rebuild-index: fix race condition by avoiding parallelism (#39594)

lib/spack/spack/binary_distribution.py

@@ -9,7 +9,6 @@
 import io
 import itertools
 import json
-import multiprocessing.pool
 import os
 import re
 import shutil
@@ -876,32 +875,18 @@ def _read_specs_and_push_index(file_list, read_method, cache_prefix, db, temp_di
         db: A spack database used for adding specs and then writing the index.
         temp_dir (str): Location to write index.json and hash for pushing
         concurrency (int): Number of parallel processes to use when fetching
-
-    Return:
-        None
     """
+    for file in file_list:
+        contents = read_method(file)
+        # Need full spec.json name or this gets confused with index.json.
+        if file.endswith(".json.sig"):
+            specfile_json = Spec.extract_json_from_clearsig(contents)
+            fetched_spec = Spec.from_dict(specfile_json)
+        elif file.endswith(".json"):
+            fetched_spec = Spec.from_json(contents)
+        else:
+            continue
 
-    def _fetch_spec_from_mirror(spec_url):
-        spec_file_contents = read_method(spec_url)
-
-        if spec_file_contents:
-            # Need full spec.json name or this gets confused with index.json.
-            if spec_url.endswith(".json.sig"):
-                specfile_json = Spec.extract_json_from_clearsig(spec_file_contents)
-                return Spec.from_dict(specfile_json)
-            if spec_url.endswith(".json"):
-                return Spec.from_json(spec_file_contents)
-
-    tp = multiprocessing.pool.ThreadPool(processes=concurrency)
-    try:
-        fetched_specs = tp.map(
-            llnl.util.lang.star(_fetch_spec_from_mirror), [(f,) for f in file_list]
-        )
-    finally:
-        tp.terminate()
-        tp.join()
-
-    for fetched_spec in fetched_specs:
         db.add(fetched_spec, None)
         db.mark(fetched_spec, "in_buildcache", True)