#!/bin/bash
# Copyright (c) 2022 Mr. Gecko's Media (James Coleman). http://mrgeckosmedia.com/

# This is for backing up block devices in virsh
# which use image files such as qcow2.
# This also works with GlusterFS so long as your
# volume is mounted.

# A file to prevent overlapping runs. This allows us to make assumptions
# that we're the only backup actively running, which allows us to recover
# if a snapshot exists before backing up.
PIDFILE="/tmp/backup-image.pid"

# If the pid file exists and process is running, exit.
if [[ -f "$PIDFILE" ]]; then
    PID=$(cat "$PIDFILE")
    if ps -p "$PID" >/dev/null; then
        echo "Backup process already running, exiting."
        exit 1
    fi
fi

# Create a new pid file for this process.
echo $BASHPID >"$PIDFILE"

# The borg repository we're backing up to.
export BORG_REPO='/media/Storage/Backup/kvm'
# If you have a passphrase for your repository,
# set it here or you can use bash to retrieve it.
# export BORG_PASSPHRASE=''
# Set answers for automation.
export BORG_UNKNOWN_UNENCRYPTED_REPO_ACCESS_IS_OK=yes
export BORG_RELOCATED_REPO_ACCESS_IS_OK=yes
export BORG_CHECK_I_KNOW_WHAT_I_AM_DOING=NO
export BORG_DELETE_I_KNOW_WHAT_I_AM_DOING=NO
# Set to empty string to disable pruning.
PRUNE_OPTIONS="--keep-daily 7 --keep-weekly 4 --keep-monthly 6"

# Remove PID file on exit.
cleanup() {
    rm "$PIDFILE"
}
trap cleanup EXIT

# Allows providing an argument of a domain to specifically backup.
BACKUP_DOMAIN="$1"

# Failures should remove pid file and exit with status code 1.
fail() {
    echo "$1"
    exit 1
}

# If the domain is running, commit the changes saved to the snapshot to the image to finish the backup.
blockCommit() {
    DOMSTATUS="$1"
    DOMAIN="$2"
    DEV="$3"
    if [[ "$DOMSTATUS" == "running" ]]; then
        echo "Commit changes for $DOMAIN ($DEV)"

        if ! virsh blockcommit \
                "$DOMAIN" \
                "$DEV" \
                --active \
                --verbose \
                --pivot \
                --delete; then
            fail "Could not commit changes $DOMAIN ($DEV). This may be a major issue and VM may be broken now."
        fi
    fi
}

# I save the status in a temporary file so I can error out and exit if a failure occurs.
DOMLIST_STATUS_TMP="/tmp/backup-image-domlist-tmp"
while read -r _ DOMAIN DOMSTATUS; do
    # If the domain is empty, its not needed.
    if [[ -z "$DOMAIN" ]]; then
        continue
    fi

    # If a backup domain was provided, we're only going to backup that domain.
    if [[ -n "$BACKUP_DOMAIN" ]] && [[ "$BACKUP_DOMAIN" != "$DOMAIN" ]]; then
        continue
    fi

    # Get the images that need backing up.
    DEVS=()
    IMAGES=()
    BLKLIST_STATUS_TMP="/tmp/backup-image-blklist-tmp"
    while read -r DEV IMAGE; do
        # Ignore empty line or no image.
        if [[ -z "$IMAGE" ]] || [[ "$IMAGE" == "-" ]]; then
            continue
        fi

        # Ignore iso files.
        if [[ "$IMAGE" =~ \.iso$ ]]; then
            continue
        fi

        # Ignore non-image files.
        if ! [[ "$IMAGE" =~ ^\/ ]]; then
            continue
        fi

        # This image needs backing up.
        DEVS+=("$DEV")
        IMAGES+=("$IMAGE")
    done < <(
        virsh domblklist "$DOMAIN" | tail -n +3
        echo "${PIPESTATUS[0]}" >"$BLKLIST_STATUS_TMP"
    )

    # Get status from the block listing.
    status=1
    if [[ -f $BLKLIST_STATUS_TMP ]]; then
        status=$(cat "$BLKLIST_STATUS_TMP")
        rm "$BLKLIST_STATUS_TMP"
    fi

