From 2fced3c55797ee7c9e9eab2f4dcd50f5fad27d02 Mon Sep 17 00:00:00 2001
From: Pavel Emelyanov <xemul@scylladb.com>
Date: Wed, 17 Apr 2024 15:50:45 +0300
Subject: [PATCH] table: Use directory_semaphore for rate-limited snapshot
 taking

The table::take_snapshot() limits its parallelizm with the help of
direcoty semaphore already, but implements it "by hand". There's already
parallel_for_each() method on the dir.sem. class that does exactly that.

Signed-off-by: Pavel Emelyanov <xemul@scylladb.com>
---
 replica/table.cc              | 4 +---
 sstables/sstable_directory.hh | 2 --
 2 files changed, 1 insertion(+), 5 deletions(-)

diff --git a/replica/table.cc b/replica/table.cc
index 8daae7b9c9..91346c74f0 100644
--- a/replica/table.cc
+++ b/replica/table.cc
@@ -2305,13 +2305,11 @@ future<table::snapshot_file_set> table::take_snapshot(database& db, sstring json
     auto table_names = std::make_unique<std::unordered_set<sstring>>();
 
     co_await io_check([&jsondir] { return recursive_touch_directory(jsondir); });
-    co_await max_concurrent_for_each(tables, db.get_sharded_sst_dir_semaphore().local()._concurrency, [&db, &jsondir, &table_names] (sstables::shared_sstable sstable) {
+    co_await db.get_sharded_sst_dir_semaphore().local().parallel_for_each(tables, [&jsondir, &table_names] (sstables::shared_sstable sstable) {
         table_names->insert(sstable->component_basename(sstables::component_type::Data));
-        return with_semaphore(db.get_sharded_sst_dir_semaphore().local()._sem, 1, [&jsondir, sstable] {
             return io_check([sstable, &dir = jsondir] {
                 return sstable->snapshot(dir);
             });
-        });
     });
     co_await io_check(sync_directory, jsondir);
     co_return make_foreign(std::move(table_names));
diff --git a/sstables/sstable_directory.hh b/sstables/sstable_directory.hh
index 8d62cc82ab..2b7490a33b 100644
--- a/sstables/sstable_directory.hh
+++ b/sstables/sstable_directory.hh
@@ -45,8 +45,6 @@ public:
     {
     }
 
-    friend class ::replica::table; // FIXME table snapshots should switch to sstable_directory
-
     template <std::ranges::range Container, typename Func>
     requires std::is_invocable_r_v<future<>, Func, typename std::ranges::range_value_t<Container>&>
     future<> parallel_for_each(Container& c, Func func) {