This can be useful if one of the ones that he has already begun downloading fails. See #287 for discussion. This fixes part of #287 which part was a regression caused by #928, namely this fixes fail-over in case a share is corrupted (or the server returns an error or disconnects). This does not fix the related issue mentioned in #287 if a server hangs and doesn't reply to requests for blocks.
This should put an end to the phenomenon I've been seeing that a single hung server can cause all downloads on a grid to hang. Also it should speed up all downloads by (a) not-waiting for responses to queries that it doesn't need, and (b) downloading shares from the servers which answered the initial query the fastest.
Also, do not count how many buckets you've gotten when deciding whether the download has enough shares or not -- instead count how many buckets to *unique* shares that you've gotten. This appears to improve a slightly weird behavior in the current download code in which receiving >= K different buckets all to the same sharenumber would make it think it had enough to download the file when in fact it hadn't.
This patch needs tests before it is actually ready for trunk.
allmydata.util.log.err() either takes a Failure as the first positional
argument, or takes no positional arguments and must be invoked in an
exception handler. Fixed its signature to match both foolscap.logging.log.err
and twisted.python.log.err . Included a brief unit test.
Stop checking separately for ConnectionDone/ConnectionLost, since those have
been folded into DeadReferenceError since foolscap-0.3.1 . Write
rrefutil.trap_deadref() in terms of rrefutil.trap_and_discard() to improve
code coverage.
Mutable servermap updates and the immutable checker, when run with
add_lease=True, send both the do-you-have-block and add-lease commands in
parallel, to avoid an extra round trip time. Many older servers have problems
with add-lease and raise various exceptions, which don't generally matter.
The client-side code was catching+ignoring some of them, but unrecognized
exceptions were passed through to the DYHB code, concealing the DYHB results
from the checker, making it think the server had no shares.
The fix is to separate the code paths. Both commands are sent at the same
time, but the errback path from add-lease is handled separately. Known
exceptions are ignored, the others (both unknown-remote and all-local) are
logged (log.WEIRD, which will trigger an Incident), but neither will affect
the DYHB results.
The add-lease message is sent first, and we know that the server handles them
synchronously. So when the checker is done, we can be sure that all the
add-lease messages have been retired. This makes life easier for unit tests.
* remove Downloader.download_to_data/download_to_filename/download_to_filehandle
* remove download.Data/FileName/FileHandle targets
* remove filenode.download/download_to_data/download_to_filename methods
* leave Downloader.download (the whole Downloader will go away eventually)
* add util.consumer.MemoryConsumer/download_to_data, for convenience
(this is mostly used by unit tests, but it gets used by enough non-test
code to warrant putting it in allmydata.util)
* update tests
* removes about 180 lines of code. Yay negative code days!
Overall plan is to rewrite immutable/download.py and leave filenode.read() as
the sole read-side API.
The proper hierarchy is:
IFilesystemNode
+IFileNode
++IMutableFileNode
++IImmutableFileNode
+IDirectoryNode
Also expand test_client.py (NodeMaker) to hit all IFilesystemNode types.
* stop caching most_recent_size in dirnode, rely upon backing filenode for it
* start caching most_recent_size in MutableFileNode
* return None when you don't know, not "?"
* only render None as "?" in the web "more info" page
* add get_size/get_current_size to UnknownNode
* "cap" means a python instance which encapsulates a filecap/dircap (uri.py)
* "uri" means a string with a "URI:" prefix
* FileNode instances are created with (and retain) a cap instance, and
generate uri strings on demand
* .get_cap/get_readcap/get_verifycap/get_repaircap return cap instances
* .get_uri/get_readonly_uri return uri strings
* add filenode.download_to_filename() for control.py, should find a better way
* use MutableFileNode.init_from_cap, not .init_from_uri
* directory URI instances: use get_filenode_cap, not get_filenode_uri
* update/cleanup bench_dirnode.py to match, add Makefile target to run it
This makes it more obvious that the Helper currently generates leases with
the Helper's own secrets, rather than getting values from the client, which
is arguably a bug that will likely be resolved with the Accounting project.
child of the client, access with client.downloader instead of
client.getServiceNamed("downloader"). The single "Downloader" instance is
scheduled for demolition anyways, to be replaced by individual
filenode.download calls.
