@Override
        protected void onTimeout(ClientRequestContext ctx, long selectionTimeoutMillis) {
            final EndpointSelectionTimeoutException ex =
                    EndpointSelectionTimeoutException.get(endpointGroup, selectionTimeoutMillis);
            ClientPendingThrowableUtil.setPendingThrowable(ctx, ex);
        }
Invoked when the {@link EndpointGroup} has been updated.
core/src/main/java/com/linecorp/armeria/client/endpoint/AbstractEndpointSelector.java