| // |
| // Copyright 2015 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/config/core_configuration.h" |
| |
| #if GRPC_ARES == 1 |
| |
| #include <limits.h> |
| #include <stdio.h> |
| #include <string.h> |
| |
| #include <address_sorting/address_sorting.h> |
| |
| #include "absl/container/inlined_vector.h" |
| #include "absl/strings/str_cat.h" |
| |
| #include <grpc/support/alloc.h> |
| #include <grpc/support/string_util.h> |
| |
| #include "src/core/ext/filters/client_channel/http_connect_handshaker.h" |
| #include "src/core/ext/filters/client_channel/lb_policy/grpclb/grpclb_balancer_addresses.h" |
| #include "src/core/ext/filters/client_channel/lb_policy_registry.h" |
| #include "src/core/ext/filters/client_channel/resolver/dns/c_ares/grpc_ares_wrapper.h" |
| #include "src/core/ext/filters/client_channel/resolver/dns/dns_resolver_selection.h" |
| #include "src/core/lib/backoff/backoff.h" |
| #include "src/core/lib/channel/channel_args.h" |
| #include "src/core/lib/gpr/string.h" |
| #include "src/core/lib/gprpp/manual_constructor.h" |
| #include "src/core/lib/iomgr/gethostname.h" |
| #include "src/core/lib/iomgr/resolve_address.h" |
| #include "src/core/lib/iomgr/timer.h" |
| #include "src/core/lib/iomgr/work_serializer.h" |
| #include "src/core/lib/json/json.h" |
| #include "src/core/lib/resolver/resolver_registry.h" |
| #include "src/core/lib/resolver/server_address.h" |
| #include "src/core/lib/service_config/service_config.h" |
| #include "src/core/lib/transport/error_utils.h" |
| |
| #define GRPC_DNS_INITIAL_CONNECT_BACKOFF_SECONDS 1 |
| #define GRPC_DNS_RECONNECT_BACKOFF_MULTIPLIER 1.6 |
| #define GRPC_DNS_RECONNECT_MAX_BACKOFF_SECONDS 120 |
| #define GRPC_DNS_RECONNECT_JITTER 0.2 |
| |
| namespace grpc_core { |
| |
| namespace { |
| |
| class AresClientChannelDNSResolver : public Resolver { |
| public: |
| explicit AresClientChannelDNSResolver(ResolverArgs args); |
| |
| void StartLocked() override; |
| |
| void RequestReresolutionLocked() override; |
| |
| void ResetBackoffLocked() override; |
| |
| void ShutdownLocked() override; |
| |
| private: |
| ~AresClientChannelDNSResolver() override; |
| |
| void MaybeStartResolvingLocked(); |
| void StartResolvingLocked(); |
| |
| static void OnNextResolution(void* arg, grpc_error_handle error); |
| static void OnResolved(void* arg, grpc_error_handle error); |
| void OnNextResolutionLocked(grpc_error_handle error); |
| void OnResolvedLocked(grpc_error_handle error); |
| |
| /// DNS server to use (if not system default) |
| std::string dns_server_; |
| /// name to resolve (usually the same as target_name) |
| std::string name_to_resolve_; |
| /// channel args |
| grpc_channel_args* channel_args_; |
| std::shared_ptr<WorkSerializer> work_serializer_; |
| std::unique_ptr<ResultHandler> result_handler_; |
| /// pollset_set to drive the name resolution process |
| grpc_pollset_set* interested_parties_; |
| |
| /// whether to request the service config |
| bool request_service_config_; |
| // whether or not to enable SRV DNS queries |
| bool enable_srv_queries_; |
| // timeout in milliseconds for active DNS queries |
| int query_timeout_ms_; |
| /// min interval between DNS requests |
| grpc_millis min_time_between_resolutions_; |
| |
| /// closures used by the work_serializer |
| grpc_closure on_next_resolution_; |
| grpc_closure on_resolved_; |
| /// are we currently resolving? |
| bool resolving_ = false; |
| /// the pending resolving request |
| grpc_ares_request* pending_request_ = nullptr; |
