Troubleshooting monitoring in Logstash

When upgrading from older versions, the built-in logstash_system user is disabled for security reasons. To resume monitoring:

Change the logstash_system password:

PUT _security/user/logstash_system/_password
{
  "password": "newpassword"
}

Re-enable the logstash_system user:

PUT _security/user/logstash_system/_enable