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https://issues.apache.org/jira/browse/HBASE-18846?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16182012#comment-16182012
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stack commented on HBASE-18846:
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.001 is a hack to standup a RegionServer with nothing but the basic threads and
'services' (chores, sleepers, managers) running. Adds config so you can turn
on/off Admin+Client Services. Adds code so if a Service/Thread/Chore has not
been initialized, it keeps going. Adds a 'masterless' config so we press on if
no Master to check-in with. Includes a config which turns off facility such as
WAL.
So, idea was to stand up a RegionServer whose only purpose in life is receiving
a Replication stream and then allow Lily override the single replicateWALEntry
method to catch the replication stream and feed a Lucene index (as it does
currently only it manually sets up an RpcServer, registers an Admin Service,
overriding all but the one method to throw NotImplementedException). The
thought was to allow override w/ a Coprocessor BUT preReplicateLogEntries just
removed the passing of WALEntries... to CPs (no PBs in CP API).... which messes
up this tack.
But, we have ReplicationSinkService. Its IA.Private currently and defaults to
calling RS methods. Let me make it so you can insert your own. The machinery
is sort-of there. We can do this for Lily crew.
TODO: Add means of inserting custom ReplicationSinkService and cleanup of
service/thread/chore startup in RS. Doc.
> Accommodate the hbase-indexer/lily/SEP consumer deploy-type
> -----------------------------------------------------------
>
> Key: HBASE-18846
> URL: https://issues.apache.org/jira/browse/HBASE-18846
> Project: HBase
> Issue Type: Bug
> Reporter: stack
> Attachments: HBASE-18846.master.001.patch, javadoc.txt
>
>
> This is a follow-on from HBASE-10504, Define a Replication Interface. There
> we defined a new, flexible replication endpoint for others to implement but
> it did little to help the case of the lily hbase-indexer. This issue takes up
> the case of the hbase-indexer.
> The hbase-indexer poses to hbase as a 'fake' peer cluster (For why
> hbase-indexer is implemented so, the advantage to having the indexing done in
> a separate process set that can be independently scaled, can participate in
> the same security realm, etc., see discussion in HBASE-10504). The
> hbase-indexer will start up a cut-down "RegionServer" processes that are just
> an instance of hbase RpcServer hosting an AdminProtos Service. They make
> themselves 'appear' to the Replication Source by hoisting up an ephemeral
> znode 'registering' as a RegionServer. The source cluster then streams
> WALEdits to the Admin Protos method:
> {code}
> public ReplicateWALEntryResponse replicateWALEntry(final RpcController
> controller,
> final ReplicateWALEntryRequest request) throws ServiceException {
> {code}
> The hbase-indexer relies on other hbase internals like Server so it can get a
> ZooKeeperWatcher instance and know the 'name' to use for this cut-down server.
> Thoughts on how to proceed include:
>
> * Better formalize its current digestion of hbase internals; make it so
> rpcserver is allowed to be used by others, etc. This would be hard to do
> given they use basics like Server, Protobuf serdes for WAL types, and
> AdminProtos Service. Any change in this wide API breaks (again)
> hbase-indexer. We have made a 'channel' for Coprocessor Endpoints so they
> continue to work though they use 'internal' types. They can use protos in
> hbase-protocol. hbase-protocol protos are in a limbo currently where they are
> sort-of 'public'; a TODO. Perhaps the hbase-indexer could do similar relying
> on the hbase-protocol (pb2.5) content and we could do something to reveal
> rpcserver and zk for hbase-indexer safe use.
> * Start an actual RegionServer only have it register the AdminProtos Service
> only -- not ClientProtos and the Service that does Master interaction, etc.
> [I checked, this is not as easy to do as I at first thought -- St.Ack] Then
> have the hbase-indexer implement an AdminCoprocessor to override the
> replicateWALEntry method (the Admin CP implementation may need work). This
> would narrow the hbase-indexer exposure to that of the Admin Coprocessor
> Interface
> * Over in HBASE-10504, [~enis] suggested "... if we want to provide
> isolation for the replication services in hbase, we can have a simple host as
> another daemon which hosts the ReplicationEndpoint implementation. RS's will
> use a built-in RE to send the edits to this layer, and the host will delegate
> it to the RE implementation. The flow would be something like: RS --> RE
> inside RS --> Host daemon for RE --> Actual RE implementation --> third party
> system..."
>
> Other crazy notions occur including the setup of an Admin Interface
> Coprocessor Endpoint. A new ReplicationEndpoint would feed the replication
> stream to the remote cluster via the CPEP registered channel.
> But time is short. Hopefully we can figure something that will work in 2.0
> timeframe w/o too much code movement.
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