| /// next resolution timer |
| bool have_next_resolution_timer_ = false; |
| grpc_timer next_resolution_timer_; |
| /// timestamp of last DNS request |
| grpc_millis last_resolution_timestamp_ = -1; |
| /// retry backoff state |
| BackOff backoff_; |
| /// currently resolving backend addresses |
| std::unique_ptr<ServerAddressList> addresses_; |
| /// currently resolving balancer addresses |
| std::unique_ptr<ServerAddressList> balancer_addresses_; |
| /// currently resolving service config |
| char* service_config_json_ = nullptr; |
| // has shutdown been initiated |
| bool shutdown_initiated_ = false; |
| }; |
| |
| AresClientChannelDNSResolver::AresClientChannelDNSResolver(ResolverArgs args) |
| : dns_server_(args.uri.authority()), |
| name_to_resolve_(absl::StripPrefix(args.uri.path(), "/")), |
| channel_args_(grpc_channel_args_copy(args.args)), |
| work_serializer_(std::move(args.work_serializer)), |
| result_handler_(std::move(args.result_handler)), |
| interested_parties_(args.pollset_set), |
| request_service_config_(!grpc_channel_args_find_bool( |
| channel_args_, GRPC_ARG_SERVICE_CONFIG_DISABLE_RESOLUTION, true)), |
| enable_srv_queries_(grpc_channel_args_find_bool( |
| channel_args_, GRPC_ARG_DNS_ENABLE_SRV_QUERIES, false)), |
| query_timeout_ms_(grpc_channel_args_find_integer( |
| channel_args_, GRPC_ARG_DNS_ARES_QUERY_TIMEOUT_MS, |
| {GRPC_DNS_ARES_DEFAULT_QUERY_TIMEOUT_MS, 0, INT_MAX})), |
| min_time_between_resolutions_(grpc_channel_args_find_integer( |
| channel_args_, GRPC_ARG_DNS_MIN_TIME_BETWEEN_RESOLUTIONS_MS, |
| {1000 * 30, 0, INT_MAX})), |
| backoff_( |
| BackOff::Options() |
| .set_initial_backoff(GRPC_DNS_INITIAL_CONNECT_BACKOFF_SECONDS * |
| 1000) |
| .set_multiplier(GRPC_DNS_RECONNECT_BACKOFF_MULTIPLIER) |
| .set_jitter(GRPC_DNS_RECONNECT_JITTER) |
| .set_max_backoff(GRPC_DNS_RECONNECT_MAX_BACKOFF_SECONDS * 1000)) { |
| // Closure initialization. |
| GRPC_CLOSURE_INIT(&on_next_resolution_, OnNextResolution, this, |
| grpc_schedule_on_exec_ctx); |
| GRPC_CLOSURE_INIT(&on_resolved_, OnResolved, this, grpc_schedule_on_exec_ctx); |
| } |
| |
| AresClientChannelDNSResolver::~AresClientChannelDNSResolver() { |
| GRPC_CARES_TRACE_LOG("resolver:%p destroying AresClientChannelDNSResolver", |
| this); |
| grpc_channel_args_destroy(channel_args_); |
| } |
| |
| void AresClientChannelDNSResolver::StartLocked() { |
| GRPC_CARES_TRACE_LOG( |
| "resolver:%p AresClientChannelDNSResolver::StartLocked() is called.", |
| this); |
| MaybeStartResolvingLocked(); |
| } |
| |
| void AresClientChannelDNSResolver::RequestReresolutionLocked() { |
| if (!resolving_) { |
| MaybeStartResolvingLocked(); |
| } |
| } |
| |
| void AresClientChannelDNSResolver::ResetBackoffLocked() { |
| if (have_next_resolution_timer_) { |
| grpc_timer_cancel(&next_resolution_timer_); |
| } |
| backoff_.Reset(); |
| } |
| |
| void AresClientChannelDNSResolver::ShutdownLocked() { |
| shutdown_initiated_ = true; |
| if (have_next_resolution_timer_) { |
| grpc_timer_cancel(&next_resolution_timer_); |
| } |
| if (pending_request_ != nullptr) { |
| grpc_cancel_ares_request(pending_request_); |
| } |
| } |
| |
| void AresClientChannelDNSResolver::OnNextResolution(void* arg, |
| grpc_error_handle error) { |
| AresClientChannelDNSResolver* r = |
| static_cast<AresClientChannelDNSResolver*>(arg); |
| (void)GRPC_ERROR_REF(error); // ref owned by lambda |
| r->work_serializer_->Run([r, error]() { r->OnNextResolutionLocked(error); }, |
| DEBUG_LOCATION); |
| } |
| |
