[
https://issues.apache.org/jira/browse/HDFS-11580?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16101998#comment-16101998
]
Chen Liang commented on HDFS-11580:
-----------------------------------
Thanks [~nandakumar131] for the comments!
As far as I remember how this JIRA has come along, the potential issue here was
that it was not clear whether the response will match the request. For example,
say, the async readfile is calling readfilesync directly, i.e.
{code}
Data readFileAsync(..) {
return readFileSync(...)
}
{code}
And we are calling readSmallFile twice, to read file1 and file2.
{code}
readFileAsync(file1)
readFileAsync(file2)
{code}
There is no guarantee which request arrives and returns first. So the
readFileSync(file2) can potentially return earlier, if so, can we be sure it's
returned gets delivered to second call definitely, instead of the first?
Essentially, the issue is, if there are two simultaneous calls of
{{supplyAsync}} with the same supplier, and the supplier returns one time,
which of the two {{supplyAsync}} will return?
This is related to {{CompletableFuture}}'s feature I haven't digged into or
tested. Totally possible that it be will handled well in some way. If you (or
anyone looking at this) have anything to add, please feel free to share. But as
I follow this JIRA, it was because of this, the implementation is that
{{sendCommandAsync}} is calling {{waitForResponse}}, which has an internal map
that matches the response to the request.
> Ozone: Support asynchronus client API for SCM and containers
> ------------------------------------------------------------
>
> Key: HDFS-11580
> URL: https://issues.apache.org/jira/browse/HDFS-11580
> Project: Hadoop HDFS
> Issue Type: Sub-task
> Components: ozone
> Affects Versions: HDFS-7240
> Reporter: Anu Engineer
> Assignee: Yiqun Lin
> Attachments: HDFS-11580-HDFS-7240.001.patch,
> HDFS-11580-HDFS-7240.002.patch, HDFS-11580-HDFS-7240.003.patch,
> HDFS-11580-HDFS-7240.004.patch, HDFS-11580-HDFS-7240.005.patch,
> HDFS-11580-HDFS-7240.006.patch, HDFS-11580-HDFS-7240.007.patch,
> HDFS-11580-HDFS-7240.008.patch, HDFS-11580-HDFS-7240.009.patch
>
>
> This is an umbrella JIRA that needs to support a set of APIs in Asynchronous
> form.
> For containers -- or the datanode API currently supports a call
> {{sendCommand}}. we need to build proper programming interface and support an
> async interface.
> There is also a set of SCM API that clients can call, it would be nice to
> support Async interface for those too.
--
This message was sent by Atlassian JIRA
(v6.4.14#64029)
---------------------------------------------------------------------
To unsubscribe, e-mail: hdfs-issues-unsubscr...@hadoop.apache.org
For additional commands, e-mail: hdfs-issues-h...@hadoop.apache.org
