I’ve seen similar issues on my mx-104s, I found some solutions and posted about them previously, check the archives for "artificially high (100%) CPU usage reported from routing engine on Juniper MX-104 w/ 550 interfaces & solution”.
I’ve also added this ignore list into my observium config.php, it overlaps my previous solution somewhat, but after a discovery it won’t even try to poll these anymore, can help if you can’t modify the juniper for some reason. Note the irb regex is commented out, I wanted stats for those but kept it around in case it’s needed. You may need gres, for instance.
#Get rid of bogus JunOS interfaces, most of these are unconfigurable
$config['bad_if_regexp'][] = '/^fxp[0-9]/'; // management interface
$config['bad_if_regexp'][] = '/^cbp[0-9]/'; // no idea
$config['bad_if_regexp'][] = '/^dsc/'; // discard interface
$config['bad_if_regexp'][] = '/^lo[0-9].*/'; // loopback
$config['bad_if_regexp'][] = '/^tap/'; // multicast tunnel
$config['bad_if_regexp'][] = '/^gre/'; // gre interfaces
$config['bad_if_regexp'][] = '/^ipip/'; // ip-in-ip interfaces
$config['bad_if_regexp'][] = '/^pim[a-z]/'; // multicast
$config['bad_if_regexp'][] = '/^mtun/'; // multicast tunnel
$config['bad_if_regexp'][] = '/^em[0-9].*/'; // ethernet management interface
$config['bad_if_regexp'][] = '/^cpb[0-9]/'; // collector interface
$config['bad_if_regexp'][] = '/^demux[0-9]/'; // demux interface
//$config['bad_if_regexp'][] = '/^irb/'; // routing and bridging interface
$config['bad_if_regexp'][] = '/^pip[0-9]/'; // no idea
$config['bad_if_regexp'][] = '/^pp[0-9]/'; // no idea
$config['bad_if_regexp'][] = '/^.*\.[0-9]{5}/'; // auto generated interfaces, e.g. pfd-0/0/0.32567
$config['bad_if_regexp'][] = '/^lc.*/'; // local interface
$config['bad_if_regexp'][] = '/^lsi.*/'; // Internally generated interface
$config['bad_if_regexp'][] = '/^pf[a-z].*/'; // no idea
$config['bad_if_regexp'][] = '/^vme.*/'; // Virtual Chassis management interface
$config['bad_if_regexp'][] = '/^bme.*/'; // Virtual Chassis management interface
$config['bad_if_regexp'][] = '/^jsrv.*/'; // Internal sFlow collector