always generate push/fetch pairs - even for read only targets

Author: bcumming

stackinator/mirror.py

@@ -403,28 +403,26 @@ def config_files(self, config_root: pathlib.Path) -> Dict[pathlib.Path, bytes]:
             # mount point: spack binaries embed the install prefix, so each mount
             # point needs its own cache to avoid relocation issues.
             mount = self._mount_path if self.buildcache["mount_specific"] else None
+            # spack requires both fetch and push connections to be present in the
+            # mirror entry, even for a read-only (keyless) build cache. Whether
+            # packages are actually pushed to the cache is governed separately by
+            # push_to_build_cache (only a build cache with a signing key is pushed to).
             entry = {
                 "source": self.buildcache["source"],
                 "binary": self.buildcache["binary"],
                 "fetch": self._connection(self.buildcache, "fetch", mount),
+                "push": self._connection(self.buildcache, "push", mount),
             }
-            # a build cache is only pushed to when it has a signing key; a keyless
-            # build cache is read-only (fetched from, never pushed to).
-            if self.push_to_build_cache is not None:
-                entry["push"] = self._connection(self.buildcache, "push", mount)
             self._add_optional_flags(entry, self.buildcache)
             spack_mirrors["mirrors"][self.buildcache["name"]] = entry
 
-        # source mirrors are read-only by default (fetch only); a push connection is
-        # emitted only when one was explicitly configured.
         for name, mirror in self.source_mirrors.items():
             entry = {
                 "source": mirror["source"],
                 "binary": mirror["binary"],
                 "fetch": self._connection(mirror, "fetch"),
+                "push": self._connection(mirror, "push"),
             }
-            if mirror.get("push") is not None:
-                entry["push"] = self._connection(mirror, "push")
             self._add_optional_flags(entry, mirror)
             spack_mirrors["mirrors"][name] = entry
 

unittests/test_mirrors.py

@@ -142,12 +142,15 @@ def test_keyless_command_line_cache(tmp_path, clean_root, mount_path, systems_pa
     # no private key is written
     assert tmp_path / "key_store" / "buildcache.priv.gpg" not in files
 
-    # the mirror is emitted with a fetch url but no push url
+    # spack requires both fetch and push to be present even for a read-only cache,
+    # so push mirrors the fetch url; whether packages are pushed is gated separately
+    # by push_to_build_cache (None here, as there is no signing key).
     data = yaml.safe_load(files[tmp_path / "mirrors.yaml"])
     assert data["mirrors"]["buildcache"] == {
         "source": False,
         "binary": True,
         "fetch": {"url": "/tmp/foo/user-environment"},
+        "push": {"url": "/tmp/foo/user-environment"},
     }
 
 
@@ -170,12 +173,15 @@ def test_readonly_buildcache(tmp_path, clean_root, mount_path, systems_path):
     # no private key is written
     assert tmp_path / "key_store" / "buildcache.priv.gpg" not in files
 
-    # the mirror is emitted with a fetch url but no push url
+    # spack requires both fetch and push to be present even for a read-only cache,
+    # so push mirrors the fetch url; whether packages are pushed is gated separately
+    # by push_to_build_cache (None here, as there is no signing key).
     data = yaml.safe_load(files[tmp_path / "mirrors.yaml"])
     assert data["mirrors"]["buildcache"] == {
         "source": False,
         "binary": True,
         "fetch": {"url": "https://mirror.spack.io"},
+        "push": {"url": "https://mirror.spack.io"},
     }