Prometheus Metrics¶

Barrel DocDB exposes metrics in Prometheus format for monitoring and alerting.

Endpoint¶

Metrics are available at:

GET /metrics

Example:

curl http://localhost:8080/metrics

Available Metrics¶

Document Operations¶

Metric	Type	Labels	Description
`barrel_doc_operations_total`	Counter	db, operation	Total document operations
`barrel_doc_operation_duration_seconds`	Histogram	db, operation	Operation latency

Operations: put, get, delete

Example:

barrel_doc_operations_total{db="mydb",operation="put"} 1234
barrel_doc_operations_total{db="mydb",operation="get"} 5678
barrel_doc_operation_duration_seconds_bucket{db="mydb",operation="get",le="0.001"} 5000

Query Operations¶

Metric	Type	Labels	Description
`barrel_query_operations_total`	Counter	db	Total query operations
`barrel_query_duration_seconds`	Histogram	db	Query latency

Example:

barrel_query_operations_total{db="mydb"} 500
barrel_query_duration_seconds_bucket{db="mydb",le="0.01"} 450

Replication¶

Metric	Type	Labels	Description
`barrel_replication_docs_total`	Counter	source, target	Documents replicated
`barrel_replication_errors_total`	Counter	source, target	Replication errors

Example:

barrel_replication_docs_total{source="mydb",target="http://remote:8080/mydb"} 10000
barrel_replication_errors_total{source="mydb",target="http://remote:8080/mydb"} 2

Federation¶

Metric	Type	Labels	Description
`barrel_federation_queries_total`	Counter	federation	Federation queries
`barrel_federation_errors_total`	Counter	federation, member	Member errors

HTTP Server¶

Metric	Type	Labels	Description
`barrel_http_requests_total`	Counter	method, path, status	HTTP requests
`barrel_http_request_duration_seconds`	Histogram	method, path	Request latency

Example:

barrel_http_requests_total{method="GET",path="/db/:db/:doc_id",status="200"} 5000
barrel_http_requests_total{method="POST",path="/db/:db/_find",status="200"} 500

Peers¶

Metric	Type	Labels	Description
`barrel_peers_active`	Gauge	-	Active peer connections
`barrel_peers_discovered_total`	Counter	-	Total peers discovered

Grafana Dashboard¶

Example queries for common dashboards:

Request Rate¶

rate(barrel_http_requests_total[5m])

Error Rate¶

sum(rate(barrel_http_requests_total{status=~"5.."}[5m]))
/
sum(rate(barrel_http_requests_total[5m]))

P99 Latency¶

histogram_quantile(0.99, rate(barrel_doc_operation_duration_seconds_bucket[5m]))

Documents per Second¶

rate(barrel_doc_operations_total{operation="put"}[5m])

Replication Lag¶

increase(barrel_replication_docs_total[1m])

Alerting Examples¶

High Error Rate¶

- alert: BarrelHighErrorRate
  expr: |
    sum(rate(barrel_http_requests_total{status=~"5.."}[5m]))
    /
    sum(rate(barrel_http_requests_total[5m])) > 0.01
  for: 5m
  labels:
    severity: warning
  annotations:
    summary: "High error rate on Barrel DocDB"

Replication Errors¶

- alert: BarrelReplicationErrors
  expr: increase(barrel_replication_errors_total[5m]) > 0
  for: 1m
  labels:
    severity: warning
  annotations:
    summary: "Replication errors detected"

High Latency¶

- alert: BarrelHighLatency
  expr: |
    histogram_quantile(0.99, rate(barrel_doc_operation_duration_seconds_bucket[5m])) > 0.1
  for: 5m
  labels:
    severity: warning
  annotations:
    summary: "High P99 latency on Barrel DocDB"

Configuration¶

Metrics are enabled by default. To disable:

{barrel_docdb, [
    {metrics_enabled, false}
]}.