Reduce flakiness of the pyspark conf test. (#11456)

Author: trivialfis

python-package/xgboost/testing/collective.py

@@ -0,0 +1,15 @@
+"""Collective module related utilities."""
+
+import socket
+
+
+def get_avail_port() -> int:
+    """Returns a port that's available during the function call. It doesn't prevent the
+    port from being used after the function returns as we can't reserve the port. The
+    utility makes a test more likely to pass.
+
+    """
+    with socket.socket(socket.AF_INET, socket.SOCK_STREAM) as server:
+        server.bind(("127.0.0.1", 0))
+        port = server.getsockname()[1]
+    return port

tests/test_distributed/test_with_spark/test_spark_local.py

@@ -31,6 +31,7 @@
 )
 from xgboost.spark.core import _non_booster_params
 from xgboost.spark.data import pred_contribs
+from xgboost.testing.collective import get_avail_port
 
 from .utils import SparkTestCase
 
@@ -1772,16 +1773,17 @@ def test_collective_conf(self):
 
         with tempfile.TemporaryDirectory() as tmpdir:
             path = "file:" + tmpdir
+            port = get_avail_port()
             classifier = SparkXGBClassifier(
                 launch_tracker_on_driver=True,
-                coll_cfg=Config(tracker_host_ip="127.0.0.1", tracker_port=58894),
+                coll_cfg=Config(tracker_host_ip="127.0.0.1", tracker_port=port),
                 num_workers=1,
                 n_estimators=1,
             )
 
             def check_conf(conf: Config) -> None:
                 assert conf.tracker_host_ip == "127.0.0.1"
-                assert conf.tracker_port == 58894
+                assert conf.tracker_port == port
 
             check_conf(classifier.getOrDefault(classifier.coll_cfg))
             classifier.write().overwrite().save(path)