SERVER-42257 Announce known emulations

(cherry picked from commit 0789a935ccee8e402cce8c7cdf52a41b9cc17010)
(cherry picked from commit 9d796ee7c61a783c0b553bf715461864ba5f6fcb)

2 files changed, 51 insertions, 0 deletions

diff --git a/src/mongo/shell/dbshell.cpp b/src/mongo/shell/dbshell.cpp
index 30b1ff718f2..1987538e20d 100644
--- a/src/mongo/shell/dbshell.cpp
+++ b/src/mongo/shell/dbshell.cpp
@@ -917,6 +917,12 @@ int _main(int argc, char* argv[], char** envp) {
                         false,
                         true,
                         false);
+
+            scope->exec("shellHelper( 'show', 'nonGenuineMongoDBCheck' )",
+                        "(nonGenuineMongoDBCheck)",
+                        false,
+                        true,
+                        false);
         }
 
         shellHistoryInit();
diff --git a/src/mongo/shell/utils.js b/src/mongo/shell/utils.js
index d45beb0d675..847f65c6196 100644
--- a/src/mongo/shell/utils.js
+++ b/src/mongo/shell/utils.js
@@ -948,6 +948,51 @@ shellHelper.show = function(what) {
         }
     }
 
+    if (what == "nonGenuineMongoDBCheck") {
+        let matchesKnownImposterSignature = false;
+
+        // A MongoDB emulation service offered by a company
+        // responsible for a certain disk operating system.
+        try {
+            const buildInfo = db.runCommand({buildInfo: 1});
+            if (buildInfo.hasOwnProperty('_t')) {
+                matchesKnownImposterSignature = true;
+            }
+        } catch (e) {
+            // Don't do anything here. Just throw the error away.
+        }
+
+        // A MongoDB emulation service offered by a company named
+        // after some sort of minor river or something.
+        if (!matchesKnownImposterSignature) {
+            try {
+                const cmdLineOpts = db.adminCommand({getCmdLineOpts: 1});
+                if (cmdLineOpts.hasOwnProperty('errmsg') &&
+                    cmdLineOpts.errmsg.indexOf('not supported') !== -1) {
+                    matchesKnownImposterSignature = true;
+                }
+            } catch (e) {
+                // Don't do anything here. Just throw the error away.
+            }
+        }
+
+        if (matchesKnownImposterSignature) {
+            print("\n" + "Warning: Non-Genuine MongoDB Detected\n\n" +
+
+                  "This server or service appears to be an emulation of MongoDB " +
+                  "rather than an official MongoDB product.\n\n" +
+
+                  "Some documented MongoDB features may work differently, " +
+                  "be entirely missing or incomplete, " +
+                  "or have unexpected performance characteristics.\n\n" +
+
+                  "To learn more please visit: " +
+                  "https://dochub.mongodb.org/core/non-genuine-mongodb-server-warning.\n");
+        }
+
+        return "";
+    }
+
     throw Error("don't know how to show [" + what + "]");
 
 };