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/*
*
* 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 "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"
//
// server_retry_throttle_data
//
struct grpc_server_retry_throttle_data {
gpr_refcount refs;
int max_milli_tokens;
int milli_token_ratio;
gpr_atm milli_tokens;
// A pointer to the replacement for this grpc_server_retry_throttle_data
// entry. If non-NULL, then this entry is stale and must not be used.
// We hold a reference to the replacement.
gpr_atm replacement;
};
static void get_replacement_throttle_data_if_needed(
grpc_server_retry_throttle_data** throttle_data) {
while (true) {
grpc_server_retry_throttle_data* new_throttle_data =
(grpc_server_retry_throttle_data*)gpr_atm_acq_load(
&(*throttle_data)->replacement);
if (new_throttle_data == nullptr) return;
*throttle_data = new_throttle_data;
}
}
bool grpc_server_retry_throttle_data_record_failure(
grpc_server_retry_throttle_data* throttle_data) {
// First, check if we are stale and need to be replaced.
get_replacement_throttle_data_if_needed(&throttle_data);
// We decrement milli_tokens by 1000 (1 token) for each failure.
const int new_value = (int)gpr_atm_no_barrier_clamped_add(
&throttle_data->milli_tokens, (gpr_atm)-1000, (gpr_atm)0,
(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 grpc_server_retry_throttle_data_record_success(
grpc_server_retry_throttle_data* throttle_data) {
// First, check if we are stale and need to be replaced.
get_replacement_throttle_data_if_needed(&throttle_data);
// We increment milli_tokens by milli_token_ratio for each success.
gpr_atm_no_barrier_clamped_add(
&throttle_data->milli_tokens, (gpr_atm)throttle_data->milli_token_ratio,
(gpr_atm)0, (gpr_atm)throttle_data->max_milli_tokens);
}
grpc_server_retry_throttle_data* grpc_server_retry_throttle_data_ref(
grpc_server_retry_throttle_data* throttle_data) {
gpr_ref(&throttle_data->refs);
return throttle_data;
}
void grpc_server_retry_throttle_data_unref(
grpc_server_retry_throttle_data* throttle_data) {
if (gpr_unref(&throttle_data->refs)) {
grpc_server_retry_throttle_data* replacement =
(grpc_server_retry_throttle_data*)gpr_atm_acq_load(
&throttle_data->replacement);
if (replacement != nullptr) {
grpc_server_retry_throttle_data_unref(replacement);
}
gpr_free(throttle_data);
}
}
static grpc_server_retry_throttle_data* grpc_server_retry_throttle_data_create(
int max_milli_tokens, int milli_token_ratio,
grpc_server_retry_throttle_data* old_throttle_data) {
grpc_server_retry_throttle_data* throttle_data =
(grpc_server_retry_throttle_data*)gpr_malloc(sizeof(*throttle_data));
memset(throttle_data, 0, sizeof(*throttle_data));
gpr_ref_init(&throttle_data->refs, 1);
throttle_data->max_milli_tokens = max_milli_tokens;
throttle_data->milli_token_ratio = milli_token_ratio;
int 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 =
(int)gpr_atm_acq_load(&old_throttle_data->milli_tokens) /
(double)old_throttle_data->max_milli_tokens;
initial_milli_tokens = (int)(token_fraction * max_milli_tokens);
}
gpr_atm_rel_store(&throttle_data->milli_tokens,
(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) {
grpc_server_retry_throttle_data_ref(throttle_data);
gpr_atm_rel_store(&old_throttle_data->replacement, (gpr_atm)throttle_data);
}
return throttle_data;
}
//
// avl vtable for string -> server_retry_throttle_data map
//
static void* copy_server_name(void* key, void* unused) {
return gpr_strdup((const char*)key);
}
static long compare_server_name(void* key1, void* key2, void* unused) {
return strcmp((const char*)key1, (const char*)key2);
}
static void destroy_server_retry_throttle_data(void* value, void* unused) {
grpc_server_retry_throttle_data* throttle_data =
(grpc_server_retry_throttle_data*)value;
grpc_server_retry_throttle_data_unref(throttle_data);
}
static void* copy_server_retry_throttle_data(void* value, void* unused) {
grpc_server_retry_throttle_data* throttle_data =
(grpc_server_retry_throttle_data*)value;
return grpc_server_retry_throttle_data_ref(throttle_data);
}
static void destroy_server_name(void* key, void* unused) { gpr_free(key); }
static 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};
//
// server_retry_throttle_map
//
static gpr_mu g_mu;
static grpc_avl g_avl;
void grpc_retry_throttle_map_init() {
gpr_mu_init(&g_mu);
g_avl = grpc_avl_create(&avl_vtable);
}
void grpc_retry_throttle_map_shutdown() {
gpr_mu_destroy(&g_mu);
grpc_avl_unref(g_avl, nullptr);
}
grpc_server_retry_throttle_data* grpc_retry_throttle_map_get_data_for_server(
const char* server_name, int max_milli_tokens, int milli_token_ratio) {
gpr_mu_lock(&g_mu);
grpc_server_retry_throttle_data* throttle_data =
(grpc_server_retry_throttle_data*)grpc_avl_get(g_avl, (char*)server_name,
nullptr);
if (throttle_data == nullptr) {
// Entry not found. Create a new one.
throttle_data = grpc_server_retry_throttle_data_create(
max_milli_tokens, milli_token_ratio, nullptr);
g_avl = grpc_avl_add(g_avl, (char*)server_name, throttle_data, nullptr);
} else {
if (throttle_data->max_milli_tokens != max_milli_tokens ||
throttle_data->milli_token_ratio != milli_token_ratio) {
// Entry found but with old parameters. Create a new one based on
// the original one.
throttle_data = grpc_server_retry_throttle_data_create(
max_milli_tokens, milli_token_ratio, throttle_data);
g_avl = grpc_avl_add(g_avl, (char*)server_name, throttle_data, nullptr);
} else {
// Entry found. Increase refcount.
grpc_server_retry_throttle_data_ref(throttle_data);
}
}
gpr_mu_unlock(&g_mu);
return throttle_data;
}
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