MongoDB crashes regularly, how to diagnose?

Question

linux

Good afternoon!
MongoDB problem. Its service (daemon) regularly crashes when inserting data is active. However, there is nothing in the logs.
How to diagnose it to understand why it falls?
The setup is now:

# mongod.conf
net:
 bindIp: 127.0.0.1
 port: 27017
storage:
 dbPath: /var/lib/mongodb
 engine: wiredTiger
 wiredTiger:
  engineConfig:
   cacheSizeGB: 3
  collectionConfig:
   blockCompressor: snappy
systemLog:
   destination: file
   path: /var/log/mongodb/mongod.log
   logAppend: true

Answer 1

Monga can crash if there is not enough disk space, but this can be seen from the logs.
If there really are no logs, then the mongu is killed "outside", for example, through kill -9. Linux has a daemon that kills applications that eat a lot of memory. How much memory do you have and the weight of the indexes, how much monga uses memory?

Answer 2

On a 5 GB system,
db.stats() returns this:

{
        "db" : "docs",
        "collections" : 5,
        "objects" : 4732852,
        "avgObjSize" : 240.48514679943509,
        "dataSize" : 1138180608,
        "storageSize" : 361570304,
        "numExtents" : 0,
        "indexes" : 7,
        "indexSize" : 110952448,
        "ok" : 1
}

In the "calm" state, the monga uses 30% of the server's memory. Here is the mongostat of this state

insert query update delete getmore command % dirty % used flushes vsize  res qr|qw ar|aw netIn netOut conn     time
    *0    *0     *0     *0       0     1|0     0.0   49.1       0  1.6G 1.5G   0|0   1|0   79b    15k    1 13:07:18
    *0    *0     *0     *0       0     1|0     0.0   49.1       0  1.6G 1.5G   0|0   1|0   79b    15k    1 13:07:19

Answer 3

Why is mongodb taking a long time to execute queries?
Maybe it will help.