pipeline,api: write metadata directly

Instead of transmitting stage metadata over a socket and then
writing it via `Object.meta.write`, use the latter and bind
mount the corresponding file into the stage so it can directly
be written to from the stage. Change `api.metadata` to do so,
which means that this change is transparent for the stages.

osbuild/api.py

@@ -142,15 +142,8 @@ class API(BaseAPI):
 
     def __init__(self, *, socket_address=None):
         super().__init__(socket_address)
-        self.metadata = {}
         self.error = None
 
-    def _set_metadata(self, message, fds):
-        fd = message["metadata"]
-        with os.fdopen(fds.steal(fd), encoding="utf8") as f:
-            data = json.load(f)
-        self.metadata.update(data)
-
     def _get_exception(self, message):
         self.error = {
             "type": "exception",
@@ -158,9 +151,7 @@ class API(BaseAPI):
         }
 
     def _message(self, msg, fds, sock):
-        if msg["method"] == 'add-metadata':
-            self._set_metadata(msg, fds)
-        elif msg["method"] == 'exception':
+        if msg["method"] == 'exception':
             self._get_exception(msg)
 
 
@@ -200,18 +191,8 @@ def arguments(path="/run/osbuild/api/arguments"):
     return data
 
 
-def metadata(data: Dict, path="/run/osbuild/api/osbuild"):
+def metadata(data: Dict, path="/run/osbuild/meta"):
     """Update metadata for the current module"""
 
-    def data_to_file():
-        with tempfile.TemporaryFile() as f:
-            f.write(json.dumps(data).encode('utf8'))
-            # re-open the file to get a read-only file descriptor
-            return open(f"/proc/self/fd/{f.fileno()}", "r", encoding="utf8")
-
-    with jsoncomm.Socket.new_client(path) as client, data_to_file() as f:
-        msg = {
-            "method": "add-metadata",
-            "metadata": 0
-        }
-        client.send(msg, fds=[f.fileno()])
+    with open(path, "w", encoding="utf8") as f:
+        json.dump(data, f, indent=2)

osbuild/pipeline.py

@@ -185,6 +185,10 @@ class Stage:
                 "mounts": mounts,
             }
 
+            meta = cm.enter_context(
+                tree.meta.write(self.id)
+            )
+
             ro_binds = [
                 f"{self.info.path}:/run/osbuild/bin/{self.name}",
                 f"{inputs_tmpdir}:{inputs_mapped}",
@@ -193,6 +197,7 @@ class Stage:
 
             binds = [
                 os.fspath(tree) + ":/run/osbuild/tree",
+                meta.name + ":/run/osbuild/meta",
                 f"{mounts_tmpdir}:{mounts_mapped}"
             ]
 
@@ -235,9 +240,6 @@ class Stage:
                                readonly_binds=ro_binds,
                                extra_env=extra_env)
 
-            if r.returncode == 0:
-                tree.meta.set(self.id, api.metadata)
-
         return BuildResult(self, r.returncode, r.output, api.error)
 
 

test/mod/test_api.py

@@ -2,8 +2,10 @@
 # Test for API infrastructure
 #
 
+import json
 import multiprocessing as mp
 import os
+import pathlib
 import tempfile
 import unittest
 
@@ -99,19 +101,14 @@ class TestAPI(unittest.TestCase):
         # Check that `api.metadata` leads to `API.metadata` being
         # set correctly
         tmpdir = self.tmp.name
-        path = os.path.join(tmpdir, "osbuild-api")
+        path = pathlib.Path(tmpdir, "metadata")
+        path.touch()
 
-        def metadata(path):
-            data = {"meta": "42"}
-            osbuild.api.metadata(data, path=path)
-            return 0
+        data = {"meta": "42"}
+        osbuild.api.metadata(data, path=path)
+
+        with open(path, "r", encoding="utf8") as f:
+            metadata = json.load(f)
 
-        api = osbuild.api.API(socket_address=path)
-        with api:
-            p = mp.Process(target=metadata, args=(path, ))
-            p.start()
-            p.join()
-            self.assertEqual(p.exitcode, 0)
-        metadata = api.metadata  # pylint: disable=no-member
         assert metadata
-        self.assertEqual(metadata, {"meta": "42"})
+        self.assertEqual(metadata, data)