add reporter for prometheus.io

reporters/prometheus.sh

@@ -0,0 +1,83 @@
+#!/bin/sh
+
+defaults () {
+  if [ -z $PROMETHEUS_PORT ]; then
+    PROMETHEUS_PORT=9100
+  fi
+  if [ -z $PROMETHEUS_METRIC_NAME ]; then
+    PROMETHEUS_METRIC_NAME="metrics_sh"
+  fi
+}
+
+start () {
+  readonly prometheus_report_header="# TYPE metrics_sh gauge"
+  readonly prometheus_stats_file=$TEMP_DIR/$(unique_id)_prometheus
+  readonly prometheus_httpd_fifo=$TEMP_DIR/$(unique_id)_prometheus_fifo
+  touch $prometheus_stats_file
+  mkfifo $prometheus_httpd_fifo
+
+  prometheus_httpd &
+  prometheus_stats_file_monitor &
+}
+
+report () {
+  local metric=$1
+  local value=$2
+
+  printf "%s{metric=\"%s\"} %s %s\n" "$PROMETHEUS_METRIC_NAME" "$metric" \
+          "$value" "$(unix_timestamp)000" >> $prometheus_stats_file
+}
+
+stop () {
+  if [ ! -z $prometheus_stats_file ] && [ -f $prometheus_stats_file ]; then
+    rm $prometheus_stats_file
+  fi
+  if [ ! -z $prometheus_httpd_fifo ] && [ -p $prometheus_httpd_fifo ]; then
+    rm $prometheus_httpd_fifo
+  fi
+}
+
+prometheus_httpd () {
+  echo "Serving prometheus HTTP endpoint at http://localhost:$PROMETHEUS_PORT/metrics"
+  while true; do
+    local REQUEST RESPONSE
+    cat $prometheus_httpd_fifo | nc -l $PROMETHEUS_PORT | while read line; do
+      line=$(echo "$line" | tr -d '[\r\n]')
+      # extract the request
+      if echo "$line" | grep -qE '^GET /'; then
+        REQUEST=$(echo "$line" | cut -d ' ' -f2)
+      # end of request
+      elif [ "x$line" = x ]; then
+        if echo $REQUEST | grep -qE '^/metrics'; then
+          RESPONSE=$(cat $prometheus_stats_file)
+          # clear
+          printf "" > $prometheus_stats_file
+          printf "HTTP/1.1 200 OK\nContent-Type: text/plain\n\n%s\n%s\n" \
+            "$prometheus_report_header" "$RESPONSE" > $prometheus_httpd_fifo
+        else
+          printf "HTTP/1.1 404 Not Found\nLocation: %s\n\n%s\n" \
+                    "$REQUEST" "404 Not Found" > $prometheus_httpd_fifo
+        fi
+      fi
+    done
+  done
+}
+
+prometheus_stats_file_monitor () {
+  while true; do
+    local bytes=$(ls -l $prometheus_stats_file | awk '{ print $5 }')
+    # clear file if bigger than 5MB
+    if [ $bytes -gt 5000000 ]; then
+      printf "" > $prometheus_stats_file
+    fi
+    sleep 120
+  done
+}
+
+docs () {
+  echo "Provide HTTP endpoint for Prometheus (http://prometheus.io)."
+  echo "Exposes metrics of type gauges in the following format:"
+  echo "$PROMETHEUS_METRIC_NAME{metric=\"<metric>\"} <value> <timestamp>"
+  echo "PROMETHEUS_PORT=$PROMETHEUS_PORT"
+  echo "PROMETHEUS_METRIC_NAME=$PROMETHEUS_METRIC_NAME"
+}