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fix for code review comments

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src/brpc/policy/weighted_round_robin_load_balancer.cpp
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// Copyright (c) 2018 Iqiyi, Inc.
//
// 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.
// Authors: Daojin Cai (caidaojin@qiyi.com)
#include "butil/fast_rand.h"
#include "brpc/socket.h"
#include "brpc/policy/weighted_round_robin_load_balancer.h"
#include "butil/strings/string_number_conversions.h"
namespace brpc {
namespace policy {
bool IsCoprime(uint32_t num1, uint32_t num2) {
uint32_t temp;
if (num1 < num2) {
temp = num1;
num1 = num2;
num2 = temp;
}
while (true) {
temp = num1 % num2;
if (temp == 0) {
break;
} else {
num1 = num2;
num2 = temp;
}
}
return num2 == 1;
}
bool WeightedRoundRobinLoadBalancer::Add(Servers& bg, const ServerId& id) {
if (bg.server_list.capacity() < 128) {
bg.server_list.reserve(128);
}
int weight = 0;
if (butil::StringToInt(id.tag, &weight) && weight > 0) {
bool insert_server =
bg.server_map.emplace(id.id, bg.server_list.size()).second;
if (insert_server) {
bg.server_list.emplace_back(id.id, weight);
bg.weight_sum += weight;
return true;
}
} else {
LOG(ERROR) << "Invalid weight is set: " << id.tag;
}
return false;
}
bool WeightedRoundRobinLoadBalancer::Remove(Servers& bg, const ServerId& id) {
auto iter = bg.server_map.find(id.id);
if (iter != bg.server_map.end()) {
const size_t index = iter->second;
bg.weight_sum -= bg.server_list[index].second;
bg.server_list[index] = bg.server_list.back();
bg.server_map[bg.server_list[index].first] = index;
bg.server_list.pop_back();
bg.server_map.erase(iter);
return true;
}
return false;
}
size_t WeightedRoundRobinLoadBalancer::BatchAdd(
Servers& bg, const std::vector<ServerId>& servers) {
size_t count = 0;
for (size_t i = 0; i < servers.size(); ++i) {
count += !!Add(bg, servers[i]);
}
return count;
}
size_t WeightedRoundRobinLoadBalancer::BatchRemove(
Servers& bg, const std::vector<ServerId>& servers) {
size_t count = 0;
for (size_t i = 0; i < servers.size(); ++i) {
count += !!Remove(bg, servers[i]);
}
return count;
}
bool WeightedRoundRobinLoadBalancer::AddServer(const ServerId& id) {
return _db_servers.Modify(Add, id);
}
bool WeightedRoundRobinLoadBalancer::RemoveServer(const ServerId& id) {
return _db_servers.Modify(Remove, id);
}
size_t WeightedRoundRobinLoadBalancer::AddServersInBatch(
const std::vector<ServerId>& servers) {
const size_t n = _db_servers.Modify(BatchAdd, servers);
LOG_IF(ERROR, n != servers.size())
<< "Fail to AddServersInBatch, expected " << servers.size()
<< " actually " << n;
return n;
}
size_t WeightedRoundRobinLoadBalancer::RemoveServersInBatch(
const std::vector<ServerId>& servers) {
const size_t n = _db_servers.Modify(BatchRemove, servers);
LOG_IF(ERROR, n != servers.size())
<< "Fail to RemoveServersInBatch, expected " << servers.size()
<< " actually " << n;
return n;
}
int WeightedRoundRobinLoadBalancer::SelectServer(const SelectIn& in, SelectOut* out) {
butil::DoublyBufferedData<Servers, TLS>::ScopedPtr s;
if (_db_servers.Read(&s) != 0) {
return ENOMEM;
}
if (s->server_list.empty()) {
return ENODATA;
}
TLS& tls = s.tls();
if (tls.IsNeededCaculateNewStride(s->weight_sum, s->server_list.size())) {
if (tls.stride == 0) {
tls.position = butil::fast_rand_less_than(s->server_list.size());
}
tls.stride = GetStride(s->weight_sum, s->server_list.size());
}
// If server list changed, the position may be out of range.