| void AresClientChannelDNSResolver::OnNextResolutionLocked( |
| grpc_error_handle error) { |
| GRPC_CARES_TRACE_LOG( |
| "resolver:%p re-resolution timer fired. error: %s. shutdown_initiated_: " |
| "%d", |
| this, grpc_error_std_string(error).c_str(), shutdown_initiated_); |
| have_next_resolution_timer_ = false; |
| if (error == GRPC_ERROR_NONE && !shutdown_initiated_) { |
| if (!resolving_) { |
| GRPC_CARES_TRACE_LOG( |
| "resolver:%p start resolving due to re-resolution timer", this); |
| StartResolvingLocked(); |
| } |
| } |
| Unref(DEBUG_LOCATION, "next_resolution_timer"); |
| GRPC_ERROR_UNREF(error); |
| } |
| |
| bool ValueInJsonArray(const Json::Array& array, const char* value) { |
| for (const Json& entry : array) { |
| if (entry.type() == Json::Type::STRING && entry.string_value() == value) { |
| return true; |
| } |
| } |
| return false; |
| } |
| |
| std::string ChooseServiceConfig(char* service_config_choice_json, |
| grpc_error_handle* error) { |
| Json json = Json::Parse(service_config_choice_json, error); |
| if (*error != GRPC_ERROR_NONE) return ""; |
| if (json.type() != Json::Type::ARRAY) { |
| *error = GRPC_ERROR_CREATE_FROM_STATIC_STRING( |
| "Service Config Choices, error: should be of type array"); |
| return ""; |
| } |
| const Json* service_config = nullptr; |
| absl::InlinedVector<grpc_error_handle, 4> error_list; |
| for (const Json& choice : json.array_value()) { |
| if (choice.type() != Json::Type::OBJECT) { |
| error_list.push_back(GRPC_ERROR_CREATE_FROM_STATIC_STRING( |
| "Service Config Choice, error: should be of type object")); |
| continue; |
| } |
| // Check client language, if specified. |
| auto it = choice.object_value().find("clientLanguage"); |
| if (it != choice.object_value().end()) { |
| if (it->second.type() != Json::Type::ARRAY) { |
| error_list.push_back(GRPC_ERROR_CREATE_FROM_STATIC_STRING( |
| "field:clientLanguage error:should be of type array")); |
| } else if (!ValueInJsonArray(it->second.array_value(), "c++")) { |
| continue; |
| } |
| } |
| // Check client hostname, if specified. |
| it = choice.object_value().find("clientHostname"); |
| if (it != choice.object_value().end()) { |
| if (it->second.type() != Json::Type::ARRAY) { |
| error_list.push_back(GRPC_ERROR_CREATE_FROM_STATIC_STRING( |
| "field:clientHostname error:should be of type array")); |
| } else { |
| char* hostname = grpc_gethostname(); |
| if (hostname == nullptr || |
| !ValueInJsonArray(it->second.array_value(), hostname)) { |
| continue; |
| } |
| } |
| } |
| // Check percentage, if specified. |
| it = choice.object_value().find("percentage"); |
| if (it != choice.object_value().end()) { |
| if (it->second.type() != Json::Type::NUMBER) { |
| error_list.push_back(GRPC_ERROR_CREATE_FROM_STATIC_STRING( |
| "field:percentage error:should be of type number")); |
| } else { |
| int random_pct = rand() % 100; |
| int percentage; |
| if (sscanf(it->second.string_value().c_str(), "%d", &percentage) != 1) { |
| error_list.push_back(GRPC_ERROR_CREATE_FROM_STATIC_STRING( |
| "field:percentage error:should be of type integer")); |
| } else if (random_pct > percentage || percentage == 0) { |
| continue; |
| } |
| } |
| } |
| // Found service config. |
| it = choice.object_value().find("serviceConfig"); |
| if (it == choice.object_value().end()) { |
| error_list.push_back(GRPC_ERROR_CREATE_FROM_STATIC_STRING( |
| "field:serviceConfig error:required field missing")); |
| } else if (it->second.type() != Json::Type::OBJECT) { |
