diff --git a/collabora/hooks/nextcloud_app-relation-joined b/collabora/hooks/nextcloud_app-relation-joined
new file mode 100755
index 0000000..277d82e
--- /dev/null
+++ b/collabora/hooks/nextcloud_app-relation-joined
@@ -0,0 +1,23 @@
+#!/bin/bash
+
+set -e
+
+NEXTCLOUD_APP_CONNECTION_DIR="$state_tmpdir/$PROJECT_NAME/$SERVICE_NAME/"
+
+mkdir -p "$NEXTCLOUD_APP_CONNECTION_DIR"
+
+# Atomicity
+i=1
+while ! mkdir "$NEXTCLOUD_APP_CONNECTION_DIR"/"$i"; do ((i++)) ; done
+
+
+if ! nextcloud_url=$(relation:get "$MASTER_TARGET_SERVICE_NAME":web-proxy url) || [ -z "$nextcloud_url" ]; then
+    nextcloud_url="http://$TARGET_SERVICE_NAME:80"
+fi
+
+config-add "\
+services:
+  $MASTER_BASE_SERVICE_NAME:
+    environment:
+      aliasgroup$i: \"${nextcloud_url}\"
+"
diff --git a/collabora/hooks/post_deploy b/collabora/hooks/post_deploy
index ec48080..eac610e 100755
--- a/collabora/hooks/post_deploy
+++ b/collabora/hooks/post_deploy
@@ -2,54 +2,85 @@
 
 set -e
 
-
-# if ! nextcloud_domain=$(relation:get "$MASTER_TARGET_SERVICE_NAME":web-proxy domain) || [ -z "$nextcloud_domain" ]; then
-#     ## No domain, probably no web-proxy then.
-
-#     container=$(get_running_containers_for_service "$MASTER_TARGET_SERVICE_NAME" | head -n 1)
-#     container_network_ip=$(get_docker_ip "$container")
-#     container_ip=${container_network_ip#*:}
-
-#     nextcloud_domain="${container_ip}:80"
-# fi
-
-if ! nextcloud_app_service=$(service:traverse "$MASTER_BASE_SERVICE_NAME":nextcloud-app); then
-    err "Couldn't find service for"\
-        "${DARKYELLOW}$MASTER_BASE_SERVICE_NAME${NORMAL}--${DARKCYAN}nextcloud-app${NORMAL}--> ?"
-    exit 1
-fi
-
-if ! collabora_domain=$(relation:get "$MASTER_BASE_SERVICE_NAME":web-proxy url) || [ -z "$collabora_domain" ]; then
-    ## No domain, probably no web-proxy then.
-
-    # container=$(get_running_containers_for_service "$MASTER_BASE_SERVICE_NAME" | head -n 1)
-    # container_network_ip=$(get_docker_ip "$container")
-    # container_ip=${container_network_ip#*:}
-
-    collabora_domain="$SERVICE_NAME:9980"
+service:relations() {
+    local service="$1" relation="$2" cache_file="$state_tmpdir/$FUNCNAME.cache.$1.$2" \
+          rn ts rc td
+    if [ -e "$cache_file" ]; then
+        #debug "$FUNCNAME: SESSION cache hit $1"
+        cat "$cache_file"
+        return 0
+    fi
+
+    while read-0-err E rn ts rc td; do
+        [ "$relation" == "$rn" ] && {
+            printf "%s\0" "$ts" "$rc" "$td"
+        }
+    done < <(p-err get_service_relations "$service") > "$cache_file"
+    if [ "$E" != 0 ]; then
+        rm -f "$cache_file"  ## no cache
+        return 1
+    fi
+    cat "$cache_file"
+}
+export -f service:relations
+
+
+
+export TRAVERSE_SEPARATOR=:
+## Traverse on all service satisfying relation
+service:traverse:all() {
+    local service_path="$1"
+    local service relation path relation
+    service=${service_path%%$TRAVERSE_SEPARATOR*}
+    path=${service_path#*$TRAVERSE_SEPARATOR}
+    if [[ "$path" == *$TRAVERSE_SEPARATOR* ]]; then
+        relation=${path%%$TRAVERSE_SEPARATOR*}
+        path=${path#*$TRAVERSE_SEPARATOR}
+    else
+        relation=$path
+        path=
+    fi
+    while read-0-err E ts _ _; do
+        if [ -n "$path" ]; then
+            service:traverse "$ts$TRAVERSE_SEPARATOR$path"
+        else
+            printf "%s\n" "$ts"
+        fi
+    done < <(p-err service:relations "${service}" "${relation}")
+    if [ "$E" != 0 ]; then
+        err "Couldn't find service for ${DARKYELLOW}$service${NORMAL}--${DARKCYAN}$relation${NORMAL}--> ?"
+        return 1
+    fi
+}
+export -f service:traverse:all
+
+
+##
+## Finish live connection for relation nextcloud_app
+##
+
+nextcloud_services=($(service:traverse:all "$MASTER_BASE_SERVICE_NAME":nextcloud-app)) || return 1
+
+if [ ${#nextcloud_services[@]} != 0 ]; then
+    if ! collabora_url=$(relation:get "$MASTER_BASE_SERVICE_NAME":web-proxy url) || [ -z "$collabora_url" ]; then
+        collabora_url="http://$BASE_SERVICE_NAME:9980"
+    fi
+    if ! get_healthy_container_ip_for_service "$SERVICE_NAME" 9980; then
+        exit 17
+    fi
+
+    info "collabora_domain: '$collabora_url'"
+
+    for nextcloud_service in "${nextcloud_services[@]}"; do
+
+        ## Activate-config will make nextcloud try to connect to collabora.
+        ## This is why we must run this in post_deploy
+
+        compose --no-relations --no-init \
+                occ "$nextcloud_service" \
+                app:install richdocuments \; \
+                config:app:set --value="${collabora_url}" richdocuments wopi_url \; \
+                richdocuments:activate-config || return 1
+
+    done
 fi
-
-info "collabora_domain: '$collabora_domain'"
-
-if ! get_healthy_container_ip_for_service "$SERVICE_NAME" 9980; then
-    exit 17
-fi
-
-
-## XXXvlab: we really need to have a state based cache thingy, because
-## setting the same password each time is really time consumming.
-compose --no-relations --no-init \
-        occ "$nextcloud_app_service" \
-        app:install richdocuments \; \
-        config:app:set --value="${collabora_domain}" richdocuments wopi_url \; \
-        richdocuments:activate-config
-
-
-# nextcloud_domain="${nextcloud_domain//./\\.}"
-
-# config-add "\
-# services:
-#   $MASTER_BASE_SERVICE_NAME:
-#     environment:
-#       domain: \"${nextcloud_domain}\"
-# "