A Cron script to report errors when nightly pgbackup backups have failed

check_backrest_last_backup_freshness.sh

#!/bin/bash

# PS Running in CRON mode - meaning output produced only on errors

# Expected inputs:
# 1) the pgbackrest config file path, e.g. /etc/pgbackrest/15/main/pgbackrest.conf
# 2) the stanza name
# 3) max age threshold in seconds of last valid backup.
#    errors if no valid backup within the threshold

which pgbackrest &>/dev/null || { echo "pgbackrest command not found"; exit 1; }

which jq &>/dev/null || { echo "jq command not found"; exit 1; }

if [ -z "$3" ]; then
  echo "usage: check_backrest.sh $BACKREST_CONFIG_FILE $STANZA_NAME $MAX_BACKUP_AGE_SECONDS"
  exit 1
fi
BACKREST_CONFIG="$1"
STANZA="$2"
MAX_AGE_SECONDS="$3"

set -u


STANZA_INFO=$(pgbackrest info --config="$BACKREST_CONFIG" --stanza="$STANZA" --output=json) || "Failed to fetch latest backup info for stanza $STANZA"

LAST_BACKUP_COMPLETED_EPOCH=$(echo "$STANZA_INFO" | jq '.[0] | .backup[-1] | .timestamp.stop') || "Failed to extract time label"

if [ "$LAST_BACKUP_COMPLETED_EPOCH" == "null" ]; then
  echo "Missing last backup info for stanza $STANZA"
  exit 1
fi

EPOCH_SECONDS=$(date +%s)
MAX_ALLOWED_THRESHOLD_EPOCH=$((EPOCH_SECONDS-MAX_AGE_SECONDS))
if [ "$LAST_BACKUP_COMPLETED_EPOCH" -lt "$MAX_ALLOWED_THRESHOLD_EPOCH" ]; then
  echo "Last backup too old for stanza $STANZA! LAST_BACKUP_COMPLETED_EPOCH: $LAST_BACKUP_COMPLETED_EPOCH, OK threshold: $MAX_ALLOWED_THRESHOLD_EPOCH"
  exit 1
fi

exit 0