| error_list.push_back(GRPC_ERROR_CREATE_FROM_STATIC_STRING( |
| "field:serviceConfig error:should be of type object")); |
| } else if (service_config == nullptr) { |
| service_config = &it->second; |
| } |
| } |
| if (!error_list.empty()) { |
| service_config = nullptr; |
| *error = GRPC_ERROR_CREATE_FROM_VECTOR("Service Config Choices Parser", |
| &error_list); |
| } |
| if (service_config == nullptr) return ""; |
| return service_config->Dump(); |
| } |
| |
| void AresClientChannelDNSResolver::OnResolved(void* arg, |
| grpc_error_handle error) { |
| AresClientChannelDNSResolver* r = |
| static_cast<AresClientChannelDNSResolver*>(arg); |
| (void)GRPC_ERROR_REF(error); // ref owned by lambda |
| r->work_serializer_->Run([r, error]() { r->OnResolvedLocked(error); }, |
| DEBUG_LOCATION); |
| } |
| |
| void AresClientChannelDNSResolver::OnResolvedLocked(grpc_error_handle error) { |
| GPR_ASSERT(resolving_); |
| resolving_ = false; |
| delete pending_request_; |
| pending_request_ = nullptr; |
| if (shutdown_initiated_) { |
| Unref(DEBUG_LOCATION, "OnResolvedLocked() shutdown"); |
| GRPC_ERROR_UNREF(error); |
| return; |
| } |
| // TODO(roth): Change logic to be able to report failures for addresses |
| // and service config independently of each other. |
| if (addresses_ != nullptr || balancer_addresses_ != nullptr) { |
| Result result; |
| if (addresses_ != nullptr) { |
| result.addresses = std::move(*addresses_); |
| } else { |
| result.addresses = ServerAddressList(); |
| } |
| if (service_config_json_ != nullptr) { |
| grpc_error_handle service_config_error = GRPC_ERROR_NONE; |
| std::string service_config_string = |
| ChooseServiceConfig(service_config_json_, &service_config_error); |
| gpr_free(service_config_json_); |
| RefCountedPtr<ServiceConfig> service_config; |
| if (service_config_error == GRPC_ERROR_NONE && |
| !service_config_string.empty()) { |
| GRPC_CARES_TRACE_LOG("resolver:%p selected service config choice: %s", |
| this, service_config_string.c_str()); |
| service_config = ServiceConfig::Create( |
| channel_args_, service_config_string, &service_config_error); |
| } |
| if (service_config_error != GRPC_ERROR_NONE) { |
| result.service_config = absl::UnavailableError( |
| absl::StrCat("failed to parse service config: ", |
| grpc_error_std_string(service_config_error))); |
| GRPC_ERROR_UNREF(service_config_error); |
| } else { |
| result.service_config = std::move(service_config); |
| } |
| } |
| absl::InlinedVector<grpc_arg, 1> new_args; |
| if (balancer_addresses_ != nullptr) { |
| new_args.push_back( |
| CreateGrpclbBalancerAddressesArg(balancer_addresses_.get())); |
| } |
| result.args = grpc_channel_args_copy_and_add(channel_args_, new_args.data(), |
| new_args.size()); |
| result_handler_->ReportResult(std::move(result)); |
| addresses_.reset(); |
| balancer_addresses_.reset(); |
| // Reset backoff state so that we start from the beginning when the |
| // next request gets triggered. |
| backoff_.Reset(); |
| } else { |
| GRPC_CARES_TRACE_LOG("resolver:%p dns resolution failed: %s", this, |
| grpc_error_std_string(error).c_str()); |
| std::string error_message; |
| grpc_error_get_str(error, GRPC_ERROR_STR_DESCRIPTION, &error_message); |
| absl::Status status = absl::UnavailableError(absl::StrCat( |
| "DNS resolution failed for ", name_to_resolve_, ": ", error_message)); |
| Result result; |
| result.addresses = status; |
| result.service_config = status; |
| result.args = grpc_channel_args_copy(channel_args_); |
