1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
|
/*
*
* Copyright 2017 gRPC authors.
*
* 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.
*
*/
#include <grpc/support/port_platform.h>
#include "src/core/ext/filters/client_channel/retry_throttle.h"
#include <limits.h>
#include <string.h>
#include <grpc/support/alloc.h>
#include <grpc/support/atm.h>
#include <grpc/support/string_util.h>
#include <grpc/support/sync.h>
#include "src/core/lib/avl/avl.h"
namespace grpc_core {
namespace internal {
//
// ServerRetryThrottleData
//
ServerRetryThrottleData::ServerRetryThrottleData(
intptr_t max_milli_tokens, intptr_t milli_token_ratio,
ServerRetryThrottleData* old_throttle_data)
: max_milli_tokens_(max_milli_tokens),
milli_token_ratio_(milli_token_ratio) {
intptr_t initial_milli_tokens = max_milli_tokens;
// If there was a pre-existing entry for this server name, initialize
// the token count by scaling proportionately to the old data. This
// ensures that if we're already throttling retries on the old scale,
// we will start out doing the same thing on the new one.
if (old_throttle_data != nullptr) {
double token_fraction =
static_cast<intptr_t>(
gpr_atm_acq_load(&old_throttle_data->milli_tokens_)) /
static_cast<double>(old_throttle_data->max_milli_tokens_);
initial_milli_tokens =
static_cast<intptr_t>(token_fraction * max_milli_tokens);
}
gpr_atm_rel_store(&milli_tokens_, static_cast<gpr_atm>(initial_milli_tokens));
// If there was a pre-existing entry, mark it as stale and give it a
// pointer to the new entry, which is its replacement.
if (old_throttle_data != nullptr) {
Ref().release(); // Ref held by pre-existing entry.
gpr_atm_rel_store(&old_throttle_data->replacement_,
reinterpret_cast<gpr_atm>(this));
}
}
ServerRetryThrottleData::~ServerRetryThrottleData() {
ServerRetryThrottleData* replacement =
reinterpret_cast<ServerRetryThrottleData*>(
gpr_atm_acq_load(&replacement_));
if (replacement != nullptr) {
replacement->Unref();
}
}
void ServerRetryThrottleData::GetReplacementThrottleDataIfNeeded(
ServerRetryThrottleData** throttle_data) {
while (true) {
ServerRetryThrottleData* new_throttle_data =
reinterpret_cast<ServerRetryThrottleData*>(
gpr_atm_acq_load(&(*throttle_data)->replacement_));
if (new_throttle_data == nullptr) return;
*throttle_data = new_throttle_data;
}
}
bool ServerRetryThrottleData::RecordFailure() {
// First, check if we are stale and need to be replaced.
ServerRetryThrottleData* throttle_data = this;
GetReplacementThrottleDataIfNeeded(&throttle_data);
// We decrement milli_tokens by 1000 (1 token) for each failure.
const intptr_t new_value =
static_cast<intptr_t>(gpr_atm_no_barrier_clamped_add(
&throttle_data->milli_tokens_, static_cast<gpr_atm>(-1000),
static_cast<gpr_atm>(0),
static_cast<gpr_atm>(throttle_data->max_milli_tokens_)));
// Retries are allowed as long as the new value is above the threshold
// (max_milli_tokens / 2).
return new_value > throttle_data->max_milli_tokens_ / 2;
}
void ServerRetryThrottleData::RecordSuccess() {
// First, check if we are stale and need to be replaced.
ServerRetryThrottleData* throttle_data = this;
GetReplacementThrottleDataIfNeeded(&throttle_data);
// We increment milli_tokens by milli_token_ratio for each success.
gpr_atm_no_barrier_clamped_add(
&throttle_data->milli_tokens_,
static_cast<gpr_atm>(throttle_data->milli_token_ratio_),
static_cast<gpr_atm>(0),
static_cast<gpr_atm>(throttle_data->max_milli_tokens_));
}
//
// avl vtable for string -> server_retry_throttle_data map
//
namespace {
void* copy_server_name(void* key, void* unused) {
return gpr_strdup(static_cast<const char*>(key));
}
long compare_server_name(void* key1, void* key2, void* unused) {
return strcmp(static_cast<const char*>(key1), static_cast<const char*>(key2));
}
void destroy_server_retry_throttle_data(void* value, void* unused) {
ServerRetryThrottleData* throttle_data =
static_cast<ServerRetryThrottleData*>(value);
throttle_data->Unref();
}
void* copy_server_retry_throttle_data(void* value, void* unused) {
ServerRetryThrottleData* throttle_data =
static_cast<ServerRetryThrottleData*>(value);
return throttle_data->Ref().release();
}
void destroy_server_name(void* key, void* unused) { gpr_free(key); }
const grpc_avl_vtable avl_vtable = {
destroy_server_name, copy_server_name, compare_server_name,
destroy_server_retry_throttle_data, copy_server_retry_throttle_data};
} // namespace
//
// ServerRetryThrottleMap
//
static gpr_mu g_mu;
static grpc_avl g_avl;
void ServerRetryThrottleMap::Init() {
gpr_mu_init(&g_mu);
g_avl = grpc_avl_create(&avl_vtable);
}
void ServerRetryThrottleMap::Shutdown() {
gpr_mu_destroy(&g_mu);
grpc_avl_unref(g_avl, nullptr);
}
RefCountedPtr<ServerRetryThrottleData> ServerRetryThrottleMap::GetDataForServer(
const char* server_name, intptr_t max_milli_tokens,
intptr_t milli_token_ratio) {
RefCountedPtr<ServerRetryThrottleData> result;
gpr_mu_lock(&g_mu);
ServerRetryThrottleData* throttle_data =
static_cast<ServerRetryThrottleData*>(
grpc_avl_get(g_avl, const_cast<char*>(server_name), nullptr));
if (throttle_data == nullptr ||
throttle_data->max_milli_tokens() != max_milli_tokens ||
throttle_data->milli_token_ratio() != milli_token_ratio) {
// Entry not found, or found with old parameters. Create a new one.
result = MakeRefCounted<ServerRetryThrottleData>(
max_milli_tokens, milli_token_ratio, throttle_data);
g_avl = grpc_avl_add(g_avl, gpr_strdup(server_name),
result->Ref().release(), nullptr);
} else {
// Entry found. Return a new ref to it.
result = throttle_data->Ref();
}
gpr_mu_unlock(&g_mu);
return result;
}
} // namespace internal
} // namespace grpc_core
|