    # If status has an error, exit.
    if ((status!=0)); then
        fail "Domain block listing failed"
    fi

    # For each image we can backup, back it up.
    for ((i = 0; i < ${#DEVS[@]}; i++)); do
        DEV=${DEVS[$i]}
        IMAGE=${IMAGES[$i]}
        IMAGEEXTENSION="${IMAGE##*.}"
        IMAGESNAPSHOT="${IMAGE%.*}.backup"
        IMAGENAME=$(basename "$IMAGE")

        # If the domain is running, we need to snapshot the disk so we can backup cleanly.
        if [[ "$DOMSTATUS" == "running" ]]; then
            # If the snapshot file exists, we should commit changes before performing another snapshot.
            # We are assuming that we created the snapshot here, and that concurrent runs are not possible.
            if [[ -e "$IMAGESNAPSHOT" ]]; then
                # Commit any blocks.
                blockCommit "$DOMSTATUS" "$DOMAIN" "$DEV"
            fi

            # Its possible that the image extension was changed to backup if a snapshot was previously made.
            # We assume it should be qcow2, and if that does not exist we will exit.
            if [[ "$IMAGEEXTENSION" == "backup" ]]; then
                IMAGE="${IMAGE%.*}.qcow2"
                if ! [ -f "$IMAGE" ]; then
                    fail "Unable to determine image name."
                fi
            fi

            echo "Creating snapshot for $DOMAIN ($DEV)"
            if ! virsh snapshot-create-as --domain "$DOMAIN" \
                    --name backup \
                    --no-metadata \
                    --atomic \
                    --disk-only \
                    --diskspec "$DEV,snapshot=external"; then
                fail "Failed to create snapshot for $DOMAIN ($DEV)"
            fi
        fi

        # Backup the image.
        echo "Creating backup for $DOMAIN ($DEV [$IMAGE])"
        if ! pv "$IMAGE" | borg create \
                --verbose \
                --stats \
                --show-rc \
                --stdin-name "$IMAGENAME" \
                "::$DOMAIN-$DEV-{now}" -; then
            # Commit any blocks.
            blockCommit "$DOMSTATUS" "$DOMAIN" "$DEV"
            fail "Failed to backup $DOMAIN ($DEV)"
        fi

        # Prune if options are configured.
        if [[ -n "$PRUNE_OPTIONS" ]]; then
            echo "Pruning backups for $DOMAIN ($DEV)"
            if ! eval borg prune --list \
                    --show-rc \
                    --glob-archives "'$DOMAIN-$DEV-*'" \
                    "$PRUNE_OPTIONS"; then
                # Commit any blocks.
                blockCommit "$DOMSTATUS" "$DOMAIN" "$DEV"
                fail "Failed to prune $DOMAIN ($DEV)"
            fi
        fi

        # Commit any blocks.
        blockCommit "$DOMSTATUS" "$DOMAIN" "$DEV"
    done

    # Backup the domain info.
    echo "Backing up $DOMAIN xml"
    if ! virsh dumpxml "$DOMAIN" | borg create \
            --verbose \
            --stats \
            --show-rc \
            "::$DOMAIN-xml-{now}" -; then
        fail "Failed to backup $DOMAIN"
    fi

    # Prune if options are configured.
    if [[ -n "$PRUNE_OPTIONS" ]]; then
        echo "Pruning backups for $IMAGE"
        if ! eval borg prune --list \
                --show-rc \
                --glob-archives "'$DOMAIN-xml-*'" \
                "$PRUNE_OPTIONS"; then
            fail "Failed to prune $DOMAIN"
        fi
    fi
done < <(
    virsh list --all | tail -n +3
    echo "${PIPESTATUS[0]}" >"$DOMLIST_STATUS_TMP"
)

# Get status from the domain listing.
status=1
if [[ -f $DOMLIST_STATUS_TMP ]]; then
    status=$(cat "$DOMLIST_STATUS_TMP")
    rm "$DOMLIST_STATUS_TMP"
fi

# If status has an error, exit.
if ((status!=0)); then
    fail "Domain listing failed"
fi

# Shrink repo.
borg compact