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https://issues.apache.org/jira/browse/HADOOP-6668?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12864128#action_12864128
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Tom White commented on HADOOP-6668:
-----------------------------------
{quote}
>Limited private for use by which components or subprojects?
Limited private to MR and HDFS.
>> How would I write my own metrics context?
Who is "I"? If MR or HDFS developer then he is part of the target audience.
If "I" is an application developer then he runs a risk using a limited-private
API - it may change in incompatible ways of the MR and HDFS projects are okay
with it.
{quote}
Sorry, "I" refers to an application developer writing a new metrics context.
There is a service provider interface in org.apache.hadoop.metrics.spi, which
clearly needs to be available to such a developer. My question was really about
what is the appropriate component for LimitedPrivate, since an application
developer may not host it in MR or HDFS. The option you outline is probably the
best - mark the SPI classes as LimitedPrivate (MR and HDFS), and then the
developer would use the developer javadoc. The only thing that isn't quite
right is that the application developer is using an interface that is private
to MR and HDFS, but it would work.
{quote}
The metrics APIs are separate form the actual metrics.
You can consider marking specific classes that implement metrics public or
private - but if you mark them as public then you are asserting that the actual
implementation classes for the specific metrics are public - ie the impl class
API is public.
If your intension is to make specific sets of metrics (say for NN) public then
you have to document that in your documentation - the annotation mechanism
cannot help here unless we extend it.
{quote}
I understand, but what we need to solve is the discoverability problem - if we
mark all the metrics classes as LimitedPrivate (which is what I think you are
suggesting), then how do users find the documentation to configure them?
> Apply audience and stability annotations to classes in common
> -------------------------------------------------------------
>
> Key: HADOOP-6668
> URL: https://issues.apache.org/jira/browse/HADOOP-6668
> Project: Hadoop Common
> Issue Type: Sub-task
> Components: documentation
> Reporter: Tom White
> Assignee: Tom White
> Priority: Blocker
> Fix For: 0.21.0
>
> Attachments: common.interface-tw-annotated.txt, HADOOP-6668.patch,
> HADOOP-6668.patch, HADOOP-6668.patch, HADOOP-6668.patch, HADOOP-6668.patch,
> HADOOP-6668.patch
>
>
> Mark private implementation classes with the InterfaceAudience.Private or
> InterfaceAudience.LimitedPrivate annotation to exclude them from user Javadoc
> and JDiff.
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