tls.position %= s->server_list.size();
// Check whether remain server was removed from server list.
if (tls.HasRemainServer() &&
s->server_map.find(tls.remain_server.first) == s->server_map.end()) {
tls.ResetRemainServer();
}
for ( uint32_t i = 0; i != tls.stride; ++i) {
int64_t best = GetBestServer(s->server_list, tls);
if (!ExcludedServers::IsExcluded(in.excluded, best)
&& Socket::Address(best, out->ptr) == 0
&& !(*out->ptr)->IsLogOff()) {
return 0;
}
}
return EHOSTDOWN;
}
int64_t WeightedRoundRobinLoadBalancer::GetBestServer(
const std::vector<std::pair<SocketId, int>>& server_list, TLS& tls) {
int64_t final_server = -1;
int stride = tls.stride;
int weight = 0;
while (stride > 0) {
if (tls.HasRemainServer()) {
weight = tls.remain_server.second;
if (weight <= stride) {
tls.ResetRemainServer();
} else {
tls.remain_server.second -= stride;
}
} else {
weight = server_list[tls.position].second;
if (weight > stride) {
tls.SetRemainServer(server_list[tls.position].first,
weight - stride);
}
tls.UpdatePosition(server_list.size());
}
stride -= weight;
}
if (tls.HasRemainServer()) {
final_server = tls.remain_server.first;
} else {
size_t index = tls.position == 0 ? server_list.size() - 1
: tls.position - 1;
final_server = server_list[index].first;
}
return final_server;
}
uint32_t WeightedRoundRobinLoadBalancer::GetStride(
const uint32_t weight_sum, const uint32_t num) {
uint32_t average_weight = weight_sum / num;
// The stride is the first number which is greater than or equal to
// average weight and coprime to weight_sum.
while (!IsCoprime(weight_sum, average_weight)) {
++average_weight;
}
return average_weight;
}
LoadBalancer* WeightedRoundRobinLoadBalancer::New() const {
return new (std::nothrow) WeightedRoundRobinLoadBalancer;
}
void WeightedRoundRobinLoadBalancer::Destroy() {
delete this;
}
void WeightedRoundRobinLoadBalancer::Describe(
std::ostream &os, const DescribeOptions& options) {
if (!options.verbose) {
os << "wrr";
return;
}
os << "WeightedRoundRobin{";
butil::DoublyBufferedData<Servers, TLS>::ScopedPtr s;
if (_db_servers.Read(&s) != 0) {
os << "fail to read _db_servers";
} else {
os << "n=" << s->server_list.size() << ':';
for (const auto& server : s->server_list) {
os << ' ' << server.first << '(' << server.second << ')';
}
}
os << '}';
}
} // namespace policy
} // namespace brpc
// Copyright (c) 2018 Iqiyi, Inc.
//
// 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.
