node_md_state did not capture "removed" state

Host operating system: output of uname -a

Linux sds-3 4.18.0-305.7.1.el8_4.x86_64 #1 SMP Tue Jun 29 21:55:12 UTC 2021 x86_64 x86_64 x86_64 GNU/Linux

node_exporter version: output of node_exporter --version

node_exporter, version 1.3.1 (branch: HEAD, revision: a2321e7b940ddcff26873612bccdf7cd4c42b6b6)
build user: root@243aafa5525c
build date: 20211205-11:09:49
go version: go1.17.3
platform: linux/amd64

node_exporter command line flags

/usr/local/bin/node_exporter --path.procfs=/proc --path.sysfs=/sys --collector.filesystem.ignored-mount-points="^/(dev|proc|sys|var/lib/docker/.+)($|/)" --collector.filesystem.ignored-fs-types="^(autofs|binfmt_misc|cgroup|configfs|debugfs|devpts|devtmpfs|fusectl|hugetlbfs|mqueue|overlay|proc|procfs|pstore|rpc_pipefs|securityfs|sysfs|tracefs)$" --no-collector.wifi

Are you running node_exporter in Docker?

no

What did you do that produced an error?

mdadm -D output

/dev/md125:
           Version : 1.0
     Creation Time : Mon Jul  5 19:40:20 2021
        Raid Level : raid1
        Array Size : 614336 (599.94 MiB 629.08 MB)
     Used Dev Size : 614336 (599.94 MiB 629.08 MB)
      Raid Devices : 2
     Total Devices : 1
       Persistence : Superblock is persistent

     Intent Bitmap : Internal

       Update Time : Sun May 22 01:00:01 2022
             State : clean, degraded
    Active Devices : 1
   Working Devices : 1
    Failed Devices : 0
     Spare Devices : 0

Consistency Policy : bitmap

              Name : sds-3:boot_efi  (local to host sds-3)
              UUID : 312be27c:732e4a9e:6b279d78:10cd6a6a
            Events : 177

    Number   Major   Minor   RaidDevice State
       -       0        0        0      removed
       1       8       18        1      active sync   /dev/sdb2

What did you expect to see?

node_md_state{device="md125", instance="sds-3", job="sds-nodes", state="removed"}

What did you see instead?

"removed" state metric not yet implemented in node_md_state

Start by locating the node_md_state collector and the code that parses mdadm -D output. Reproduce the RAID1 case with a removed device and inspect the collector's existing state handling. Done means node_md_state exposes state="removed" for the affected array, with collector tests covering the output.