NethVoice - Improve backup procedure to avoid temporary database duplication

[nrauso]

Description

During the NethVoice backup, the module-dump-state action can require a very large amount of temporary disk space when the MariaDB database is large.

In a reported case, the node had a 100 GB disk, with about 50% already used:

~]# df -h /
Filesystem      Size  Used Avail Use% Mounted on
/dev/vda4        99G   49G   51G  50% /

The NethVoice instance had a database of about 25 GB:

~]# du -h /home/nethvoice1 2>/dev/null | sort -h | tail -n 10
6.0G    /home/nethvoice1/.local/share/containers/storage/overlay
23G     /home/nethvoice1/.local/share/containers/storage/volumes/mariadb-data/_data/asteriskcdrdb
24G     /home/nethvoice1/.local/share/containers/storage/volumes/mariadb-data
24G     /home/nethvoice1/.local/share/containers/storage/volumes/mariadb-data/_data
25G     /home/nethvoice1/.local/share/containers/storage/volumes
31G     /home/nethvoice1
31G     /home/nethvoice1/.local
31G     /home/nethvoice1/.local/share
31G     /home/nethvoice1/.local/share/containers
31G     /home/nethvoice1/.local/share/containers/storage

The current module-dump-state logic creates the MariaDB backup inside the container under /tmp/db_backup, then copies it to the local filesystem:

## MariaDB
# exec mariabackup to save database in /tmp/db_backup
podman exec mariadb \
    mariabackup \
        --backup \
        --target-dir=/tmp/db_backup \
        --user=root \
        --password="${MARIADB_ROOT_PASSWORD}"

# copy db_backup in local filesystem
podman cp mariadb:/tmp/db_backup db_backup

This causes the database content to temporarily exist three times:

• the production MariaDB volume;
• the temporary backup inside the container;
• the final db_backup directory in the app home.

With a large database, this can almost fill the root filesystem, as happened in the reported case:

~]# df -h /
Filesystem      Size  Used Avail Use% Mounted on
/dev/vda4        99G   95G  4.6G  96% /

On systems where the disk is already more than half full, the backup can fail with no space left on device, and the application can be temporarily affected.

Example failure:

"/db_backup/asteriskcdrdb/report_queue_callers.MYD": copier: put: error writing file "/db_backup/asteriskcdrdb/report_queue_callers.MYD": write /db_backup/asteriskcdrdb/report_queue_callers.MYD: no space left on device
Apr 24 00:05:22 ns8 backup1[1073652]:         * copying from container: copier: get: "/tmp/db_backup"("/tmp/db_backup"): copying /tmp/db_backup/asteriskcdrdb/report_queue_callers.MYD: io: read/write on closed pipe
Apr 24 00:05:22 ns8 backup1[1073991]: Error: saving container fd9da0c00d270d92808345eae29b22e74d4ad000c94d05f7b6389adf6e10e9ed state: writing container fd9da0c00d270d92808345eae29b22e74d4ad000c94d05f7b6389adf6e10e9ed state: unable to open database file: no such file or directory
Apr 24 00:05:22 ns8 backup1[1072277]: [ERROR] module-dump-state failed. Command '['module-dump-state', '10']' returned non-zero exit status 255.
Apr 24 00:05:22 ns8 backup1[1072277]: [ERROR] module-backup aborted.

The purpose of this request is to make the NethVoice backup process safer and more space-efficient, especially for installations with large CDR databases.