| result_handler_->ReportResult(std::move(result)); |
| // Set retry timer. |
| // InvalidateNow to avoid getting stuck re-initializing this timer |
| // in a loop while draining the currently-held WorkSerializer. |
| // Also see https://github.com/grpc/grpc/issues/26079. |
| ExecCtx::Get()->InvalidateNow(); |
| grpc_millis next_try = backoff_.NextAttemptTime(); |
| grpc_millis timeout = next_try - ExecCtx::Get()->Now(); |
| GRPC_CARES_TRACE_LOG("resolver:%p dns resolution failed (will retry): %s", |
| this, grpc_error_std_string(error).c_str()); |
| GPR_ASSERT(!have_next_resolution_timer_); |
| have_next_resolution_timer_ = true; |
| // TODO(roth): We currently deal with this ref manually. Once the |
| // new closure API is done, find a way to track this ref with the timer |
| // callback as part of the type system. |
| Ref(DEBUG_LOCATION, "retry-timer").release(); |
| if (timeout > 0) { |
| GRPC_CARES_TRACE_LOG("resolver:%p retrying in %" PRId64 " milliseconds", |
| this, timeout); |
| } else { |
| GRPC_CARES_TRACE_LOG("resolver:%p retrying immediately", this); |
| } |
| grpc_timer_init(&next_resolution_timer_, next_try, &on_next_resolution_); |
| } |
| Unref(DEBUG_LOCATION, "dns-resolving"); |
| GRPC_ERROR_UNREF(error); |
| } |
| |
| void AresClientChannelDNSResolver::MaybeStartResolvingLocked() { |
| // If there is an existing timer, the time it fires is the earliest time we |
| // can start the next resolution. |
| if (have_next_resolution_timer_) return; |
| if (last_resolution_timestamp_ >= 0) { |
| // InvalidateNow to avoid getting stuck re-initializing this timer |
| // in a loop while draining the currently-held WorkSerializer. |
| // Also see https://github.com/grpc/grpc/issues/26079. |
| ExecCtx::Get()->InvalidateNow(); |
| const grpc_millis earliest_next_resolution = |
| last_resolution_timestamp_ + min_time_between_resolutions_; |
| const grpc_millis ms_until_next_resolution = |
| earliest_next_resolution - ExecCtx::Get()->Now(); |
| if (ms_until_next_resolution > 0) { |
| const grpc_millis last_resolution_ago = |
| ExecCtx::Get()->Now() - last_resolution_timestamp_; |
| GRPC_CARES_TRACE_LOG( |
| "resolver:%p In cooldown from last resolution (from %" PRId64 |
| " ms ago). Will resolve again in %" PRId64 " ms", |
| this, last_resolution_ago, ms_until_next_resolution); |
| have_next_resolution_timer_ = true; |
| // TODO(roth): We currently deal with this ref manually. Once the |
| // new closure API is done, find a way to track this ref with the timer |
| // callback as part of the type system. |
| Ref(DEBUG_LOCATION, "next_resolution_timer_cooldown").release(); |
| grpc_timer_init(&next_resolution_timer_, |
| ExecCtx::Get()->Now() + ms_until_next_resolution, |
| &on_next_resolution_); |
| return; |
| } |
| } |
| StartResolvingLocked(); |
| } |
| |
| void AresClientChannelDNSResolver::StartResolvingLocked() { |
| // TODO(roth): We currently deal with this ref manually. Once the |
| // new closure API is done, find a way to track this ref with the timer |
| // callback as part of the type system. |
| Ref(DEBUG_LOCATION, "dns-resolving").release(); |
| GPR_ASSERT(!resolving_); |
| resolving_ = true; |
| service_config_json_ = nullptr; |
| pending_request_ = grpc_dns_lookup_ares( |
| dns_server_.c_str(), name_to_resolve_.c_str(), kDefaultSecurePort, |
| interested_parties_, &on_resolved_, &addresses_, |
| enable_srv_queries_ ? &balancer_addresses_ : nullptr, |
| request_service_config_ ? &service_config_json_ : nullptr, |
| query_timeout_ms_); |
