Improvements to Horizon build/start process

- default options for all variables;
- provide default values if some variables are not defined;
- generate SECRET_KEY dynamically;
- add support of Memcached;

Default for KEYSTONE_ADDRESS is 127.0.0.1, and if that is not accessible -
container will halt.

Full list of supported variables:
- KEYSTONE_ADDRESS
- HORIZON_SECRET_KEY
- MEMCACHED_LOCATION (in format of IP:port)

Change-Id: I3f959c3dee285b3c0ad49cc4ffa06cda206309cd

docker/horizon/local_settings

@@ -133,11 +133,7 @@ SECRET_KEY = 'Secret_String'
 #    },
 #}
 
-CACHES = {
-    'default': {
-        'BACKEND': 'django.core.cache.backends.locmem.LocMemCache',
-    },
-}
+CACHES = {'default': {'BACKEND': 'django.core.cache.backends.locmem.LocMemCache',},}
 
 # Send email to the console by default
 EMAIL_BACKEND = 'django.core.mail.backends.console.EmailBackend'

docker/horizon/start.sh

@@ -5,12 +5,27 @@
 
 source /etc/apache2/envvars
 
-sed -i "s/Secret_String/${HORIZON_SECRET_KEY}/g" \
-    /etc/openstack-dashboard/local_settings
-sed -i "s/KEYSTONE_ADDRESS/${KEYSTONE_ADDRESS}/g" \
-    /etc/openstack-dashboard/local_settings
+DASHBOARD="/etc/openstack-dashboard/local_settings"
+BACKEND="django.core.cache.backends.memcached.MemcachedCache"
 
-#check does keyston is alive
+if [ -z "$HORIZON_SECRET_KEY" ]; then
+    KEY=$(cat /dev/urandom | tr -dc 'a-zA-Z0-9' | fold -w 32 | head -n 1)
+    HORIZON_SECRET_KEY=$KEY
+fi
+
+if [ -z "$KEYSTONE_ADDRESS" ]; then
+    KEYSTONE_ADDRESS="127.0.0.1"
+fi
+
+sed -i "s/Secret_String/${HORIZON_SECRET_KEY}/g" $DASHBOARD
+sed -i "s/KEYSTONE_ADDRESS/${KEYSTONE_ADDRESS}/g" $DASHBOARD
+
+if [ -n "$MEMCACHED_LOCATION" ]; then
+    CONF="{'default':{'BACKEND':'$BACKEND','LOCATION':'$MEMCACHED_LOCATION',},}"
+    sed -i 's/^CACHES = .*$/CACHES = $CONF/g' $DASHBOARD
+fi
+
+#check if keystone is alive
 nc -z -v -w5 ${KEYSTONE_ADDRESS} 5000
 if [ $? -ne 0 ];then
     exit 1