Monitor Java application with prometheus

Prometheus provides JMX exporter which can export JVM information.

1. Create JMX exporter configuration. Let's call it jmx_exporter_config.yml.

---
rules:
  - pattern: "java.lang.*"

2. Download JMX exporter

You can find the URL of JMX exporter jar file in Github repository.

https://github.com/prometheus/jmx_exporter

Here is the URL for 0.16.1

https://repo1.maven.org/maven2/io/prometheus/jmx/jmx_prometheus_javaagent/0.16.1/jmx_prometheus_javaagent-0.16.1.jar

3. Start your Java application

For example, your application is packaged as a jar file myapp_1.jar. jmx_prometheus_javaagent-0.16.1.jar and jmx_exporter_config.yml are saved in /app. We expose port 8080 to export metrics.

java -javaagent:/app/jmx_prometheus_javaagent-0.16.1.jar=8080:/app/jmx_exporter_config.yml -jar myapp_1.jar

4. Download Prometheus

You can find the URL of Prometheus in its official site.

https://prometheus.io/download/

Here is the URL of 2.33.0 (MacOS).

https://github.com/prometheus/prometheus/releases/download/v2.33.0/prometheus-2.33.0.darwin-amd64.tar.gz

5. Unzip Prometheus

After it is downloaded, unzip it and go to its directory.

tar xvfz prometheus-*.tar.gz
cd prometheus-*

6. Update prometheus configuration

Add the following to the prometheus.yml (under scrape_configs). We adds label to help querying.

  - job_name: "apps"

    static_configs:
      - targets: ["localhost:8080"]
        labels:
          instance: 'myapp_1'

The whole file should look like this.

# my global config
global:
  scrape_interval: 15s # Set the scrape interval to every 15 seconds. Default is every 1 minute.
  evaluation_interval: 15s # Evaluate rules every 15 seconds. The default is every 1 minute.
  # scrape_timeout is set to the global default (10s).

# Alertmanager configuration
alerting:
  alertmanagers:
    - static_configs:
        - targets:
          # - alertmanager:9093

# Load rules once and periodically evaluate them according to the global 'evaluation_interval'.
rule_files:
  # - "first_rules.yml"
  # - "second_rules.yml"

# A scrape configuration containing exactly one endpoint to scrape:
# Here it's Prometheus itself.
scrape_configs:
  # The job name is added as a label `job=<job_name>` to any timeseries scraped from this config.
  - job_name: "prometheus"

    # metrics_path defaults to '/metrics'
    # scheme defaults to 'http'.

    static_configs:
      - targets: ["localhost:9090"]

  - job_name: "apps"

    static_configs:
      - targets: ["localhost:8080"]
        labels:
          instance: 'myapp_1'

7. Start Prometheus

./prometheus --config.file=prometheus.yml

8. Query JVM information

http://localhost:9090/

Query jvm_memory_bytes_used{area="heap",instance="myapp_1"}

Here is the query result.

Or you prefer a graph (You may need to refresh the browser if you want to see the latest data)

Here are other metrics you can try.

• jvm_gc_collection_seconds_count

• jvm_gc_collection_seconds_sum

• jvm_memory_bytes_used -

• jvm_memory_bytes_committed

• jvm_memory_bytes_max

• jvm_memory_bytes_init

• process_cpu_seconds_total