composeappmanager: Make app stopping configurable

Introduce a new configuration var, `[pacman].stop_apps_before_update`,
to control whether apps should be forcibly stopped just before their
update during an "app-only" update (when no OSTree update is involved).

By default, this variable is set to true, meaning apps are stopped
before their update even if no OSTree update occurs.

If there is OSTree update too, then apps are stopped unconditionally;
the new conf var is ignored.

Signed-off-by: Mike Sul <[email protected]>

src/composeappmanager.cc

@@ -83,6 +83,10 @@ ComposeAppManager::Config::Config(const PackageConfig& pconfig) {
     create_containers_before_reboot = boost::lexical_cast<bool>(raw.at("create_containers_before_reboot"));
   }
 
+  if (raw.count("stop_apps_before_update") > 0) {
+    stop_apps_before_update = boost::lexical_cast<bool>(raw.at("stop_apps_before_update"));
+  }
+
   if (raw.count("storage_watermark") > 0) {
     const std::string storage_watermark_str{raw.at("storage_watermark")};
 
@@ -355,9 +359,12 @@ data::InstallationResult ComposeAppManager::install(const Uptane::Target& target
   // the subsequent "sync target" process will restart the apps (excluding those removed from the configuration).
   stopDisabledComposeApps(target);
 
-  if (getCurrent().sha256Hash() != target.sha256Hash()) {
-    // If this ostree + apps update, then stop the Apps that is about to be updated
-    // so they are not started automatically by dockerd just after reboot.
+  if (getCurrent().sha256Hash() != target.sha256Hash() || cfg_.stop_apps_before_update) {
+    // If this is "ostree + apps" update or the `stop_apps_before_update` configuration variable is set to `true`,
+    // then stop the Apps that is about to be updated
+    // so they are not started automatically by dockerd just after reboot
+    // or it is required by the app use case to force stopping of all app services/containers if
+    // at least one of its container images is updated (`docker compose up` restarts only updated containers).
     // If ostree is not updated then the updated Apps will be started in this context.
     // If ostree is updated and a device is suddenly rebooted before Apps installation, then
     // it ensures that the previous version Apps are not automatically started on boot.

src/composeappmanager.h

@@ -35,6 +35,7 @@ class ComposeAppManager : public RootfsTreeManager {
     std::string docker_images_reload_cmd{"systemctl reload docker"};
     std::string hub_auth_creds_endpoint{Docker::RegistryClient::DefAuthCredsEndpoint};
     bool create_containers_before_reboot{true};
+    bool stop_apps_before_update{true};
     int storage_watermark{80};
   };