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Do not save service config in DNS resolver

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reviewable/pr18946/r2
Yash Tibrewal 6 years ago
parent 587ae4a2d9
commit aa0a26cdbc
2 changed files with 53 additions and 58 deletions
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  1. 101
      src/core/ext/filters/client_channel/resolver/dns/c_ares/dns_resolver_ares.cc
  2. 10
      test/cpp/end2end/service_config_end2end_test.cc

101
src/core/ext/filters/client_channel/resolver/dns/c_ares/dns_resolver_ares.cc
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@ -110,8 +110,6 @@ class AresDnsResolver : public Resolver {
UniquePtr<ServerAddressList> addresses_;
/// currently resolving service config
char* service_config_json_ = nullptr;
/// last valid service config
RefCountedPtr<ServiceConfig> saved_service_config_;
// has shutdown been initiated
bool shutdown_initiated_ = false;
// timeout in milliseconds for active DNS queries
@ -232,66 +230,93 @@ bool ValueInJsonArray(grpc_json* array, const char* value) {
char* ChooseServiceConfig(char* service_config_choice_json,
grpc_error** error) {
grpc_json* choices_json = grpc_json_parse_string(service_config_choice_json);
if (choices_json == nullptr || choices_json->type != GRPC_JSON_ARRAY) {
if (choices_json == nullptr) {
*error = GRPC_ERROR_CREATE_FROM_STATIC_STRING(
"cannot parse service config JSON string");
"Service Config JSON Parsing, error: could not parse");
return nullptr;
}
if (choices_json->type != GRPC_JSON_ARRAY) {
*error = GRPC_ERROR_CREATE_FROM_STATIC_STRING(
"Service Config Choices, error: should be of type array");
return nullptr;
}
char* service_config = nullptr;
InlinedVector<grpc_error*, 4> error_list;
bool found_choice = false; // have we found a choice?
for (grpc_json* choice = choices_json->child; choice != nullptr;
choice = choice->next) {
if (choice->type != GRPC_JSON_OBJECT) {
*error = GRPC_ERROR_CREATE_FROM_STATIC_STRING(
"cannot parse service config JSON string");
break;
error_list.push_back(GRPC_ERROR_CREATE_FROM_STATIC_STRING(
"Service Config Choice, error: should be of type object"));
continue;
}
grpc_json* service_config_json = nullptr;
bool not_choice = false; // has this choice been rejected?
for (grpc_json* field = choice->child; field != nullptr;
field = field->next) {
// Check client language, if specified.
if (strcmp(field->key, "clientLanguage") == 0) {
if (field->type != GRPC_JSON_ARRAY || !ValueInJsonArray(field, "c++")) {
service_config_json = nullptr;
break;
if (field->type != GRPC_JSON_ARRAY) {
error_list.push_back(GRPC_ERROR_CREATE_FROM_STATIC_STRING(
"field:clientLanguage error:should be of type array"));
} else if (!ValueInJsonArray(field, "c++")) {
not_choice = true;
}
}
// Check client hostname, if specified.
if (strcmp(field->key, "clientHostname") == 0) {
if (field->type != GRPC_JSON_ARRAY) {
error_list.push_back(GRPC_ERROR_CREATE_FROM_STATIC_STRING(
"field:clientHostname error:should be of type array"));
continue;
}
char* hostname = grpc_gethostname();
if (hostname == nullptr || field->type != GRPC_JSON_ARRAY ||
!ValueInJsonArray(field, hostname)) {
service_config_json = nullptr;
break;
if (hostname == nullptr || !ValueInJsonArray(field, hostname)) {
not_choice = true;
}
}
// Check percentage, if specified.
if (strcmp(field->key, "percentage") == 0) {
if (field->type != GRPC_JSON_NUMBER) {
service_config_json = nullptr;
break;
error_list.push_back(GRPC_ERROR_CREATE_FROM_STATIC_STRING(
"field:percentage error:should be of type number"));
continue;
}
int random_pct = rand() % 100;
int percentage;
