From ec160939f7a8ea6ec9a912109555a987bb2dc318 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Fredrik=20Adel=C3=B6w?= <freben@gmail.com>
Date: Fri, 16 Feb 2024 11:07:31 +0100
Subject: [PATCH] add cmd limiter to the cli
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Signed-off-by: Fredrik Adelöw <freben@gmail.com>
---
 .changeset/nasty-suns-speak.md           |  5 +++
 packages/repo-tools/src/commands/util.ts | 54 +++++++++++++++---------
 2 files changed, 38 insertions(+), 21 deletions(-)
 create mode 100644 .changeset/nasty-suns-speak.md

diff --git a/.changeset/nasty-suns-speak.md b/.changeset/nasty-suns-speak.md
new file mode 100644
index 0000000000..2c5fff25a1
--- /dev/null
+++ b/.changeset/nasty-suns-speak.md
@@ -0,0 +1,5 @@
+---
+'@backstage/repo-tools': patch
+---
+
+Add an internal limiter on concurrency when launching processes
diff --git a/packages/repo-tools/src/commands/util.ts b/packages/repo-tools/src/commands/util.ts
index 933945bc5c..e28aae6267 100644
--- a/packages/repo-tools/src/commands/util.ts
+++ b/packages/repo-tools/src/commands/util.ts
@@ -13,29 +13,41 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
+
 import { execFile } from 'child_process';
+import os from 'os';
+import pLimit from 'p-limit';
+
+// Some commands launch full node processes doing heavy work, which at high
+// concurrency levels risk exhausting system resources. Placing the limiter here
+// at the root level ensures that the concurrency boundary applies globally, not
+// just per-runner.
+const limiter = pLimit(os.cpus().length);
 
 export function createBinRunner(cwd: string, path: string) {
   return async (...command: string[]) =>
-    new Promise<string>((resolve, reject) => {
-      execFile(
-        'node',
-        [path, ...command],
-        {
-          cwd,
-          shell: true,
-          timeout: 60000,
-          maxBuffer: 1024 * 1024,
-        },
-        (err, stdout, stderr) => {
-          if (err) {
-            reject(new Error(`${err.message}\n${stderr}`));
-          } else if (stderr) {
-            reject(new Error(`Command printed error output: ${stderr}`));
-          } else {
-            resolve(stdout);
-          }
-        },
-      );
-    });
+    limiter(
+      () =>
+        new Promise<string>((resolve, reject) => {
+          execFile(
+            'node',
+            [path, ...command],
+            {
+              cwd,
+              shell: true,
+              timeout: 60000,
+              maxBuffer: 1024 * 1024,
+            },
+            (err, stdout, stderr) => {
+              if (err) {
+                reject(new Error(`${err.message}\n${stderr}`));
+              } else if (stderr) {
+                reject(new Error(`Command printed error output: ${stderr}`));
+              } else {
+                resolve(stdout);
+              }
+            },
+          );
+        }),
+    );
 }