* stop using IURI as an adapter
* pass cap strings around instead of URI instances
* move filenode/dirnode creation duties from Client to new NodeMaker class
* move other Client duties to KeyGenerator, SecretHolder, History classes
* stop passing Client reference to dirnode/filenode constructors
- pass less-powerful references instead, like StorageBroker or Uploader
* always create DirectoryNodes by wrapping a filenode (mutable for now)
* remove some specialized mock classes from unit tests
Detailed list of changes (done one at a time, then merged together)
always pass a string to create_node_from_uri(), not an IURI instance
always pass a string to IFilesystemNode constructors, not an IURI instance
stop using IURI() as an adapter, switch on cap prefix in create_node_from_uri()
client.py: move SecretHolder code out to a separate class
test_web.py: hush pyflakes
client.py: move NodeMaker functionality out into a separate object
LiteralFileNode: stop storing a Client reference
immutable Checker: remove Client reference, it only needs a SecretHolder
immutable Upload: remove Client reference, leave SecretHolder and StorageBroker
immutable Repairer: replace Client reference with StorageBroker and SecretHolder
immutable FileNode: remove Client reference
mutable.Publish: stop passing Client
mutable.ServermapUpdater: get StorageBroker in constructor, not by peeking into Client reference
MutableChecker: reference StorageBroker and History directly, not through Client
mutable.FileNode: removed unused indirection to checker classes
mutable.FileNode: remove Client reference
client.py: move RSA key generation into a separate class, so it can be passed to the nodemaker
move create_mutable_file() into NodeMaker
test_dirnode.py: stop using FakeClient mockups, use NoNetworkGrid instead. This simplifies the code, but takes longer to run (17s instead of 6s). This should come down later when other cleanups make it possible to use simpler (non-RSA) fake mutable files for dirnode tests.
test_mutable.py: clean up basedir names
client.py: move create_empty_dirnode() into NodeMaker
dirnode.py: get rid of DirectoryNode.create
remove DirectoryNode.init_from_uri, refactor NodeMaker for customization, simplify test_web's mock Client to match
stop passing Client to DirectoryNode, make DirectoryNode.create_with_mutablefile the normal DirectoryNode constructor, start removing client from NodeMaker
remove Client from NodeMaker
move helper status into History, pass History to web.Status instead of Client
test_mutable.py: fix minor typo
If you open up a directory containing thousands of files, it currently computes the cache filename and checks for the cache file on disk immediately for each immutble file in that directory. With this patch, it delays those steps until you try to do something with an immutable file that could use the cache.
and deny the Helper the ability to mount a partial-information-guessing
attack. This will probably break compatibility between new clients and very
old (pre-1.0) helpers.
instead of examining the value returned by f.trap, because the latter appears
to squash exception types down into their base classes (i.e. since
ShareVersionIncompatible is a subclass of LayoutInvalid,
f.trap(Failure(ShareVersionIncompatible)) == LayoutInvalid).
All this resulted in 'incompatible' shares being misclassified as 'corrupt'.
This is probably the cause of the very rare "loss of progress" bug. This is tested by unit tests. A recent patch changed this to errback instead of losing progress, and now this patch is changing it again to return a short read instead of errbacking. Returning a short read is what the uploader (in encode.py) is expecting, when it is reading the last block of the ciphertext, which might be shorter than the other blocks.
It is currently hardcoded in setup.py to be 'allmydata-tahoe'. Ticket #556 is to make it configurable by a runtime command-line argument to setup.py: "--appname=foo", but I suddenly wondered if we really wanted that and at the same time realized that we don't need that for tahoe-1.3.0 release, so this patch just hardcodes it in setup.py.
setup.py inspects a file named 'src/allmydata/_appname.py' and assert that it contains the string "__appname__ = 'allmydata-tahoe'", and creates it if it isn't already present. src/allmydata/__init__.py import _appname and reads __appname__ from it. The rest of the Python code imports allmydata and inspects "allmydata.__appname__", although actually every use it uses "allmydata.__full_version__" instead, where "allmydata.__full_version__" is created in src/allmydata/__init__.py to be:
__full_version__ = __appname + '-' + str(__version__).
All the code that emits an "application version string" when describing what version of a protocol it supports (introducer server, storage server, upload helper), or when describing itself in general (introducer client), usese allmydata.__full_version__.
This fixes ticket #556 at least well enough for tahoe-1.3.0 release.
(There is a bug in the current DownUpConnector which can cause it to give more bytes than you asked for on one request, and then less on the next, effectively shifting some of the bytes to an earlier request, but I think this bug never gets triggered in practice.)
This implements an immutable repairer by marrying a CiphertextDownloader to a CHKUploader. It extends the IDownloadTarget interface so that the downloader can provide some metadata that the uploader requires.
The processing is incremental -- it uploads the first segments before it finishes downloading the whole file. This is necessary so that you can repair large files without running out of RAM or using a temporary file on the repairer.
It requires only a verifycap, not a readcap. That is: it doesn't need or use the decryption key, only the integrity check codes.
There are several tests marked TODO and several instances of XXX in the source code. I intend to open tickets to document further improvements to functionality and testing, but the current version is probably good enough for Tahoe-1.3.0.
