Files
scylladb/db/commitlog/replay_position.hh
Calle Wilund ea38b223bd Commitlog: change the ID generation scheme
* Make it more like origin, i.e. based on wall clock time of app start
* Encode shard ID in the, RP segement ID, to ensure RP:s and segement names
  are unique per shard
2015-08-31 14:29:46 +02:00

81 lines
2.5 KiB
C++

/*
* 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.
*/
/*
* Modified by Cloudius Systems
* Copyright 2015 Cloudius Systems
*/
#pragma once
#include <stdint.h>
namespace db {
using segment_id_type = uint64_t;
using position_type = uint32_t;
struct replay_position {
static const constexpr size_t max_cpu_bits = 10; // 1024 cpus. should be enough for anyone
static const constexpr size_t max_ts_bits = 8 * sizeof(segment_id_type) - max_cpu_bits;
static const constexpr segment_id_type ts_mask = (segment_id_type(1) << max_ts_bits) - 1;
static const constexpr segment_id_type cpu_mask = ~ts_mask;
segment_id_type id;
position_type pos;
replay_position(segment_id_type i = 0, position_type p = 0)
: id(i), pos(p)
{}
replay_position(unsigned shard, segment_id_type i, position_type p = 0)
: id((segment_id_type(shard) << max_ts_bits) | i), pos(p)
{
if (i & cpu_mask) {
throw std::invalid_argument("base id overflow: " + std::to_string(i));
}
}
bool operator<(const replay_position & r) const {
return id < r.id ? true : (r.id < id ? false : pos < r.pos);
}
bool operator==(const replay_position & r) const {
return id == r.id && pos == r.pos;
}
bool operator!=(const replay_position & r) const {
return !(*this == r);
}
unsigned shard_id() const {
return unsigned(id >> max_ts_bits);
}
segment_id_type base_id() const {
return id & ts_mask;
}
replay_position base() const {
return replay_position(base_id(), pos);
}
template <typename Describer>
auto describe_type(Describer f) { return f(id, pos); }
};
std::ostream& operator<<(std::ostream& out, const replay_position& s);
}