ethtool collector doesn't properly work when 2 interfaces are present

[aned]

node_exporter version="1.2.0"
Running on

node_uname_info{domainname="(none)",machine="x86_64",nodename="host A",release="5.4.80",sysname="Linux",version="#1 SMP Mon Dec 7 00:28:18 UTC 2020"} 1

2 interfaces present enp23s0f0 and enp23s0f1

ip link show
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN mode DEFAULT group default qlen 1000
    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
6: enp23s0f0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc mq state UP mode DEFAULT group default qlen 1000
    link/ether 0c:42:a1:a0:1e:e1 brd ff:ff:ff:ff:ff:ff
7: enp23s0f1: <BROADCAST,MULTICAST> mtu 1500 qdisc noop state DOWN mode DEFAULT group default qlen 1000
    link/ether 0c:42:a1:a0:1e:e2 brd ff:ff:ff:ff:ff:ff

It collects only "node_network" stats on enp23s0f0, it should have ethtool stats but it doesn't:

curl localhost:9100/metrics | grep enp23s0f0
node_network_address_assign_type{device="enp23s0f0"} 0
node_network_carrier{device="enp23s0f0"} 1
node_network_carrier_changes_total{device="enp23s0f0"} 13
node_network_carrier_down_changes_total{device="enp23s0f0"} 6
...
node_network_up{device="enp23s0f0"} 1

It works as expected on enp23s0f1 interface (with all 0 values since the interface is down)

curl localhost:9100/metrics | grep enp23s0f1
node_ethtool_ch0_aff_change{device="enp23s0f1"} 0
node_ethtool_ch0_arm{device="enp23s0f1"} 0
node_ethtool_ch0_eq_rearm{device="enp23s0f1"} 0
node_ethtool_ch0_events{device="enp23s0f1"} 0
node_ethtool_ch0_force_irq{device="enp23s0f1"} 0
node_ethtool_ch0_poll{device="enp23s0f1"} 0
node_ethtool_ch10_aff_change{device="enp23s0f1"} 0
node_ethtool_ch10_arm{device="enp23s0f1"} 0
node_ethtool_ch10_eq_rearm{device="enp23s0f1"} 0
...
node_ethtool_received_prio5_discards{device="enp23s0f1"} 0
node_ethtool_received_prio5_packets{device="enp23s0f1"} 0
node_ethtool_received_prio6_bytes{device="enp23s0f1"} 0
node_ethtool_received_prio6_discards{device="enp23s0f1"} 0
node_ethtool_received_prio6_packets{device="enp23s0f1"} 0
node_ethtool_received_prio7_bytes{device="enp23s0f1"} 0
node_ethtool_received_prio7_discards{device="enp23s0f1"} 0
node_ethtool_received_prio7_packets{device="enp23s0f1"} 0
....
node_ethtool_transmitted_prio0_bytes{device="enp23s0f1"} 0
node_ethtool_transmitted_prio0_packets{device="enp23s0f1"} 0
node_ethtool_transmitted_prio1_bytes{device="enp23s0f1"} 0
node_ethtool_transmitted_prio1_packets{device="enp23s0f1"} 0
node_ethtool_transmitted_prio2_bytes{device="enp23s0f1"} 0
node_ethtool_transmitted_prio2_packets{device="enp23s0f1"} 0
node_ethtool_transmitted_prio3_bytes{device="enp23s0f1"} 0
node_ethtool_transmitted_prio3_packets{device="enp23s0f1"} 0
node_ethtool_transmitted_prio4_bytes{device="enp23s0f1"} 0
node_ethtool_transmitted_prio4_packets{device="enp23s0f1"} 0
node_ethtool_transmitted_prio5_bytes{device="enp23s0f1"} 0
node_ethtool_transmitted_prio5_packets{device="enp23s0f1"} 0
...
node_network_address_assign_type{device="enp23s0f1"} 0
node_network_carrier_changes_total{device="enp23s0f1"} 0
node_network_carrier_down_changes_total{device="enp23s0f1"} 0
node_network_carrier_up_changes_total{device="enp23s0f1"} 0
node_network_device_id{device="enp23s0f1"} 0
node_network_flags{device="enp23s0f1"} 4098

[ventifus]

If you run ethtool -S enp23s0f0 do you get any stats for that interface? Also, node_exporter should log some messages when it can't ethtool-stat an interface, can you try running node_exporter --log.level=debug. You'll get some log entries along the lines of
level=debug ts=2021-08-17T22:55:27.738Z caller=ethtool_linux.go:219 collector=ethtool msg="ethtool stats error" err="operation not supported" device=lo errno=95

[aned]

Yes, ethtool -S enp23s0f0 works from cli:

ethtool -S enp23s0f0
NIC statistics:
     rx_packets: 18149198
     rx_bytes: 13248502341
     tx_packets: 13820797
     tx_bytes: 4783009187
     tx_tso_packets: 505056
     tx_tso_bytes: 2452267774
     tx_tso_inner_packets: 0
     tx_tso_inner_bytes: 0
     tx_added_vlan_packets: 0
...

This is the error log:

level=error ts=2021-08-17T23:34:43.225Z caller=ethtool_linux.go:154 collector=ethtool msg="ethtool stats error" err="ethtool currently doesn't support more than 8192 entries, received 9945" device=enp23s0f0

[ventifus]

This is a limitation in the ethtool library we use (github.com/safchain/ethtool). But you're in luck, @fach just merged a bump to that limit specifically for node_exporter. Thank you @fach!