// Authors: Daojin Cai (caidaojin@qiyi.com)
#include <algorithm>
#include "butil/fast_rand.h"
#include "brpc/socket.h"
#include "brpc/policy/weighted_round_robin_load_balancer.h"
#include "butil/strings/string_number_conversions.h"
namespace brpc {
namespace policy {
const std::vector<uint32_t> prime_stride = {
2,3,5,11,17,29,47,71,107,137,163,251,307,379,569,683,
857,1289,1543,1949,2617,2927,3407,4391,6599,9901,14867,
22303,33457,50207,75323,112997,169501,254257,381389,572087};
bool IsCoprime(uint32_t num1, uint32_t num2) {
uint32_t temp;
if (num1 < num2) {
temp = num1;
num1 = num2;
num2 = temp;
}
while (true) {
temp = num1 % num2;
if (temp == 0) {
break;
} else {
num1 = num2;
num2 = temp;
}
}
return num2 == 1;
}
bool WeightedRoundRobinLoadBalancer::Add(Servers& bg, const ServerId& id) {
if (bg.server_list.capacity() < 128) {
bg.server_list.reserve(128);
}
int weight = 0;
if (butil::StringToInt(id.tag, &weight) && weight > 0) {
bool insert_server =
bg.server_map.emplace(id.id, bg.server_list.size()).second;
if (insert_server) {
bg.server_list.emplace_back(id.id, weight);
bg.weight_sum += weight;
return true;
}
} else {
LOG(ERROR) << "Invalid weight is set: " << id.tag;
}
return false;
}
bool WeightedRoundRobinLoadBalancer::Remove(Servers& bg, const ServerId& id) {
auto iter = bg.server_map.find(id.id);
if (iter != bg.server_map.end()) {
const size_t index = iter->second;
bg.weight_sum -= bg.server_list[index].weight;
bg.server_list[index] = bg.server_list.back();
bg.server_map[bg.server_list[index].id] = index;
bg.server_list.pop_back();
bg.server_map.erase(iter);
return true;
}
return false;
}
size_t WeightedRoundRobinLoadBalancer::BatchAdd(
Servers& bg, const std::vector<ServerId>& servers) {
size_t count = 0;
for (size_t i = 0; i < servers.size(); ++i) {
count += !!Add(bg, servers[i]);
}
return count;
}
size_t WeightedRoundRobinLoadBalancer::BatchRemove(
Servers& bg, const std::vector<ServerId>& servers) {
size_t count = 0;
for (size_t i = 0; i < servers.size(); ++i) {
count += !!Remove(bg, servers[i]);
}
return count;
}
bool WeightedRoundRobinLoadBalancer::AddServer(const ServerId& id) {
return _db_servers.Modify(Add, id);
}
bool WeightedRoundRobinLoadBalancer::RemoveServer(const ServerId& id) {
return _db_servers.Modify(Remove, id);
}
size_t WeightedRoundRobinLoadBalancer::AddServersInBatch(
const std::vector<ServerId>& servers) {
const size_t n = _db_servers.Modify(BatchAdd, servers);
LOG_IF(ERROR, n != servers.size())
<< "Fail to AddServersInBatch, expected " << servers.size()
<< " actually " << n;
return n;
}
size_t WeightedRoundRobinLoadBalancer::RemoveServersInBatch(
const std::vector<ServerId>& servers) {
const size_t n = _db_servers.Modify(BatchRemove, servers);
LOG_IF(ERROR, n != servers.size())
<< "Fail to RemoveServersInBatch, expected " << servers.size()
<< " actually " << n;
return n;
}
int WeightedRoundRobinLoadBalancer::SelectServer(const SelectIn& in, SelectOut* out) {
butil::DoublyBufferedData<Servers, TLS>::ScopedPtr s;
if (_db_servers.Read(&s) != 0) {
return ENOMEM;
}
if (s->server_list.empty()) {
return ENODATA;
}
TLS& tls = s.tls();
if (tls.IsNeededCaculateNewStride(s->weight_sum, s->server_list.size())) {
if (tls.stride == 0) {
tls.position = butil::fast_rand_less_than(s->server_list.size());
}
tls.stride = GetStride(s->weight_sum, s->server_list.size());
}
// If server list changed, the position may be out of range.
tls.position %= s->server_list.size();
// Check whether remain server was removed from server list.
