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Monitor Apache Cassandra metrics with OpenTelemetry and Last9

Use OpenTelemetry to monitor your Apache Cassandra cluster and send telemetry data to Last9. This integration runs the opentelemetry-jmx-metrics JAR as a service alongside Cassandra to collect JMX metrics, which are forwarded to the OTel Collector via OTLP.

Read the sample configuration for more details.

Prerequisites

  • Apache Cassandra 3.x or 4.x installed and running
  • Java 11+ installed on the host (required by the JMX metrics JAR)
  • JMX enabled in Cassandra (enabled by default on port 7199)
  • Last9 account with integration credentials

Verify JMX Access

Cassandra enables JMX on port 7199 by default. Verify it is reachable:

ss -tlnp | grep 7199

Install OpenTelemetry Collector

sudo apt-get update && sudo apt-get install -y wget
wget https://github.com/open-telemetry/opentelemetry-collector-releases/releases/download/v0.144.0/otelcol-contrib_0.144.0_linux_amd64.deb
sudo dpkg -i otelcol-contrib_0.144.0_linux_amd64.deb

Download JMX Metrics JAR

The JMX receiver requires a metrics collection JAR:

sudo mkdir -p /opt
sudo wget -O /opt/opentelemetry-jmx-metrics.jar \
  https://github.com/open-telemetry/opentelemetry-java-contrib/releases/download/v1.43.0/opentelemetry-jmx-metrics.jar

Configure JMX Metrics Collection

  1. Create the JMX config

    Create /etc/otelcol-contrib/jmx-config.properties:

    otel.exporter.otlp.endpoint = http://localhost:4317
    otel.jmx.interval.milliseconds = 60000
    otel.jmx.service.url = service:jmx:rmi:///jndi/rmi://localhost:7199/jmxrmi
    otel.jmx.target.system = cassandra
    otel.metrics.exporter = otlp

    If JMX authentication is enabled, add:

    otel.jmx.username = <jmx_username>
    otel.jmx.password = <jmx_password>

  2. Run the JMX metrics JAR as a service

    Create /etc/systemd/system/cassandra-jmx-metrics.service:

    [Unit]
    Description=Cassandra JMX Metrics Collector
    After=cassandra.service
    

    [Service]
    ExecStart=java -jar /opt/opentelemetry-jmx-metrics.jar -config /etc/otelcol-contrib/jmx-config.properties
    Restart=always
    RestartSec=10
    

    [Install]
    WantedBy=multi-user.target
    sudo systemctl daemon-reload
    sudo systemctl enable --now cassandra-jmx-metrics

  3. Create the Collector Configuration

    Create /etc/otelcol-contrib/config.yaml:

    receivers:
      otlp:
        protocols:
          grpc:
            endpoint: 0.0.0.0:4317
    

      hostmetrics:
        collection_interval: 60s
        scrapers:
          cpu:
            metrics:
              system.cpu.logical.count:
                enabled: true
          memory:
            metrics:
              system.memory.utilization:
                enabled: true
              system.memory.limit:
                enabled: true
          load:
          disk:
          filesystem:
            metrics:
              system.filesystem.utilization:
                enabled: true
          network:
          paging:
    

    processors:
      batch:
        timeout: 5s
        send_batch_size: 10000
        send_batch_max_size: 10000
      resourcedetection/system:
        detectors: ["system"]
        system:
          hostname_sources: ["os"]
      transform/add_db_system:
        metric_statements:
          - context: datapoint
            statements:
              - set(attributes["host.name"], resource.attributes["host.name"])
              - set(attributes["db.system"], "cassandra")
    

    exporters:
      otlp/last9:
        endpoint: "{{ .Logs.WriteURL }}"
        headers:
          "Authorization": "{{ .Logs.AuthValue }}"
    

    service:
      pipelines:
        metrics/jmx:
          receivers: [otlp]
          processors: [batch, transform/add_db_system]
          exporters: [otlp/last9]
        metrics/host:
          receivers: [hostmetrics]
          processors: [batch, resourcedetection/system, transform/add_db_system]
          exporters: [otlp/last9]

    Replace endpoint and Authorization with your Last9 credentials from the Integrations page.

  4. Start the Collector

    sudo systemctl enable --now otelcol-contrib

Nodetool Metrics (Extended Collection)

JMX covers per-table latency and request counts, but some cluster-level metrics are only accessible via nodetool. The integration includes a nodetool exporter that runs alongside Cassandra and exposes these additional metrics on port 9500.

Bare-metal setup — create /etc/systemd/system/cassandra-nodetool-exporter.service:

[Unit]
Description=Cassandra Nodetool Prometheus Exporter
After=cassandra.service


[Service]
Environment=CASSANDRA_HOST=localhost
Environment=CASSANDRA_JMX_PORT=7199
Environment=EXPORTER_PORT=9500
ExecStart=python3 /opt/nodetool-exporter.py
Restart=always
RestartSec=15


[Install]
WantedBy=multi-user.target

Download the exporter script:

sudo wget -O /opt/nodetool-exporter.py \
  https://raw.githubusercontent.com/last9/opentelemetry-examples/main/otel-collector/cassandra/nodetool-exporter.py
sudo systemctl daemon-reload && sudo systemctl enable --now cassandra-nodetool-exporter

Add the following receiver and pipeline to your OTel Collector config:

receivers:
  prometheus/nodetool:
    config:
      scrape_configs:
        - job_name: cassandra_nodetool
          scrape_interval: 60s
          static_configs:
            - targets: ["localhost:9500"]


service:
  pipelines:
    metrics/nodetool:
      receivers: [prometheus/nodetool]
      processors: [batch, transform/add_db_system]
      exporters: [otlp/last9]

Metrics Collected

Metric categoryExamples
Read/write latencycassandra_client_request_read_latency_50p_microseconds, cassandra_client_request_write_latency_99p_microseconds
Request countscassandra_client_request_count_total, cassandra_client_request_error_count_total
Compactioncassandra_compaction_tasks_completed_total, cassandra_compaction_tasks_pending
Storagecassandra_storage_load_count_bytes, cassandra_storage_hints_count_total
Cluster topologycassandra_nodetool_nodes_up, cassandra_nodetool_nodes_down
Thread poolscassandra_nodetool_thread_pool_pending, cassandra_nodetool_thread_pool_blocked
Heap & cachecassandra_nodetool_heap_used_mb, cassandra_nodetool_key_cache_hit_rate
SystemCPU, memory, disk, network via hostmetrics

Verification

  1. Check Collector Status

    sudo systemctl status otelcol-contrib

  2. View Collector Logs

    sudo journalctl -u otelcol-contrib -f

  3. Verify Metrics in Last9

    Log into your Last9 account and check that Cassandra metrics are being received. Look for metric names starting with cassandra..

Troubleshooting

  • JMX connection refused

    # Verify JMX port is listening
    ss -tlnp | grep 7199
    

    # Check Cassandra is running
    nodetool status
    

    # Test JMX connectivity
    java -jar /opt/opentelemetry-jmx-metrics.jar \
      -targetSystem cassandra \
      -endpoint service:jmx:rmi:///jndi/rmi://localhost:7199/jmxrmi

  • ClassNotFoundException or JAR issues

    # Verify Java is installed
    java -version
    

    # Check JAR is present and readable
    ls -la /opt/opentelemetry-jmx-metrics.jar

  • Collector not starting

    sudo journalctl -u otelcol-contrib -n 100 --no-pager

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