[PATCH v3 0/3] tests/functional/asset: improve partial-download handling

[PATCH v3 0/3] tests/functional/asset: improve partial-download handling

[Nicholas Piggin]

v2 discussion:

https://lore.kernel.org/qemu-devel/20250312122559.944533-1-npiggin@gmail.com/T/#m9e610343e190d6e65148eb6c9d2e8f4eb8b857b8

Changes since v2:
- Fixed junk in patch 3.
- Add R-B.

Test results for functional-system-debian and -fedora can be seen here:
https://gitlab.com/npiggin/qemu/-/jobs/9387494994
https://gitlab.com/npiggin/qemu/-/jobs/9387495000

Including the short download and retry exceeded failures and skipping
the subtests without failing the entire job.

Thanks,
Nick

Nicholas Piggin (3):
  tests/functional/asset: Fail assert fetch when retries are exceeded
  tests/functional/asset: Verify downloaded size
  tests/functional/asset: Add AssetError exception class

 tests/functional/qemu_test/asset.py | 58 ++++++++++++++++++++++-------
 1 file changed, 44 insertions(+), 14 deletions(-)

-- 
2.47.1

[PATCH v3 1/3] tests/functional/asset: Fail assert fetch when retries are exceeded

[Nicholas Piggin]

Currently the fetch code does not fail gracefully when retry limit is
exceeded, it just falls through the loop with no file, which ends up
hitting other errors.

Add a check for non-existing file, which indicates the retry limit was
exceeded.

Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
---
 tests/functional/qemu_test/asset.py | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/tests/functional/qemu_test/asset.py b/tests/functional/qemu_test/asset.py
index f0730695f09..27dd839e705 100644
--- a/tests/functional/qemu_test/asset.py
+++ b/tests/functional/qemu_test/asset.py
@@ -138,6 +138,9 @@ def fetch(self):
                 tmp_cache_file.unlink()
                 raise
 
+        if not os.path.exists(tmp_cache_file):
+            raise Exception("Retries exceeded downloading %s", self.url)
+
         try:
             # Set these just for informational purposes
             os.setxattr(str(tmp_cache_file), "user.qemu-asset-url",
-- 
2.47.1

[PATCH v3 2/3] tests/functional/asset: Verify downloaded size

[Nicholas Piggin]

If the server provides a Content-Length header, use that to verify the
size of the downloaded file. This catches cases where the connection
terminates early, and gives the opportunity to retry. Without this, the
checksum will likely mismatch and fail without retry.

Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
---
 tests/functional/qemu_test/asset.py | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/tests/functional/qemu_test/asset.py b/tests/functional/qemu_test/asset.py
index 27dd839e705..6bbfb9e1cad 100644
--- a/tests/functional/qemu_test/asset.py
+++ b/tests/functional/qemu_test/asset.py
@@ -121,6 +121,20 @@ def fetch(self):
                 with tmp_cache_file.open("xb") as dst:
                     with urllib.request.urlopen(self.url) as resp:
                         copyfileobj(resp, dst)
+                        length_hdr = resp.getheader("Content-Length")
+
+                # Verify downloaded file size against length metadata, if
+                # available.
+                if length_hdr is not None:
+                    length = int(length_hdr)
+                    fsize = tmp_cache_file.stat().st_size
+                    if fsize != length:
+                        self.log.error("Unable to download %s: "
+                                       "connection closed before "
+                                       "transfer complete (%d/%d)",
+                                       self.url, fsize, length)
+                        tmp_cache_file.unlink()
+                        continue
                 break
             except FileExistsError:
                 self.log.debug("%s already exists, "
-- 
2.47.1

[PATCH v3 3/3] tests/functional/asset: Add AssetError exception class

[Nicholas Piggin]

Assets are uniquely identified by human-readable-ish url, so make an
AssetError exception class that prints url with error message.

A property 'transient' is used to capture whether the client may retry
or try again later, or if it is a serious and likely permanent error.
This is used to retain the existing behaviour of treating HTTP errors
other than 404 as 'transient' and not causing precache step to fail.
Additionally, partial-downloads and stale asset caches that fail to
resolve after the retry limit are now treated as transient and do not
cause precache step to fail.

