Jetty

The OpenTelemetry JMX Scraper collects 9 Jetty-specific metrics and 18 JVM metrics from Eclipse Jetty 9.x through 12.x, including thread pool utilization, I/O select counts, and session activity. Jetty requires explicit JMX enablement — unlike Tomcat, JMX MBean registration is not configured by default. The scraper connects to Jetty via JMX, converts MBeans into OpenTelemetry metrics, and exports them over OTLP to the Collector. This guide enables JMX on Jetty, configures the scraper, and ships metrics to base14 Scout.

Prerequisites

Requirement	Minimum	Recommended
Eclipse Jetty	9.4	12.0+
JMX Scraper	1.46.0	1.54.0+
Java (scraper)	11	17+
OTel Collector	0.90.0	latest
base14 Scout	Any	—

Before starting:

Jetty must be accessible from the host running the JMX Scraper (JMX port, default 1099)
The JMX Scraper runs as a standalone Java process — it requires its own JRE
Jetty's jmx module must be enabled for MBean registration
OTel Collector installed — see Docker Compose Setup

What You'll Monitor

Threads: count, limit, busy count, idle count, queue size
I/O: select count
Sessions: active count (Jetty 12+), created count (9-11), duration sum (9-11)
JVM (with jvm target): heap and non-heap memory, GC count and duration, thread states, CPU utilization, class loading, buffer pools

Session metrics only appear when web applications with active sessions are deployed.

Full metric reference: OTel Jetty JMX Metrics

Access Setup

Jetty JMX is disabled by default. Two steps are required: enable the jmx module (registers Jetty MBeans) and configure remote JMX access (opens a port for the scraper).

Enable JMX on Jetty

For standalone Jetty, enable the JMX module and add remote access flags:

Enable Jetty JMX module and remote access
# Enable Jetty JMX MBean registration
java -jar $JETTY_HOME/start.jar --add-module=jmx

# Add remote JMX access flags to start.d
cat >> $JETTY_BASE/start.d/jmx-remote.ini << 'EOF'
--exec
-Dcom.sun.management.jmxremote.port=1099
-Dcom.sun.management.jmxremote.rmi.port=1099
-Dcom.sun.management.jmxremote.ssl=false
-Dcom.sun.management.jmxremote.authenticate=false
-Djava.rmi.server.hostname=<jetty-host>
EOF

Setting rmi.port to the same value as port prevents RMI from using a random second port, which simplifies firewall and Docker networking.

For Docker deployments, the Jetty image requires a custom Dockerfile to enable the jmx module during build. JMX remote access flags are passed via JAVA_OPTIONS:

jetty/Dockerfile
FROM jetty:12.0-jdk17

USER root
RUN java -jar "$JETTY_HOME/start.jar" --add-module=jmx
USER jetty

docker-compose.yaml (Jetty service)
jetty:
  build: ./jetty
  hostname: jetty
  environment:
    JAVA_OPTIONS: >-
      -Dcom.sun.management.jmxremote.port=1099
      -Dcom.sun.management.jmxremote.rmi.port=1099
      -Dcom.sun.management.jmxremote.ssl=false
      -Dcom.sun.management.jmxremote.authenticate=false
      -Djava.rmi.server.hostname=jetty

With Authentication (Production)

For production environments, enable JMX authentication:

start.d/jmx-remote.ini (authenticated)
--exec
-Dcom.sun.management.jmxremote.port=1099
-Dcom.sun.management.jmxremote.rmi.port=1099
-Dcom.sun.management.jmxremote.ssl=true
-Dcom.sun.management.jmxremote.authenticate=true
-Dcom.sun.management.jmxremote.password.file=/path/to/jmxremote.password
-Dcom.sun.management.jmxremote.access.file=/path/to/jmxremote.access
-Djava.rmi.server.hostname=<jetty-host>

The JMX Scraper supports authenticated connections via OTEL_JMX_USERNAME and OTEL_JMX_PASSWORD environment variables.

Configuration

Jetty monitoring uses two components: the JMX Scraper (connects to Jetty, exports OTLP) and the OTel Collector (receives OTLP, ships to Scout).

