new: [mariadb] added ``backup`` relation.

Signed-off-by: Valentin Lab <valentin.lab@kalysto.org>

mariadb/hooks/backup-relation-joined

@@ -0,0 +1,21 @@
+#!/bin/bash
+
+## When writing relation script, remember:
+##  - they should be idempotents
+##  - they can be launched while the dockers is already up
+##  - they are launched from the host
+##  - the target of the link is launched first, and get a chance to ``relation-set``
+##  - both side of the scripts get to use ``relation-get``.
+
+. lib/common
+
+set -e
+
+## if I'm not linked to a schedule-command, then complain
+if read-0 ts _ _ < <(get_service_relation "$SERVICE_NAME" "schedule-command"); then
+    debug "schedule-command relation fullfilled"
+else
+    ## XXXvlab: relation dependence as this one could actually be implemented in compose-core
+    err "backup relation requires schedule-command relation to be set"
+    exit 1
+fi

mariadb/metadata.yml

@@ -16,3 +16,19 @@ uses:
       backup: "Automatic regular dumps for backuping purpose"
     default-options:
       schedule: "31 * * * *"  ## schedule backup every hour
+  ## This one is useful only if previous relation is used
+  backup:
+    constraint: optional
+    auto: pair
+    solves:
+      backup: "Automatic regular backups of dumps"
+    default-options:
+      ## First pattern matching wins, no pattern matching includes.
+      ## include-patterns are checked first, then exclude-patterns
+      ## Patterns rules:
+      ##  - ending / for directory
+      ##  - '*' authorized
+      ##  - must start with a '/', will start from $SERVICE_DATASTORE
+      exclude-patterns:
+        - "/var/lib/"                         ## mariadb working data files
+        - "/var/backups/mysql/*.inprogress"   ## database dump in progress