Mongoose appears unclean full-time diagnostic data? ?

  mongodb, question

2017-03-08T15:21:16.453+0800 I NETWORK [thread1] waiting for connections on port 27017

2017-03-08T15:21:17.026+0800 I FTDC [ftdc] Unclean full-time diagnostic data capture shutdown detected, found interim file, some metrics may have been lost.

Why did the following sentence appear after waiting for the port connection to appear? What causes it? Novice solution

1. Delete diagnostic Data:

rm -f /var/lib/mongo/diagnostic.data/*

2. Start mongodb.

For reference.

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