Support the Redis "QUIT" command properly

The QUIT command so far was handled by just closing the connection on
the server side and did not respect the contract of the QUIT command.

The Redis documentation states that the QUIT command must return
"+OK\r\n" back to the client so that the client can close the connection
on its side.

This patch takes advantage of simulating a datastore response from the
previous patch to achieve this.

src/dyn_client.c

@@ -365,9 +365,13 @@ static bool req_filter(struct context *ctx, struct conn *conn,
   if (req->quit) {
     ASSERT(conn->rmsg == NULL);
     log_debug(LOG_VERB, "%s filter quit %s", print_obj(conn), print_obj(req));
+
+    // The client expects to receive an "+OK\r\n" response, so make sure
+    // to do that.
+    IGNORE_RET_VAL(simulate_ok_rsp(ctx, conn, req));
+
     conn->eof = 1;
     conn->recv_ready = 0;
-    req_put(req);
     return true;
   }
 

src/dyn_message.c

@@ -923,7 +923,7 @@ static rstatus_t msg_repair(struct context *ctx, struct conn *conn,
  *
  * Returns a 'msg' with the expected success response.
  */
-static struct msg *simulate_ok_rsp(struct context *ctx, struct conn *conn,
+static struct msg *craft_ok_rsp(struct context *ctx, struct conn *conn,
     struct msg *req) {
 
   ASSERT(req->is_request);
@@ -951,6 +951,24 @@ static struct msg *simulate_ok_rsp(struct context *ctx, struct conn *conn,
   return rsp;
 }
 
+rstatus_t simulate_ok_rsp(struct context *ctx, struct conn *conn,
+    struct msg *msg) {
+  // Create an OK response.
+  struct msg *ok_rsp = craft_ok_rsp(ctx, conn, msg);
+
+  // Add it to the outstanding messages dictionary, so that 'conn_handle_response'
+  // can process it appropriately.
+  dictAdd(conn->outstanding_msgs_dict, &msg->id, msg);
+
+  // Enqueue the message in the outbound queue so that the code on the response
+  // path can find it.
+  conn_enqueue_outq(ctx, conn, msg);
+
+  THROW_STATUS(conn_handle_response(ctx, conn,
+      msg->parent_id ? msg->parent_id : msg->id, ok_rsp));
+
+  return DN_OK;
+}
 
 /*
  * If the command sent to Dynomite was a special Dynomite configuration
@@ -979,19 +997,7 @@ static rstatus_t msg_apply_config(struct context *ctx, struct conn *conn,
   // Set the consistency to DC_ONE, since this is just a configuration setting.
   msg->consistency = DC_ONE;
 
-  // Create an OK response.
-  struct msg *ok_rsp = simulate_ok_rsp(ctx, conn, msg);
-
-  // Add it to the outstanding messages dictionary, so that 'conn_handle_response'
-  // can process it appropriately.
-  dictAdd(conn->outstanding_msgs_dict, &msg->id, msg);
-
-  // Enqueue the message in the outbound queue so that the code on the response
-  // path can find it.
-  conn_enqueue_outq(ctx, conn, msg);
-
-  THROW_STATUS(conn_handle_response(ctx, conn,
-      msg->parent_id ? msg->parent_id : msg->id, ok_rsp));
+  THROW_STATUS(simulate_ok_rsp(ctx, conn, msg));
 
   return DN_OK;
 }

src/dyn_message.h

@@ -641,6 +641,16 @@ rstatus_t dnode_peer_req_forward(struct context *ctx, struct conn *c_conn,
 void dnode_peer_gossip_forward(struct context *ctx, struct conn *conn,
                                struct mbuf *data);
 
+/*
+ * Simulates a successful response as though the datastore sent it.
+ * Also, does the necessary to make sure that the response path is
+ * able to send this response back to the client.
+ *
+ * Returns DN_OK on success and an appropriate error otherwise.
+ */
+rstatus_t simulate_ok_rsp(struct context *ctx, struct conn *conn,
+    struct msg *msg);
+
 // Returns 'true' if 'msg_type' is a Dynomite configuration command.
 bool is_msg_type_dyno_config(msg_type_t msg_type);