SERVER-21757 ServerStatus advisoryHostFQDNs should be optional

4 files changed, 52 insertions, 21 deletions

diff --git a/src/mongo/db/commands/SConscript b/src/mongo/db/commands/SConscript
index 75c10c03af7..3a1a9f34b66 100644
--- a/src/mongo/db/commands/SConscript
+++ b/src/mongo/db/commands/SConscript
@@ -17,7 +17,7 @@ env.Library(
         'server_status_metric.cpp',
         ],
     LIBDEPS=[
-        '$BUILD_DIR/mongo/util/net/hostname_canonicalization_worker',
+        '$BUILD_DIR/mongo/util/net/network',
         '$BUILD_DIR/mongo/base'
         ]
     )
diff --git a/src/mongo/db/commands/server_status.cpp b/src/mongo/db/commands/server_status.cpp
index ff0b1cbb376..dbbf5582323 100644
--- a/src/mongo/db/commands/server_status.cpp
+++ b/src/mongo/db/commands/server_status.cpp
@@ -50,7 +50,7 @@
 #include "mongo/transport/message_compressor_registry.h"
 #include "mongo/transport/transport_layer.h"
 #include "mongo/util/log.h"
-#include "mongo/util/net/hostname_canonicalization_worker.h"
+#include "mongo/util/net/hostname_canonicalization.h"
 #include "mongo/util/net/ssl_manager.h"
 #include "mongo/util/processinfo.h"
 #include "mongo/util/ramlog.h"
@@ -99,13 +99,10 @@ public:
         BSONObjBuilder timeBuilder(256);
 
         const auto authSession = AuthorizationSession::get(Client::getCurrent());
-        auto canonicalizer = HostnameCanonicalizationWorker::get(service);
 
         // --- basic fields that are global
 
         result.append("host", prettyHostName());
-        result.append("advisoryHostFQDNs", canonicalizer->getCanonicalizedFQDNs());
-
         result.append("version", VersionInfoInterface::instance().version());
         result.append("process", serverGlobalParams.binaryName);
         result.append("pid", ProcessId::getCurrent().asLongLong());
@@ -129,20 +126,16 @@ public:
                 continue;
 
             bool include = section->includeByDefault();
-
-            BSONElement e = cmdObj[section->getSectionName()];
-            if (e.type()) {
-                include = e.trueValue();
+            const auto& elem = cmdObj[section->getSectionName()];
+            if (elem.type()) {
+                include = elem.trueValue();
             }
 
-            if (!include)
-                continue;
-
-            BSONObj data = section->generateSection(txn, e);
-            if (data.isEmpty())
+            if (!include) {
                 continue;
+            }
 
-            result.append(section->getSectionName(), data);
+            section->appendSection(txn, elem, &result);
             timeBuilder.appendNumber(
                 static_cast<string>(str::stream() << "after " << section->getSectionName()),
                 durationCount<Milliseconds>(clock->now() - runStart));
@@ -332,6 +325,23 @@ public:
         }
     }
 } memBase;
-}
+
+class AdvisoryHostFQDNs final : public ServerStatusSection {
+public:
+    AdvisoryHostFQDNs() : ServerStatusSection("advisoryHostFQDNs") {}
+
+    bool includeByDefault() const override {
+        return false;
+    }
+
+    void appendSection(OperationContext* txn,
+                       const BSONElement& configElement,
+                       BSONObjBuilder* out) const override {
+        out->append(
+            "advisoryHostFQDNs",
+            getHostFQDNs(getHostNameCached(), HostnameCanonicalizationMode::kForwardAndReverse));
+    }
+} advisoryHostFQDNs;
+}  // namespace
 
 }  // namespace mongo
diff --git a/src/mongo/db/commands/server_status.h b/src/mongo/db/commands/server_status.h
index 862cf1960e9..b017688acf2 100644
--- a/src/mongo/db/commands/server_status.h
+++ b/src/mongo/db/commands/server_status.h
@@ -73,11 +73,35 @@ public:
 
     /**
      * actually generate the result
+     *
+     * You should either implement this function or appendSection below, but not both. In
+     * most cases you should just implement this function.
+     *
      * @param configElement the element from the actual command related to this section
      *                      so if the section is 'foo', this is cmdObj['foo']
      */
-    virtual BSONObj generateSection(OperationContext* txn,
-                                    const BSONElement& configElement) const = 0;
+    virtual BSONObj generateSection(OperationContext* txn, const BSONElement& configElement) const {
+        return BSONObj{};
+    };
+
+    /**
+     * This is what gets called by the serverStatus command to append the section to the
+     * command result.
+     *
+     * If you are just implementing a normal ServerStatusSection, then you don't need to
+     * implement this.
+     *
+     * If you are doing something a bit more complicated, you can implement this and have
+     * full control over what gets included in the command result.
+     */
+    virtual void appendSection(OperationContext* txn,
+                               const BSONElement& configElement,
+                               BSONObjBuilder* result) const {
+        const auto ret = generateSection(txn, configElement);
+        if (ret.isEmpty())
+            return;
+        result->append(getSectionName(), ret);
+    }
 
 private:
     const std::string _sectionName;
diff --git a/src/mongo/db/db.cpp b/src/mongo/db/db.cpp
index 68a60d4e2b5..6ac580e3d17 100644
--- a/src/mongo/db/db.cpp
+++ b/src/mongo/db/db.cpp
@@ -128,7 +128,6 @@
 #include "mongo/util/exit.h"
 #include "mongo/util/fast_clock_source_factory.h"
 #include "mongo/util/log.h"
-#include "mongo/util/net/hostname_canonicalization_worker.h"
 #include "mongo/util/net/listen.h"
 #include "mongo/util/net/ssl_manager.h"
 #include "mongo/util/ntservice.h"
@@ -719,8 +718,6 @@ static ExitCode _initAndListen(int listenPort) {
               << startupWarningsLog;
     }
 
-    HostnameCanonicalizationWorker::start(getGlobalServiceContext());
-
     uassertStatusOK(ShardingState::get(startupOpCtx.get())
                         ->initializeShardingAwarenessIfNeeded(startupOpCtx.get()));