It used to be a map from shnum to a string saying "placed this share on XYZ server". The new definition is more in keeping with the "sharemap" object that results from immutable file checking and repair, and it is more useful to the repairer, which is a consumer of immutable upload results.
Rename "downloadable" to "target".
Rename "u" to "v" in FileDownloader.__init__().
Rename "_uri" to "_verifycap" in FileDownloader.
Rename "_downloadable" to "_target" in FileDownloader.
Rename "FileDownloader" to "CiphertextDownloader".
FileDownloader takes a verify cap and produces ciphertext, instead of taking a read cap and producing plaintext.
FileDownloader does all integrity checking including the mandatory ciphertext hash tree and the optional ciphertext flat hash, rather than expecting its target to do some of that checking.
Rename immutable.download.Output to immutable.download.DecryptingOutput. An instance of DecryptingOutput can be passed to FileDownloader to use as the latter's target. Text pushed to the DecryptingOutput is decrypted and then pushed to *its* target.
DecryptingOutput satisfies the IConsumer interface, and if its target also satisfies IConsumer, then it forwards and pause/unpause signals to its producer (which is the FileDownloader).
This patch also changes some logging code to use the new logging mixin class.
Check integrity of a segment and decrypt the segment one block-sized buffer at a time instead of copying the buffers together into one segment-sized buffer (reduces peak memory usage, I think, and is probably a tad faster/less CPU, depending on your encoding parameters).
Refactor FileDownloader so that processing of segments and of tail-segment share as much code is possible.
FileDownloader and FileNode take caps as instances of URI (Python objects), not as strings.
pyflakes pointed out to me that I had committed some code that is untested, since it uses an undefined name. This patch exercises that code -- the validation of the ciphertext hash tree -- by corrupting some of the share files in a very specific way, and also fixes the bug.
Once again I inserted a bug into the code, and once again it was hidden by something catching arbitrary exception/failure and assuming that it means the server failed to provide valid data.
We were not making sure that we really got all the crypttext hashes during download. If a server were to return less than the complete set of crypttext hashes, then our subsequent attempt to verify the correctness of the ciphertext would fail. (And it wouldn't be obvious without very careful debugging why it had failed.)
This patch makes it so that you keep trying to get ciphertext hashes until you have a full set or you run out of servers to ask.
This makes Uploader take an EncryptedUploadable object instead of an Uploadable object. I also changed it to return a verify cap instead of a tuple of the bits of data that one finds in a verify cap.
This will facilitate hooking together an Uploader and a Downloader to make a Repairer.
Also move offloaded.py into src/allmydata/immutable/.
New checker and verifier use the new download class. They are robust against various sorts of failures or corruption. They return detailed results explaining what they learned about your immutable files. Some grotesque sorts of corruption are not properly handled yet, and those ones are marked as TODO or commented-out in the unit tests.
There is also a repairer module in this patch with the beginnings of a repairer in it. That repairer is mostly just the interface to the outside world -- the core operation of actually reconstructing the missing data blocks and uploading them is not in there yet.
This patch also refactors the unit tests in test_immutable so that the handling of each kind of corruption is reported as passing or failing separately, can be separately TODO'ified, etc. The unit tests are also improved in various ways to require more of the code under test or to stop requiring unreasonable things of it. :-)
The code for validating the share hash tree and the block hash tree has been rewritten to make sure it handles all cases, to share metadata about the file (such as the share hash tree, block hash trees, and UEB) among different share downloads, and not to require hashes to be stored on the server unnecessarily, such as the roots of the block hash trees (not needed since they are also the leaves of the share hash tree), and the root of the share hash tree (not needed since it is also included in the UEB). It also passes the latest tests including handling corrupted shares well.
ValidatedReadBucketProxy takes a share_hash_tree argument to its constructor, which is a reference to a share hash tree shared by all ValidatedReadBucketProxies for that immutable file download.
ValidatedReadBucketProxy requires the block_size and share_size to be provided in its constructor, and it then uses those to compute the offsets and lengths of blocks when it needs them, instead of reading those values out of the share. The user of ValidatedReadBucketProxy therefore has to have first used a ValidatedExtendedURIProxy to compute those two values from the validated contents of the URI. This is pleasingly simplifies safety analysis: the client knows which span of bytes corresponds to a given block from the validated URI data, rather than from the unvalidated data stored on the storage server. It also simplifies unit testing of verifier/repairer, because now it doesn't care about the contents of the "share size" and "block size" fields in the share. It does not relieve the need for share data v2 layout, because we still need to store and retrieve the offsets of the fields which come after the share data, therefore we still need to use share data v2 with its 8-byte fields if we want to store share data larger than about 2^32.
Specify which subset of the block hashes and share hashes you need while downloading a particular share. In the future this will hopefully be used to fetch only a subset, for network efficiency, but currently all of them are fetched, regardless of which subset you specify.
