fix(observabilidade): corrigir labels e migrar dashboard MongoDB para Grafana v2

[diego64]

Summary

• Migrate MongoDB dashboard from Grafana v1 schema (schemaVersion: 38, flat panels[]) to Grafana v2 API format (apiVersion: dashboard.grafana.app/v2, elements{} + RowsLayout)
• Fix all metric label mismatches introduced by percona/mongodb_exporter upgrade to v0.44
• Reorganize layout into four collapsible sections for better readability

Root cause

The dashboard was built targeting an older exporter version. After upgrading to percona/mongodb_exporter:0.44.0, all label names changed and every panel returned "No data":

Metric	Old label (broken)	New label (correct)
mongodb_ss_connections	state	conn_type
mongodb_ss_opcounters	metric was _total, label type	no suffix, label legacy_op_type
mongodb_ss_metrics_document	metric was _total, label state	no suffix, label doc_op_type
mongodb_ss_metrics_cursor_open	label state	csr_type
mongodb_ss_globalLock_currentQueue	metric was _total	no suffix, label count_type
mongodb_ss_network_bytes_*	mongodb_ss_network_bytes_in_total	mongodb_ss_network_bytesIn

Changes

observabilidade/grafana/dashboards/mongodb.json

• Format: migrated from v1 panels[] to v2 elements{} + RowsLayout required by Grafana 13
• All PromQL expressions updated with correct labels per exporter v0.44
• Layout reorganized into 4 sections:
  1. Status Geral — mongodb_up, conexões ativas/disponíveis, memória residente, fila bloqueada, taxa de operações
  2. Memória e Rede — mongodb_ss_mem_resident + virtual over time, mongodb_ss_network_bytesIn/Out rate
  3. Documentos e Cursores — mongodb_ss_metrics_document by doc_op_type, cursores abertos (csr_type="total"), conexões over time
  4. Logs — LogQL stream {container="bv-mongodb"} via Loki datasource loki-bv

Test plan

• All containers healthy: docker compose ps — all services Up (healthy)
• Exporter exposing metrics: curl localhost:9216/metrics | grep mongodb_up returns 1
• Prometheus scraping: curl localhost:9090/api/v1/query?query=mongodb_up returns result[0].value = "1"
• Grafana dashboard at http://localhost:3001 — all panels show data, no "No data" banners
• Stat panels: Status MongoDB = "Online", Conexões Ativas ≥ 1, Memória Residente > 0
• Timeseries panels: Taxa de Operações, Memória, Rede show historical data (may need 1–2 min of scrape history)
• Logs panel: shows bv-mongodb container log stream

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