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Merge pull request #2404 from coreos-inc/cas-gc-fix

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Fix GC handling around CAS paths
This commit is contained in:
josephschorr 2017-03-10 17:34:21 -05:00 committed by GitHub
commit cbac673d58
3 changed files with 149 additions and 8 deletions
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11
data/database.py
View file

@ -7,6 +7,7 @@ import sys
import time
import uuid
from contextlib import contextmanager
from collections import defaultdict
from datetime import datetime
from random import SystemRandom
@ -230,6 +231,7 @@ db_match_func = CallableProxy()
db_for_update = CallableProxy()
db_transaction = CallableProxy()
db_concat_func = CallableProxy()
ensure_under_transaction = CallableProxy()
def validate_database_url(url, db_kwargs, connect_timeout=5):
@ -286,7 +288,16 @@ def configure(config_object):
def _db_transaction():
return config_object['DB_TRANSACTION_FACTORY'](db)
@contextmanager
def _ensure_under_transaction():
if not config_object['TESTING']:
if db.transaction_depth() == 0:
raise Exception('Expected to be under a transaction')
yield
db_transaction.initialize(_db_transaction)
ensure_under_transaction.initialize(_ensure_under_transaction)
def random_string_generator(length=16):
def random_string():

48
data/model/storage.py
View file

@ -8,7 +8,8 @@ from data.model import (config, db_transaction, InvalidImageException, TorrentIn
DataModelException, _basequery)
from data.database import (ImageStorage, Image, ImageStoragePlacement, ImageStorageLocation,
ImageStorageTransformation, ImageStorageSignature,
ImageStorageSignatureKind, Repository, Namespace, TorrentInfo)
ImageStorageSignatureKind, Repository, Namespace, TorrentInfo,
ensure_under_transaction)
logger = logging.getLogger(__name__)
@ -79,10 +80,38 @@ def garbage_collect_storage(storage_id_whitelist):
if len(storage_id_whitelist) == 0:
return []
def placements_query_to_paths_set(placements_query):
return {(get_image_location_for_id(placement.location_id).name,
get_layer_path(placement.storage))
for placement in placements_query}
def placements_to_filtered_paths_set(placements_list):
""" Returns the list of paths to remove from storage, filtered from the given placements
query by removing any CAS paths that are still referenced by storage(s) in the database.
"""
with ensure_under_transaction():
if not placements_list:
return set()
# Find the content checksums not referenced by other storages. Any that are, we cannot
# remove.
content_checksums = set([placement.storage.content_checksum for placement in placements_list
if placement.storage.cas_path])
unreferenced_checksums = set()
if content_checksums:
query = (ImageStorage
.select(ImageStorage.content_checksum)
.where(ImageStorage.content_checksum << list(content_checksums)))
referenced_checksums = set([image_storage.content_checksum for image_storage in query])
if referenced_checksums:
logger.warning('GC attempted to remove CAS checksums %s, which are still referenced',
referenced_checksums)
unreferenced_checksums = content_checksums - referenced_checksums
# Return all placements for all image storages found not at a CAS path or with a content
# checksum that is referenced.
return {(get_image_location_for_id(placement.location_id).name,
get_layer_path(placement.storage))
for placement in placements_list
if not placement.storage.cas_path or
placement.storage.content_checksum in unreferenced_checksums}
# Note: Both of these deletes must occur in the same transaction (unfortunately) because a
# storage without any placement is invalid, and a placement cannot exist without a storage.
@ -96,12 +125,10 @@ def garbage_collect_storage(storage_id_whitelist):
return []
placements_to_remove = list(ImageStoragePlacement
.select()
.select(ImageStoragePlacement, ImageStorage)
.join(ImageStorage)
.where(ImageStorage.id << orphaned_storage_ids))
paths_to_remove = placements_query_to_paths_set(placements_to_remove)
# Remove the placements for orphaned storages
if len(placements_to_remove) > 0:
placement_ids_to_remove = [placement.id for placement in placements_to_remove]
@ -130,6 +157,11 @@ def garbage_collect_storage(storage_id_whitelist):
.execute())
logger.debug('Removed %s image storage records', storages_removed)
# Determine the paths to remove. We cannot simply remove all paths matching storages, as CAS
# can share the same path. We further filter these paths by checking for any storages still in
# the database with the same content checksum.
paths_to_remove = placements_to_filtered_paths_set(placements_to_remove)
# We are going to make the conscious decision to not delete image storage blobs inside
# transactions.
# This may end up producing garbage in s3, trading off for higher availability in the database.

