[mariadb] Fix incremental backup using correct base dir

The original script used --incremental-history-name and compressed
full backups as gzip streams. This failed because mariabackup expects
an actual decompressed base directory for incremental backups.

This patch:
- Decompresses the latest full backup into a temporary directory
- Uses that as --incremental-basedir
- Aligns the backup flow with official Mariabackup documentation:
  https://mariadb.com/kb/en/incremental-backup-and-restore-with-mariabackup/

This makes the incremental process reliable and fully supported.

Closes-Bug: #2111620

Change-Id: I562ce5e54752015863a20bf113bce74a69e02331

3 files changed, 89 insertions, 47 deletions

diff --git a/docker/mariadb/mariadb-server/backup.sh b/docker/mariadb/mariadb-server/backup.sh
index 30796fa4e..be63cd938 100644
--- a/docker/mariadb/mariadb-server/backup.sh
+++ b/docker/mariadb/mariadb-server/backup.sh
@@ -6,49 +6,66 @@ set -o pipefail
 # Execute a full backup
 backup_full() {
     echo "Taking a full backup"
-    LAST_FULL_DATE=$(date +%d-%m-%Y)
+    LAST_FULL_DATE=$(date +%d-%m-%Y-%s)
+    BACKUP_FILE="mysqlbackup-${LAST_FULL_DATE}.qp.xbc.xbs.gz"
+    BACKUP_PATH="$BACKUP_DIR/full-${LAST_FULL_DATE}"
+    mkdir -p "$BACKUP_PATH"
+
     mariabackup \
         --defaults-file=/etc/mysql/my.cnf \
         --backup \
         --stream=xbstream \
         --history=$LAST_FULL_DATE | gzip > \
-        $BACKUP_DIR/mysqlbackup-$(date +%d-%m-%Y-%s).qp.xbc.xbs.gz
-    echo $LAST_FULL_DATE > $BACKUP_DIR/last_full_date
+        "$BACKUP_PATH/$BACKUP_FILE"
+
+    echo "$BACKUP_PATH/$BACKUP_FILE" > "$BACKUP_DIR/last_full_file"
 }
 
 # Execute an incremental backup
 backup_incremental() {
     echo "Taking an incremental backup"
-    if [ -r $BACKUP_DIR/last_full_date ]; then
-        LAST_FULL_DATE=$(cat $BACKUP_DIR/last_full_date)
-    fi
-    if [ -z $LAST_FULL_DATE ]; then
-        LAST_FULL_DATE=$(date +%d-%m-%Y)
+
+    if [ ! -r "$BACKUP_DIR/last_full_file" ]; then
+        echo "Error: No full backup file found."
+        exit 1
     fi
+
+    FULL_BACKUP_FILE=$(cat "$BACKUP_DIR/last_full_file")
+    LAST_FULL_DATE=$(basename "$(dirname "$FULL_BACKUP_FILE")" | sed 's/^full-//')
+    NOW=$(date +%H-%M-%S-%d-%m-%Y)
+    INCR_DIR="$BACKUP_DIR/incr-${NOW}-since-${LAST_FULL_DATE}"
+    mkdir -p "$INCR_DIR"
+
+    TMP_BASEDIR=$(mktemp -d)
+    echo "Decompressing full backup to temp dir: $TMP_BASEDIR"
+    gunzip -c "$FULL_BACKUP_FILE" | mbstream -x -C "$TMP_BASEDIR"
+
     mariabackup \
         --defaults-file=/etc/mysql/my.cnf \
         --backup \
         --stream=xbstream \
-        --incremental-history-name=$LAST_FULL_DATE \
-        --history=$LAST_FULL_DATE | gzip > \
-        $BACKUP_DIR/incremental-$(date +%H)-mysqlbackup-$(date +%d-%m-%Y-%s).qp.xbc.xbs.gz
+        --incremental-basedir="$TMP_BASEDIR" \
+        --history="incr-${NOW}" | gzip > \
+        "$INCR_DIR/incremental-${NOW}-mysqlbackup-${LAST_FULL_DATE}.qp.xbc.xbs.gz"
+
+    rm -rf "$TMP_BASEDIR"
 }
 
 BACKUP_DIR=/backup/
-cd $BACKUP_DIR
+cd "$BACKUP_DIR"
 
