Aleksey Yeschenko created CASSANDRA-15299:
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Summary: 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: Aleksey Yeschenko
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 parcicular, 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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