With few packs a request per pack is fewer requests than 256 listings. On
FTP every listing takes a data connection; the FTP server of the integration
tests has ten passive ports, and 256 listings in a row slowed it down until a
read failed ("Not found: snapshots/...").
A Hetzner Storage Box drops an SFTP connection that carried a lot of data
and then stayed quiet for a few minutes; files_external keeps using the dead
client, on which every file looks missing. StorageBackend now checks the
connection after a minute without requests, and replaces a connection that
is dead after a failed request (once per request; put, move and delete are
not repeated). SftpReadStream closes a connection it left in an unknown state.
The verify cache refresh took more than 6 minutes on PostgreSQL for 27,547
packs, one autocommitted insert per pack: putMany()/replaceAll() write in one
transaction. After a verify the cache holds the index files as they are, so a
blob in two packs stays cached for both.
files_external's SFTP read stream asks for the next 256 KiB only after
the previous answer has arrived, so reading costs one round trip per
request whatever the line speed: 4.9 MB/s at 47 ms to a Hetzner Storage
Box. SftpReadStream keeps up to eight READ requests in flight over the
same phpseclib connection (15 MB/s on that link), starting with one so
a small read does not fetch megabytes ahead.
A server that answers less than asked is handled by asking again from
where the answer ended; when more data follows, that size is used for
later reads over the same connection, never below the 32 KiB every
server must support. Without the needed connection methods, or when the
open fails, the storage's own stream is used as before.
Review notes on the open pack stream: it stayed open while a backup run went on to upload
(e.g. the snapshot after reading the file list back), which SFTP cannot do on one connection.
Reading moves to PackReader, and Repository reaches the location through PackReaderGuard,
which closes the stream before every other request. A pack stream that cannot seek is read up
to the offset. Deep verify no longer reports an \Error during decoding as damage.
Restores and deep verifies requested every blob separately: a new file handle and a seek on
the location each time. They read the blobs of a snapshot in the order they were written, so
the stream of the pack read last now stays open and is read on; a jump backwards, to another
pack, or more than 8 MiB ahead opens the pack again at the offset, as before. On a Hetzner
Storage Box over SMB, restoring 86 MB in 202 files went from 0.78 MB/s to 4.2 MB/s.
holdIndexCache() ran before beginTransaction(), outside the try, and the release came after
rollBack(); an exception from either left later cache writes queued for the rest of the run.
Opening a repository lists index/, which holds one file per pack.
StorageBackend::list() checked every entry with is_dir(), and on a
remote storage each check is a round trip. Over SFTP to a Hetzner Storage
Box (33 ms) with a 60 GiB repository, occ backup:run (30 s steps) spent
nearly every step on these requests and uploaded 45 KiB/s; with this
change it uploads 5.8 MB/s. The cost grows with the number of packs.
index/, snapshots/, catalog/ and trash/info/ only ever hold objects:
list them with the new IBackend::listFiles(), one listing without
per-entry checks.
A run only showed "running (files)", which says nothing during a backup
of a terabyte. The files phase now records an expected size on its first
step: the previous snapshot's size, or for a first backup the users'
files, versions and trash from Nextcloud's file cache (approximate, shown
with a ~). The web interface and occ backup:status show the share of it
done so far, including a large file that is still being read; it stays
below 100% until the run finishes.
A database dump that fills a whole pack (32 MiB) uploads that pack while
the dump transaction is still open, and the pack's index cache row was
inserted on the same connection. PostgreSQL refuses that (25006, read-only
transaction) and the run failed; on other databases the row was rolled
back with the dump transaction. The index now holds those cache writes
back until the transaction is over.
A changed password or host name could only be handled by adding a new
location, which starts an empty repository and, with a retention lock at
the provider, keeps the old one billed. Edit now changes a location in
place (web interface and occ backup:target:edit). The settings are only
saved when they lead to the same repository; a failed connection and a
missing repository give separate errors, and the folder is not created
while checking. Stored passwords are never sent to the browser: an empty
password field keeps the stored value.
Catch \Exception (storage adapters throw their own exception types) instead
of \Throwable, so an \Error such as a TypeError is not retried and reported
as an unreadable blob.
An unreadable blob may still be a truncated pack, so don't rule out damage
in the verify message; README: Hetzner needs WebDAV/SMB and external
reachability enabled for the sub-account.
Tested both on sub-accounts: works end to end; WebDAV needs an existing
root, SMB needs port 445 and the smbclient extension; fixed cost per run
and slow deep verify over remote storage.
verifyBlob() caught every exception from loading a blob and counted it as
a failed (corrupted or tampered) blob, so a transient network error during
a deep verify over WebDAV looked like data corruption. Read the range
separately, retry it, and report a read that keeps failing as unreadable
with its error; only a blob that was read but does not decrypt or match
its id counts as failed.
addTarget requires a recent password confirmation, but the form never
asked for one. Within 30 minutes of logging in that went unnoticed; after
that, adding a location failed with a bare 403.
Add three screenshots (backups, restore, settings) taken on a demo
instance, plus website, repository and the HOWTO as admin documentation
in info.xml.
Fixes found while taking them:
- the "new folder" restore option lost "<date>" (l10n sanitizes it as
a tag); show the folder name pattern via a placeholder instead
- the restore-point dropdown cut off the time
- passphrase actions stacked vertically in the slot table
- HOWTO: SFTP example used "sftp::password", the auth mechanism is
"password::password"
dillard
Dillard Blom