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From Stack <st...@duboce.net>
Subject Re: [DISCUSS] Punt the Coprocessor TableWrapper and CoprocessorHConnection?
Date Thu, 19 Oct 2017 04:51:36 GMT
HBASE-19043
S

On Wed, Oct 18, 2017 at 3:29 PM, Andrew Purtell <apurtell@apache.org> wrote:

> > I remember Andrew saying same thing about CoprocessorEnvironment#
> getTable
> functions during the review of HBASE-17732, that we should get rid of them
> and let CP do their own table resource management like all other things.
>
> Yes
>
> > The above 'trick' is now commonplace in servers as the Master and
> RegionServer
> always make Connections that will short-circuit if an opportunity
>
> No need for CoprocessorHConnection, then.
>
>
>
> On Wed, Oct 18, 2017 at 3:12 PM, Apekshit Sharma <appy@cloudera.com>
> wrote:
>
> > +1
> > I remember Andrew saying same thing about CoprocessorEnvironment#
> getTable
> > functions during the review of HBASE-17732, that we should get rid of
> them
> > and let CP do their own table resource management like all other things.
> >
> > On Wed, Oct 18, 2017 at 2:45 PM, Stack <stack@duboce.net> wrote:
> >
> > > tl;dr I believe the original intent for TableWrapper and
> > > CoprocessorHConnection can now be gotten elsewhere so we should purge
> > these
> > > classes.
> > >
> > > In base CoprocessorEnvironment, there are methods to return a Table
> > > instance. There are none to return an Admin. In our code base, the only
> > > user is the AccessController. Phoenix uses it twice in its Indexer
> > > implementation.
> > >
> > > When you call CE#getTable, the default implementation in
> > > BaseEnvironemnt calls HTableWrapper.createWrapper which takes a
> > > BaseEnvironment List in which we keep all Table instances. On shutdown
> of
> > > the coprocessor, the list is iterated and all tables are closed.
> > >
> > > Going via TableWrapper, the class comment says:
> > >
> > > * A wrapper for HTable. Can be used to restrict privilege.
> > > *
> > > * Currently it just helps to track tables opened by a Coprocessor and
> > > * facilitate close of them if it is aborted.
> > > *
> > > * We also disallow row locking.
> > > *
> > > * There is nothing now that will stop a coprocessor from using HTable
> > > * objects directly instead of this API, but in the future we intend to
> > > * analyze coprocessor implementations as they are loaded and reject
> those
> > > * which attempt to use objects and methods outside the Environment
> > > * sandbox.
> > >
> > >
> > > TableWrapper by my reading delegates all calls to a Table instance with
> > no
> > > interception (there is not rowlocking to override anymore). On open, we
> > do
> > > ensure the Table is up on a CoprocessorHConnection which does the
> > > following:
> > >
> > > * Connection to an HTable from within a Coprocessor. We can do some
> > > nice tricks since we know we
> > > * are on a regionserver, for instance skipping the full
> > > serialization/deserialization of objects
> > > * when talking to the server.
> > >
> > >
> > > The above 'trick' is now commonplace in servers as the Master and
> > > RegionServer always make Connections that will short-circuit if an
> > > opportunity.
> > >
> > > As I read TableWrapper and CoprocessorHConnection, they were written at
> > > another time when Table construction was heavyweight and Table#close
> was
> > > not expected of clients and before the introduction of the general
> > > Server-side short-circuit Connection facility.
> > >
> > > Unless objection, I think we should purge them.
> > >
> > > Writing here in case I'm missing some key facility they provide.
> > >
> > > Thanks,
> > > St.Ack
> > >
> >
> >
> >
> > --
> >
> > -- Appy
> >
>
>
>
> --
> Best regards,
> Andrew
>
> Words like orphans lost among the crosstalk, meaning torn from truth's
> decrepit hands
>    - A23, Crosstalk
>

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