prometheus_elasticsearch_exporter.sh

#!/bin/bash
# Required binaries: jq, date, curl, sed

# Prometheus text file format is described here:
# http://prometheus.io/docs/instrumenting/exposition_formats/

# Returns epoch + made up milliseconds timestamp
get_timestamp() {
    date "+%s000"
}

# Args:
# metric name - What to call the metric in Prometheus. *Required*
# metric_value - Value to report to Prometheus. *Required*
# type - The Prometheus metric type. Default: counter
# help - Helpful description. Optional.
# timestamp - Timestamp of when data was collected. Optional.
emit_metric() {
    metric_name=$1
    metric_value=$2
    type=${3:-counter}
    help=${4}
    timestamp=${5}
    
    if [ -z "$timestamp" ]; then
        timestamp=$(get_timestamp)
    fi
    
    {
        if [ -n "$help" ] ; then
            echo "# HELP $metric_name $help"
        fi
        echo "# TYPE $metric_name $type"
        echo "$metric_name $metric_value $timestamp"
        echo
    } >> $OUTPUT.$$
}

OUTPUT="/var/spool/your_org/prometheus/elasticsearch_cluster_stats.prom"
METRIC_PREFIX="elasticsearch_cluster"

############################
## MAIN PROGRAM begins here:
############################

CLUSTER_HEALTH_JSON=$(curl --max-time 30 -s '0:9200/_cluster/health?local=true')
TIMESTAMP=$(date "+%s000")

declare -a KEYS
KEYS=( $(echo ${CLUSTER_HEALTH_JSON=$} | jq --raw-output '.|keys|.[]') )

# for each value in the json
for i in ${KEYS[*]} ; do
  [[ $i == "cluster_name" ]] && continue
  emit_metric "${METRIC_PREFIX}_$i" \
              $(echo ${CLUSTER_HEALTH_JSON=$} | jq --raw-output ".$i") \
              gauge \
              "value from _cluster/health/" \
              ${TIMESTAMP}
done

# Coerce known string-valued metrics to integer-values
sed -i  -e 's/ false / 0 /'  \
        -e 's/ true / 1 /'   \
        -e 's/ green / 0 /'  \
        -e 's/ yellow / 1 /' \
        -e 's/ red / 2 /'    \
    $OUTPUT.$$

mv ${OUTPUT}.$$ ${OUTPUT}