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

envoy/network/dns_resolver.h

@@ -26,6 +26,8 @@ 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); }
+  virtual void init() {}
+  virtual void cleanup() {}
 };
 
 } // namespace Network

source/common/network/dns_resolver/dns_factory_util.cc

@@ -79,8 +79,11 @@ 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);
+  // Perform factory initialization.
+  factory.init();
+  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 +57,11 @@ ProcessWide::~ProcessWide() {
 
   ASSERT(init_data.count_ > 0);
   if (--init_data.count_ == 0) {
-    ares_library_cleanup();
+    // Cleanup c-ares library if it is linked in.
+    if (auto* dns_factory = Config::Utility::getAndCheckFactoryByName<Network::DnsResolverFactory>(
+            std::string(Network::CaresDnsResolver), true)) {
+      dns_factory->cleanup();
+    }
   }
 }
 

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

@@ -521,6 +521,23 @@ class CaresDnsResolverFactory : public DnsResolverFactory {
     }
     return std::make_shared<Network::DnsResolverImpl>(cares, dispatcher, resolvers);
   }
+
+  void init() override {
+    // Initialize c-ares library in case first time.
+    if (!ares_library_initialized_) {
+      ares_library_initialized_ = true;
+      ares_library_init(ARES_LIB_INIT_ALL);
+    }
+  }
+  void cleanup() override {
+    // Cleanup c-ares library if initialized.
+    if (ares_library_initialized_) {
+      ares_library_cleanup();
+    }
+  }
+
+private:
+  mutable bool ares_library_initialized_{false};
 };
 
 // Register the CaresDnsResolverFactory