How to set up Grafana HTTPS for secure web traffic

Grafana Configuration
3

this config leading to an error - grafana-server is failing to start

  [server]
    # Protocol (http or https)
    protocol = https

    # The ip address to bind to, empty will bind to all interfaces
    ;http_addr =

    # The http port  to use
    #http_port = 3000

    # The public facing domain name used to access grafana from a browser
    #domain = localhost

    # Redirect to correct domain if host header does not match domain
    # Prevents DNS rebinding attacks
    #enforce_domain = false

    # The full public facing url you use in browser, used for redirects and emails
    # If you use reverse proxy and sub path specify full url (with sub path)
    root_url = https://community.grafana.com

    # Log web requests
    #router_logging = false

    # the path relative working path
    #static_root_path = public

    # enable gzip
    #enable_gzip = false

    # https certs & key file
    cert_file = /etc/letsencrypt/live/mysite/fullchain.pem
    cert_key = /etc/letsencrypt/live/mysite/privkey.pem

is there someone who did such kind of thing?

UPD: in grafana log file I found

t=2017-04-13T14:48:42+0000 lvl=info msg="Initializing HTTP Server" logger=http.server address=0.0.0.0:3000 protocol=https subUrl=
t=2017-04-13T14:48:42+0000 lvl=eror msg="Fail to start server" logger=server error="open /etc/letsencrypt/live/mysite/fullchain.pem: permission denied"
t=2017-04-13T14:48:42+0000 lvl=info msg="Shutdown started" logger=server code=1 reason="Startup failed"

and that is weird, because

root@server:~# stat /etc/letsencrypt/live/mysite/fullchain.pem
  File: ‘/etc/letsencrypt/live/mysite/fullchain.pem’ -> ‘../../archive/mysite/fullchain1.pem’
  Size: 48              Blocks: 0          IO Block: 4096   symbolic link
Device: b302h/45826d    Inode: 517147      Links: 1
Access: (0777/lrwxrwxrwx)  Uid: (    0/    root)   Gid: (    0/    root)
Access: 2017-04-10 11:38:32.720709836 +0000
Modify: 2017-04-10 11:38:32.720709836 +0000
Change: 2017-04-10 11:38:32.720709836 +0000
 Birth: -