Only call ares_library_init()/cleanup() routines in process_wide() if ares extension used in DNS resolving.

envoy/network/dns_resolver.h

@@ -15,7 +15,7 @@ constexpr absl::string_view DnsResolverCategory = "envoy.network.dns_resolver";
 
 class DnsResolverFactory : public Config::TypedFactory {
 public:
-  /*
+  /**
    * @returns a DnsResolver object.
    * @param dispatcher: the local dispatcher thread
    * @param api: API interface to interact with system resources
@@ -26,6 +26,20 @@ class DnsResolverFactory : public Config::TypedFactory {
       const envoy::config::core::v3::TypedExtensionConfig& typed_dns_resolver_config) const PURE;
 
   std::string category() const override { return std::string(DnsResolverCategory); }
+
+  /**
+   * Initialize the related data for this type of DNS resolver.
+   * For some DNS resolvers, like c-ares, there are some specific data structure
+   * needs to be initialized before using it to resolve target.
+   */
+  virtual void initialize() {}
+
+  /**
+   * Cleanup the related data for this type of DNS resolver.
+   * For some DNS resolvers, like c-ares, there are some specific data structure
+   * needs to be cleaned up before terminates Envoy.
+   */
+  virtual void terminate() {}
 };
 
 } // namespace Network

source/common/config/utility.h

@@ -241,6 +241,17 @@ class Utility {
                                    POOL_HISTOGRAM(scope))};
   }
 
+
+
+  /**
+   * Get the hash map for this factory.
+   */
+  template <class Factory>
+  static absl::flat_hash_map<std::string, Factory*>&  getFactoryMap() {
+    return Registry::FactoryRegistry<Factory>::factories();
+  }
+
+
   /**
    * Get a Factory from the registry with a particular name (and templated type) with error checking
    * to ensure the name and factory are valid.

source/common/network/dns_resolver/dns_factory_util.cc

@@ -79,8 +79,10 @@ void handleLegacyDnsResolverData(
 Network::DnsResolverFactory& createDnsResolverFactoryFromTypedConfig(
     const envoy::config::core::v3::TypedExtensionConfig& typed_dns_resolver_config) {
   ENVOY_LOG_MISC(debug, "create DNS resolver type: {}", typed_dns_resolver_config.name());
-  return Config::Utility::getAndCheckFactory<Network::DnsResolverFactory>(
-      typed_dns_resolver_config);
+  auto& factory =
+      Config::Utility::getAndCheckFactory<Network::DnsResolverFactory>(typed_dns_resolver_config);
+  factory.initialize();
+  return factory;
 }
 
 // Create the default DNS resolver factory. apple for MacOS or c-ares for all others.

source/exe/BUILD

@@ -141,8 +141,8 @@ envoy_cc_library(
     name = "process_wide_lib",
     srcs = ["process_wide.cc"],
     hdrs = ["process_wide.h"],
-    external_deps = ["ares"],
     deps = [
+        "//envoy/network:dns_resolver_interface",
         "//source/common/common:assert_lib",
         "//source/common/event:libevent_lib",
         "//source/common/http/http2:nghttp2_lib",

source/exe/process_wide.cc

@@ -1,12 +1,12 @@
 #include "source/exe/process_wide.h"
 
+#include "envoy/network/dns_resolver.h"
+
 #include "source/common/common/assert.h"
 #include "source/common/event/libevent.h"
 #include "source/common/http/http2/nghttp2.h"
 #include "source/server/proto_descriptors.h"
 
-#include "ares.h"
-
 namespace Envoy {
 namespace {
 
@@ -30,7 +30,6 @@ ProcessWide::ProcessWide() {
   if (init_data.count_++ == 0) {
     // TODO(mattklein123): Audit the following as not all of these have to be re-initialized in the
     // edge case where something does init/destroy/init/destroy.
-    ares_library_init(ARES_LIB_INIT_ALL);
     Event::Libevent::Global::initialize();
     Envoy::Server::validateProtoDescriptors();
     Http::Http2::initializeNghttp2Logging();
@@ -58,7 +57,10 @@ ProcessWide::~ProcessWide() {
 
   ASSERT(init_data.count_ > 0);
   if (--init_data.count_ == 0) {
-    ares_library_cleanup();
+    for (const auto& dns_factory :
+         Config::Utility::getFactoryMap<Network::DnsResolverFactory>()) {
+      dns_factory.second->terminate();
+    }
   }
 }
 

source/extensions/network/dns_resolver/cares/dns_impl.cc

@@ -521,6 +521,27 @@ class CaresDnsResolverFactory : public DnsResolverFactory {
     }
     return std::make_shared<Network::DnsResolverImpl>(cares, dispatcher, resolvers);
   }
+
+  void initialize() override {
+    // Initialize c-ares library in case first time.
+    absl::MutexLock lock(&mutex_);
+    if (!ares_library_initialized_) {
+      ares_library_initialized_ = true;
+      ares_library_init(ARES_LIB_INIT_ALL);
+    }
+  }
+  void terminate() override {
+    // Cleanup c-ares library if initialized.
+    absl::MutexLock lock(&mutex_);
+    if (ares_library_initialized_) {
+      ares_library_initialized_ = false;
+      ares_library_cleanup();
+    }
+  }
+
+private:
+  bool ares_library_initialized_ ABSL_GUARDED_BY(mutex_){false};
+  absl::Mutex mutex_;
 };
 
 // Register the CaresDnsResolverFactory