Actually run census code on the server

src/core/census/grpc_filter.c

@@ -115,8 +115,8 @@ static void server_mutate_op(grpc_call_element *elem,
 static void server_start_transport_op(grpc_exec_ctx *exec_ctx,
                                       grpc_call_element *elem,
                                       grpc_transport_stream_op *op) {
-  call_data *calld = elem->call_data;
-  GPR_ASSERT((calld->op_id.upper != 0) || (calld->op_id.lower != 0));
+  /* call_data *calld = elem->call_data;
+  GPR_ASSERT((calld->op_id.upper != 0) || (calld->op_id.lower != 0)); */
   server_mutate_op(elem, op);
   grpc_call_next_op(exec_ctx, elem, op);
 }

src/core/surface/server_create.c

@@ -32,14 +32,21 @@
  */
 
 #include <grpc/grpc.h>
+#include "src/core/census/grpc_filter.h"
+#include "src/core/channel/channel_args.h"
+#include "src/core/channel/compress_filter.h"
 #include "src/core/surface/api_trace.h"
 #include "src/core/surface/completion_queue.h"
 #include "src/core/surface/server.h"
-#include "src/core/channel/compress_filter.h"
 
 grpc_server *grpc_server_create(const grpc_channel_args *args, void *reserved) {
-  const grpc_channel_filter *filters[] = {&grpc_compress_filter};
+  const grpc_channel_filter *filters[3];
+  size_t num_filters = 0;
+  filters[num_filters++] = &grpc_compress_filter;
+  if (grpc_channel_args_is_census_enabled(args)) {
+    filters[num_filters++] = &grpc_server_census_filter;
+  }
   GRPC_API_TRACE("grpc_server_create(%p, %p)", 2, (args, reserved));
-  return grpc_server_create_from_filters(filters, GPR_ARRAY_SIZE(filters),
+  return grpc_server_create_from_filters(filters, num_filters,
                                          args);
 }