Method TryQueryRetry

be/src/runtime/query-driver.cc:167–265

}

void QueryDriver::TryQueryRetry(
    ClientRequestState* client_request_state, Status* error, bool* was_retried) {
  DCHECK(error != nullptr);
  if (was_retried != nullptr) *was_retried = false;

  // Get the most recent query attempt, and retry it.
  const TUniqueId& query_id = client_request_state->query_id();
  DCHECK(client_request_state->schedule() != nullptr);

  DCHECK(exec_request_ != nullptr);
  if (exec_request_->query_options.retry_failed_queries) {
    lock_guard<mutex> l(*client_request_state->lock());

    if (client_request_state->stmt_type() != TStmtType::QUERY) {
      // Retrying DML queries would be useful but currently it is
      // buggy / untested (see IMPALA-10585).
      return;
    }

    // Queries can only be retried if no rows for the query have been fetched
    // (IMPALA-9225).
    if (client_request_state->fetched_rows()) {
      string err_msg = Substitute("Skipping retry of query_id=$0 because the client has "
                                  "already fetched some rows",
          PrintId(query_id));
      VLOG_QUERY << err_msg;
      error->AddDetail(err_msg);
      return;
    }

    // If a retry for the failed query has already been scheduled, don't retry it
    // again.
    if (client_request_state->WasRetried()) {
      return;
    }

    // Queries can only be retried once (IMPALA-9200).
    if (client_request_state->IsRetriedQuery()) {
      VLOG_QUERY << Substitute(
          "Skipping retry of query_id=$0 because it has already been retried",
          PrintId(query_id));
      // If query retries are enabled, but the max number of retries has been hit,
      // include the number of retries in the error message.
      error->AddDetail("Max retry limit was hit. Query was retried 1 time(s).");
      return;
    }

    const TUniqueId& query_id = client_request_state_->query_id();

    // Triggering a retry from the INITIALIZED phase is possible: the
    // cancellation thread pool can kill a query while it is in the INITIALIZATION phase.
    // Triggering a retry from the FINISHED phase is also possible: the retryable failure
    // happens after rows are available and before the client fetches any rows.
    ClientRequestState::ExecState exec_state = client_request_state_->exec_state();
    DCHECK(exec_state == ClientRequestState::ExecState::INITIALIZED
        || exec_state == ClientRequestState::ExecState::PENDING
        || exec_state == ClientRequestState::ExecState::RUNNING
        || exec_state == ClientRequestState::ExecState::FINISHED)