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https://issues.apache.org/jira/browse/CASSANDRA-15299?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17231545#comment-17231545
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Adam Holmberg edited comment on CASSANDRA-15299 at 11/13/20, 2:57 PM:
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{quote}This is the thing I'm unsure about - the python driver is not an asf
project (yet), so it's not really up to me/us whether we update that branch ...
TBH, I don't recall the full reasoning for using the cassandra-test branch in
the first place ...{quote}
The {{cassandra-test}} branch was created explicitly to allow server-side
testing of merged client-impacting features, independent of driver releases. It
was born of a time when there were multiple client-impacting changes in flight
so a single commit would not suffice. Normally we would coordinate a merge into
that driver branch with a PR for the server, so CI could be tested with it.
Updating the branch should not be an issue. I, or [~aboudreault] can facilitate.
was (Author: aholmber):
{quote}This is the thing I'm unsure about - the python driver is not an asf
project (yet), so it's not really up to me/us whether we update that branch ...
TBH, I don't recall the full reasoning for using the cassandra-test branch in
the first place ...{quote}
The {{cassandra-test}} branch was created explicitly to allow server-side
testing of merged client-impacting features, independent of driver releases. It
was born of a time when there were multiple client-impacting changes in-flight
so a single commit would not suffice. Normally we would coordinate a merge into
that driver branch with a PR for the server, so CI could be tested with it.
Updating the branch should not be an issue. I, or [~aboudreault] can facilitate.
> CASSANDRA-13304 follow-up: improve checksumming and compression in protocol
> v5-beta
> -----------------------------------------------------------------------------------
>
> Key: CASSANDRA-15299
> URL: https://issues.apache.org/jira/browse/CASSANDRA-15299
> Project: Cassandra
> Issue Type: Improvement
> Components: Messaging/Client
> Reporter: Aleksey Yeschenko
> Assignee: Sam Tunnicliffe
> Priority: Normal
> Labels: protocolv5
> Fix For: 4.0-alpha
>
> Attachments: Process CQL Frame.png, V5 Flow Chart.png
>
>
> CASSANDRA-13304 made an important improvement to our native protocol: it
> introduced checksumming/CRC32 to request and response bodies. It’s an
> important step forward, but it doesn’t cover the entire stream. In
> particular, the message header is not covered by a checksum or a crc, which
> poses a correctness issue if, for example, {{streamId}} gets corrupted.
> Additionally, we aren’t quite using CRC32 correctly, in two ways:
> 1. We are calculating the CRC32 of the *decompressed* value instead of
> computing the CRC32 on the bytes written on the wire - losing the properties
> of the CRC32. In some cases, due to this sequencing, attempting to decompress
> a corrupt stream can cause a segfault by LZ4.
> 2. When using CRC32, the CRC32 value is written in the incorrect byte order,
> also losing some of the protections.
> See https://users.ece.cmu.edu/~koopman/pubs/KoopmanCRCWebinar9May2012.pdf for
> explanation for the two points above.
> Separately, there are some long-standing issues with the protocol - since
> *way* before CASSANDRA-13304. Importantly, both checksumming and compression
> operate on individual message bodies rather than frames of multiple complete
> messages. In reality, this has several important additional downsides. To
> name a couple:
> # For compression, we are getting poor compression ratios for smaller
> messages - when operating on tiny sequences of bytes. In reality, for most
> small requests and responses we are discarding the compressed value as it’d
> be smaller than the uncompressed one - incurring both redundant allocations
> and compressions.
> # For checksumming and CRC32 we pay a high overhead price for small messages.
> 4 bytes extra is *a lot* for an empty write response, for example.
> To address the correctness issue of {{streamId}} not being covered by the
> checksum/CRC32 and the inefficiency in compression and checksumming/CRC32, we
> should switch to a framing protocol with multiple messages in a single frame.
> I suggest we reuse the framing protocol recently implemented for internode
> messaging in CASSANDRA-15066 to the extent that its logic can be borrowed,
> and that we do it before native protocol v5 graduates from beta. See
> https://github.com/apache/cassandra/blob/trunk/src/java/org/apache/cassandra/net/FrameDecoderCrc.java
> and
> https://github.com/apache/cassandra/blob/trunk/src/java/org/apache/cassandra/net/FrameDecoderLZ4.java.
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