ReadBucketProxy hides the question of whether it has "started" or not (sent a request to the server to get metadata) from its user.
Download is optimized to do as few roundtrips and as few requests as possible, hopefully speeding up download a bit.
To fix this error from the Windows buildslave:
[ERROR]: allmydata.test.test_immutable.Test.test_download_from_only_3_remaining_shares
Traceback (most recent call last):
File "C:\Documents and Settings\buildslave\windows-native-tahoe\windows\build\src\allmydata\immutable\download.py", line 135, in _bad
raise NotEnoughSharesError("ran out of peers, last error was %s" % (f,))
allmydata.interfaces.NotEnoughSharesError: ran out of peers, last error was [Failure instance: Traceback: <class 'struct.error'>: unpack requires a string argument of length 4
c:\documents and settings\buildslave\windows-native-tahoe\windows\build\support\lib\site-packages\foolscap-0.3.2-py2.5.egg\foolscap\call.py:667:_done
c:\documents and settings\buildslave\windows-native-tahoe\windows\build\support\lib\site-packages\foolscap-0.3.2-py2.5.egg\foolscap\call.py:53:complete
c:\Python25\lib\site-packages\twisted\internet\defer.py:239:callback
c:\Python25\lib\site-packages\twisted\internet\defer.py:304:_startRunCallbacks
--- <exception caught here> ---
c:\Python25\lib\site-packages\twisted\internet\defer.py:317:_runCallbacks
C:\Documents and Settings\buildslave\windows-native-tahoe\windows\build\src\allmydata\immutable\layout.py:374:_got_length
C:\Python25\lib\struct.py:87:unpack
]
===============================================================================
One of the instances of the name accidentally didn't get changed, and pyflakes noticed. The new downloader/checker/verifier/repairer unit tests would also have noticed, but those tests haven't been rolled into a patch and applied to this repo yet...
I get confused about whether a given argument or return value is a uri-as-string or uri-as-object. This patch adds a lot of assertions that it is one or the other, and also changes CheckerResults to take objects not strings.
In the future, I hope that we generally use Python objects except when importing into or exporting from the Python interpreter e.g. over the wire, the UI, or a stored file.
Refactor into a class the logic of asking each server in turn until one of them gives an answer
that validates. It is called ValidatedThingObtainer.
Refactor the downloading and verification of the URI Extension Block into a class named
ValidatedExtendedURIProxy.
The new logic of validating UEBs is minimalist: it doesn't require the UEB to contain any
unncessary information, but of course it still accepts such information for backwards
compatibility (so that this new download code is able to download files uploaded with old, and
for that matter with current, upload code).
The new logic of validating UEBs follows the practice of doing all validation up front. This
practice advises one to isolate the validation of incoming data into one place, so that all of
the rest of the code can assume only valid data.
If any redundant information is present in the UEB+URI, the new code cross-checks and asserts
that it is all fully consistent. This closes some issues where the uploader could have
uploaded inconsistent redundant data, which would probably have caused the old downloader to
simply reject that download after getting a Python exception, but perhaps could have caused
greater harm to the old downloader.
I removed the notion of selecting an erasure codec from codec.py based on the string that was
passed in the UEB. Currently "crs" is the only such string that works, so
"_assert(codec_name == 'crs')" is simpler and more explicit. This is also in keeping with the
"validate up front" strategy -- now if someone sets a different string than "crs" in their UEB,
the downloader will reject the download in the "validate this UEB" function instead of in a
separate "select the codec instance" function.
I removed the code to check plaintext hashes and plaintext Merkle Trees. Uploaders do not
produce this information any more (since it potentially exposes confidential information about
the file), and the unit tests for it were disabled. The downloader before this patch would
check that plaintext hash or plaintext merkle tree if they were present, but not complain if
they were absent. The new downloader in this patch complains if they are present and doesn't
check them. (We might in the future re-introduce such hashes over the plaintext, but encrypt
the hashes which are stored in the UEB to preserve confidentiality. This would be a double-
check on the correctness of our own source code -- the current Merkle Tree over the ciphertext
is already sufficient to guarantee the integrity of the download unless there is a bug in our
Merkle Tree or AES implementation.)
This patch increases the lines-of-code count by 8 (from 17,770 to 17,778), and reduces the
uncovered-by-tests lines-of-code count by 24 (from 1408 to 1384). Those numbers would be more
meaningful if we omitted src/allmydata/util/ from the test-coverage statistics.
* the two kinds of immutable filenode now have a common base class
* they store only an instance of their URI, not both an instance and a string
* they delegate comparison to that instance
to make the internal ones use binary strings (nodeid, storage index) and
the web/JSON ones use base32-encoded strings. The immutable verifier is
still incomplete (it returns imaginary healty results).
