构建记录的CSV并上传到S3 // AWSLambda //行为不一致

Question

我正在编写一个在DynamoDB事件上触发的lambda。记录更改的记录，构建csv文件，然后将其上传到s3。

当我在日志中打印更改的记录时，可以看到记录。但是，当我生成一个csv文件并上载它时，有时它确实会生成该文件并上载它。有时，它仅上传没有标题的文件。

以下是代码段：

private void buildAndUploadCSV(List<Map<String, AttributeValue>> changedRecords, Context context, String tableName)
            throws IOException {
        Calendar calendar = Calendar.getInstance();
        SimpleDateFormat formatter = new SimpleDateFormat("yyyyMMddHHmmss");
        String outputName = tableName + "_" + formatter.format(calendar.getTime()) + ".csv";
        List<String> headers = changedRecords.stream().flatMap(map -> map.keySet().stream()).distinct()
                .collect(Collectors.toList());
        Path filePath = Paths.get("/tmp", outputName);
        try (BufferedWriter bw = new BufferedWriter(
                new OutputStreamWriter(new FileOutputStream(filePath.toFile()), StandardCharsets.UTF_8))) 
        {
            StringBuilder headerContent = new StringBuilder();
            for (String string : headers) {
                headerContent.append(string);
                headerContent.append(",");
            }
            StringBuilder strBuilder = new StringBuilder();
            for (Map<String, AttributeValue> lmap : changedRecords) {
                StringBuilder stringBuilder = new StringBuilder("");
                String sep = "";
                for (Entry<String, AttributeValue> string2 : lmap.entrySet()) {
                    String value = string2.getValue().getS();
                    stringBuilder.append(sep).append("\"").append(value).append("\"");
                    sep = ",";
                }
                if (!stringBuilder.toString().isEmpty()) {
                    strBuilder.append(stringBuilder).append(System.getProperty("line.separator"));
                }
            }
            bw.append(headerContent);
            bw.append("\n");
            bw.append(strBuilder);
            context.getLogger().log("[DEBUG] String Builder is: " + strBuilder);
            PutObjectRequest request = new PutObjectRequest("bucket", "data/" + outputName,
                    filePath.toFile());
            s3.putObject(request);
        } catch (IOException e) {
            context.getLogger().log("[ERROR] - IOException " + e);
        }
    }

关于为什么某些文件为空的任何建议/输入？