Prometheus exporter for restic snapshot age

restic-snapshot-exporter.sh

#!/bin/bash

# get current time to be used to compute age
NOW_SECONDS=$(date '+%s')

JSONDIR="/var/lib/restic-snapshot-dump"
PROMDIR="/var/lib/node_exporter"

# following will be replaced with actual restic snapshots command
for JSONFILE in "${JSONDIR}"/*.json; do
    # loop over each snapshot
    PROMFILE="${JSONFILE##*/}"                    # strip dirname
    PROMFILE="${PROMDIR}/${PROMFILE%.json}.prom"  # replace extension

    echo "# HELP restic_snapshot_age_seconds Time since the last successful restic snapshot" > "${PROMFILE}.$$"
    echo "# TYPE restic_snapshot_age_seconds gauge" >> "${PROMFILE}.$$"

    jq -c '.[]' "${JSONFILE}" | while read SNAPSHOT_LINE; do
        S_HOSTNAME=$(jq -r '.hostname' <<< "${SNAPSHOT_LINE}")
        S_TAG=$(jq -r '.tags[0]' <<< "${SNAPSHOT_LINE}")                      # assume one tag
        S_TIME=$(date --date="$(jq -r '.time' <<< "${SNAPSHOT_LINE}")" '+%s')
        let S_AGE=NOW_SECONDS-S_TIME

        # multiple paths (potentially)
        jq -c '.paths' <<< "${SNAPSHOT_LINE}" | while read PATH_LINE; do
            S_PATH=$(jq -r '.[]' <<< "${PATH_LINE}")
            echo "restic_snapshot_age_seconds{tag=\"${S_TAG}\",hostname=\"${S_HOSTNAME}\",path=\"${S_PATH}\"} ${S_AGE}"
        done
    done >> "${PROMFILE}.$$"
    mv "${PROMFILE}.$$" "${PROMFILE}"
done