我将请求发送到Web服务，将结果转换为一个大的 csv 并将csv行保存到数据库中。
由于请求是长时间运行的（10-20秒），我想并行化请求。我一次收集了所有的数据 StringBuilder 保存转换的csv行的。
问题：如果在csv中达到了1000行的数据块，那么如何将数据取出进行持久化，而任何其他并发响应都将写入新的 StringBuilder ?
因为，流的最终变量无法重新初始化。

final StringBuilder sb = new StringBuilder();
AtomicInteger count = new AtomicInteger();
Flux.fromIterable(requests)
    .flatMap(req -> {
        return webClientService.send(req); //assume long running response
    }, 8) //send 8 requests in parallel, as response takes up to 10s
    .map(rsp -> {
        //convert response to csv values and add to StringBuilder
        int c = addCsv(sb, rsp);
        if (count.addAndGet(c) > 1000) {
            //TODO how can I assign a new StringBuilder,
            //so that all further finished responses will append the csv to the new builder?
            //same problem with the counter.
            databaseWriter.write(sb.build()); //writes the content so far to db, but not threadsafe so far
        }
        return c;
    })
    .blockLast();