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https://issues.apache.org/jira/browse/CASSANDRA-15066?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16801284#comment-16801284
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Benedict commented on CASSANDRA-15066:
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h2. Handshake
During audit of the code it became apparent that our legacy handshake protocol
had a number of issues:
* Requires three messages, and multiple connection attempts in mixed version
clusters
* Differed unnecessarily between streaming and messaging
* Messages could be corrupted, leading to unknown connection state
We have attempted to address these issues with a new handshake protocol for
post40 nodes, that sends only two messages: Initiate and Accept
* Initiate, contains
** Compression, CRC and Streaming flags
** Messaging versions the initiating node will accept
** The broadcast address of the initiating node
* Accept, contains
** The messaging version to use, if any overlap is possible (or the nearest
acceptable version otherwise)
** The receiving node’s current messaging version
Both messages contain a CRC trailer for verifying their contents. Streaming
and Messaging both use the same protocol, just with different messaging
versions in the Initiate message (for streaming, only {{current_version}} is
accepted). This change makes it very easy to support mixed-version streaming
from old to new nodes.
Note: this patch has removed streaming versioning, since it was not seemingly
useful.
> Improvements to Internode Messaging
> -----------------------------------
>
> Key: CASSANDRA-15066
> URL: https://issues.apache.org/jira/browse/CASSANDRA-15066
> Project: Cassandra
> Issue Type: Improvement
> Components: Messaging/Internode
> Reporter: Benedict
> Assignee: Benedict
> Priority: Normal
> Fix For: 4.0
>
>
> CASSANDRA-8457 introduced asynchronous networking to internode messaging, but
> there have been several follow-up endeavours to improve some semantic issues.
> CASSANDRA-14503 and CASSANDRA-13630 are the latest such efforts, and were
> combined some months ago into a single overarching refactor of the original
> work, to address some of the issues that have been discovered. Given the
> criticality of this work to the project, we wanted to bring some more eyes to
> bear to ensure the release goes ahead smoothly. In doing so, we uncovered a
> number of issues with messaging, some of which long standing, that we felt
> needed to be addressed. This patch widens the scope of CASSANDRA-14503 and
> CASSANDRA-13630 in an effort to close the book on the messaging service, at
> least for the foreseeable future.
> The patch includes a number of clarifying refactors that touch outside of the
> {{net.async}} package, and a number of semantic changes to the {{net.async}}
> packages itself. We believe it clarifies the intent and behaviour of the
> code while improving system stability, which we will outline in comments
> below.
> https://github.com/belliottsmith/cassandra/tree/messaging-improvements
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