From d0c4d8f95d34cb140209090ee1bf239fe8a87b76 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Micha=C5=82=20Chojnowski?= <michal.chojnowski@scylladb.com>
Date: Fri, 29 May 2026 12:32:35 +0200
Subject: [PATCH] api: add system/shard_to_numa_node_mapping

Intended for test usage.
(Specifically there's a test which checks memory usage by compression
dictionaries, and that depends on the number of NUMA nodes, since dicts
get a copy for each NUMA node).
---
 api/api-doc/system.json | 18 ++++++++++++++++++
 api/system.cc           |  5 +++++
 2 files changed, 23 insertions(+)

diff --git a/api/api-doc/system.json b/api/api-doc/system.json
index 4bcbd10734..3582983b54 100644
--- a/api/api-doc/system.json
+++ b/api/api-doc/system.json
@@ -224,6 +224,24 @@
                "parameters":[]
             }
          ]
+      },
+      {
+         "path":"/system/shard_to_numa_node_mapping",
+         "operations":[
+            {
+               "method":"GET",
+               "summary":"Get the shard-to-NUMA-node mapping. The nth element is the NUMA node ID of the nth shard.",
+               "type":"array",
+               "items":{
+                  "type":"long"
+               },
+               "nickname":"get_shard_to_numa_node_mapping",
+               "produces":[
+                  "application/json"
+               ],
+               "parameters":[]
+            }
+         ]
       }
    ]
 }
diff --git a/api/system.cc b/api/system.cc
index d560a8a86d..e40b5869f2 100644
--- a/api/system.cc
+++ b/api/system.cc
@@ -197,6 +197,11 @@ void set_system(http_context& ctx, routes& r) {
             return make_ready_future<json::json_return_type>(seastar::to_sstring(format));
         });
     });
+
+    hs::get_shard_to_numa_node_mapping.set(r, [](const_req req) {
+        auto mapping = local_engine->smp().shard_to_numa_node_mapping();
+        return std::vector<unsigned>(mapping.begin(), mapping.end());
+    });
 }
 
 }