Files
scylladb/alternator/consumed_capacity.cc
Nadav Har'El f23e796e76 alternator: fix typos in comments and variable names
Copilot found these typos in comments and variable name in alternator/,
so might as well fix them.

There are no functional changes in this patch.

Signed-off-by: Nadav Har'El <nyh@scylladb.com>

Closes scylladb/scylladb#28447
2026-02-02 19:16:43 +03:00

97 lines
3.4 KiB
C++

/*
* Copyright 2024-present ScyllaDB
*/
/*
* SPDX-License-Identifier: LicenseRef-ScyllaDB-Source-Available-1.0
*/
#include "consumed_capacity.hh"
#include "error.hh"
#include "utils/rjson.hh"
#include <fmt/format.h>
namespace alternator {
/*
* \brief DynamoDB counts read capacity in half-integers - a short
* eventually-consistent read is counted as 0.5 unit.
* Because we want our counter to be an integer, it counts half units.
* Both read and write counters count in these half-units, and should be
* multiply by 0.5 (HALF_UNIT_MULTIPLIER) to get the DynamoDB-compatible RCU or WCU numbers.
*/
static constexpr double HALF_UNIT_MULTIPLIER = 0.5;
static constexpr uint64_t KB = 1024ULL;
static constexpr uint64_t RCU_BLOCK_SIZE_LENGTH = 4*KB;
static constexpr uint64_t WCU_BLOCK_SIZE_LENGTH = 1*KB;
bool consumed_capacity_counter::should_add_capacity(const rjson::value& request) {
const rjson::value* return_consumed = rjson::find(request, "ReturnConsumedCapacity");
if (!return_consumed) {
return false;
}
if (!return_consumed->IsString()) {
throw api_error::validation("Non-string ReturnConsumedCapacity field in request");
}
std::string_view consumed = rjson::to_string_view(*return_consumed);
if (consumed == "INDEXES") {
throw api_error::validation("INDEXES consumed capacity is not supported");
}
if (consumed != "TOTAL") {
throw api_error::validation(fmt::format("Unknown consumed capacity {}", consumed));
}
return true;
}
void consumed_capacity_counter::add_consumed_capacity_to_response_if_needed(rjson::value& response) const noexcept {
if (_should_add_to_response) {
auto consumption = rjson::empty_object();
rjson::add(consumption, "CapacityUnits", get_consumed_capacity_units());
rjson::add(response, "ConsumedCapacity", std::move(consumption));
}
}
static uint64_t calculate_half_units(uint64_t unit_block_size, uint64_t total_bytes, bool is_quorum) {
uint64_t half_units = (total_bytes + unit_block_size -1) / unit_block_size; //divide by unit_block_size and round up
if (is_quorum) {
half_units *= 2;
}
return half_units;
}
rcu_consumed_capacity_counter::rcu_consumed_capacity_counter(const rjson::value& request, bool is_quorum) :
consumed_capacity_counter(should_add_capacity(request)),_is_quorum(is_quorum) {
}
uint64_t rcu_consumed_capacity_counter::get_half_units(uint64_t total_bytes, bool is_quorum) noexcept {
return calculate_half_units(RCU_BLOCK_SIZE_LENGTH, total_bytes, is_quorum);
}
uint64_t rcu_consumed_capacity_counter::get_half_units() const noexcept {
return get_half_units(_total_bytes, _is_quorum);
}
uint64_t wcu_consumed_capacity_counter::get_half_units() const noexcept {
return calculate_half_units(WCU_BLOCK_SIZE_LENGTH, _total_bytes, true);
}
uint64_t wcu_consumed_capacity_counter::get_units(uint64_t total_bytes) noexcept {
return calculate_half_units(WCU_BLOCK_SIZE_LENGTH, total_bytes, true) * HALF_UNIT_MULTIPLIER;
}
wcu_consumed_capacity_counter::wcu_consumed_capacity_counter(const rjson::value& request) :
consumed_capacity_counter(should_add_capacity(request)) {
}
consumed_capacity_counter& consumed_capacity_counter::operator +=(uint64_t units) {
_total_bytes += units;
return *this;
}
double consumed_capacity_counter::get_consumed_capacity_units() const noexcept {
return get_half_units() * HALF_UNIT_MULTIPLIER;
}
}