Add test for fixed storage broker issue (#9311)

Adds a test for the (now fixed) storage broker limit issue, see #9268
for the description and #9299 for the fix.

Also fix a race condition with endpoint creation/starts running in parallel,
leading to file not found errors.

control_plane/src/endpoint.rs

@@ -97,7 +97,21 @@ impl ComputeControlPlane {
         for endpoint_dir in std::fs::read_dir(env.endpoints_path())
             .with_context(|| format!("failed to list {}", env.endpoints_path().display()))?
         {
-            let ep = Endpoint::from_dir_entry(endpoint_dir?, &env)?;
+            let ep_res = Endpoint::from_dir_entry(endpoint_dir?, &env);
+            let ep = match ep_res {
+                Ok(ep) => ep,
+                Err(e) => match e.downcast::<std::io::Error>() {
+                    Ok(e) => {
+                        // A parallel task could delete an endpoint while we have just scanned the directory
+                        if e.kind() == std::io::ErrorKind::NotFound {
+                            continue;
+                        } else {
+                            Err(e)?
+                        }
+                    }
+                    Err(e) => Err(e)?,
+                },
+            };
             endpoints.insert(ep.endpoint_id.clone(), Arc::new(ep));
         }
 

test_runner/regress/test_tenants.py

@@ -2,6 +2,7 @@ from __future__ import annotations
 
 import concurrent.futures
 import os
+import threading
 import time
 from contextlib import closing
 from datetime import datetime
@@ -10,7 +11,7 @@ from pathlib import Path
 
 import pytest
 import requests
-from fixtures.common_types import Lsn, TenantId
+from fixtures.common_types import Lsn, TenantId, TimelineId
 from fixtures.log_helper import log
 from fixtures.metrics import (
     PAGESERVER_GLOBAL_METRICS,
@@ -476,3 +477,34 @@ def test_pageserver_metrics_many_relations(neon_env_builder: NeonEnvBuilder):
     assert counts
     log.info(f"directory counts: {counts}")
     assert counts[2] > COUNT_AT_LEAST_EXPECTED
+
+
+def test_timelines_parallel_endpoints(neon_simple_env: NeonEnv):
+    """
+    (Relaxed) regression test for issue that led to https://github.com/neondatabase/neon/pull/9268
+    Create many endpoints in parallel and then restart them
+    """
+    env = neon_simple_env
+
+    # This param needs to be 200+ to reproduce the limit issue
+    n_threads = 16
+    barrier = threading.Barrier(n_threads)
+
+    def test_timeline(branch_name: str, timeline_id: TimelineId):
+        endpoint = env.endpoints.create_start(branch_name)
+        endpoint.stop()
+        # Use a barrier to make sure we restart endpoints at the same time
+        barrier.wait()
+        endpoint.start()
+
+    workers = []
+
+    for i in range(0, n_threads):
+        branch_name = f"branch_{i}"
+        timeline_id = env.create_branch(branch_name)
+        w = threading.Thread(target=test_timeline, args=[branch_name, timeline_id])
+        workers.append(w)
+        w.start()
+
+    for w in workers:
+        w.join()