-if [ -n $BACKUP_TYPE ]; then
-    case $BACKUP_TYPE in
+if [ -n "${BACKUP_TYPE:-}" ]; then
+    case "$BACKUP_TYPE" in
         "full")
-        backup_full
-        ;;
+            backup_full
+            ;;
         "incremental")
-        backup_incremental
-        ;;
+            backup_incremental
+            ;;
         *)
-        echo "Only full or incremental options are supported."
-        exit 1
-        ;;
+            echo "Only full or incremental options are supported."
+            exit 1
+            ;;
     esac
 else
     echo "You need to specify either full or incremental backup options."
diff --git a/docker/mariadb/mariadb-server/backup_replica.sh b/docker/mariadb/mariadb-server/backup_replica.sh
index 7f86a18a7..ebdcbf6b0 100644
--- a/docker/mariadb/mariadb-server/backup_replica.sh
+++ b/docker/mariadb/mariadb-server/backup_replica.sh
@@ -23,35 +23,48 @@ cd "${BACKUP_DIR}"
 backup_full() {
     echo "Taking a full backup"
     LAST_FULL_DATE=$(date +%d-%m-%Y-%s)
+    BACKUP_FILE="backup-full-${LAST_FULL_DATE}.mbs.gz"
+    BACKUP_PATH="${BACKUP_DIR}/full-${LAST_FULL_DATE}"
+    mkdir -p "${BACKUP_PATH}"
+
     mariabackup \
         --defaults-file="${REPLICA_MY_CNF}" \
         --backup \
         --stream=mbstream \
-        --history="${LAST_FULL_DATE}" | gzip > \
-        "${BACKUP_DIR}/mysqlbackup-${LAST_FULL_DATE}.qp.mbc.mbs.gz" && \
-    echo "${LAST_FULL_DATE}" > "${BACKUP_DIR}/last_full_date"
+        --history="${LAST_FULL_DATE}" \
+        | gzip > "${BACKUP_PATH}/${BACKUP_FILE}"
+
+    echo "${BACKUP_PATH}/${BACKUP_FILE}" > "${BACKUP_DIR}/last_full_file"
 }
 
 # Execute an incremental backup
 backup_incremental() {
-    if [ -r "${BACKUP_DIR}/last_full_date" ]; then
-        LAST_FULL_DATE=$(cat "${BACKUP_DIR}/last_full_date")
-    else
-        LAST_FULL_DATE=""
-    fi
-    if [ ! -z "${LAST_FULL_DATE}" ]; then
-        echo "Taking an incremental backup"
-        mariabackup \
-            --defaults-file="${REPLICA_MY_CNF}" \
-            --backup \
-            --stream=mbstream \
-            --incremental-history-name="${LAST_FULL_DATE}" \
-            --history="${LAST_FULL_DATE}" | gzip > \
-            "${BACKUP_DIR}/incremental-$(date +%H)-mysqlbackup-${LAST_FULL_DATE}.qp.mbc.mbs.gz"
-    else
-        echo "Error: Full backup don't exist."
+    if [ ! -r "${BACKUP_DIR}/last_full_file" ]; then
+        echo "Error: No full backup file found."
         exit 1
     fi
+
+    FULL_BACKUP_FILE=$(cat "${BACKUP_DIR}/last_full_file")
+    LAST_FULL_DATE=$(basename "$(dirname "${FULL_BACKUP_FILE}")" | sed 's/^full-//')
+    NOW=$(date +%H-%M-%S-%d-%m-%Y)
+    INCR_DIR="${BACKUP_DIR}/incr-${NOW}-since-${LAST_FULL_DATE}"
+    mkdir -p "${INCR_DIR}"
+
+    # Temp dir for full base restore
+    TMP_BASEDIR=$(mktemp -d)
+
+    echo "Decompressing full backup to temp dir: ${TMP_BASEDIR}"
+    gunzip -c "${FULL_BACKUP_FILE}" | mbstream -x -C "${TMP_BASEDIR}"
+
+    mariabackup \
+        --defaults-file="${REPLICA_MY_CNF}" \
+        --backup \
+        --stream=mbstream \
+        --incremental-basedir="${TMP_BASEDIR}" \
+        --history="incr-${NOW}" \
+        | gzip > "${INCR_DIR}/backup-incremental-${NOW}.mbs.gz"
+
+    rm -rf "${TMP_BASEDIR}"
 }
 
 # Retry logic for database queries
@@ -119,15 +132,15 @@ if [ -n "${BACKUP_TYPE}" ]; then
     get_and_set_replica_server
     case "${BACKUP_TYPE}" in
         "full")
-        backup_full
-        ;;
+            backup_full
+            ;;
         "incremental")
-        backup_incremental
-        ;;
+            backup_incremental
+            ;;
         *)
-        echo "Only full or incremental options are supported."
-        exit 1
-        ;;
+            echo "Only full or incremental options are supported."
+            exit 1
+            ;;
     esac
 else
     echo "You need to specify either full or incremental backup options."
diff --git a/releasenotes/notes/bug-2111620-e40e1dec6fed309f.yaml b/releasenotes/notes/bug-2111620-e40e1dec6fed309f.yaml
new file mode 100644
index 000000000..e5c9f8198
--- /dev/null
+++ b/releasenotes/notes/bug-2111620-e40e1dec6fed309f.yaml
@@ -0,0 +1,12 @@
+---
+fixes:
+  - |
+    Fixes incremental MariaDB backups by switching to directory-based base backups,
+    following official Mariabackup recommendations.
+    `LP#2111620 <https://bugs.launchpad.net/kolla/+bug/2111620>`__
+upgrade:
+  - |
+    Backup files are now stored in timestamped directories and have new filenames.
+    This does not affect restore, as Kolla Ansible does not support automated restore;
+    users perform restores manually. A new full backup is recommended after upgrade
+    to ensure incremental backups work correctly.