CDRIVER-2376 fix performance loss

Starting in commit #9f9934dcd, the driver had incorrectly called "ping"
before nearly every command when in single-threaded mode. This was due
to the mongoc_topology_scanner_node_t.last_update field not being
updated, so the driver thought each server's socket had been idle and
needed to be checked with "ping", even when the socket had been used
recently.

In this commit, update last_used after every command so we don't call
"ping" unnecessarily.

Author: ajdavis

src/mongoc/mongoc-cluster.c

@@ -433,6 +433,7 @@ mongoc_cluster_run_command_monitored (mongoc_cluster_t *cluster,
 {
    bool retval;
    uint32_t request_id = ++cluster->request_id;
+   uint32_t server_id;
    mongoc_apm_callbacks_t *callbacks;
    mongoc_apm_command_started_t started_event;
    mongoc_apm_command_succeeded_t succeeded_event;
@@ -444,6 +445,7 @@ mongoc_cluster_run_command_monitored (mongoc_cluster_t *cluster,
    int32_t compressor_id;
 
    server_stream = cmd->server_stream;
+   server_id = server_stream->sd->id;
    compressor_id = mongoc_server_description_compressor_id (server_stream->sd);
 
    callbacks = &cluster->client->apm_callbacks;
@@ -476,7 +478,7 @@ mongoc_cluster_run_command_monitored (mongoc_cluster_t *cluster,
                                          request_id,
                                          cmd->operation_id,
                                          &server_stream->sd->host,
-                                         server_stream->sd->id,
+                                         server_id,
                                          cluster->client->apm_context);
 
       callbacks->succeeded (&succeeded_event);
@@ -490,18 +492,21 @@ mongoc_cluster_run_command_monitored (mongoc_cluster_t *cluster,
                                       request_id,
                                       cmd->operation_id,
                                       &server_stream->sd->host,
-                                      server_stream->sd->id,
+                                      server_id,
                                       cluster->client->apm_context);
 
       callbacks->failed (&failed_event);
       mongoc_apm_command_failed_cleanup (&failed_event);
    }
    if (!retval) {
-      handle_not_master_error (cluster, server_stream->sd->id, error);
+      handle_not_master_error (cluster, server_id, error);
    }
    if (reply == &reply_local) {
       bson_destroy (&reply_local);
    }
+
+   _mongoc_topology_update_last_used (cluster->client->topology, server_id);
+
    return retval;
 }
 
@@ -556,6 +561,9 @@ mongoc_cluster_run_command_private (mongoc_cluster_t *cluster,
       handle_not_master_error (cluster, server_stream->sd->id, error);
    }
 
+   _mongoc_topology_update_last_used (cluster->client->topology,
+                                      server_stream->sd->id);
+
    return retval;
 }
 
@@ -2248,7 +2256,9 @@ mongoc_cluster_check_interval (mongoc_cluster_t *cluster, uint32_t server_id)
  *
  * mongoc_cluster_legacy_rpc_sendv_to_server --
  *
- *       Sends the given RPCs to the given server.
+ *       Sends the given RPCs to the given server. Used for OP_QUERY cursors,
+ *       OP_KILLCURSORS, and legacy writes with OP_INSERT, OP_UPDATE, and
+ *       OP_DELETE. This function is *not* in the OP_QUERY command path.
  *
  * Returns:
  *       True if successful.
@@ -2270,7 +2280,6 @@ mongoc_cluster_legacy_rpc_sendv_to_server (
    bson_error_t *error)
 {
    uint32_t server_id;
-   mongoc_topology_scanner_node_t *scanner_node;
    int32_t max_msg_size;
    bool ret = false;
    int32_t compressor_id = 0;
@@ -2326,14 +2335,7 @@ mongoc_cluster_legacy_rpc_sendv_to_server (
       GOTO (done);
    }
 
-   if (cluster->client->topology->single_threaded) {
-      scanner_node = mongoc_topology_scanner_get_node (
-         cluster->client->topology->scanner, server_id);
-
-      if (scanner_node) {
-         scanner_node->last_used = bson_get_monotonic_time ();
-      }
-   }
+   _mongoc_topology_update_last_used (cluster->client->topology, server_id);
 
    ret = true;
 

src/mongoc/mongoc-topology-private.h

@@ -111,6 +111,10 @@ bool
 _mongoc_topology_update_from_handshake (mongoc_topology_t *topology,
                                         const mongoc_server_description_t *sd);
 
+void
+_mongoc_topology_update_last_used (mongoc_topology_t *topology,
+                                   uint32_t server_id);
+
 int64_t
 mongoc_topology_server_timestamp (mongoc_topology_t *topology, uint32_t id);
 

src/mongoc/mongoc-topology.c

@@ -928,6 +928,34 @@ _mongoc_topology_update_from_handshake (mongoc_topology_t *topology,
    return has_server;
 }
 
+/*
+ *--------------------------------------------------------------------------
+ *
+ * _mongoc_topology_update_last_used --
+ *
+ *       Internal function. In single-threaded mode only, track when the socket
+ *       to a particular server was last used. This is required for
+ *       mongoc_cluster_check_interval to know when a socket has been idle.
+ *
+ *--------------------------------------------------------------------------
+ */
+
+void
+_mongoc_topology_update_last_used (mongoc_topology_t *topology,
+                                   uint32_t server_id)
+{
+   mongoc_topology_scanner_node_t *node;
+
+   if (!topology->single_threaded) {
+      return;
+   }
+
+   node = mongoc_topology_scanner_get_node (topology->scanner, server_id);
+   if (node) {
+      node->last_used = bson_get_monotonic_time ();
+   }
+}
+
 /*
  *--------------------------------------------------------------------------
  *