if (sscanf(field->value, "%d", &percentage) != 1 ||
random_pct > percentage || percentage == 0) {
service_config_json = nullptr;
break;
if (sscanf(field->value, "%d", &percentage) != 1) {
error_list.push_back(GRPC_ERROR_CREATE_FROM_STATIC_STRING(
"field:percentage error:should be of type integer"));
continue;
}
if (random_pct > percentage || percentage == 0) {
not_choice = true;
}
}
// Save service config.
if (strcmp(field->key, "serviceConfig") == 0) {
if (field->type == GRPC_JSON_OBJECT) {
service_config_json = field;
} else {
error_list.push_back(GRPC_ERROR_CREATE_FROM_STATIC_STRING(
"field:serviceConfig error:should be of type object"));
}
}
}
if (service_config_json != nullptr) {
if (!found_choice && !not_choice && service_config_json != nullptr) {
service_config = grpc_json_dump_to_string(service_config_json, 0);
break;
found_choice = true;
}
}
grpc_json_destroy(choices_json);
return service_config;
if (error_list.empty()) {
return service_config;
} else {
gpr_free(service_config);
*error = GRPC_ERROR_CREATE_FROM_VECTOR("Service Config Choices Parser",
&error_list);
return nullptr;
}
}
void AresDnsResolver::OnResolvedLocked(void* arg, grpc_error* error) {
@ -308,38 +333,18 @@ void AresDnsResolver::OnResolvedLocked(void* arg, grpc_error* error) {
Result result;
result.addresses = std::move(*r->addresses_);
if (r->service_config_json_ != nullptr) {
grpc_error* service_config_error = GRPC_ERROR_NONE;
char* service_config_string =
ChooseServiceConfig(r->service_config_json_, &service_config_error);
char* service_config_string = ChooseServiceConfig(
r->service_config_json_, &result.service_config_error);
gpr_free(r->service_config_json_);
RefCountedPtr<ServiceConfig> new_service_config;
if (service_config_error == GRPC_ERROR_NONE &&
if (result.service_config_error == GRPC_ERROR_NONE &&
service_config_string != nullptr) {
GRPC_CARES_TRACE_LOG("resolver:%p selected service config choice: %s",
r, service_config_string);
new_service_config =
ServiceConfig::Create(service_config_string, &service_config_error);
result.service_config = ServiceConfig::Create(
service_config_string, &result.service_config_error);
}
gpr_free(service_config_string);
if (service_config_error == GRPC_ERROR_NONE) {
// Valid service config receivd
r->saved_service_config_ = std::move(new_service_config);
} else {
if (r->saved_service_config_ != nullptr) {
// Ignore the new service config error, since we have a previously
// saved service config
GRPC_ERROR_UNREF(service_config_error);
} else {
// No previously valid service config found.
// service_config_error is passed to the channel.
result.service_config_error = service_config_error;
}
}
} else {
// No service config received
r->saved_service_config_.reset();
}
result.service_config = r->saved_service_config_;
result.args = grpc_channel_args_copy(r->channel_args_);
r->result_handler()->ReturnResult(std::move(result));
r->addresses_.reset();

10
test/cpp/end2end/service_config_end2end_test.cc
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@ -201,16 +201,6 @@ class ServiceConfigEnd2endTest : public ::testing::Test {
response_generator_->SetResponse(result);
}
void SetNextResolutionUponError(const std::vector<int>& ports) {
grpc_core::ExecCtx exec_ctx;
response_generator_->SetReresolutionResponse(BuildFakeResults(ports));
}
void SetFailureOnReresolution() {
grpc_core::ExecCtx exec_ctx;
response_generator_->SetFailureOnReresolution();
}
std::vector<int> GetServersPorts(size_t start_index = 0) {
std::vector<int> ports;
for (size_t i = start_index; i < servers_.size(); ++i) {

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