h1. Prometheus


h2. Connecting to Petals JMX

Petals exposes its metrics on [JMX|https://en.wikipedia.org/wiki/Java_Management_Extensions], but Prometheus itself cannot natively gather metrics through JMX. So we need to expose those metrics on HTTP, which Prometheus can access.   
Luckily Prometheus maintains [jmx_exporter|https://github.com/prometheus/jmx_exporter] which exposes metrics on HTTP. It can either act as a java agent injected into the [JVM|https://en.wikipedia.org/wiki/Java_virtual_machine] during Petals ESB startup or an independent server connecting to Petals ESB by [RMI|https://en.wikipedia.org/wiki/Java_remote_method_invocation].

h3. Official packages jmx_exporter :

* Copy *jmx_prometheus_javaagent-XXX.jar* in _petals-esb-directory/lib_ folder
* Create a yaml config file in _petals-esb-directory/conf_ folder, here it is named *prometheus-jmx.yaml*

The file can be empty for now, but this default config will display everything available :

{code}
startDelaySeconds: 0
rules:
-pattern: ".*"
{code}
* Add the following line to *petals-esb.sh*, just before the “_exec_” command at the very end of the script. _8585_ is the port number on which HTTP metrics will be exposed (once gathered by the jmx_exporter), set is as you see fit.

{code}JAVA_OPTS="$JAVA_OPTS -javaagent:${PETALS_LIB_DIR}/jmx_prometheus_javaagent-0.3.1.jar=8585:${PETALS_CONF_DIR}/prometheus-jmx.yaml"{code}

* Run _petals-esb.sh_
* JVM metrics are available at [*http://localhost:8585/metrics*|http://localhost:8484/metrics*]


{color:#492562}{*}Install Prometheus{*}{color}

Install : [https://prometheus.io/docs/prometheus/latest/getting_started/|https://prometheus.io/docs/prometheus/latest/getting_started/]

use this *prometheus.yml* config:

{code}
# my global config
global:
scrape_interval: 5s # Set the scrape interval to every 15 seconds. Default is every 1 minute.
evaluation_interval: 5s # Evaluate rules every 15 seconds. The default is every 1 minute.

# 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: 'petals monitoring'

# Override the global default and scrape targets from this job every 5 seconds.
scrape_interval: 5s

# metrics_path defaults to '/metrics'
# scheme defaults to 'http'.
static_configs:
- targets: ['localhost:8484']
labels:
groups: 'petals'
{code}


h2. Configure jmx agent

Jmx agent can be configured in its yaml config file.

Note that :

{code}
rules:
- pattern: 'java.lang<type=Runtime, key=java.runtime.name><>SystemProperties: (.*)'
name: aaaa_test
value: 1
labels:
runtime: "$1"

- pattern: '(.*)<(.*)><(.*)>(.*)'
name: aaaa_petals_test
value: 1
labels:
mouais: "$1 $2 $3 $3"

- pattern: '(\w+)<type=(\w+), name=(\w+)><>Value: (\w+)'
name: $1_$2_$3
value: 1
help: "$1 metric $2 $3"
labels:
value: "$3: $4"
{code}