          request.operationHandle.operationId, &query_id, &op_secret),
      SQLSTATE_GENERAL_ERROR);

  TExecSummary summary;
  Status status = GetExecSummary(query_id, GetEffectiveUser(*session), &summary);
  HS2_RETURN_IF_ERROR(return_val, status, SQLSTATE_GENERAL_ERROR);
  return_val.__set_summary(summary);
  return_val.status.__set_statusCode(thrift::TStatusCode::SUCCESS_STATUS);
}

void ImpalaServer::GetRuntimeProfile(
    TGetRuntimeProfileResp& return_val, const TGetRuntimeProfileReq& request) {
  TUniqueId session_id;
  TUniqueId secret;
  HS2_RETURN_IF_ERROR(return_val, THandleIdentifierToTUniqueId(
      request.sessionHandle.sessionId, &session_id, &secret), SQLSTATE_GENERAL_ERROR);
  ScopedSessionState session_handle(this);
  shared_ptr<SessionState> session;
  HS2_RETURN_IF_ERROR(return_val,
      session_handle.WithSession(
          session_id, SecretArg::Session(secret), &session),
      SQLSTATE_GENERAL_ERROR);
  if (session == NULL) {
    HS2_RETURN_ERROR(return_val, Substitute("Invalid session id: $0",
        PrintId(session_id)), SQLSTATE_GENERAL_ERROR);
  }

  TUniqueId query_id, op_secret;
  HS2_RETURN_IF_ERROR(return_val, THandleIdentifierToTUniqueId(
      request.operationHandle.operationId, &query_id, &op_secret),
      SQLSTATE_GENERAL_ERROR);

  stringstream ss;
  TRuntimeProfileTree thrift_profile;
  rapidjson::Document json_profile(rapidjson::kObjectType);
  HS2_RETURN_IF_ERROR(return_val,
      GetRuntimeProfileOutput(query_id, GetEffectiveUser(*session), request.format, &ss,
          &thrift_profile, &json_profile),
      SQLSTATE_GENERAL_ERROR);
  if (request.format == TRuntimeProfileFormat::THRIFT) {
    return_val.__set_thrift_profile(thrift_profile);
  } else if (request.format == TRuntimeProfileFormat::JSON) {
    rapidjson::StringBuffer sb;
    rapidjson::PrettyWriter<rapidjson::StringBuffer> writer(sb);
    json_profile.Accept(writer);
    ss << sb.GetString();
    return_val.__set_profile(ss.str());
  } else {
    DCHECK(request.format == TRuntimeProfileFormat::STRING
        || request.format == TRuntimeProfileFormat::BASE64);
    return_val.__set_profile(ss.str());
  }
  return_val.status.__set_statusCode(thrift::TStatusCode::SUCCESS_STATUS);
}

void ImpalaServer::GetDelegationToken(TGetDelegationTokenResp& return_val,
    const TGetDelegationTokenReq& req) {
  return_val.status.__set_statusCode(thrift::TStatusCode::ERROR_STATUS);
  return_val.status.__set_errorMessage("Not implemented");
}

void ImpalaServer::CancelDelegationToken(TCancelDelegationTokenResp& return_val,
    const TCancelDelegationTokenReq& req) {
  return_val.status.__set_statusCode(thrift::TStatusCode::ERROR_STATUS);
  return_val.status.__set_errorMessage("Not implemented");
}

void ImpalaServer::RenewDelegationToken(TRenewDelegationTokenResp& return_val,
    const TRenewDelegationTokenReq& req) {
  return_val.status.__set_statusCode(thrift::TStatusCode::ERROR_STATUS);
  return_val.status.__set_errorMessage("Not implemented");
}

void ImpalaServer::AddSessionToConnection(
    const TUniqueId& session_id, SessionState* session) {
  const TUniqueId& connection_id = ThriftServer::GetThreadConnectionId();
  {
    boost::lock_guard<boost::mutex> l(connection_to_sessions_map_lock_);
    connection_to_sessions_map_[connection_id].insert(session_id);
  }

  boost::lock_guard<boost::mutex> session_lock(session->lock);
  if (session->connections.empty()) {
    // This session was previously disconnected but now has an associated
    // connection. It should no longer be considered for the disconnected timeout.
    UnregisterSessionTimeout(FLAGS_disconnected_session_timeout);
  }
  session->connections.insert(connection_id);
}

void ImpalaServer::PingImpalaHS2Service(TPingImpalaHS2ServiceResp& return_val,
    const TPingImpalaHS2ServiceReq& req) {
  VLOG_QUERY << "PingImpalaHS2Service(): request=" << ThriftDebugString(req);
  TUniqueId session_id;
  TUniqueId secret;
  HS2_RETURN_IF_ERROR(return_val,
      THandleIdentifierToTUniqueId(req.sessionHandle.sessionId, &session_id, &secret),
      SQLSTATE_GENERAL_ERROR);
  ScopedSessionState session_handle(this);
  shared_ptr<SessionState> session;
  HS2_RETURN_IF_ERROR(return_val,
      session_handle.WithSession(session_id, SecretArg::Session(secret), &session),
      SQLSTATE_GENERAL_ERROR);
  if (session == NULL) {
    HS2_RETURN_ERROR(return_val,
        Substitute("Invalid session id: $0", PrintId(session_id)),
        SQLSTATE_GENERAL_ERROR);
  }

  return_val.__set_version(GetVersionString(true));
  return_val.__set_webserver_address(ExecEnv::GetInstance()->webserver()->url());
  VLOG_RPC << "PingImpalaHS2Service(): return_val=" << ThriftDebugString(return_val);
}
}