[service template] Starting new docker when HWSKU change is detected (#946)

Existing dockers has paths mounted according to the HWSKU. When HWSKU
changes, these dockers need to be destroyed and recreated with the
correct paths mounted.

files/build_templates/docker_image_ctl.j2

@@ -1,17 +1,56 @@
 #!/bin/bash
 
-# Obtain our platform and HWSKU as we will mount directories with these names in each docker
+function getMountPoint()
-PLATFORM=`sonic-cfggen -v platform`
+{
+    echo $1 |  python -c "import sys, json, os; mnts = [x for x in json.load(sys.stdin)[0]['Mounts'] if x['Destination'] == '/usr/share/sonic/hwsku']; print '' if len(mnts) == 0 else os.path.basename(mnts[0]['Source'])" 2>/dev/null
+}
+
+function postStartAction()
+{
 {%- if docker_container_name != "database" %}
+    :
+{%- else %}
+    while true; do
+        if [[ "$(docker exec -i database redis-cli ping)" =~ PONG.* ]]; then
+            break
+        fi
+        sleep 1
+    done
+{%- endif %}
+}
+
+# Obtain our platform as we will mount directories with these names in each docker
+PLATFORM=`sonic-cfggen -v platform`
+
+{%- if docker_container_name == "database" %}
+# Don't mount HWSKU in {{docker_container_name}} container.
+HWSKU=""
+{%- else %}
+# Obtain our HWSKU as we will mount directories with these names in each docker
 HWSKU=`sonic-cfggen -d -v 'DEVICE_METADATA["localhost"]["hwsku"]'`
 {%- endif %}
 
 start() {
-    docker inspect --type container {{docker_container_name}} &>/dev/null
+    DOCKERCHECK=`docker inspect --type container {{docker_container_name}} 2>/dev/null`
     if [ "$?" -eq "0" ]; then
+        DOCKERMOUNT=`getMountPoint "$DOCKERCHECK"`
+        if [ "$DOCKERMOUNT" == "$HWSKU" ]; then
+            echo "Starting existing {{docker_container_name}} container with HWSKU $HWSKU"
             docker start {{docker_container_name}}
-    else
+            postStartAction
+            exit 0
+        fi
 
+        # docker created with a different HWSKU, remove and recreate
+        echo "Removing obsolete {{docker_container_name}} container with HWSKU $DOCKERMOUNT"
+        docker rm {{docker_container_name}}
+    fi
+
+{%- if docker_container_name == "database" %}
+    echo "Starting new {{docker_container_name}} container"
+{%- else %}
+    echo "Starting new {{docker_container_name}} container with HWSKU $HWSKU"
+{%- endif %}
     docker run -d {{docker_image_run_opt}} \
 {%- if '--log-driver=json-file' in docker_image_run_opt or '--log-driver' not in docker_image_run_opt %}
         --log-opt max-size=2M --log-opt max-file=5 \
@@ -22,15 +61,8 @@ start() {
         -v /usr/share/sonic/device/$PLATFORM/$HWSKU:/usr/share/sonic/hwsku:ro \
 {%- endif %}
         --name={{docker_container_name}} {{docker_image_name}}:latest
-    fi
+
-{%- if docker_container_name == "database" %}
+    postStartAction
-    while true; do
-        if [[ "$(docker exec -i database redis-cli ping)" =~ PONG.* ]]; then
-            break
-        fi
-        sleep 1
-    done
-{%- endif %}
 }
 
 attach() {