Jetty (JMX:1099) ← JMX/RMI → JMX Scraper → OTLP → OTel Collector → Scout

JMX Scraper

Download the scraper JAR from Maven Central and run it:

Run the JMX Scraper
OTEL_JMX_SERVICE_URL=service:jmx:rmi:///jndi/rmi://localhost:1099/jmxrmi \
OTEL_JMX_TARGET_SYSTEM=jvm,jetty \
OTEL_EXPORTER_OTLP_ENDPOINT=http://localhost:4317 \
OTEL_METRIC_EXPORT_INTERVAL=10000 \
java -jar opentelemetry-jmx-scraper-1.54.0-alpha.jar

Move the JAR to a permanent location:

Install the scraper
sudo mkdir -p /opt/otel
sudo mv opentelemetry-jmx-scraper-1.54.0-alpha.jar /opt/otel/

Create a systemd service to run the scraper as a managed service:

/etc/systemd/system/otel-jmx-scraper.service
sudo tee /etc/systemd/system/otel-jmx-scraper.service > /dev/null <<'EOF'
[Unit]
Description=OpenTelemetry JMX Scraper for Jetty
After=network.target jetty.service

[Service]
Type=simple
Environment=OTEL_JMX_SERVICE_URL=service:jmx:rmi:///jndi/rmi://localhost:1099/jmxrmi
Environment=OTEL_JMX_TARGET_SYSTEM=jvm,jetty
Environment=OTEL_EXPORTER_OTLP_ENDPOINT=http://localhost:4317
Environment=OTEL_METRIC_EXPORT_INTERVAL=10000
ExecStart=/usr/bin/java -jar /opt/otel/opentelemetry-jmx-scraper-1.54.0-alpha.jar
Restart=always
RestartSec=5

[Install]
WantedBy=multi-user.target
EOF

Start the scraper:

Enable and start the scraper
sudo systemctl daemon-reload
sudo systemctl enable --now otel-jmx-scraper

For Docker, build a simple image with the scraper JAR:

jmx-scraper/Dockerfile
FROM eclipse-temurin:17-jre

ARG SCRAPER_VERSION=1.54.0-alpha   # Update to match your target version

ADD https://repo1.maven.org/maven2/io/opentelemetry/contrib/opentelemetry-jmx-scraper/${SCRAPER_VERSION}/opentelemetry-jmx-scraper-${SCRAPER_VERSION}.jar /opt/scraper.jar

ENTRYPOINT ["java", "-jar", "/opt/scraper.jar"]

OTel Collector

The Collector receives metrics from the JMX Scraper over OTLP:

config/otel-collector.yaml
receivers:
  otlp:
    protocols:
      grpc:
        endpoint: 0.0.0.0:4317

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: [otlp]
      processors: [resource, batch]
      exporters: [otlphttp/b14]

Environment Variables

.env
# JMX Scraper
OTEL_JMX_SERVICE_URL=service:jmx:rmi:///jndi/rmi://jetty:1099/jmxrmi
OTEL_JMX_TARGET_SYSTEM=jvm,jetty
OTEL_METRIC_EXPORT_INTERVAL=10000
# OTEL_JMX_USERNAME=monitor          # Uncomment for authenticated JMX
# OTEL_JMX_PASSWORD=your_password    # Uncomment for authenticated JMX

# OTel Collector
ENVIRONMENT=your_environment
SERVICE_NAME=your_service_name
OTEL_EXPORTER_OTLP_ENDPOINT=https://<your-tenant>.base14.io

Docker Compose

Full working example with all three components:

docker-compose.yaml
services:
  jetty:
    build: ./jetty
    hostname: jetty
    ports:
      - "8080:8080"
      - "1099:1099"
    environment:
      JAVA_OPTIONS: >-
        -Dcom.sun.management.jmxremote.port=1099
        -Dcom.sun.management.jmxremote.rmi.port=1099
        -Dcom.sun.management.jmxremote.ssl=false
        -Dcom.sun.management.jmxremote.authenticate=false
        -Djava.rmi.server.hostname=jetty
    healthcheck:
      test: ["CMD-SHELL", "curl -so /dev/null http://localhost:8080/ || exit 1"]
      interval: 10s
      timeout: 5s
      retries: 10
      start_period: 30s

  jmx-scraper:
    build: ./jmx-scraper
    environment:
      OTEL_JMX_SERVICE_URL: ${OTEL_JMX_SERVICE_URL}
      OTEL_JMX_TARGET_SYSTEM: ${OTEL_JMX_TARGET_SYSTEM}
      OTEL_EXPORTER_OTLP_ENDPOINT: http://otel-collector:4317
      OTEL_METRIC_EXPORT_INTERVAL: ${OTEL_METRIC_EXPORT_INTERVAL}
    depends_on:
      jetty:
        condition: service_healthy

  otel-collector:
    image: otel/opentelemetry-collector-contrib:0.120.0
    container_name: otel-collector
    volumes:
      - ./config/otel-collector.yaml:/etc/otelcol-contrib/config.yaml:ro
    depends_on:
      - jetty

Verify the Setup

Start the Collector and check for metrics within 60 seconds:

Verify metrics collection
# Check JMX Scraper logs for successful connection
docker logs jetty-telemetry-jmx-scraper-1 2>&1 | head -10

# Verify Jetty started with JMX enabled
docker logs jetty 2>&1 \
  | grep "jmx"

# Check Collector logs for Jetty metrics
docker logs otel-collector 2>&1 \
  | grep "jetty"

Troubleshooting

JMX connection refused

Cause: The JMX Scraper cannot reach Jetty's JMX port.

