Docker optional backup and restore with documentation (#1692)

* Make backups optional with env ENABLE vars.
Use a dedicated backup directory instead of priv.

* Docker optional backup and restore documentation

docs/docker/tips.md

@@ -57,3 +57,26 @@ cardanocommunity/cardano-node:latest          # Mandatory: image to run
 
 #### Un-Official Docker managment cli tool
 - [Lazydocker](https://github.com/jesseduffield/lazydocker)
+
+### Docker backups and restores
+
+The docker container has an optional backup and restore functionality that can be used to backup the `/opt/cardano/cnode/db` directory. To have the 
+backup persist longer than the countainer, the backup directory should be mounted as a volume.
+
+[!NOTE]
+The backup and restore functionality is disabled by default.
+
+[!WARNING]
+Make sure adequate space exists on the host as the backup will double the space consumed by the database. 
+
+#### Creating a Backup
+
+When the container is started with the **ENABLE_BACKUP** environment variable set to **Y** the container will automatically create a
+backup in the `/opt/cardano/cnode/backup/$NETWORK-db` directory. The backup will be created when the container is started and if the
+backup directory is smaller than the db directory.
+
+#### Restoring from a Backup
+
+When the container is started with the **ENABLE_RESTORE** environment variable set to **Y** the container will automatically restore
+the latest backup from the `/opt/cardano/cnode/backup/$NETWORK-db` directory. The database will be restored when the container is started
+and if the backup directory is larger than the db directory.

files/docker/node/addons/entrypoint.sh

@@ -16,15 +16,21 @@ echo "NETWORK: $NETWORK $POOL_NAME $TOPOLOGY";
 echo "NODE: $HOSTNAME - Port:$CNODE_PORT - $POOL_NAME";
 cardano-node --version;
 
-dbsize=$(du -s ${CNODE_HOME}/db | awk '{print $1}')
-bksizedb=$(du -s $CNODE_HOME/priv/$NETWORK-db 2>/dev/null | awk '{print $1}')
+if [[ "${ENABLE_BACKUP}" == "Y" ]] || [[ "${ENABLE_RESTORE}" == "Y" ]]; then
+    [[ ! -d "${CNODE_HOME}"/backup/$NETWORK-db ]] && mkdir -p $CNODE_HOME/backup/$NETWORK-db
+    dbsize=$(du -s $CNODE_HOME/db | awk '{print $1}')
+    bksizedb=$(du -s $CNODE_HOME/backup/$NETWORK-db 2>/dev/null | awk '{print $1}')
+    if [[ "${ENABLE_RESTORE}" == "Y" ]] && [[ "$dbsize" -lt "$bksizedb" ]]; then
+        echo "Backup Started"
+        cp -rf "${CNODE_HOME}"/backup/"${NETWORK}"-db/* "${CNODE_HOME}"/db 2>/dev/null
+        echo "Backup Finished"
+    fi
 
-if [[ "$dbsize" -lt "$bksizedb" ]]; then
-cp -rf $CNODE_HOME/priv/$NETWORK-db/* ${CNODE_HOME}/db 2>/dev/null
-fi
-
-if [[ "$dbsize" -gt "$bksizedb" ]]; then
-cp -rf $CNODE_HOME/db/* $CNODE_HOME/priv/$NETWORK-db/ 2>/dev/null
+    if [[ "${ENABLE_BACKUP}" == "Y" ]] && [[ "$dbsize" -gt "$bksizedb" ]]; then
+        echo "Restore Started"
+        cp -rf "${CNODE_HOME}"/db/* "${CNODE_HOME}"/backup/"${NETWORK}"-db/ 2>/dev/null
+        echo "Restore Finished"
+    fi
 fi
 
 # Customisation