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// Copyright 2022 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/lib/experiments/config.h"
#include <string.h>
#include <algorithm>
#include <atomic>
#include <util/generic/string.h>
#include <util/string/cast.h>
#include "y_absl/strings/ascii.h"
#include "y_absl/strings/str_cat.h"
#include "y_absl/strings/str_split.h"
#include "y_absl/strings/string_view.h"
#include <grpc/support/log.h>
#include "src/core/lib/config/config_vars.h"
#include "src/core/lib/experiments/experiments.h"
#include "src/core/lib/gprpp/crash.h" // IWYU pragma: keep
#include "src/core/lib/gprpp/no_destruct.h"
#ifndef GRPC_EXPERIMENTS_ARE_FINAL
namespace grpc_core {
namespace {
struct Experiments {
bool enabled[kNumExperiments];
};
struct ForcedExperiment {
bool forced = false;
bool value;
};
ForcedExperiment g_forced_experiments[kNumExperiments];
std::atomic<bool> g_loaded;
GPR_ATTRIBUTE_NOINLINE Experiments LoadExperimentsFromConfigVariable() {
GPR_ASSERT(g_loaded.exchange(true, std::memory_order_relaxed) == false);
// Set defaults from metadata.
Experiments experiments;
for (size_t i = 0; i < kNumExperiments; i++) {
if (!g_forced_experiments[i].forced) {
experiments.enabled[i] = g_experiment_metadata[i].default_value;
} else {
experiments.enabled[i] = g_forced_experiments[i].value;
}
}
// For each comma-separated experiment in the global config:
for (auto experiment : y_absl::StrSplit(
y_absl::string_view(ConfigVars::Get().Experiments()), ',')) {
// Strip whitespace.
experiment = y_absl::StripAsciiWhitespace(experiment);
// Handle ",," without crashing.
if (experiment.empty()) continue;
// Enable unless prefixed with '-' (=> disable).
bool enable = true;
if (experiment[0] == '-') {
enable = false;
experiment.remove_prefix(1);
}
// See if we can find the experiment in the list in this binary.
bool found = false;
for (size_t i = 0; i < kNumExperiments; i++) {
if (experiment == g_experiment_metadata[i].name) {
experiments.enabled[i] = enable;
found = true;
break;
}
}
// If not found log an error, but don't take any other action.
// Allows us an easy path to disabling experiments.
if (!found) {
gpr_log(GPR_ERROR, "Unknown experiment: %s",
TString(experiment).c_str());
}
}
return experiments;
}
} // namespace
bool IsExperimentEnabled(size_t experiment_id) {
// One time initialization:
static const NoDestruct<Experiments> experiments{
LoadExperimentsFromConfigVariable()};
// Normal path: just return the value;
return experiments->enabled[experiment_id];
}
void PrintExperimentsList() {
size_t max_experiment_length = 0;
for (size_t i = 0; i < kNumExperiments; i++) {
max_experiment_length =
std::max(max_experiment_length, strlen(g_experiment_metadata[i].name));
}
for (size_t i = 0; i < kNumExperiments; i++) {
gpr_log(GPR_DEBUG, "%s",
y_absl::StrCat(
"gRPC EXPERIMENT ", g_experiment_metadata[i].name,
TString(max_experiment_length -
strlen(g_experiment_metadata[i].name) + 1,
' '),
IsExperimentEnabled(i) ? "ON " : "OFF", " (default:",
g_experiment_metadata[i].default_value ? "ON" : "OFF",
g_forced_experiments[i].forced
? y_absl::StrCat(" force:",
g_forced_experiments[i].value ? "ON" : "OFF")
: TString(),
")")
.c_str());
}
}
void ForceEnableExperiment(y_absl::string_view experiment, bool enable) {
GPR_ASSERT(g_loaded.load(std::memory_order_relaxed) == false);
for (size_t i = 0; i < kNumExperiments; i++) {
if (g_experiment_metadata[i].name != experiment) continue;
if (g_forced_experiments[i].forced) {
GPR_ASSERT(g_forced_experiments[i].value == enable);
} else {
g_forced_experiments[i].forced = true;
g_forced_experiments[i].value = enable;
}
return;
}
gpr_log(GPR_INFO, "gRPC EXPERIMENT %s not found to force %s",
TString(experiment).c_str(), enable ? "enable" : "disable");
}
} // namespace grpc_core
#else
namespace grpc_core {
void PrintExperimentsList() {}
void ForceEnableExperiment(y_absl::string_view experiment_name, bool) {
Crash(y_absl::StrCat("ForceEnableExperiment(\"", experiment_name,
"\") called in final build"));
}
} // namespace grpc_core
#endif
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