Fix:

Verify Jetty is running: docker ps | grep jetty
Confirm JMX remote access is enabled — check that -Dcom.sun.management.jmxremote.port=1099 is in JAVA_OPTIONS or start.d/jmx-remote.ini
Verify the JMX port matches between Jetty config and scraper's OTEL_JMX_SERVICE_URL
In Docker, ensure hostname is set on the Jetty container and matches -Djava.rmi.server.hostname

Only JVM metrics, no Jetty metrics

Cause: Jetty's jmx module is not enabled, so Jetty components are not registered as MBeans.

Fix:

Enable the JMX module: java -jar start.jar --add-module=jmx
In Docker, use the custom Dockerfile that runs --add-module=jmx during build
Verify OTEL_JMX_TARGET_SYSTEM includes jetty

Session metrics missing

Cause: Session metrics (jetty.session.active.count, jetty.session.created.count, jetty.session.duration.sum) only appear when web applications with active sessions are deployed.

Fix:

Deploy a WAR file with session usage to Jetty
Session MBeans are created per web application context

No metrics appearing in Scout

Cause: Metrics are collected but not exported.

Fix:

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

FAQ

Does this work with embedded Jetty (Spring Boot/Dropwizard)?

Yes. Spring Boot and Dropwizard embed Jetty and register MBeans automatically when spring.jmx.enabled=true (Spring Boot) or JMX is enabled in the Dropwizard config. Enable remote JMX access with the same -Dcom.sun.management.jmxremote.* JVM flags on the application.

Which Jetty version should I use?

Jetty 12 is recommended. Session metrics improved in Jetty 12+ (jetty.session.active.count replaces jetty.session.count). Thread and I/O metrics are consistent across all supported versions (9.4+).

How do I monitor multiple Jetty instances?

Run one JMX Scraper per instance, each configured with a different OTEL_JMX_SERVICE_URL. All scrapers export to the same Collector:

docker-compose.yaml (multiple instances)
jmx-scraper-primary:
  environment:
    OTEL_JMX_SERVICE_URL: service:jmx:rmi:///jndi/rmi://jetty-1:1099/jmxrmi
    OTEL_JMX_TARGET_SYSTEM: jvm,jetty
    OTEL_EXPORTER_OTLP_ENDPOINT: http://otel-collector:4317

jmx-scraper-replica:
  environment:
    OTEL_JMX_SERVICE_URL: service:jmx:rmi:///jndi/rmi://jetty-2:1099/jmxrmi
    OTEL_JMX_TARGET_SYSTEM: jvm,jetty
    OTEL_EXPORTER_OTLP_ENDPOINT: http://otel-collector:4317

Does this work with Jetty in Kubernetes?

Yes. Run the JMX Scraper as a sidecar container in the same pod. Set OTEL_JMX_SERVICE_URL to service:jmx:rmi:///jndi/rmi:// localhost:1099/jmxrmi since both containers share the pod network. No firewall rules needed for intra-pod communication.

What's Next?

Create Dashboards: Explore pre-built dashboards or build your own. See Create Your First Dashboard
Monitor More Components: Add monitoring for Tomcat, Nginx, and other web servers
Fine-tune Collection: Adjust OTEL_METRIC_EXPORT_INTERVAL to control scrape frequency

JMX Metrics Collection Guide — Compare JMX Scraper vs JMX Exporter
OTel Collector Configuration — Advanced collector configuration
Docker Compose Setup — Run the Collector locally
Kubernetes Helm Setup — Production deployment
Tomcat Monitoring — Another Java application server setup
Creating Alerts — Alert on Jetty metrics

Was this page helpful?

Prerequisites​

What You'll Monitor​

Access Setup​

Enable JMX on Jetty​

With Authentication (Production)​

Configuration​

JMX Scraper​

OTel Collector​

Environment Variables​

Docker Compose​

Verify the Setup​

Troubleshooting​

JMX connection refused​

Only JVM metrics, no Jetty metrics​

Session metrics missing​

No metrics appearing in Scout​

FAQ​

What's Next?​

Related Guides​

Prerequisites

What You'll Monitor

Access Setup

Enable JMX on Jetty

With Authentication (Production)

Configuration

JMX Scraper

OTel Collector

Environment Variables

Docker Compose

Verify the Setup

Troubleshooting

JMX connection refused

Only JVM metrics, no Jetty metrics

Session metrics missing

No metrics appearing in Scout

FAQ

What's Next?

Related Guides