StorageGRID collectors should support only_cluster_instance

[cgrinds]

Discussed in #2540

Thanks to @santosh725 for raising.

[Hardikl]

Without only_cluster_instance: true flag the SG metrics haven't been exported.

harvest % ./bin/poller -p sg-tudor -o Health --promPort 14001
2024-02-13T14:53:32+05:30 INF poller/poller.go:215 > Init Poller=sg-tudor asup=false confPath=conf config=harvest.yml configPath=harvest.yml daemon=false debug=false homePath= hostname=hardikl-mac-0 logLevel=info logPath=/var/log/harvest/ profiling=0 promPort=18001 version="harvest version 24.02.1313-v23.11.0 (commit febb62c5) (build date 2024-02-13T13:36:45+0530) darwin/amd64"
2024-02-13T14:53:32+05:30 INF poller/poller.go:239 > started in foreground Poller=sg-tudor pid=27686
2024-02-13T14:53:34+05:30 INF collector/helpers.go:84 > best-fit template Poller=sg-tudor collector=StorageGrid:Health path=conf/storagegrid/11.6.0/health.yaml v=11.7.0
2024-02-13T14:53:34+05:30 INF storagegrid/storagegrid.go:83 > initialized Poller=sg-tudor collector=StorageGrid:Health
2024-02-13T14:53:34+05:30 INF poller/poller.go:357 > Autosupport scheduled. Poller=sg-tudor asupSchedule=24h
2024-02-13T14:53:34+05:30 INF poller/poller.go:366 > poller start-up complete Poller=sg-tudor
2024-02-13T14:53:34+05:30 INF prometheus/httpd.go:40 > server listen Poller=sg-tudor exporter=prometheus1 url=http://:18001/metrics
2024-02-13T14:53:34+05:30 INF poller/poller.go:523 > updated status, up collectors: 1 (of 1), up exporters: 1 (of 1) Poller=sg-tudor
2024-02-13T14:53:35+05:30 INF collector/collector.go:585 > Collected Poller=sg-tudor apiMs=245 calcMs=0 collector=StorageGrid:Health exportMs=0 instances=0 instancesExported=0 metrics=0 metricsExported=0 parseMs=0 pluginMs=0 pollMs=245 zBegin=1707816214846

Tested in main with commit febb62c

Template used for testing.

name: Health
query: grid/health
object: storagegrid

schedule:
  - data: 1m

counters:
  - alarms.critical => alarms_critical
  - alarms.major => alarms_major
  - alarms.minor => alarms_minor
  - nodes.connected => nodes_connected
  - nodes.administratively-down => nodes_admin_down
  - nodes.unknown => nodes_unknown

only_cluster_instance: true

export_options:
  include_all_labels: true

harvest % ./bin/poller -p sg-tudor -o Health --promPort 14001
2024-02-13T14:55:54+05:30 INF poller/poller.go:215 > Init Poller=sg-tudor asup=false confPath=conf config=harvest.yml configPath=harvest.yml daemon=false debug=false homePath= hostname=hardikl-mac-0 logLevel=info logPath=/var/log/harvest/ profiling=0 promPort=14001 version="harvest version 24.02.1313-v23.11.0 (commit febb62c5) (build date 2024-02-13T13:36:45+0530) darwin/amd64"
2024-02-13T14:55:54+05:30 INF poller/poller.go:239 > started in foreground Poller=sg-tudor pid=27832
2024-02-13T14:55:56+05:30 INF collector/helpers.go:84 > best-fit template Poller=sg-tudor collector=StorageGrid:Health path=conf/storagegrid/11.6.0/health.yaml v=11.7.0
2024-02-13T14:55:56+05:30 INF storagegrid/storagegrid.go:83 > initialized Poller=sg-tudor collector=StorageGrid:Health
2024-02-13T14:55:56+05:30 INF poller/poller.go:357 > Autosupport scheduled. Poller=sg-tudor asupSchedule=24h
2024-02-13T14:55:56+05:30 INF poller/poller.go:366 > poller start-up complete Poller=sg-tudor
2024-02-13T14:55:56+05:30 INF prometheus/httpd.go:40 > server listen Poller=sg-tudor exporter=prometheus1 url=http://:14001/metrics
2024-02-13T14:55:56+05:30 INF poller/poller.go:523 > updated status, up collectors: 1 (of 1), up exporters: 1 (of 1) Poller=sg-tudor
2024-02-13T14:55:56+05:30 INF collector/collector.go:585 > Collected Poller=sg-tudor apiMs=239 calcMs=0 collector=StorageGrid:Health exportMs=0 instances=1 instancesExported=1 metrics=6 metricsExported=18 parseMs=0 pluginMs=0 pollMs=239 zBegin=1707816356415
2024-02-13T14:56:57+05:30 INF collector/collector.go:585 > Collected Poller=sg-tudor apiMs=714 calcMs=0 collector=StorageGrid:Health exportMs=0 instances=1 instancesExported=1 metrics=6 metricsExported=18 parseMs=0 pluginMs=0 pollMs=714 zBegin=1707816416416
2024-02-13T14:57:57+05:30 INF collector/collector.go:585 > Collected Poller=sg-tudor apiMs=712 calcMs=0 collector=StorageGrid:Health exportMs=0 instances=1 instancesExported=1 metrics=6 metricsExported=18 parseMs=0 pluginMs=0 pollMs=712 zBegin=1707816476418
2024-02-13T14:58:57+05:30 INF collector/collector.go:585 > Collected Poller=sg-tudor apiMs=721 calcMs=0 collector=StorageGrid:Health exportMs=0 instances=1 instancesExported=1 metrics=6 metricsExported=18 parseMs=0 pluginMs=0 pollMs=721 zBegin=1707816536419

harvest % curl -s http://localhost:14001/metrics | grep -Ev "#|metadata_"           
storagegrid_nodes_unknown{cluster="SG5712FP",datacenter="rtp"} 3
storagegrid_alarms_critical{cluster="SG5712FP",datacenter="rtp"} 0
storagegrid_alarms_major{cluster="SG5712FP",datacenter="rtp"} 0
storagegrid_alarms_minor{cluster="SG5712FP",datacenter="rtp"} 0
storagegrid_nodes_connected{cluster="SG5712FP",datacenter="rtp"} 2
storagegrid_nodes_admin_down{cluster="SG5712FP",datacenter="rtp"} 0
harvest %