For background: The NetBSD archive is, at the time of writing, failing
with short transfer. Retrying the fetch at that position (as wget does)
results in a "503 backend unavailable" error. We would like to get that
error code directly, but I have not found a way to do that with urllib,
so treating the short-copy as a transient failure covers that case (and
seems like a reasonable way to handle it in general).

Reviewed-by: Thomas Huth <thuth@redhat.com>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
---
 tests/functional/qemu_test/asset.py | 43 +++++++++++++++++++----------
 1 file changed, 28 insertions(+), 15 deletions(-)

diff --git a/tests/functional/qemu_test/asset.py b/tests/functional/qemu_test/asset.py
index 6bbfb9e1cad..704b84d0ea6 100644
--- a/tests/functional/qemu_test/asset.py
+++ b/tests/functional/qemu_test/asset.py
@@ -17,6 +17,14 @@
 from shutil import copyfileobj
 from urllib.error import HTTPError
 
+class AssetError(Exception):
+    def __init__(self, asset, msg, transient=False):
+        self.url = asset.url
+        self.msg = msg
+        self.transient = transient
+
+    def __str__(self):
+        return "%s: %s" % (self.url, self.msg)
 
 # Instances of this class must be declared as class level variables
 # starting with a name "ASSET_". This enables the pre-caching logic
@@ -51,7 +59,7 @@ def _check(self, cache_file):
         elif len(self.hash) == 128:
             hl = hashlib.sha512()
         else:
-            raise Exception("unknown hash type")
+            raise AssetError(self, "unknown hash type")
 
         # Calculate the hash of the file:
         with open(cache_file, 'rb') as file:
@@ -111,7 +119,8 @@ def fetch(self):
             return str(self.cache_file)
 
         if not self.fetchable():
-            raise Exception("Asset cache is invalid and downloads disabled")
+            raise AssetError(self,
+                             "Asset cache is invalid and downloads disabled")
 
         self.log.info("Downloading %s to %s...", self.url, self.cache_file)
         tmp_cache_file = self.cache_file.with_suffix(".download")
@@ -147,13 +156,23 @@ def fetch(self):
                                tmp_cache_file)
                 tmp_cache_file.unlink()
                 continue
+            except HTTPError as e:
+                tmp_cache_file.unlink()
+                self.log.error("Unable to download %s: HTTP error %d",
+                               self.url, e.code)
+                # Treat 404 as fatal, since it is highly likely to
+                # indicate a broken test rather than a transient
+                # server or networking problem
+                if e.code == 404:
+                    raise AssetError(self, "Unable to download: "
+                                     "HTTP error %d" % e.code)
+                continue
             except Exception as e:
-                self.log.error("Unable to download %s: %s", self.url, e)
                 tmp_cache_file.unlink()
-                raise
+                raise AssetError(self, "Unable to download: " % e)
 
         if not os.path.exists(tmp_cache_file):
-            raise Exception("Retries exceeded downloading %s", self.url)
+            raise AssetError(self, "Download retries exceeded", transient=True)
 
         try:
             # Set these just for informational purposes
@@ -167,8 +186,7 @@ def fetch(self):
 
         if not self._check(tmp_cache_file):
             tmp_cache_file.unlink()
-            raise Exception("Hash of %s does not match %s" %
-                            (self.url, self.hash))
+            raise AssetError(self, "Hash does not match %s" % self.hash)
         tmp_cache_file.replace(self.cache_file)
         # Remove write perms to stop tests accidentally modifying them
         os.chmod(self.cache_file, stat.S_IRUSR | stat.S_IRGRP)
@@ -190,15 +208,10 @@ def precache_test(test):
                 log.info("Attempting to cache '%s'" % asset)
                 try:
                     asset.fetch()
-                except HTTPError as e:
-                    # Treat 404 as fatal, since it is highly likely to
-                    # indicate a broken test rather than a transient
-                    # server or networking problem
-                    if e.code == 404:
+                except AssetError as e:
+                    if not e.transient:
                         raise
-
-                    log.debug(f"HTTP error {e.code} from {asset.url} " +
-                              "skipping asset precache")
+                    log.error("%s: skipping asset precache" % e)
 
         log.removeHandler(handler)
 
-- 
2.47.1