SERVER-62680 write cache retrievals into a tmp location before final destination.

(cherry picked from commit d20d317c08fd48b71f790c1bb013aa61c6f0f4b7)

2 files changed, 15 insertions, 4 deletions

diff --git a/buildscripts/scons_cache_prune.py b/buildscripts/scons_cache_prune.py
index 9b32db16b1f..4306cc56a96 100644
--- a/buildscripts/scons_cache_prune.py
+++ b/buildscripts/scons_cache_prune.py
@@ -100,6 +100,12 @@ def prune_cache(cache_path, cache_size_gb, clean_ratio):
                 return False
 
             cache_item = contents.pop()
+
+            # check the atime again just to make sure something wasn't accessed while
+            # we pruning other files.
+            if cache_item.time < os.stat(cache_item.path).st_atime:
+                continue
+
             to_remove = cache_item.path + ".del"
             try:
                 os.rename(cache_item.path, to_remove)
diff --git a/site_scons/site_tools/validate_cache_dir.py b/site_scons/site_tools/validate_cache_dir.py
index 2c78fb7deca..2fc62e31c2d 100644
--- a/site_scons/site_tools/validate_cache_dir.py
+++ b/site_scons/site_tools/validate_cache_dir.py
@@ -26,6 +26,7 @@ import logging
 import os
 import pathlib
 import shutil
+import tempfile
 import traceback
 
 
@@ -107,10 +108,14 @@ class CacheDirValidate(SCons.CacheDir.CacheDir):
             if not csig:
                 raise InvalidChecksum(cls.get_hash_path(src_file), dst, f"no content_hash data found")
 
-        try:
-            shutil.copy2(src_file, dst)
-        except OSError as ex:
-            raise CacheTransferFailed(src_file, dst, f"failed to copy from cache: {ex}") from ex
+        with tempfile.TemporaryDirectory() as tmpdirname:
+            dst_tmp = pathlib.Path(tmpdirname) / os.path.basename(dst)
+            try:
+                shutil.copy2(src_file, dst_tmp)
+            except OSError as ex:
+                raise CacheTransferFailed(src_file, dst, f"failed to copy from cache: {ex}") from ex
+            else:
+                shutil.move(dst_tmp, dst)
 
         new_csig = SCons.Util.MD5filesignature(dst,
             chunksize=SCons.Node.FS.File.md5_chunksize*1024)