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

envoy/network/dns_resolver.h

@@ -26,6 +26,7 @@ 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 cleanup() {}
 };
 
 } // namespace Network

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

@@ -495,6 +495,7 @@ DnsResolverImpl::AddrInfoPendingResolution::availableInterfaces() {
 // c-ares DNS resolver factory
 class CaresDnsResolverFactory : public DnsResolverFactory {
 public:
+  CaresDnsResolverFactory() : ares_library_initialized_(false) {}
   std::string name() const override { return std::string(CaresDnsResolver); }
 
   ProtobufTypes::MessagePtr createEmptyConfigProto() override {
@@ -507,6 +508,11 @@ class CaresDnsResolverFactory : public DnsResolverFactory {
                                              typed_dns_resolver_config) const override {
     envoy::extensions::network::dns_resolver::cares::v3::CaresDnsResolverConfig cares;
     std::vector<Network::Address::InstanceConstSharedPtr> resolvers;
+    // Initialize c-ares library in case first time.
+    if (!ares_library_initialized_) {
+      ares_library_init(ARES_LIB_INIT_ALL);
+      ares_library_initialized_ = true;
+    }
 
     ASSERT(dispatcher.isThreadSafe());
     // Only c-ares DNS factory will call into this function.
@@ -521,6 +527,16 @@ class CaresDnsResolverFactory : public DnsResolverFactory {
     }
     return std::make_shared<Network::DnsResolverImpl>(cares, dispatcher, resolvers);
   }
+
+  void cleanup() override {
+    // Cleanup c-ares library if initialized.
+    if (ares_library_initialized_) {
+      ares_library_cleanup();
+    }
+  }
+
+private:
+  mutable bool ares_library_initialized_;
 };
 
 // Register the CaresDnsResolverFactory