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Solr

Solr exposes Prometheus-format metrics at /solr/admin/metrics?wt=prometheus. The OpenTelemetry Collector scrapes this endpoint using the Prometheus receiver, collecting 17+ metrics across JVM heap and GC statistics, HTTP request rates, thread pool activity, and core status. This guide configures the receiver, connects to a Solr node, and ships metrics to base14 Scout.

Prerequisites​

RequirementMinimumRecommended
Solr7.x9.x+
OTel Collector Contrib0.90.0latest
base14 ScoutAny—

Before starting:

  • Solr HTTP port (8983) must be accessible from the host running the Collector
  • The /admin/metrics endpoint is enabled by default
  • OTel Collector installed — see Docker Compose Setup

What You'll Monitor​

  • HTTP (Jetty): dispatches, requests by method, responses by status code class
  • JVM: heap and non-heap memory, GC count and time, thread counts by state, buffer pools, memory pool details
  • OS: CPU load, memory usage, file descriptors
  • Node: connections, core counts, filesystem space, request counts by handler, request time, thread pool tasks

Full metric list: run curl -s http://localhost:8983/solr/admin/metrics?wt=prometheus against your Solr instance.

Access Setup​

Verify your Solr instance is accessible:

Verify access
# Check Solr status
curl -s http://localhost:8983/solr/admin/info/system | head -20

# List cores
curl -s http://localhost:8983/solr/admin/cores

# Verify Prometheus metrics endpoint
curl -s 'http://localhost:8983/solr/admin/metrics?wt=prometheus' \
  | head -20

No authentication is required by default. For clusters with authentication enabled, see Authentication below.

The Collector's Prometheus receiver must use a custom metrics_path and params to scrape Solr — the default /metrics path does not work. Both are configured in the Configuration section below.

Configuration​

config/otel-collector.yaml
receivers:
  prometheus:
    config:
      scrape_configs:
        - job_name: solr
          scrape_interval: 30s
          metrics_path: /solr/admin/metrics
          params:
            wt: [prometheus]
          static_configs:
            - targets:
                - ${env:SOLR_HOST}:8983

processors:
  resource:
    attributes:
      - key: environment
        value: ${env:ENVIRONMENT}
        action: upsert
      - key: service.name
        value: ${env:SERVICE_NAME}
        action: upsert

  batch:
    timeout: 10s
    send_batch_size: 1024

# Export to base14 Scout
exporters:
  otlphttp/b14:
    endpoint: ${env:OTEL_EXPORTER_OTLP_ENDPOINT}
    tls:
      insecure_skip_verify: true

service:
  pipelines:
    metrics:
      receivers: [prometheus]
      processors: [resource, batch]
      exporters: [otlphttp/b14]

Environment Variables​

.env
SOLR_HOST=localhost
ENVIRONMENT=your_environment
SERVICE_NAME=your_service_name
OTEL_EXPORTER_OTLP_ENDPOINT=https://<your-tenant>.base14.io

Authentication​

For Solr clusters with Basic Authentication enabled:

config/otel-collector.yaml (auth)
receivers:
  prometheus:
    config:
      scrape_configs:
        - job_name: solr
          metrics_path: /solr/admin/metrics
          params:
            wt: [prometheus]
          basic_auth:
            username: ${env:SOLR_USERNAME}
            password: ${env:SOLR_PASSWORD}
          static_configs:
            - targets:
                - ${env:SOLR_HOST}:8983

Filtering Metrics​

To collect only specific metric groups, use Solr's group parameter:

config/otel-collector.yaml (filter)
receivers:
  prometheus:
    config:
      scrape_configs:
        - job_name: solr
          metrics_path: /solr/admin/metrics
          params:
            wt: [prometheus]
            group: [jvm, node, jetty]
          static_configs:
            - targets:
                - ${env:SOLR_HOST}:8983

Available groups: jvm, jetty, node, core, overseer.

Verify the Setup​

Start the Collector and check for metrics within 60 seconds:

Verify metrics collection
# Check Collector logs for successful scrape
docker logs otel-collector 2>&1 | grep -i "solr"

# Verify Solr is running
curl -s http://localhost:8983/solr/admin/info/system \
  | grep -i "status"

# Check metrics endpoint directly
curl -s 'http://localhost:8983/solr/admin/metrics?wt=prometheus' \
  | grep solr_metrics_jvm_heap

Troubleshooting​

Connection refused on port 8983​

Cause: Collector cannot reach Solr at the configured address.

Fix:

  1. Verify Solr is running: docker ps | grep solr or systemctl status solr
  2. Confirm Solr is listening on the expected port: curl http://localhost:8983/solr/
  3. Check firewall rules if the Collector runs on a separate host

Metrics endpoint returns JSON instead of Prometheus format​

Cause: The wt=prometheus parameter is missing from the scrape config.

Fix:

  1. Ensure params: { wt: [prometheus] } is set in the scrape job config
  2. Verify with curl: curl 'http://localhost:8983/solr/admin/metrics?wt=prometheus'
  3. Without wt=prometheus, Solr returns JSON which the Prometheus receiver cannot parse

No metrics appearing in Scout​

Cause: Metrics are collected but not exported.

Fix:

  1. Check Collector logs for export errors: docker logs otel-collector
  2. Verify OTEL_EXPORTER_OTLP_ENDPOINT is set correctly
  3. Confirm the pipeline includes both the receiver and exporter

Core-level metrics missing​

Cause: Core metrics only appear when at least one Solr core exists.

Fix:

  1. Create a core: curl 'http://localhost:8983/solr/admin/cores?action=CREATE&name=mycore&configSet=_default'
  2. Core metrics (solr_metrics_core_*) are per-core and only appear after indexing begins
  3. Verify cores exist: curl http://localhost:8983/solr/admin/cores

FAQ​

Does this work with Solr running in Kubernetes?

Yes. Set targets to the Solr pod or service DNS (e.g., solr-0.solr.default.svc.cluster.local:8983). The Collector can run as a sidecar or DaemonSet.

How do I monitor a SolrCloud cluster?

Add all Solr node endpoints to the scrape config:

receivers:
  prometheus:
    config:
      scrape_configs:
        - job_name: solr
          metrics_path: /solr/admin/metrics
          params:
            wt: [prometheus]
          static_configs:
            - targets:
                - solr-1:8983
                - solr-2:8983
                - solr-3:8983

Each node is scraped independently and identified by its instance label.

What is the difference between node and core metrics?

Node metrics (solr_metrics_node_*) cover the entire Solr instance — connections, filesystem, and aggregate request counts. Core metrics (solr_metrics_core_*) are per-collection and include index size, update handler stats, and query handler performance. Core metrics only appear when cores are loaded.

Why are overseer metrics missing?

Overseer metrics only appear in SolrCloud mode when the node is elected as the overseer. Standalone Solr instances do not emit overseer metrics.

What's Next?​

  • Create Dashboards: Explore pre-built dashboards or build your own. See Create Your First Dashboard
  • Monitor More Components: Add monitoring for Elasticsearch, Redis, and other components
  • Fine-tune Collection: Use the group parameter to limit metric collection to specific categories
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