98
test/test_gc.py
View file

@ -1,5 +1,6 @@
import unittest
import time
import hashlib
from contextlib import contextmanager
from playhouse.test_utils import assert_query_count
@ -183,6 +184,12 @@ class TestGarbageCollection(unittest.TestCase):
self.assertEquals(expect_storage_removed, bool(removed_image_storages))
# Ensure all CAS storage is in the storage engine.
preferred = storage.preferred_locations[0]
for storage_row in ImageStorage.select():
if storage_row.cas_path:
storage.get_content({preferred}, storage.blob_path(storage_row.content_checksum))
def test_has_garbage(self):
""" Remove all existing repositories, then add one without garbage, check, then add one with
garbage, and check again.
@ -405,6 +412,97 @@ class TestGarbageCollection(unittest.TestCase):
self.assertDeleted(repository, 'i1')
self.assertNotDeleted(repository, 'i2')
def test_image_with_cas(self):
""" A repository with a tag pointing to an image backed by CAS. Deleting and GCing the tag
should result in the storage and its CAS data being removed.
"""
with self.assert_gc_integrity(expect_storage_removed=True):
repository = self.createRepository()
# Create an image storage record under CAS.
content = 'hello world'
digest = 'sha256:' + hashlib.sha256(content).hexdigest()
preferred = storage.preferred_locations[0]
storage.put_content({preferred}, storage.blob_path(digest), content)
image_storage = database.ImageStorage.create(content_checksum=digest, uploading=False)
location = database.ImageStorageLocation.get(name=preferred)
database.ImageStoragePlacement.create(location=location, storage=image_storage)
# Ensure the CAS path exists.
self.assertTrue(storage.exists({preferred}, storage.blob_path(digest)))
# Create the image and the tag.
first_image = Image.create(docker_image_id='i1',
repository=repository, storage=image_storage,
ancestors='/')
model.tag.store_tag_manifest(repository.namespace_user.username, repository.name,
'first', first_image.docker_image_id,
'sha:someshahere1', '{}')
self.assertNotDeleted(repository, 'i1')
# Delete the tag.
self.deleteTag(repository, 'first')
self.assertDeleted(repository, 'i1')
# Ensure the CAS path is gone.
self.assertFalse(storage.exists({preferred}, storage.blob_path(digest)))
def test_images_shared_cas(self):
""" A repository, each two tags, pointing to the same image, which has image storage
with the same *CAS path*, but *distinct records*. Deleting the first tag should delete the
first image, and its storage, but not the file in storage, as it shares its CAS path.
"""
with self.assert_gc_integrity(expect_storage_removed=True):
repository = self.createRepository()
# Create two image storage records with the same content checksum.
content = 'hello world'
digest = 'sha256:' + hashlib.sha256(content).hexdigest()
preferred = storage.preferred_locations[0]
storage.put_content({preferred}, storage.blob_path(digest), content)
is1 = database.ImageStorage.create(content_checksum=digest, uploading=False)
is2 = database.ImageStorage.create(content_checksum=digest, uploading=False)
location = database.ImageStorageLocation.get(name=preferred)
database.ImageStoragePlacement.create(location=location, storage=is1)
database.ImageStoragePlacement.create(location=location, storage=is2)
# Ensure the CAS path exists.
self.assertTrue(storage.exists({preferred}, storage.blob_path(digest)))
# Create two images in the repository, and two tags, each pointing to one of the storages.
first_image = Image.create(docker_image_id='i1',
repository=repository, storage=is1,
ancestors='/')
second_image = Image.create(docker_image_id='i2',
repository=repository, storage=is2,
ancestors='/')
model.tag.store_tag_manifest(repository.namespace_user.username, repository.name,
'first', first_image.docker_image_id,
'sha:someshahere1', '{}')
model.tag.store_tag_manifest(repository.namespace_user.username, repository.name,
'second', second_image.docker_image_id,
'sha:someshahere2', '{}')
self.assertNotDeleted(repository, 'i1', 'i2')
# Delete the first tag.
self.deleteTag(repository, 'first')
self.assertDeleted(repository, 'i1')
self.assertNotDeleted(repository, 'i2')
# Ensure the CAS path still exists.
self.assertTrue(storage.exists({preferred}, storage.blob_path(digest)))
if __name__ == '__main__':
unittest.main()