From 6add9edf8a760c12cccb488ae0bf1380f8fac199 Mon Sep 17 00:00:00 2001
From: Aleksandra Martyniuk <aleksandra.martyniuk@scylladb.com>
Date: Wed, 15 May 2024 14:18:03 +0200
Subject: [PATCH] tasks: change _children type

Keep task children in a map. It's a preparation for further changes.
---
 api/task_manager.cc   |  5 +++--
 tasks/task_manager.cc | 14 ++++++++------
 tasks/task_manager.hh |  6 +++---
 3 files changed, 14 insertions(+), 11 deletions(-)

diff --git a/api/task_manager.cc b/api/task_manager.cc
index c384f4fe23..6a4c24a817 100644
--- a/api/task_manager.cc
+++ b/api/task_manager.cc
@@ -103,7 +103,8 @@ future<full_task_status> retrieve_status(const tasks::task_manager::foreign_task
     s.progress.completed = progress.completed;
     s.progress.total = progress.total;
     std::vector<std::string> ct{task->get_children().size()};
-    boost::transform(task->get_children(), ct.begin(), [] (const auto& child) {
+    boost::transform(task->get_children(), ct.begin(), [] (const auto& child_entry) {
+        const auto& [child_id, child] = child_entry;
         return child->id().to_sstring();
     });
     s.children_ids = std::move(ct);
@@ -231,7 +232,7 @@ void set_task_manager(http_context& ctx, routes& r, sharded<tasks::task_manager>
         while (!q.empty()) {
             auto& current = q.front();
             res.push_back(co_await retrieve_status(current));
-            for (auto& child: current->get_children()) {
+            for (const auto& [_, child] : current->get_children()) {
                 q.push(co_await child.copy());
             }
             q.pop();
diff --git a/tasks/task_manager.cc b/tasks/task_manager.cc
index 246a5c40ea..45225fcca7 100644
--- a/tasks/task_manager.cc
+++ b/tasks/task_manager.cc
@@ -70,8 +70,8 @@ future<task_manager::task::progress> task_manager::task::impl::get_progress() co
     }
 
     tasks::task_manager::task::progress progress{};
-    for (auto& child: _children) {
-        progress += co_await smp::submit_to(child.get_owner_shard(), [&child] {
+    for (auto& [id, child]: _children) {
+        progress += co_await smp::submit_to(child.get_owner_shard(), [&child = child] {
             return child->get_progress();
         });
     }
@@ -92,8 +92,9 @@ future<> task_manager::task::impl::abort() noexcept {
         _as.request_abort();
 
         std::vector<task_info> children_info{_children.size()};
-        boost::transform(_children, children_info.begin(), [] (const auto& child) {
-            return task_info{child->id(), child.get_owner_shard()};
+        boost::transform(_children, children_info.begin(), [] (const auto& child_entry) {
+            const auto& [child_id, child] = child_entry;
+            return task_info{child_id, child.get_owner_shard()};
         });
 
         co_await coroutine::parallel_for_each(children_info, [this] (auto info) {
@@ -183,7 +184,8 @@ void task_manager::task::change_state(task_state state) noexcept {
 }
 
 void task_manager::task::add_child(foreign_task_ptr&& child) {
-    _impl->_children.push_back(std::move(child));
+    auto inserted = _impl->_children.emplace(child->id(), std::move(child)).second;
+    assert(inserted);
 }
 
 void task_manager::task::start() {
@@ -254,7 +256,7 @@ void task_manager::task::unregister_task() noexcept {
     _impl->_module->unregister_task(id());
 }
 
-const task_manager::foreign_task_list& task_manager::task::get_children() const noexcept {
+const task_manager::foreign_task_map& task_manager::task::get_children() const noexcept {
     return _impl->_children;
 }
 
diff --git a/tasks/task_manager.hh b/tasks/task_manager.hh
index 8a496686b6..73f3972596 100644
--- a/tasks/task_manager.hh
+++ b/tasks/task_manager.hh
@@ -42,7 +42,7 @@ public:
     using task_ptr = lw_shared_ptr<task_manager::task>;
     using task_map = std::unordered_map<task_id, task_ptr>;
     using foreign_task_ptr = foreign_ptr<task_ptr>;
-    using foreign_task_list = std::list<foreign_task_ptr>;
+    using foreign_task_map = std::unordered_map<task_id, foreign_task_ptr>;
     using module_ptr = shared_ptr<module>;
     using modules = std::unordered_map<std::string, module_ptr>;
 private:
@@ -109,7 +109,7 @@ public:
         protected:
             status _status;
             task_id _parent_id;
-            foreign_task_list _children;
+            foreign_task_map _children;
             shared_promise<> _done;
             module_ptr _module;
             seastar::abort_source _as;
@@ -167,7 +167,7 @@ public:
         future<> done() const noexcept;
         void register_task();
         void unregister_task() noexcept;
-        const foreign_task_list& get_children() const noexcept;
+        const foreign_task_map& get_children() const noexcept;
         bool is_complete() const noexcept;
 
         friend class test_task;