if (tls.HasRemainServer() &&
tls.remain_server.id != s->server_list[tls.position].id) {
tls.ResetRemainServer();
}
for (uint32_t i = 0; i != tls.stride; ++i) {
int64_t server_id = GetServerInNextStride(s->server_list, tls);
if (!ExcludedServers::IsExcluded(in.excluded, server_id)
&& Socket::Address(server_id, out->ptr) == 0
&& !(*out->ptr)->IsLogOff()) {
return 0;
}
}
return EHOSTDOWN;
}
int64_t WeightedRoundRobinLoadBalancer::GetServerInNextStride(
const std::vector<Server>& server_list, TLS& tls) {
int64_t final_server = -1;
int stride = tls.stride;
if (tls.HasRemainServer()) {
final_server = tls.remain_server.id;
if (tls.remain_server.weight > stride) {
tls.remain_server.weight -= stride;
return final_server;
} else {
stride -= tls.remain_server.weight;
tls.ResetRemainServer();
tls.UpdatePosition(server_list.size());
}
}
while (stride > 0) {
final_server = server_list[tls.position].id;
if (server_list[tls.position].weight > stride) {
tls.SetRemainServer(server_list[tls.position].id,
server_list[tls.position].weight - stride);
return final_server;
}
stride -= server_list[tls.position].weight;
tls.UpdatePosition(server_list.size());
}
return final_server;
}
uint32_t WeightedRoundRobinLoadBalancer::GetStride(
const uint32_t weight_sum, const uint32_t num) {
uint32_t average_weight = weight_sum / num;
auto iter = std::lower_bound(prime_stride.begin(), prime_stride.end(),
average_weight);
while (iter != prime_stride.end()
&& !IsCoprime(weight_sum, *iter)) {
++iter;
}
CHECK(iter != prime_stride.end()) << "Failed to get stride";
return *iter > weight_sum ? *iter % weight_sum : *iter;
}
LoadBalancer* WeightedRoundRobinLoadBalancer::New() const {
return new (std::nothrow) WeightedRoundRobinLoadBalancer;
}
void WeightedRoundRobinLoadBalancer::Destroy() {
delete this;
}
void WeightedRoundRobinLoadBalancer::Describe(
std::ostream &os, const DescribeOptions& options) {
if (!options.verbose) {
os << "wrr";
return;
}
os << "WeightedRoundRobin{";
butil::DoublyBufferedData<Servers, TLS>::ScopedPtr s;
if (_db_servers.Read(&s) != 0) {
os << "fail to read _db_servers";
} else {
os << "n=" << s->server_list.size() << ':';
for (const auto& server : s->server_list) {
os << ' ' << server.id << '(' << server.weight << ')';
}
}
os << '}';
}
} // namespace policy
} // namespace brpc
src/brpc/policy/weighted_round_robin_load_balancer.h
View file @ 54df0863
......@@ -39,27 +39,31 @@ public:
void Describe(std::ostream&, const DescribeOptions& options);
private:
struct Server {
Server(SocketId s_id = 0, int s_w = 0): id(s_id), weight(s_w) {}
SocketId id;
int weight;
};
struct Servers {
// The value is configured weight for each server.
std::vector<std::pair<SocketId, int>> server_list;
std::vector<Server> server_list;
// The value is the index of the server in "server_list".
std::map<SocketId, size_t> server_map;
uint32_t weight_sum = 0;
};
struct TLS {
TLS(): remain_server(0, 0) { }
uint32_t position = 0;
uint32_t stride = 0;
std::pair<SocketId, int> remain_server;
Server remain_server;
bool HasRemainServer() const {
return remain_server.second != 0;
return remain_server.weight != 0;
}
void SetRemainServer(const SocketId id, const int weight) {
remain_server.first = id;
remain_server.second = weight;
remain_server.id = id;
remain_server.weight = weight;
}
void ResetRemainServer() {
remain_server.second = 0;
remain_server.weight = 0;
}
void UpdatePosition(const uint32_t size) {
++position;
......@@ -84,9 +88,8 @@ private:
static bool Remove(Servers& bg, const ServerId& id);
static size_t BatchAdd(Servers& bg, const std::vector<ServerId>& servers);
static size_t BatchRemove(Servers& bg, const std::vector<ServerId>& servers);
static int64_t GetBestServer(
const std::vector<std::pair<SocketId, int>>& server_list,
TLS& tls);
static int64_t GetServerInNextStride(const std::vector<Server>& server_list,
TLS& tls);
// Get a reasonable stride according to weights configured of servers.
static uint32_t GetStride(const uint32_t weight_sum, const uint32_t num);
......
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