[
https://issues.apache.org/jira/browse/CASSANDRA-8984?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14503381#comment-14503381
]
Joshua McKenzie commented on CASSANDRA-8984:
--------------------------------------------
h6. Feedback:
There's enough usage of finish() and finishAndClose() floating around that it
comes off as an undocumented extension to the Transactional interface. Given
how clear the flow of usage is documented in the header on Transactional, it's
a bit surprising to see finish() and finishAndClose() calls with the frequency
they have - there might be some value in codifying those methods / documenting
their idiomatic usage.
BigTableWriter reaching into the guts of IndexWriter is error-prone as future
changes to resources in IndexWriter would need to be managed in the TxnProxy in
BigTableWriter. Perhaps we could change IndexWriter to implement Transactional
and keep the management of its resources more localized?
For instance, rather than seeing:
{noformat}
protected Throwable doCleanup(Throwable accumulate)
{
accumulate = iwriter.summary.close(accumulate);
accumulate = iwriter.bf.close(accumulate);
accumulate = iwriter.builder.close(accumulate);
accumulate = dbuilder.close(accumulate);
return accumulate;
}
{noformat}
I'd be much more comfortable seeing:
{noformat}
protected Throwable doCleanup(Throwable accumulate)
{
accumulate = iwriter.close(accumulate);
accumulate = dbuilder.close(accumulate);
return accumulate;
}
{noformat}
h6. Nits:
We may want to convert the touched /io tests to take advantage of and exercise
the various writers being Transactional
Formatting change in SSTableImport.java for JsonFactory factory decl/init is
unnecessary
Tests look good on both linux and windows.
> Introduce Transactional API for behaviours that can corrupt system state
> ------------------------------------------------------------------------
>
> Key: CASSANDRA-8984
> URL: https://issues.apache.org/jira/browse/CASSANDRA-8984
> Project: Cassandra
> Issue Type: Improvement
> Components: Core
> Reporter: Benedict
> Assignee: Benedict
> Fix For: 2.1.5
>
> Attachments: 8984_windows_timeout.txt
>
>
> As a penultimate (and probably final for 2.1, if we agree to introduce it
> there) round of changes to the internals managing sstable writing, I've
> introduced a new API called "Transactional" that I hope will make it much
> easier to write correct behaviour. As things stand we conflate a lot of
> behaviours into methods like "close" - the recent changes unpicked some of
> these, but didn't go far enough. My proposal here introduces an interface
> designed to support four actions (on top of their normal function):
> * prepareToCommit
> * commit
> * abort
> * cleanup
> In normal operation, once we have finished constructing a state change we
> call prepareToCommit; once all such state changes are prepared, we call
> commit. If at any point everything fails, abort is called. In _either_ case,
> cleanup is called at the very last.
> These transactional objects are all AutoCloseable, with the behaviour being
> to rollback any changes unless commit has completed successfully.
> The changes are actually less invasive than it might sound, since we did
> recently introduce abort in some places, as well as have commit like methods.
> This simply formalises the behaviour, and makes it consistent between all
> objects that interact in this way. Much of the code change is boilerplate,
> such as moving an object into a try-declaration, although the change is still
> non-trivial. What it _does_ do is eliminate a _lot_ of special casing that we
> have had since 2.1 was released. The data tracker API changes and compaction
> leftover cleanups should finish the job with making this much easier to
> reason about, but this change I think is worthwhile considering for 2.1,
> since we've just overhauled this entire area (and not released these
> changes), and this change is essentially just the finishing touches, so the
> risk is minimal and the potential gains reasonably significant.
--
This message was sent by Atlassian JIRA
(v6.3.4#6332)
