new: [mongo] added regular dump for backup

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

mongo/build/Dockerfile

@@ -2,7 +2,9 @@
 ## is a simple copy of alpine:3.9
 FROM docker.0k.io/alpine:3.9 as common
 
-RUN apk add --no-cache mongodb
+## mongodb-tools is only required because we expect and use mongodump
+## XXXvlab: bash is only required by mongo-backup, we could probably only use sh
+RUN apk add --no-cache mongodb mongodb-tools bash
 
 RUN mkdir -p /var/lib/mongod
 RUN chown -R mongodb:mongodb /var/lib/mongod

mongo/hooks/schedule_command-relation-joined

@@ -0,0 +1,43 @@
+#!/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
+
+label=${SERVICE_NAME}-backup
+DST=$CONFIGSTORE/$TARGET_SERVICE_NAME/etc/cron/$label
+schedule=$(relation-get schedule)
+
+if ! echo "$schedule" | egrep '^\s*(([0-9/,*-]+\s+){4,4}[0-9/,*-]+|@[a-z]+)\s*$' >/dev/null 2>&1; then
+    err "Unrecognized schedule '$schedule'."
+    exit 1
+fi
+
+exclude_dbs=$(relation-get exclude-dbs 2>/dev/null) || true
+exclude_dbs=$(echo "$exclude_dbs" | shyaml get-values 2>/dev/null |
+                  nspc) || true
+
+## Warning: 'docker -v' will use HOST directory even if launched from
+##   'cron' container.
+file_put "$DST" <<EOF
+COMPOSE_LAUNCHER_OPTS=$COMPOSE_LAUNCHER_OPTS
+
+$schedule     root  lock $label -D -p 10 -c "\
+    docker run --rm \
+        -u 0 \
+        -e MONGO_HOST=${SERVICE_NAME} \
+        -e exclude_dbs=\"$exclude_dbs\" \
+        --network ${PROJECT_NAME}_default \
+        -v \"$HOST_CHARM_STORE/${CHARM_REL_PATH#${CHARM_STORE}/}/resources/bin/mongo-backup:/usr/sbin/mongo-backup\" \
+        -v \"$SERVICE_DATASTORE/var/backups/mongo:/var/backups/mongo\" \
+        --entrypoint mongo-backup \
+        \"$DOCKER_BASE_IMAGE\"" 2>&1 | ts '\%F \%T \%Z' >> /var/log/cron/${label}_script.log
+EOF
+chmod +x "$DST"

mongo/metadata.yml

@@ -6,3 +6,12 @@ config-resources:
   - /etc/mongod.conf
 provides:
   mongo-database:
+
+uses:
+  schedule-command:
+    constraint: optional
+    auto: pair
+    solves:
+      backup: "Automatic regular backups"
+    default-options:
+      schedule: "47 * * * *"  ## schedule backup every hour

mongo/resources/bin/mongo-backup

@@ -0,0 +1,49 @@
+#!/bin/bash
+
+[ "$MONGO_HOST" ] || {
+    echo "You must define \$MONGO_HOST variable." >&2
+    exit 1
+}
+
+
+mongo_databases() {
+    echo "show dbs" | mongo --quiet --host "$MONGO_HOST"  | cut -f 1 -d " "
+}
+
+dbs=$(mongo_databases)
+
+BACKUP_ROOT=/var/backups/mongo
+mkdir -p "$BACKUP_ROOT"
+for db in $dbs; do
+    if [[ "$db" == "local" || "$db" == "config" ]]; then
+        continue
+    fi
+    for exclude_db in $exclude_dbs; do
+        if [ "$exclude_db" == "$db" ]; then
+            echo "No backup for database $db as it is listed in 'exclude-dbs'."
+            continue 2
+        fi
+    done
+
+    dst="$BACKUP_ROOT/$db"
+    [ -d "$dst.old" ] && rm -rf "$dst.old"
+    [ -d "$dst" ] && mv "$dst" "$dst.old"
+    mkdir -p "$dst.inprogress"
+    (( start = SECONDS ))
+    echo "Dumping database $db..." >&2
+    mongodump --host "$MONGO_HOST" --db "$db" --out "$dst.inprogress" &&
+        mv "$dst.inprogress/$db/"* "$dst.inprogress/" &&
+        rmdir "$dst.inprogress/$db"
+    errlvl="${PIPESTATUS[0]}"
+    (( elapsed = SECONDS - start ))
+    if [ "$errlvl" != "0" ]; then
+        echo "  !! Error when dumping database $db." >&2
+        rm -rf "$dst.inprogress" &&
+        [ -d "$dst.old" ] && rm -rf "$dst.old"
+    else
+        mv "$dst.inprogress" "$dst"
+        [ -d "$dst.old" ] && rm -rf "$dst.old"
+        printf "  ..dumped %-35s (%12s in %10s)\n" "$db" "$(du -sh "$dst" | cut -f 1)" "${elapsed}s" >&2
+    fi
+done
+