collstats metrics for shard cluster is incomplete

[abelite-fang]

Describe the bug
We are using mongodb_exporter on our shard cluster via SRV record, the collstats metrics like mongodb_collstats_storageStats_count{} return single shard count, and there is no label to identify which shard it is.

To Reproduce
Steps to reproduce the behavior:

1. Parameters:

serviceMonitor:
  enabled: true
  interval: 10s
  scrapeTimeout: 9s
  additionalLabels:
    release: prometheus-operator
  metricRelabelings:
    - targetLabel: cl_name
      replacement: core

existingSecret:
  name: "prometheus-mongodb-exporter"
  key: "mongodb-uri"

extraArgs:
  - --collector.indexstats
  - --collector.collstats
  - --collector.collstats-limit=0
  - --collect-all=true
  - --discovering-mode=true
  - --no-mongodb.direct-connect

2. connection string set to SRV record, and designate collection label to a sharded collection, exporter will only return single shard collstats.

Expected behavior
Expect to have collstats (e.g. document counts, logical data size, etc.) for each shard on a sharded cluster, identify by shard name (replicaset name) or any other label.

Logs
no relevance error log.

Environment

• environment: Kubernetes (EKS)
• MongoDB Atlas (managed), version: 5.0.25
• helm chart: prometheus-community/prometheus-mongodb-exporter version 3.5.0
• image: percona/mongodb_exporter:0.40.0

[igroene]

the rs_nm label should be useful to know which shard it belongs to

[steveteuber]

Today we realized that the collstats (e.g. document counts) are just from a single shard...
So, I think this bug still exists in the current version or have I missed something?

extraArgs::
  - --web.listen-address=:9216
  - --no-mongodb.direct-connect
  - --discovering-mode
  - --collector.collstats
  - --collector.indexstats
  - --collector.shards

Environment

MongoDB Atlas Version: 7.0.14
Helm Chart: prometheus-community/prometheus-mongodb-exporter:3.8.0
Exporter Image: percona/mongodb_exporter:0.42.0

[igroene]

this is working as intended. The exporter collects data from a single shard. You can use aggregation functions to get the total values per cluster.

[steveteuber]

I understand, but there is no extra label on the mongodb_collstats_storageStats_count metric to identify the shard:

# HELP mongodb_collstats_storageStats_count collstats.storageStats.
# TYPE mongodb_collstats_storageStats_count counter
mongodb_collstats_storageStats_count{cl_id="62fc834eee3dc317bcef0fed",cl_role="",collection="browseItems",database="cache"} 5.7282281e+07

In comparison, the arg --collector.shards generates the following metrics with a shard label that we would expect for the metric above:

# HELP mongodb_shards_collection_chunks_count shards collection chunks.
# TYPE mongodb_shards_collection_chunks_count counter
mongodb_shards_collection_chunks_count{collection="browseItems",database="cache",shard="atlas-100236-shard-0"} 103
mongodb_shards_collection_chunks_count{collection="browseItems",database="cache",shard="atlas-100236-shard-1"} 92
mongodb_shards_collection_chunks_count{collection="browseItems",database="cache",shard="atlas-100236-shard-2"} 210
mongodb_shards_collection_chunks_count{collection="browseItems",database="cache",shard="atlas-100236-shard-3"} 256
mongodb_shards_collection_chunks_count{collection="browseItems",database="cache",shard="atlas-100236-shard-4"} 80
mongodb_shards_collection_chunks_count{collection="browseItems",database="cache",shard="atlas-100236-shard-5"} 200
mongodb_shards_collection_chunks_count{collection="browseItems",database="cache",shard="atlas-100236-shard-6"} 325
mongodb_shards_collection_chunks_count{collection="browseItems",database="cache",shard="atlas-100236-shard-7"} 364
mongodb_shards_collection_chunks_count{collection="browseItems",database="cache",shard="atlas-100236-shard-8"} 224
mongodb_shards_collection_chunks_count{collection="browseItems",database="cache",shard="atlas-100236-shard-9"} 231

[igroene]

you are correct. I was seeing the rs_nm label but looks like that is something that PMM-agent adds. The exporter needs to have this.