appengine: Optimize app fetch check

If an app is successfully fetched and checked then mark it as "fetched"
so the next time when the app fetch check is called, then no need to
invoke the full blown check performed by `composectl`.

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

src/composeapp/appengine.cc

@@ -14,6 +14,9 @@ static bool checkAppStatus(const AppEngine::App& app, const Json::Value& status)
 AppEngine::Result AppEngine::fetch(const App& app) {
   Result res{false};
   try {
+    // If a given app was fetched before, then don't consider it as a fetched app if a caller tries to fetch it again
+    // for one reason or another - hence remove it from the set of fetched apps.
+    fetched_apps_.erase(app.uri);
     if (local_source_path_.empty()) {
       exec(boost::format{"%s --store %s pull -p %s --storage-usage-watermark %d"} % composectl_cmd_ % storeRoot() %
                app.uri % storage_watermark_,
@@ -24,6 +27,7 @@ AppEngine::Result AppEngine::fetch(const App& app) {
            "failed to pull compose app");
     }
     res = true;
+    fetched_apps_.insert(app.uri);
   } catch (const ExecError& exc) {
     if (exc.ExitCode == static_cast<int>(ExitCode::ExitCodeInsufficientSpace)) {
       const auto usage_stat{Utils::parseJSON(exc.StdErr)};
@@ -40,6 +44,7 @@ AppEngine::Result AppEngine::fetch(const App& app) {
 
 void AppEngine::remove(const App& app) {
   try {
+    fetched_apps_.erase(app.uri);
     // "App removal" in this context refers to deleting app images from the Docker store
     // and removing the app compose project (app uninstall).
     // Unused app blobs will be removed from the blob store via the prune() method,
@@ -114,6 +119,7 @@ void AppEngine::prune(const Apps& app_shortlist) {
       }
     }
     for (const auto& app : apps_to_prune) {
+      fetched_apps_.erase(app.uri);
       exec(boost::format{"%s --store %s rm %s --prune=false --quiet"} % composectl_cmd_ % storeRoot() % app.uri,
            "failed to remove app");
     }
@@ -143,6 +149,9 @@ void AppEngine::prune(const Apps& app_shortlist) {
 
 bool AppEngine::isAppFetched(const App& app) const {
   bool res{false};
+  if (fetched_apps_.count(app.uri) > 0) {
+    return true;
+  }
   try {
     std::future<std::string> output;
     exec(boost::format{"%s --store %s check %s --local --format json"} % composectl_cmd_ % storeRoot() % app.uri, "",
@@ -152,6 +161,7 @@ bool AppEngine::isAppFetched(const App& app) const {
     if (app_fetch_status.isMember("fetch_check") && app_fetch_status["fetch_check"].isMember("missing_blobs") &&
         app_fetch_status["fetch_check"]["missing_blobs"].empty()) {
       res = true;
+      fetched_apps_.insert(app.uri);
     }
   } catch (const ExecError& exc) {
     LOG_DEBUG << "app is not fully fetched; app: " << app.name << ", status: " << exc.what();

src/composeapp/appengine.h

@@ -37,6 +37,7 @@ class AppEngine : public Docker::RestorableAppEngine {
   const std::string composectl_cmd_;
   const int storage_watermark_;
   const std::string local_source_path_;
+  mutable std::set<std::string> fetched_apps_;
 };
 
 }  // namespace composeapp