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https://issues.apache.org/jira/browse/CASSANDRA-13304?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16599223#comment-16599223
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Sam Tunnicliffe commented on CASSANDRA-13304:
---------------------------------------------
thanks both. [~jrwest], I've pulled your patch into my branch and add a couple
more tests.
bq. Protocol comments
I agree that this could be useful, so I've implemented a first cut of it to
validate the protocol changes. The test for whether compression is applied or
not is super-brutal (i.e. it just does applies the compression and checks the
compressed size) but that could be refined later. I haven't updated either the
diagram in {{ChecksummingTransformer}}, or the protocol spec, but those can
come later (soon) if we commit this.
bq. In ChecksummingTransformer::transformOutbound L185 - consider adding a
debug log statement as this is an unexpected event.
I considered this, but decided in the end that it wouldn't really be
actionable, so a bit redundant. It would more useful to add a metric for the
number of times where we have to resize a buffer, but probably only in
conjunction with some targetted testing which we can't easily do with the
existing drivers. I'll open a follow up JIRA for that.
bq. In ChecksummingTransformerTest - Could you add a zero length round trip
test so we cover that corner case as well?
Added when pulling in Jordan's conversion of ChecksummingTransformerTest to a
property-based test.
bq. cassandra.yaml entry for compression/checksum block size is missing
Added, thanks.
bq. There was some conversation above about using ProtocolException instead of
IOException when the checksums don't match. It seemed like there was agreement
on using ProtocolException but the code still uses IOException.
Good catch, thanks.
bq. Would be nice to move ChecksummingTransformer#readUnsignedShort to
something like ByteBufUtil#readUnsignedShort. Similar to
ByteBufferUtil#readShortLength.
I've moved it to CBUtil, which is the defacto equivalent of {{ByteBufferUtil}}
bq. I thought that Optionals were not adding much value
bq. StartupMessage#getChecksumType/getCompressor(): I'm not sure there is much
benefit to using optional here given how its used at the call sites.
argh, both good catches. The use of {{Optional}} was much more widespread
earlier on & I thought I'd removed it all, but I missed this.
bq. The comment about why the frame.compress package defines an
ICompressor-Like interface was removed but is helpful since its not obvious at
first. It should probably be expanded on a bit as well.
https://github.com/apache/cassandra/blob/trunk/src/java/org/apache/cassandra/transport/FrameCompressor.java#L37
I've added some javadoc to {{o.a.c.transport.frame.compress.Compressor}}
bq. The created by comment at the top of ChecksummingCompressorTest should be
removed
Done
> Add checksumming to the native protocol
> ---------------------------------------
>
> Key: CASSANDRA-13304
> URL: https://issues.apache.org/jira/browse/CASSANDRA-13304
> Project: Cassandra
> Issue Type: Improvement
> Components: Core
> Reporter: Michael Kjellman
> Assignee: Sam Tunnicliffe
> Priority: Blocker
> Labels: client-impacting
> Fix For: 4.x
>
> Attachments: 13304_v1.diff, boxplot-read-throughput.png,
> boxplot-write-throughput.png
>
>
> The native binary transport implementation doesn't include checksums. This
> makes it highly susceptible to silently inserting corrupted data either due
> to hardware issues causing bit flips on the sender/client side, C*/receiver
> side, or network in between.
> Attaching an implementation that makes checksum'ing mandatory (assuming both
> client and server know about a protocol version that supports checksums) --
> and also adds checksumming to clients that request compression.
> The serialized format looks something like this:
> {noformat}
> * 1 1 1 1 1 1 1 1 1 1 2 2 2 2 2 2 2 2 2 2 3 3
> * 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
> * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
> * | Number of Compressed Chunks | Compressed Length (e1) /
> * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
> * / Compressed Length cont. (e1) | Uncompressed Length (e1) /
> * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
> * | Uncompressed Length cont. (e1)| CRC32 Checksum of Lengths (e1)|
> * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
> * | Checksum of Lengths cont. (e1)| Compressed Bytes (e1) +//
> * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
> * | CRC32 Checksum (e1) ||
> * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
> * | Compressed Length (e2) |
> * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
> * | Uncompressed Length (e2) |
> * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
> * | CRC32 Checksum of Lengths (e2) |
> * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
> * | Compressed Bytes (e2) +//
> * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
> * | CRC32 Checksum (e2) ||
> * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
> * | Compressed Length (en) |
> * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
> * | Uncompressed Length (en) |
> * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
> * | CRC32 Checksum of Lengths (en) |
> * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
> * | Compressed Bytes (en) +//
> * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
> * | CRC32 Checksum (en) ||
> * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
> {noformat}
> The first pass here adds checksums only to the actual contents of the frame
> body itself (and doesn't actually checksum lengths and headers). While it
> would be great to fully add checksuming across the entire protocol, the
> proposed implementation will ensure we at least catch corrupted data and
> likely protect ourselves pretty well anyways.
> I didn't go to the trouble of implementing a Snappy Checksum'ed Compressor
> implementation as it's been deprecated for a while -- is really slow and
> crappy compared to LZ4 -- and we should do everything in our power to make
> sure no one in the community is still using it. I left it in (for obvious
> backwards compatibility aspects) old for clients that don't know about the
> new protocol.
> The current protocol has a 256MB (max) frame body -- where the serialized
> contents are simply written in to the frame body.
> If the client sends a compression option in the startup, we will install a
> FrameCompressor inline. Unfortunately, we went with a decision to treat the
> frame body separately from the header bits etc in a given message. So,
> instead we put a compressor implementation in the options and then if it's
> not null, we push the serialized bytes for the frame body *only* thru the
> given FrameCompressor implementation. The existing implementations simply
> provide all the bytes for the frame body in one go to the compressor
> implementation and then serialize it with the length of the compressed bytes
> up front.
> Unfortunately, this won't work for checksum'ing for obvious reasons as we
> can't naively just checksum the entire (potentially) 256MB frame body and
> slap it at the end... so,
> The best place to start with the changes is in {{ChecksumedCompressor}}. I
> implemented one single place to perform the checksuming (and to support
> checksuming) the actual required chunking logic. Implementations of
> ChecksumedCompressor only implement the actual calls to the given compression
> algorithm for the provided bytes.
> Although the interface takes a {{Checksum}}, right now the attached patch
> uses CRC32 everywhere. As of right now, given JDK8+ has support for doing the
> calculation with the Intel instruction set, CRC32 is about as fast as we can
> get right now.
> I went with a 32kb "default" for the chunk size -- meaning we will chunk the
> entire frame body into 32kb chunks, compress each one of those chunks, and
> checksum the chunk. Upon discussing with a bunch of people and researching
> how checksums actually work and how much data they will protect etc -- if we
> use 32kb chunks with CRC32 we can catch up to 32 bits flipped in a row (but
> more importantly catch the more likely corruption where a single bit is
> flipped) with pretty high certainty. 64kb seems to introduce too much of a
> probability of missing corruption.
> The maximum block size LZ4 operates on is a 64kb chunk -- so this combined
> with the need to make sure the CRC32 checksums are actually going to catch
> stuff -- chunking at 32kb seemed like a good reasonable value to use when
> weighing both checksums and compression (to ensure we don't kill our
> compression ratio etc).
> I'm not including client changes here -- I asked around and I'm not really
> sure what the policy there is -- do we update the python driver? java driver?
> how has the timing of this stuff been handled in the past?
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