1 files changed, 26 insertions, 0 deletions
diff --git a/jstests/sharding/mongos_helloOk_protocol.js b/jstests/sharding/mongos_helloOk_protocol.js
new file mode 100644
index 00000000000..2579d0404a6
--- /dev/null
+++ b/jstests/sharding/mongos_helloOk_protocol.js
@@ -0,0 +1,26 @@
+/*
+ * Tests that when a client sends "helloOk: true" as a part of their isMaster request, mongos
+ * will respond with helloOk: true. This ensures that the client knows it can send the hello
+ * command.
+ *
+ * In practice, drivers will send "helloOk: true" in the initial handshake when
+ * opening a connection to the database.
+ */
+(function() {
+"use strict";
+const st = new ShardingTest({shards: 1, mongos: 1});
+const mongos = st.s;
+
+// Simulate an initial handshake request without "helloOk: true". Mongos should not return
+// "helloOk: true" in its response.
+let res = assert.commandWorked(mongos.adminCommand({isMaster: 1}));
+assert.eq(res.helloOk, undefined);
+
+// Simulate an initial handshake request with "helloOk: true". Mongos should now return
+// "helloOk: true" in its response.
+res = assert.commandWorked(mongos.adminCommand({isMaster: 1, helloOk: true}));
+assert.eq("boolean", typeof res.helloOk, "helloOk field is not a boolean" + tojson(res));
+assert.eq(res.helloOk, true);
+
+st.stop();
+})();
+\ No newline at end of file