folly/folly/stats/DigestBuilder.h

/*
 * Copyright (c) Meta Platforms, Inc. and affiliates.
 *
 * Licensed 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.
 */

#pragma once

#include <memory>
#include <vector>

#include <folly/Memory.h>
#include <folly/SpinLock.h>

namespace folly {

/*
 * Stat digests, such as TDigest, can be expensive to merge. It is faster to
 * buffer writes and merge them in larger chunks. DigestBuilder buffers writes
 * to improve performance.
 *
 * Values are stored in a cpu local buffer. Hot stats will merge the cpu local
 * buffer into a cpu-local digest when the buffer size is reached.
 *
 * All methods in this class are thread safe, but it probably doesn't make sense
 * for multiple threads to call build simultaneously. A typical usage is to
 * buffer writes for a period of time, and then have one thread call build to
 * merge the buffer into some other DigestT instance.
 */
template <typename DigestT>
class DigestBuilder { … };

} // namespace folly

#include <folly/stats/DigestBuilder-inl.h>