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https://issues.apache.org/jira/browse/CASSANDRA-15350?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16986310#comment-16986310
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Yifan Cai commented on CASSANDRA-15350:
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[~ifesdjeen] and [~spod], big thanks for reviewing the patch!
Renaming the exception to {{CasWriteStalledException}} and the suggested
rephrased description for {{CAS_UNCERTAINTY}} sounds good.
The meaning of {{CasWriteUncertainty}} is vague, and as being pointed out, the
WTE indicates that the result is uncertain too. {{CasWriteStalled}} describes
what happened better.
I meant to put _Paxos read_ when writing the description for the
{{CAS_UNVERTAINTY}} clause. I will update the description with the suggested
one considered.
Regarding the cross-version scenarios, I may be wrong, but my current
understanding is that the ErrorMessage is *not* involved in internode
messageing. ErrorMessage, derived from
{{org.apache.cassandra.transport.Message.Response}}, is client-facing. When a
sub-V5 (i.e. V4) client connects to the V5 server and gets the
{{CasWriteTimeoutException}}, the server encoding makes sure to produce a
backward compatible one, so the sub-V5 client is still good to understand the
server response.
The {{decode}} method in {{ErrorMessage}} seems to be only useful for
{{org.apache.cassandra.transport.SimpleClient/Client}}, which is not started in
cassandra server.
{quote}Unless you're submitting patches to 2.2, 3.0, and 3.11, let's roll back
changes to IMessageFilters, since their API has to be binary compatible with
older versions.
{quote}
The test cases in {{CasWriteTest}} relies on the message intercept function. I
will back-port the changes to IMessageFilter to the prior versions.
{quote}Should we add timeout tests for responses as well as requests in
CasWriteTest?
{quote}
Sure. Sound good.
{quote}Is it possible to try and simplify testCasWriteTimeoutDueToContention,
can we achieve contention with N threads?
{quote}
The test does achieve contention with N threads (1 thread per client). In
addition, the scenario was carefully crafted to be deterministic and aims to
produce the same kind of contention.
{quote}both tests peer quite a lot into implementation internals.
{quote}
The test cases mainly manipulate the internode networking to introduce
latency/partition. In order to produce (and always produce) a rare contention
scenario, I think those fine-grained control is necessary.
{quote}In ErrorMessage#decode, there are extra brackets around WRITE_TIMEOUT
clause. You can remove those and fix indentation. Same happens in
CAS_UNCERTAINTY case.
{quote}
Removing the brackets in the {{switch-case}} statements gives syntax error
since we are defining the variables with the same name. The brackets help to
scope the variables.
{quote}If we add comments for activate and deactivate for off/on, maybe it's
worth to call those off/on?
{quote}
Do you mean rename the method to activate/deactivate, or change the comments to
on/off? Both sound good to me.
> Add CAS “uncertainty” and “contention" messages that are currently propagated
> as a WriteTimeoutException.
> ---------------------------------------------------------------------------------------------------------
>
> Key: CASSANDRA-15350
> URL: https://issues.apache.org/jira/browse/CASSANDRA-15350
> Project: Cassandra
> Issue Type: Improvement
> Components: Feature/Lightweight Transactions
> Reporter: Alex Petrov
> Assignee: Yifan Cai
> Priority: Normal
> Labels: protocolv5, pull-request-available
> Attachments: Utf8StringEncodeBench.java
>
> Time Spent: 20m
> Remaining Estimate: 0h
>
> Right now, CAS uncertainty introduced in
> https://issues.apache.org/jira/browse/CASSANDRA-6013 is propagating as
> WriteTimeout. One of this conditions it manifests is when there’s at least
> one acceptor that has accepted the value, which means that this value _may_
> still get accepted during the later round, despite the proposer failure.
> Similar problem happens with CAS contention, which is also indistinguishable
> from the “regular” timeout, even though it is visible in metrics correctly.
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