#!/bin/bash
# {{ ansible_managed }}
# Pull application data from the cloud hosts into hardlinked snapshots
# rsnapshot-style: rsync --link-dest
set -uo pipefail

ROOT={{ backup_root }}
KEY={{ backup_key_path }}
RETAIN={{ backup_retain_recent | default(14) }}
RETAIN_MONTHLY={{ backup_retain_monthly | default(6) }}
SSH="ssh -i $KEY -o StrictHostKeyChecking=accept-new -o BatchMode=yes"
STAMP=$(date +%Y-%m-%d_%H%M)

exec 9> "$ROOT/.lock" || exit 1
flock -n 9 || { echo "another backup run is active, aborting"; exit 1; }

overall_rc=0

{% raw %}
prune() {
    local host_root=$1
    local -a snaps
    mapfile -t snaps < <(find "$host_root" -mindepth 1 -maxdepth 1 -type d -name '20*' | sort)
    ((${#snaps[@]})) || return 0
    declare -A keep_set month_first
    # newest RETAIN snapshots
    local n=${#snaps[@]} start=0
    ((n > RETAIN)) && start=$((n - RETAIN))
    for s in "${snaps[@]:$start}"; do keep_set[$s]=1; done
    # oldest snapshot of each month, for the RETAIN_MONTHLY most recent months
    for s in "${snaps[@]}"; do
        local m; m=$(basename "$s" | cut -c1-7)
        [[ -z ${month_first[$m]:-} ]] && month_first[$m]=$s
    done
    mapfile -t months < <(printf '%s\n' "${!month_first[@]}" | sort | tail -n "$RETAIN_MONTHLY")
    for m in "${months[@]}"; do keep_set[${month_first[$m]}]=1; done
    for s in "${snaps[@]}"; do
        if [[ -z ${keep_set[$s]:-} ]]; then
            echo "pruning $s"
            rm -rf "$s"
        fi
    done
}
{% endraw %}

{% for host in groups['backup_sources'] %}
##### {{ host }} #####
host={{ host }}
addr={{ hostvars[host].ansible_host }}
host_root=$ROOT/$host
new=$host_root/incomplete
mkdir -p "$host_root"
rm -rf "$new"
mkdir "$new"
link_dest=()
[[ -d $host_root/latest/. ]] && link_dest=(--link-dest="$host_root/latest/")
host_rc=0
{% for path in hostvars[host].backup_paths %}
rsync -aR --numeric-ids --delete --delete-excluded \
    {% for ex in hostvars[host].backup_excludes | default([]) %}--exclude='{{ ex }}' {% endfor %}\
    -e "$SSH" "${link_dest[@]}" \
    "backup@$addr:{{ path }}" "$new/"
rc=$?
if ((rc != 0 && rc != 24)); then
    echo "ERROR: $host:{{ path }} failed with rsync exit $rc" >&2
    host_rc=1
fi
{% endfor %}
if ((host_rc == 0)); then
    mv "$new" "$host_root/$STAMP"
    ln -sfn "$STAMP" "$host_root/latest"
    prune "$host_root"
    echo "$host: snapshot $STAMP complete"
else
    echo "$host: snapshot FAILED, keeping previous 'latest'" >&2
    overall_rc=1
fi

{% endfor %}
exit $overall_rc