private void finish(ChannelHandlerContext ctx) {
        try {
            onDrainEnd(ctx);
        } catch (Exception e) {
            logger.warn("{} Unexpected exception:", ctx.channel(), e);
        }
    }
Code executed on the connection drain end. Executed at most once.
core/src/main/java/com/linecorp/armeria/internal/common/GracefulConnectionShutdownHandler.java