I add a proxy in between Kibana and Elasticsearch,then
{"type":"log","@timestamp":"2017-09-20T21:27:06Z","tags":
["license","warning","xpack"],"pid":38255,"message":"License information could not be obtained from Elasticsearch. [security_exception] missing authentication token for REST request [/_xpack], with { header={ WWW- Authenticate=\"Basic realm=\\\"security\\\" charset=\\\"UTF-8\\\"\" } } :: {\"path\":\"/_xpack\",\"statusCode\":401,\"response\":\"{\\\"error\\\":{\\\"root_cause\\\": [{\\\"type\\\":\\\"security_exception\\\",\\\"reason\\\":\\\"missing authentication token for REST request [/_xpack]\\\",\\\"header\\\":{\\\"WWW-Authenticate\\\":\\\"Basic realm=\\\\\\\"security\\\\\\\" charset=\\\\\\\"UTF- 8\\\\\\\"\\\"}}],\\\"type\\\":\\\"security_exception\\\",\\\"reason\\\":\\\"missing authentication token for REST request [/_xpack]\\\",\\\"header\\\":{\\\"WWW-Authenticate\\\":\\\"Basic realm=\\\\\\\"security\\\\\\\" charset=\\\\\\\"UTF- 8\\\\\\\"\\\"}},\\\"status\\\":401}\",\"wwwAuthenticateDirective\":\"Basic realm=\\\"security\\\" charset=\\\"UTF- 8\\\"\"}"}