Also i receive such kind of kibana logs in /var/log/kibana:
"type":"log","@timestamp":"2019-12-28T11:04:25Z","tags":["debug","http","server","Kibana","cookie-session-storage"],"pid":28206,"message":"Error: Unauthorized"}
{"type":"log","@timestamp":"2019-12-28T11:04:25Z","tags":["debug","plugins","security","basic"],"pid":28206,"message":"Trying to perform a login."}
{"type":"log","@timestamp":"2019-12-28T11:04:25Z","tags":["debug","plugins","security","basic"],"pid":28206,"message":"Failed to perform a login: [security_exception] missing authentication credentials for REST request [/_security/_authenticate], with { header={ WWW-Authenticate=\"Basic realm=\\\"security\\\" charset=\\\"UTF-8\\\"\" } }"}
{"type":"log","@timestamp":"2019-12-28T11:04:25Z","tags":["license","debug","xpack"],"pid":28206,"message":"Calling [data] Elasticsearch _xpack API. Polling frequency: 30001"}
{"type":"response","@timestamp":"2019-12-28T11:04:25Z","tags":[],"pid":28206,"method":"post","statusCode":401,"req":{"url":"/api/security/v1/login","method":"post","headers":{"host":"10.0.139.79:5601","connection":"keep-alive","content-length":"43","accept":"application/json, text/plain, */*","origin":"http://10.0.139.79:5601","kbn-version":"7.5.0","user-agent":"Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/78.0.3904.108 Safari/537.36","content-type":"application/json;charset=UTF-8","referer":"http://10.0.139.79:5601/login?next=%2F","accept-encoding":"gzip, deflate","accept-language":"en-US,en;q=0.9"},"remoteAddress":"10.0.206.38","userAgent":"10.0.206.38","referer":"http://10.0.139.79:5601/login?next=%2F"},"res":{"statusCode":401,"responseTime":27,"contentLength":9},"message":"POST /api/security/v1/login 401 27ms - 9.0B"}
{"type":"log","@timestamp":"2019-12-28T11:04:25Z","tags":["debug","monitoring","kibana-monitoring"],"pid":28206,"message":"Received Kibana Ops event data"}
{"type":"log","@timestamp":"2019-12-28T11:04:25Z","tags":["debug","monitoring","kibana-monitoring"],"pid":28206,"message":"Received Kibana Ops event data"}
{"type":"log","@timestamp":"2019-12-28T11:04:25Z","tags":["debug","stats-collection"],"pid":28206,"message":"Fetching data from kibana_stats collector"}
{"type":"log","@timestamp":"2019-12-28T11:04:25Z","tags":["debug","stats-collection"],"pid":28206,"message":"Fetching data from kibana_settings collector"}
{"type":"log","@timestamp":"2019-12-28T11:04:25Z","tags":["debug","stats-collection"],"pid":28206,"message":"not sending [kibana_settings] monitoring document because [undefined] is null or invalid."}
{"type":"log","@timestamp":"2019-12-28T11:04:25Z","tags":["debug","monitoring","kibana-monitoring"],"pid":28206,"message":"Uploading bulk stats payload to the local cluster"}
{"type":"log","@timestamp":"2019-12-28T11:04:25Z","tags":["debug","monitoring","kibana-monitoring"],"pid":28206,"message":"Uploaded bulk stats payload to the local cluster"}
{"type":"log","@timestamp":"2019-12-28T11:04:26Z","tags":["plugin","debug"],"pid":28206,"message":"Checking Elasticsearch version"}
{"type":"ops","@timestamp":"2019-12-28T11:04:26Z","tags":[],"pid":28206,"os":{"load":[0.189453125,0.712890625,0.75439453125],"mem":{"total":25196810240,"free":1758330880},"uptime":9432669},"proc":{"uptime":111.582,"mem":{"rss":347217920,"heapTotal":260194304,"heapUsed":212437248,"external":1790392},"delay":0.12874412536621094},"load":{"requests":{"5601":{"total":1,"disconnects":0,"statusCodes":{"401":1}}},"responseTimes":{"5601":{"avg":27,"max":27}},"sockets":{"http":{"total":3,"169.254.169.254:80:":3},"https":{"total":0}}},"message":"memory: 202.6MB uptime: 0:01:52 load: [0.19 0.71 0.75] delay: 0.129"}
^C{"type":"log","@timestamp":"2019-12-28T11:04:28Z","tags":["plugin","debug"],"pid":28206,"message":"Checking Elasticsearch version"}