From: Michael Tremer <michael.tremer@ipfire.org>
Date: Wed, 8 Mar 2023 11:05:40 +0000 (+0000)
Subject: repositories: Compose them seperately and atomically swap
X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=10aaca72cdb9a52cc66d0577c2f771f1245b82e4;p=pbs.git

repositories: Compose them seperately and atomically swap

We will now create the repositories in our temporary space, which will
allow us to be sure that we generated a consistent repository.

We will then swap the new directory with the former one atomically so
that the repository is accessible at all times.

Signed-off-by: Michael Tremer <michael.tremer@ipfire.org>
---

diff --git a/src/buildservice/repository.py b/src/buildservice/repository.py
index 58d44210..6ea60abe 100644
--- a/src/buildservice/repository.py
+++ b/src/buildservice/repository.py
@@ -6,6 +6,8 @@ import datetime
 import io
 import logging
 import os.path
+import shutil
+import tempfile
 
 import pakfire
 
@@ -614,17 +616,40 @@ class Repository(base.DataObject):
 	def _write(self):
 		log.info("Writing repository %s..." % self)
 
+		# Write any new repositories to the temporary space first
+		tmp = self.backend.path("tmp")
+
 		# Create a new pakfire instance
-		with self.pakfire() as p:
-			for arch in self.arches:
+		with tempfile.TemporaryDirectory(dir=tmp, prefix="pakfire-repo-") as t:
+			with self.pakfire() as p:
+				for arch in self.arches:
+					# Destination path for this architecture
+					path = os.path.join(t, arch)
+
+					# Fetch packages
+					packages = self.get_packages(arch)
+
+					# Make filelist (if they exist)
+					files = [p.path for p in packages if os.path.exists(p.path)]
+
+					# Write repository metadata
+					p.repo_compose(path=path, files=files)
+
+			# Mark the repository as read-only
+			os.chmod(t, 0o755)
+
+			# Perform an atomic replace of the repository directory
+			with tempfile.TemporaryDirectory(dir=tmp, prefix="pakfire-repo-") as bin:
 				# Local path
-				path = self.local_path(arch)
+				path = self.local_path()
 
-				# Fetch packages
-				packages = self.get_packages(arch)
+				# Move the old data to the temporary space
+				try:
+					shutil.move(path, bin)
 
-				# Make filelist (if they exist)
-				files = [p.path for p in packages if os.path.exists(p.path)]
+				# Ignore if this repository is being created for the first time
+				except FileNotFoundError:
+					pass
 
-				# Write repository metadata
-				p.repo_compose(path=path, files=files)
+				# Move the new repository data to its destination
+				shutil.move(t, path)