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https://issues.apache.org/jira/browse/HBASE-17732?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16183142#comment-16183142
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Appy commented on HBASE-17732:
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h4. Commit message
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HBASE-17732 Coprocessor Design Improvements
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TL;DR
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We are moving from Inheritence
- Observer *is* Coprocessor
- FooService *is* CoprocessorService
To Composition
- Coprocessor *has* Observer
- Coprocessor *has* Service
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Design Changes
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- Adds four new interfaces - MasterCoprocessor, RegionCoprocessor,
RegionServierCoprocessor,
WALCoprocessor
- These new *Coprocessor interfaces have a get*Observer() function for each
observer type
supported by them.
- Added Coprocessor#getService() to base interface. All extending
*Coprocessor interfaces will
get it from the base interface.
- Added BulkLoadObserver hooks to RegionCoprocessorHost instad of
SecureBulkLoadManager doing its
own trickery.
- CoprocessorHost#find*() fuctions: Too many testing hooks digging into CP
internals.
Deleted if can, else marked @VisibleForTesting.
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Backward Compatibility
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- Old coprocessors implementing *Observer won't get loaded (no backward
compatibility guarantees).
- Third party coprocessors only implementing Coprocessor will not get
loaded (just like Observers).
- Old coprocessors implementing CoprocessorService (for master/region host)
/SingletonCoprocessorService (for RegionServer host) will continue to
work with 2.0.
- Added test to ensure backward compatibility of
CoprocessorService/SingletonCoprocessorService
- Note that if a coprocessor implements both observer and service in same
class, its service
component will continue to work but it's observer component won't work.
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Notes
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Did a side-by-side comparison of CPs in master and after patch. These
coprocessors which were just
CoprocessorService earlier, needed a home in some coprocessor in new
design. For most it was clear
since they were using a particular type of environment. Some were tricky.
- JMXListener - MasterCoprocessor and RSCoprocessor (because jmx listener
makes sense for
processes?)
- RSGroupAdminEndpoint --> MasterCP
- VisibilityController -> MasterCP and RegionCP
These were converted to RegionCoprocessor because they were using
RegionCoprocessorEnvironment
which can only come from a RegionCPHost.
- AggregateImplementation
- BaseRowProcessorEndpoint
- BulkDeleteEndpoint
- Export
- RefreshHFilesEndpoint
- RowCountEndpoint
- MultiRowMutationEndpoint
- SecureBulkLoadEndpoint
- TokenProvider
{noformat}
> Coprocessor Design Improvements
> -------------------------------
>
> Key: HBASE-17732
> URL: https://issues.apache.org/jira/browse/HBASE-17732
> Project: HBase
> Issue Type: Improvement
> Reporter: Appy
> Assignee: Appy
> Priority: Critical
> Fix For: 2.0.0-alpha-4
>
> Attachments: HBASE-17732.master.001.patch,
> HBASE-17732.master.002.patch, HBASE-17732.master.003.patch,
> HBASE-17732.master.004.patch, HBASE-17732.master.005.patch,
> HBASE-17732.master.006.patch, HBASE-17732.master.007.patch,
> HBASE-17732.master.008.patch, HBASE-17732.master.009.patch,
> HBASE-17732.master.010.patch, HBASE-17732.master.011.patch,
> HBASE-17732.master.012.patch, HBASE-17732.master.013.patch,
> HBASE-17732.master.014.patch
>
>
> The two main changes are:
> * *Adding template for coprocessor type to CoprocessorEnvironment i.e.
> {{interface CoprocessorEnvironment<C extends Coprocessor>}}*
> ** Enables us to load only relevant coprocessors in hosts. Right now each
> type of host loads all types of coprocs and it's only during execOperation
> that it checks if the coproc is of correct type i.e. XCoprocessorHost will
> load XObserver, YObserver, and all others, and will check in execOperation if
> {{coproc instanceOf XObserver}} and ignore the rest.
> ** Allow sharing of a bunch functions/classes which are currently
> duplicated in each host. For eg. CoprocessorOperations,
> CoprocessorOperationWithResult, execOperations().
> * *Introduce 4 coprocessor classes and use composition between these new
> classes and and old observers*
> ** The real gold here is, moving forward, we'll be able to break down giant
> everything-in-one observers (masterobserver has 100+ functions) into smaller,
> more focused observers. These smaller observer can then have different compat
> guarantees!!
> Here's a more detailed design doc:
> https://docs.google.com/document/d/1mPkM1CRRvBMZL4dBQzrus8obyvNnHhR5it2yyhiFXTg/edit?usp=sharing
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