SERVER-42888 Deprecate CodeWScope in MapReduce

2 files changed, 8 insertions, 1 deletions

diff --git a/src/mongo/db/commands/mr.cpp b/src/mongo/db/commands/mr.cpp
index 0e6d4baa02b..75dde5374ad 100644
--- a/src/mongo/db/commands/mr.cpp
+++ b/src/mongo/db/commands/mr.cpp
@@ -231,8 +231,12 @@ JSFunction::JSFunction(const std::string& type, const BSONElement& e) {
     _type = type;
     _code = e._asCode();
 
-    if (e.type() == CodeWScope)
+    if (e.type() == CodeWScope) {
+        if (_sampler.tick())
+            warning() << "Use of CodeWScope with MapReduce is deprecated. Prefer putting all scope "
+                         "variables in the scope parameter of the MapReduce command";
         _wantedScope = e.codeWScopeObject();
+    }
 }
 
 void JSFunction::init(State* state) {
diff --git a/src/mongo/db/commands/mr.h b/src/mongo/db/commands/mr.h
index aab8f011d09..70cdaebcbd5 100644
--- a/src/mongo/db/commands/mr.h
+++ b/src/mongo/db/commands/mr.h
@@ -39,6 +39,7 @@
 #include "mongo/db/namespace_string.h"
 #include "mongo/platform/atomic_word.h"
 #include "mongo/scripting/engine.h"
+#include "mongo/util/debug_util.h"
 
 namespace mongo {
 
@@ -129,6 +130,8 @@ private:
     std::string _type;
     std::string _code;     // actual javascript code
     BSONObj _wantedScope;  // this is for CodeWScope
+    // Used to log occassional deprecation warnings when CodeWScope is used in MapReduce.
+    Rarely _sampler;
 
     Scope* _scope;  // this is not owned by us, and might be shared
     ScriptingFunction _func;