项目启动异常报错的大概内容是：

    1. about to fork child process, waiting until server is ready for connections.
    2. forked process: 25468
    3. ERROR: child process failed, exited with error number 1
    4. To see additional information in this output, start without the "--fork" option.

    mongodb非正常关闭后，再次启动会产生about to fork child process, waiting until server is ready for connection此异常。

    解决方案：
    删除mongodb 的data目录下的mongod.lock文件，重启mongodb即可。该文件会生成在日志文件下（跟bin目录同级）
    记得加sudo重启