| /* |
| * |
| * 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 <inttypes.h> |
| #include <climits> |
| #include <cstring> |
| |
| #include <grpc/support/alloc.h> |
| #include <grpc/support/string_util.h> |
| #include <grpc/support/time.h> |
| |
| #include "src/core/ext/filters/client_channel/resolver/dns/dns_resolver_selection.h" |
| #include "src/core/ext/filters/client_channel/resolver_registry.h" |
| #include "src/core/ext/filters/client_channel/server_address.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/combiner.h" |
| #include "src/core/lib/iomgr/resolve_address.h" |
| #include "src/core/lib/iomgr/timer.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 { |
| |
| const char kDefaultPort[] = "https"; |
| |
| class NativeDnsResolver : public Resolver { |
| public: |
| explicit NativeDnsResolver(ResolverArgs args); |
| |
| void StartLocked() override; |
| |
| void RequestReresolutionLocked() override; |
| |
| void ResetBackoffLocked() override; |
| |
| void ShutdownLocked() override; |
| |
| private: |
| virtual ~NativeDnsResolver(); |
| |
| void MaybeStartResolvingLocked(); |
| void StartResolvingLocked(); |
| |
| static void OnNextResolutionLocked(void* arg, grpc_error* error); |
| static void OnResolvedLocked(void* arg, grpc_error* error); |
| |
| /// name to resolve |
| char* name_to_resolve_ = nullptr; |
| /// channel args |
| grpc_channel_args* channel_args_ = nullptr; |
| /// pollset_set to drive the name resolution process |
| grpc_pollset_set* interested_parties_ = nullptr; |
| /// are we shutting down? |
| bool shutdown_ = false; |
| /// are we currently resolving? |
| bool resolving_ = false; |
| grpc_closure on_resolved_; |
| /// next resolution timer |
| bool have_next_resolution_timer_ = false; |
| grpc_timer next_resolution_timer_; |
| grpc_closure on_next_resolution_; |
| /// min time between DNS requests |
| grpc_millis min_time_between_resolutions_; |
| /// timestamp of last DNS request |
| grpc_millis last_resolution_timestamp_ = -1; |
| /// retry backoff state |
| BackOff backoff_; |
| /// currently resolving addresses |
| grpc_resolved_addresses* addresses_ = nullptr; |
| }; |
| |
| NativeDnsResolver::NativeDnsResolver(ResolverArgs args) |
| : Resolver(args.combiner, std::move(args.result_handler)), |
| 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)) { |
| char* path = args.uri->path; |
| if (path[0] == '/') ++path; |
| name_to_resolve_ = gpr_strdup(path); |
| channel_args_ = grpc_channel_args_copy(args.args); |
| const grpc_arg* arg = grpc_channel_args_find( |
| args.args, GRPC_ARG_DNS_MIN_TIME_BETWEEN_RESOLUTIONS_MS); |
| min_time_between_resolutions_ = |
| grpc_channel_arg_get_integer(arg, {1000, 0, INT_MAX}); |
| interested_parties_ = grpc_pollset_set_create(); |
| if (args.pollset_set != nullptr) { |
| grpc_pollset_set_add_pollset_set(interested_parties_, args.pollset_set); |
| } |
| GRPC_CLOSURE_INIT(&on_next_resolution_, |
| NativeDnsResolver::OnNextResolutionLocked, this, |
| grpc_combiner_scheduler(args.combiner)); |
| GRPC_CLOSURE_INIT(&on_resolved_, NativeDnsResolver::OnResolvedLocked, this, |
| grpc_combiner_scheduler(args.combiner)); |
| } |
| |
| NativeDnsResolver::~NativeDnsResolver() { |
| grpc_channel_args_destroy(channel_args_); |
| grpc_pollset_set_destroy(interested_parties_); |
| gpr_free(name_to_resolve_); |
| } |
| |
| void NativeDnsResolver::StartLocked() { MaybeStartResolvingLocked(); } |
| |
| void NativeDnsResolver::RequestReresolutionLocked() { |
| if (!resolving_) { |
| MaybeStartResolvingLocked(); |
| } |
| } |
| |
| void NativeDnsResolver::ResetBackoffLocked() { |
| if (have_next_resolution_timer_) { |
| grpc_timer_cancel(&next_resolution_timer_); |
| } |
| backoff_.Reset(); |
| } |
| |
| void NativeDnsResolver::ShutdownLocked() { |
| shutdown_ = true; |
| if (have_next_resolution_timer_) { |
| grpc_timer_cancel(&next_resolution_timer_); |
| } |
| } |
| |
| void NativeDnsResolver::OnNextResolutionLocked(void* arg, grpc_error* error) { |
| NativeDnsResolver* r = static_cast<NativeDnsResolver*>(arg); |
| r->have_next_resolution_timer_ = false; |
| if (error == GRPC_ERROR_NONE && !r->resolving_) { |
| r->StartResolvingLocked(); |
| } |
| r->Unref(DEBUG_LOCATION, "retry-timer"); |
| } |
| |
| void NativeDnsResolver::OnResolvedLocked(void* arg, grpc_error* error) { |
