From cb1d05d65a2a121d9b4cb0f1237b64d22f45df4e Mon Sep 17 00:00:00 2001
From: Pavel Emelyanov <xemul@scylladb.com>
Date: Wed, 28 Jan 2026 14:24:29 +0300
Subject: [PATCH] streaming: Get streaming sched group from debug:: namespace

In a lambda returned from make_streaming_consumer() there's a check for
current scheudling group being streaming one. It came from #17090 where
streaming code was launched in wrong sched group thus affecting user
groups in a bad way.

The check is nice and useful, but it abuses replica::database by getting
unrelated information from it.

To preserve the check and to stop using database as provider of configs,
keep the streaming scheduling group handle in the debug namespace. This
emphasises that this global variable is purely for debugging purposes.

Signed-off-by: Pavel Emelyanov <xemul@scylladb.com>

Closes scylladb/scylladb#28410
---
 debug.cc                 | 1 +
 debug.hh                 | 2 +-
 main.cc                  | 1 +
 streaming/consumer.cc    | 3 ++-
 test/lib/cql_test_env.cc | 1 +
 5 files changed, 6 insertions(+), 2 deletions(-)

diff --git a/debug.cc b/debug.cc
index ad1f5f29c2..dc1e5354a8 100644
--- a/debug.cc
+++ b/debug.cc
@@ -11,5 +11,6 @@
 namespace debug {
 
 seastar::sharded<replica::database>* volatile the_database = nullptr;
+seastar::scheduling_group streaming_scheduling_group;
 
 }
diff --git a/debug.hh b/debug.hh
index 39f9ff84eb..c608b40351 100644
--- a/debug.hh
+++ b/debug.hh
@@ -17,7 +17,7 @@ class database;
 namespace debug {
 
 extern seastar::sharded<replica::database>* volatile the_database;
-
+extern seastar::scheduling_group streaming_scheduling_group;
 
 }
 
diff --git a/main.cc b/main.cc
index 194006a041..b70878c498 100644
--- a/main.cc
+++ b/main.cc
@@ -906,6 +906,7 @@ To start the scylla server proper, simply invoke as: scylla server (or just scyl
 
             auto background_reclaim_scheduling_group = create_scheduling_group("background_reclaim", "bgre", 50).get();
             auto maintenance_scheduling_group = create_scheduling_group("streaming", "strm", 200).get();
+            debug::streaming_scheduling_group = maintenance_scheduling_group;
 
             smp::invoke_on_all([&cfg, background_reclaim_scheduling_group] {
                 logalloc::tracker::config st_cfg;
diff --git a/streaming/consumer.cc b/streaming/consumer.cc
index 2d012b34b1..8c6d40c997 100644
--- a/streaming/consumer.cc
+++ b/streaming/consumer.cc
@@ -18,6 +18,7 @@
 #include "db/view/view_update_checks.hh"
 #include "sstables/sstables.hh"
 #include "sstables/sstables_manager.hh"
+#include "debug.hh"
 
 namespace streaming {
 
@@ -33,7 +34,7 @@ mutation_reader_consumer make_streaming_consumer(sstring origin,
     return [&db, &vb = vb.container(), &vbw, estimated_partitions, reason, offstrategy, origin = std::move(origin), frozen_guard, on_sstable_written] (mutation_reader reader) -> future<> {
         std::exception_ptr ex;
         try {
-            if (current_scheduling_group() != db.local().get_streaming_scheduling_group()) {
+            if (current_scheduling_group() != debug::streaming_scheduling_group) {
                 on_internal_error(sstables::sstlog, format("The stream consumer is not running in streaming group current_scheduling_group={}",
                         current_scheduling_group().name()));
             }
diff --git a/test/lib/cql_test_env.cc b/test/lib/cql_test_env.cc
index 95e3fbe72c..1b03f783af 100644
--- a/test/lib/cql_test_env.cc
+++ b/test/lib/cql_test_env.cc
@@ -577,6 +577,7 @@ private:
             }
 
             auto scheduling_groups = get_scheduling_groups().get();
+            debug::streaming_scheduling_group = scheduling_groups.streaming_scheduling_group;
 
             auto notify_set = init_configurables
                 ? configurable::init_all(*cfg, init_configurables->extensions, service_set(