| last_resolution_timestamp_ = ExecCtx::Get()->Now(); |
| GRPC_CARES_TRACE_LOG("resolver:%p Started resolving. pending_request_:%p", |
| this, pending_request_); |
| } |
| |
| // |
| // Factory |
| // |
| class AresClientChannelDNSResolverFactory : public ResolverFactory { |
| public: |
| absl::string_view scheme() const override { return "dns"; } |
| |
| bool IsValidUri(const URI& uri) const override { |
| if (absl::StripPrefix(uri.path(), "/").empty()) { |
| gpr_log(GPR_ERROR, "no server name supplied in dns URI"); |
| return false; |
| } |
| return true; |
| } |
| |
| OrphanablePtr<Resolver> CreateResolver(ResolverArgs args) const override { |
| return MakeOrphanable<AresClientChannelDNSResolver>(std::move(args)); |
| } |
| }; |
| |
| class AresDNSResolver : public DNSResolver { |
| public: |
| class AresRequest : public DNSResolver::Request { |
| public: |
| AresRequest( |
| absl::string_view name, absl::string_view default_port, |
| grpc_pollset_set* interested_parties, |
| std::function<void(absl::StatusOr<std::vector<grpc_resolved_address>>)> |
| on_resolve_address_done) |
| : name_(std::string(name)), |
| default_port_(std::string(default_port)), |
| interested_parties_(interested_parties), |
| on_resolve_address_done_(std::move(on_resolve_address_done)) { |
| GRPC_CARES_TRACE_LOG("AresRequest:%p ctor", this); |
| GRPC_CLOSURE_INIT(&on_dns_lookup_done_, OnDnsLookupDone, this, |
| grpc_schedule_on_exec_ctx); |
| } |
| |
| ~AresRequest() override { |
| GRPC_CARES_TRACE_LOG("AresRequest:%p dtor ares_request_:%p", this, |
| ares_request_.get()); |
| } |
| |
| void Start() override { |
| absl::MutexLock lock(&mu_); |
| Ref().release(); // ref held by resolution |
| ares_request_ = std::unique_ptr<grpc_ares_request>(grpc_dns_lookup_ares( |
| "" /* dns_server */, name_.c_str(), default_port_.c_str(), |
| interested_parties_, &on_dns_lookup_done_, &addresses_, |
| nullptr /* balancer_addresses */, nullptr /* service_config_json */, |
| GRPC_DNS_ARES_DEFAULT_QUERY_TIMEOUT_MS)); |
| GRPC_CARES_TRACE_LOG("AresRequest:%p Start ares_request_:%p", this, |
| ares_request_.get()); |
| } |
| |
| void Orphan() override { |
| { |
| absl::MutexLock lock(&mu_); |
| GRPC_CARES_TRACE_LOG("AresRequest:%p Orphan ares_request_:%p", this, |
| ares_request_.get()); |
| if (ares_request_ != nullptr) { |
| grpc_cancel_ares_request(ares_request_.get()); |
| } |
| } |
| Unref(); |
| } |
| |
| private: |
| static void OnDnsLookupDone(void* arg, grpc_error_handle error) { |
| AresRequest* r = static_cast<AresRequest*>(arg); |
| std::vector<grpc_resolved_address> resolved_addresses; |
| { |
| absl::MutexLock lock(&r->mu_); |
| GRPC_CARES_TRACE_LOG("AresRequest:%p OnDnsLookupDone error:%s", r, |
| grpc_error_std_string(error).c_str()); |
| if (r->addresses_ != nullptr) { |
| resolved_addresses.reserve(r->addresses_->size()); |
| for (const auto& server_address : *r->addresses_) { |
| resolved_addresses.push_back(server_address.address()); |
| } |
| } |
| } |
| if (error == GRPC_ERROR_NONE) { |
| // it's safe to run this inline since we've already been scheduled |
| // on the ExecCtx |
| r->on_resolve_address_done_(std::move(resolved_addresses)); |
| } else { |
| r->on_resolve_address_done_(grpc_error_to_absl_status(error)); |
| } |
| r->Unref(); |
| } |
| |
| // mutex to synchronize access to this object (but not to the ares_request |
| // object itself). |
| absl::Mutex mu_; |
| // the name to resolve |
| const std::string name_; |
| // the default port to use if name doesn't have one |
