nginx - What does the error starting mongodb on the server mean?

Question

2017-05-02T16:16:31.190+0800 I CONTROL  [initandlisten] ** WARNING: /sys/kernel/mm/transparent_hugepage/defrag is 'always'.
2017-05-02T16:16:31.190+0800 I CONTROL  [initandlisten] **        We suggest setting it to 'never'
2017-05-02T16:16:31.190+0800 I CONTROL  [initandlisten]
2017-05-02T16:16:31.190+0800 I CONTROL  [initandlisten] ** WARNING: soft rlimits too low. rlimits set to 3901 processes, 1000000 files. Number of processes should be at least 500000 : 0.5 times number of files.
2017-05-02T16:16:31.190+0800 I CONTROL  [initandlisten]
2017-05-02T16:16:31.265+0800 I FTDC     [initandlisten] Initializing full-time diagnostic data capture with directory '/var/mongodb/data/diagnostic.data'
2017-05-02T16:16:31.279+0800 I NETWORK  [HostnameCanonicalizationWorker] Starting hostname canonicalization worker
2017-05-02T16:16:31.282+0800 I NETWORK  [initandlisten] waiting for connections on port 27017
2017-05-02T17:13:19.617+0800 I NETWORK  [initandlisten] connection accepted from 127.0.0.1:52260 #1 (1 connection now open)
2017-05-02T17:13:48.843+0800 I NETWORK  [conn1] end connection 127.0.0.1:52260 (0 connections now open)
2017-05-02T17:26:19.310+0800 I CONTROL  [signalProcessingThread] got signal 15 (Terminated), will terminate after current cmd ends
2017-05-02T17:26:19.310+0800 I FTDC     [signalProcessingThread] Shutting down full-time diagnostic data capture
2017-05-02T17:26:19.312+0800 I CONTROL  [signalProcessingThread] now exiting
2017-05-02T17:26:19.312+0800 I NETWORK  [signalProcessingThread] shutdown: going to close listening sockets...
2017-05-02T17:26:19.312+0800 I NETWORK  [signalProcessingThread] closing listening socket: 6
2017-05-02T17:26:19.312+0800 I NETWORK  [signalProcessingThread] closing listening socket: 7
2017-05-02T17:26:19.312+0800 I NETWORK  [signalProcessingThread] removing socket file: /tmp/mongodb-27017.sock
2017-05-02T17:26:19.313+0800 I NETWORK  [signalProcessingThread] shutdown: going to flush diaglog...
2017-05-02T17:26:19.313+0800 I NETWORK  [signalProcessingThread] shutdown: going to close sockets...
2017-05-02T17:26:19.313+0800 I STORAGE  [signalProcessingThread] WiredTigerKVEngine shutting down
2017-05-02T17:26:19.547+0800 I STORAGE  [signalProcessingThread] shutdown: removing fs lock...
2017-05-02T17:26:19.547+0800 I CONTROL  [signalProcessingThread] dbexit:  rc: 0

Answer 1

The ones listed here are only WARNINGs and will not cause the server to exit. If you are interested in these two WARNINGs, you can view the document:
Disable Transparent Huge Pages (THP)
UNIX ulimit Settings
The reason for the server exit is:

2017-05-02T17:26:19.310+0800 I CONTROL [signalProcessingThread] got signal 15 (Terminated), will terminate after current cmd ends

Actually this is a normal ending, probably kill或其他类似的命令结束了mongod.

Answer 2

There is a warning: soft rlimits too low