| NativeDnsResolver* r = static_cast<NativeDnsResolver*>(arg); |
| GPR_ASSERT(r->resolving_); |
| r->resolving_ = false; |
| if (r->shutdown_) { |
| r->Unref(DEBUG_LOCATION, "dns-resolving"); |
| return; |
| } |
| if (r->addresses_ != nullptr) { |
| Result result; |
| for (size_t i = 0; i < r->addresses_->naddrs; ++i) { |
| result.addresses.emplace_back(&r->addresses_->addrs[i].addr, |
| r->addresses_->addrs[i].len, |
| nullptr /* args */); |
| } |
| grpc_resolved_addresses_destroy(r->addresses_); |
| result.args = grpc_channel_args_copy(r->channel_args_); |
| r->result_handler()->ReturnResult(std::move(result)); |
| // Reset backoff state so that we start from the beginning when the |
| // next request gets triggered. |
| r->backoff_.Reset(); |
| } else { |
| gpr_log(GPR_INFO, "dns resolution failed (will retry): %s", |
| grpc_error_string(error)); |
| // Return transient error. |
| r->result_handler()->ReturnError(grpc_error_set_int( |
| GRPC_ERROR_CREATE_REFERENCING_FROM_STATIC_STRING( |
| "DNS resolution failed", &error, 1), |
| GRPC_ERROR_INT_GRPC_STATUS, GRPC_STATUS_UNAVAILABLE)); |
| // Set up for retry. |
| grpc_millis next_try = r->backoff_.NextAttemptTime(); |
| grpc_millis timeout = next_try - ExecCtx::Get()->Now(); |
| GPR_ASSERT(!r->have_next_resolution_timer_); |
| r->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. |
| r->Ref(DEBUG_LOCATION, "next_resolution_timer").release(); |
| if (timeout > 0) { |
| gpr_log(GPR_DEBUG, "retrying in %" PRId64 " milliseconds", timeout); |
| } else { |
| gpr_log(GPR_DEBUG, "retrying immediately"); |
| } |
| grpc_timer_init(&r->next_resolution_timer_, next_try, |
| &r->on_next_resolution_); |
| } |
| r->Unref(DEBUG_LOCATION, "dns-resolving"); |
| } |
| |
| void NativeDnsResolver::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) { |
| const grpc_millis earliest_next_resolution = |
| last_resolution_timestamp_ + min_time_between_resolutions_; |
| const grpc_millis ms_until_next_resolution = |
| earliest_next_resolution - grpc_core::ExecCtx::Get()->Now(); |
| if (ms_until_next_resolution > 0) { |
| const grpc_millis last_resolution_ago = |
| grpc_core::ExecCtx::Get()->Now() - last_resolution_timestamp_; |
| gpr_log(GPR_DEBUG, |
| "In cooldown from last resolution (from %" PRId64 |
| " ms ago). Will resolve again in %" PRId64 " ms", |
| 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 NativeDnsResolver::StartResolvingLocked() { |
| gpr_log(GPR_DEBUG, "Start resolving."); |
| // 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; |
| addresses_ = nullptr; |
| grpc_resolve_address(name_to_resolve_, kDefaultPort, interested_parties_, |
| &on_resolved_, &addresses_); |
| last_resolution_timestamp_ = grpc_core::ExecCtx::Get()->Now(); |
| } |
| |
| // |
| // Factory |
| // |
| |
| class NativeDnsResolverFactory : public ResolverFactory { |
| public: |
| bool IsValidUri(const grpc_uri* uri) const override { |
| if (GPR_UNLIKELY(0 != strcmp(uri->authority, ""))) { |
| gpr_log(GPR_ERROR, "authority based dns uri's not supported"); |
| return false; |
| } |
| return true; |
| } |
| |
| OrphanablePtr<Resolver> CreateResolver(ResolverArgs args) const override { |
| if (!IsValidUri(args.uri)) return nullptr; |
| return OrphanablePtr<Resolver>(New<NativeDnsResolver>(std::move(args))); |
| } |
| |
| const char* scheme() const override { return "dns"; } |
| }; |
| |
| } // namespace |
| |
| } // namespace grpc_core |
| |
| void grpc_resolver_dns_native_init() { |
| grpc_core::UniquePtr<char> resolver = |
| GPR_GLOBAL_CONFIG_GET(grpc_dns_resolver); |
| if (gpr_stricmp(resolver.get(), "native") == 0) { |
| gpr_log(GPR_DEBUG, "Using native dns resolver"); |
| grpc_core::ResolverRegistry::Builder::RegisterResolverFactory( |
| grpc_core::UniquePtr<grpc_core::ResolverFactory>( |
| grpc_core::New<grpc_core::NativeDnsResolverFactory>())); |
| } else { |
| grpc_core::ResolverRegistry::Builder::InitRegistry(); |
| grpc_core::ResolverFactory* existing_factory = |
| grpc_core::ResolverRegistry::LookupResolverFactory("dns"); |
| if (existing_factory == nullptr) { |
| gpr_log(GPR_DEBUG, "Using native dns resolver"); |
| grpc_core::ResolverRegistry::Builder::RegisterResolverFactory( |
| grpc_core::UniquePtr<grpc_core::ResolverFactory>( |
| grpc_core::New<grpc_core::NativeDnsResolverFactory>())); |
| } |
| } |
| } |
| |
| void grpc_resolver_dns_native_shutdown() {} |