| const std::string default_port_; |
| // parties interested in our I/O |
| grpc_pollset_set* const interested_parties_; |
| // user-provided completion callback |
| const std::function<void( |
| absl::StatusOr<std::vector<grpc_resolved_address>>)> |
| on_resolve_address_done_; |
| // currently resolving addresses |
| std::unique_ptr<ServerAddressList> addresses_ ABSL_GUARDED_BY(mu_); |
| // closure to call when the resolve_address_ares request completes |
| // a closure wrapping on_resolve_address_done, which should be invoked |
| // when the grpc_dns_lookup_ares operation is done. |
| grpc_closure on_dns_lookup_done_ ABSL_GUARDED_BY(mu_); |
| // underlying ares_request that the query is performed on |
| std::unique_ptr<grpc_ares_request> ares_request_ ABSL_GUARDED_BY(mu_); |
| }; |
| |
| // gets the singleton instance, possibly creating it first |
| static AresDNSResolver* GetOrCreate() { |
| static AresDNSResolver* instance = new AresDNSResolver(); |
| return instance; |
| } |
| |
| OrphanablePtr<DNSResolver::Request> ResolveName( |
| absl::string_view name, absl::string_view default_port, |
| grpc_pollset_set* interested_parties, |
| std::function<void(absl::StatusOr<std::vector<grpc_resolved_address>>)> |
| on_done) override { |
| return MakeOrphanable<AresRequest>(name, default_port, interested_parties, |
| std::move(on_done)); |
| } |
| |
| absl::StatusOr<std::vector<grpc_resolved_address>> ResolveNameBlocking( |
| absl::string_view name, absl::string_view default_port) override { |
| // TODO(apolcyn): change this to wrap the async version of the c-ares |
| // API with a promise, and remove the reference to the previous resolver. |
| return default_resolver_->ResolveNameBlocking(name, default_port); |
| } |
| |
| private: |
| // the previous default DNS resolver, used to delegate blocking DNS calls to |
| DNSResolver* default_resolver_ = GetDNSResolver(); |
| }; |
| |
| bool ShouldUseAres(const char* resolver_env) { |
| return resolver_env == nullptr || strlen(resolver_env) == 0 || |
| gpr_stricmp(resolver_env, "ares") == 0; |
| } |
| |
| bool UseAresDnsResolver() { |
| static const bool result = []() { |
| UniquePtr<char> resolver = GPR_GLOBAL_CONFIG_GET(grpc_dns_resolver); |
| bool result = ShouldUseAres(resolver.get()); |
| if (result) gpr_log(GPR_DEBUG, "Using ares dns resolver"); |
| return result; |
| }(); |
| return result; |
| } |
| |
| } // namespace |
| |
| void RegisterAresDnsResolver(CoreConfiguration::Builder* builder) { |
| if (UseAresDnsResolver()) { |
| builder->resolver_registry()->RegisterResolverFactory( |
| absl::make_unique<AresClientChannelDNSResolverFactory>()); |
| } |
| } |
| |
| } // namespace grpc_core |
| |
| void grpc_resolver_dns_ares_init() { |
| if (grpc_core::UseAresDnsResolver()) { |
| address_sorting_init(); |
| grpc_error_handle error = grpc_ares_init(); |
| if (error != GRPC_ERROR_NONE) { |
| GRPC_LOG_IF_ERROR("grpc_ares_init() failed", error); |
| return; |
| } |
| grpc_core::SetDNSResolver(grpc_core::AresDNSResolver::GetOrCreate()); |
| } |
| } |
| |
| void grpc_resolver_dns_ares_shutdown() { |
| if (grpc_core::UseAresDnsResolver()) { |
| address_sorting_shutdown(); |
| grpc_ares_cleanup(); |
| } |
| } |
| |
| #else /* GRPC_ARES == 1 */ |
| |
| namespace grpc_core { |
| void RegisterAresDnsResolver(CoreConfiguration::Builder*) {} |
| } // namespace grpc_core |
| |
| void grpc_resolver_dns_ares_init() {} |
| |
| void grpc_resolver_dns_ares_shutdown() {} |
| |
| #endif /* GRPC_ARES == 1 */ |
