我在 glassfish 服务器上运行后端部署，当应用程序的前端需要某些数据时，它会发送 REST 请求。此外，后端还连接到 mongo 数据库：
前端<----rest---->后端<---->DB。
我的后端通过 glassfish 5 部署在 ubuntu 虚拟机上，前端在 apache 网络服务器上运行。
经过一段时间的使用后，比如说 5 分钟后，尤其是当多个用户使用该应用程序时，glassfish 服务器在尝试访问数据库时大多数时候都会崩溃并出现错误：java.net.SocketException: Too many open files。
当然，我已经在 Google 上搜索过这个问题了，有很多建议说只要增加现在打开的文件的数量1024。
我现在的问题是，这些打开的文件是什么？即使我增加它们的数量，一段时间后是否也会达到限制。增加是唯一的解决方案，还是我的编码可能有错误？提前致谢。
以下是我的 ubuntu 机器的 netstat 输出的片段：
tcp 0 0 localhost:27017 localhost:44856 ESTABLISHED -
tcp 0 0 localhost:27017 localhost:44980 ESTABLISHED -
tcp 0 0 localhost:27017 localhost:44794 ESTABLISHED -
tcp 0 0 localhost:27017 localhost:45132 ESTABLISHED -
tcp 0 0 localhost:27017 localhost:44764 ESTABLISHED -
tcp 0 0 localhost:27017 localhost:44814 ESTABLISHED -
tcp 0 0 localhost:27017 localhost:44756 ESTABLISHED -
tcp 0 0 localhost:27017 localhost:44374 ESTABLISHED -
tcp 0 0 localhost:27017 localhost:44926 ESTABLISHED -
tcp 0 0 localhost:27017 localhost:45040 ESTABLISHED -
tcp 0 0 localhost:27017 localhost:45276 ESTABLISHED -
tcp 0 0 localhost:27017 localhost:44858 ESTABLISHED -
tcp 0 0 localhost:27017 localhost:45052 ESTABLISHED -
tcp 0 0 localhost:27017 localhost:45310 ESTABLISHED -
tcp 0 0 localhost:27017 localhost:44806 ESTABLISHED -
tcp 0 0 localhost:27017 localhost:44840 ESTABLISHED -
tcp 0 0 localhost:27017 localhost:45046 ESTABLISHED -
tcp 0 0 localhost:27017 localhost:45222 ESTABLISHED -
tcp 0 0 localhost:27017 localhost:45160 ESTABLISHED -
tcp 0 0 localhost:27017 localhost:44990 ESTABLISHED -
tcp 0 0 localhost:27017 localhost:44914 ESTABLISHED -
tcp 0 0 localhost:27017 localhost:45274 ESTABLISHED -
tcp 0 0 localhost:27017 localhost:44998 ESTABLISHED -
tcp 0 0 localhost:27017 localhost:44788 ESTABLISHED -
tcp6 0 0 localhost:45176 localhost:27017 ESTABLISHED 5204/java
tcp6 0 0 localhost:45136 localhost:27017 ESTABLISHED 5204/java
tcp6 0 0 localhost:45058 localhost:27017 ESTABLISHED 5204/java
tcp6 0 0 localhost:44926 localhost:27017 ESTABLISHED 5204/java
tcp6 0 0 localhost:44968 localhost:27017 ESTABLISHED 5204/java
tcp6 0 0 localhost:45190 localhost:27017 ESTABLISHED 5204/java
tcp6 0 0 localhost:45050 localhost:27017 ESTABLISHED 5204/java
tcp6 0 0 localhost:44886 localhost:27017 ESTABLISHED 5204/java
tcp6 0 0 localhost:45308 localhost:27017 ESTABLISHED 5204/java
tcp6 0 0 localhost:44978 localhost:27017 ESTABLISHED 5204/java
tcp6 0 0 localhost:45086 localhost:27017 ESTABLISHED 5204/java
tcp6 0 0 localhost:45198 localhost:27017 ESTABLISHED 5204/java
tcp6 0 0 localhost:44922 localhost:27017 ESTABLISHED 5204/java
tcp6 0 0 localhost:44938 localhost:27017 ESTABLISHED 5204/java
tcp6 0 0 localhost:45020 localhost:27017 ESTABLISHED 5204/java
tcp6 0 0 localhost:44896 localhost:27017 ESTABLISHED 5204/java
tcp6 0 0 localhost:44830 localhost:27017 ESTABLISHED 5204/java
tcp6 0 0 localhost:44960 localhost:27017 ESTABLISHED 5204/java
tcp6 0 0 localhost:44776 localhost:27017 ESTABLISHED 5204/java
如您所见，与 localhost：27017（即 mongo 数据库）建立了许多连接。