hbase/hbase-endpoint/README.txt

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ON PROTOBUFS
This maven module has protobuf definition files ('.protos') used by hbase
Coprocessor Endpoints that ship with hbase core including tests. Coprocessor
Endpoints are meant to be standalone, independent code not reliant on hbase
internals. They define their Service using protobuf. The protobuf version
they use can be distinct from that used by HBase internally since HBase started
shading its protobuf references. Endpoints have no access to the shaded protobuf
hbase uses. They do have access to the content of hbase-protocol but avoid using
as much of this as you can as it is liable to change.
Generation of java files from protobuf .proto files included here is done apart
from the build. Run the generation whenever you make changes to the .orotos files
and then check in the produced java (The reasoning is that change is infrequent
so why pay the price of generating files anew on each build.
To generate java files from protos run:
$ mvn compile -Dcompile-protobuf
HBASE-15638 Shade protobuf Which includes HBASE-16742 Add chapter for devs on how we do protobufs going forward HBASE-16741 Amend the generate protobufs out-of-band build step to include shade, pulling in protobuf source and a hook for patching protobuf Removed ByteStringer from hbase-protocol-shaded. Use the protobuf-3.1.0 trick directly instead. Makes stuff cleaner. All under 'shaded' dir is now generated. HBASE-16567 Upgrade to protobuf-3.1.x Regenerate all protos in this module with protoc3. Redo ByteStringer to use new pb3.1.0 unsafebytesutil instead of HBaseZeroCopyByteString HBASE-16264 Figure how to deal with endpoints and shaded pb Shade our protobufs. Do it in a manner that makes it so we can still have in our API references to com.google.protobuf (and in REST). The c.g.p in API is for Coprocessor Endpoints (CPEP) This patch is Tactic #4 from Shading Doc attached to the referenced issue. Figuring an appoach took a while because we have Coprocessor Endpoints mixed in with the core of HBase that are tough to untangle (FIX). Tactic #4 (the fourth attempt at addressing this issue) is COPY all but the CPEP .proto files currently in hbase-protocol to a new module named hbase-protocol-shaded. Generate .protos again in the new location and then relocate/shade the generated files. Let CPEPs keep on with the old references at com.google.protobuf.* and org.apache.hadoop.hbase.protobuf.* but change the hbase core so all instead refer to the relocated files in their new location at org.apache.hadoop.hbase.shaded.com.google.protobuf.*. Let the new module also shade protobufs themselves and change hbase core to pick up this shaded protobuf rather than directly reference com.google.protobuf. This approach allows us to explicitly refer to either the shaded or non-shaded version of a protobuf class in any particular context (though usually context dictates one or the other). Core runs on shaded protobuf. CPEPs continue to use whatever is on the classpath with com.google.protobuf.* which is pb2.5.0 for the near future at least. See above cited doc for follow-ons and downsides. In short, IDEs will complain about not being able to find the shaded protobufs since shading happens at package time; will fix by checking in all generated classes and relocated protobuf in a follow-on. Also, CPEPs currently suffer an extra-copy as marshalled from non-shaded to shaded. To fix. Finally, our .protos are duplicated; once shaded, and once not. Pain, but how else to reveal our protos to CPEPs or C++ client that wants to talk with HBase AND shade protobuf. Details: Add a new hbase-protocol-shaded module. It is a copy of hbase-protocol i with all relocated offset from o.a.h.h. to o.a.h.h.shaded. The new module also includes the relocated pb. It does not include CPEPs. They stay in their old location. Add another module hbase-endpoint which has in it all the endpoints that ship as part of hbase -- at least the ones that are not entangled with core such as AccessControl and Auth. Move all protos for these CPEPs here as well as their unit tests (mostly moving a bunch of stuff out of hbase-server module) Much of the change looks like this: -import org.apache.hadoop.hbase.protobuf.ProtobufUtil; -import org.apache.hadoop.hbase.protobuf.generated.ClusterIdProtos; +import org.apache.hadoop.hbase.protobuf.shaded.ProtobufUtil; +import org.apache.hadoop.hbase.shaded.protobuf.generated.ClusterIdProtos; In HTable and in HBaseAdmin, regularize the way Callables are used and also hide protobuf usage as much as possible moving it up into Callable super classes or out to utility classes. Still TODO is adding in of retries, etc., but can wait on procedure which will redo all this. Also in HTable and HBaseAdmin as well as in HRegionServer and Server, be explicit when using non-shaded protobuf. Do the full-path so it is clear. This is around endpoint coprocessors registration of services and execution of CPEP methods. Shrunk ProtobufUtil by moving methods used by one CPEP only back to the CPEP either into Client class or as new Util class; e.g. AccessControlUtil. There are actually two versions of ProtobufUtil now; a shaded one and a subset that is used by CPEPs doing non-shaded work. Made it so hbase-common no longer depends on hbase-protocol (with Matteo's help) R*Converter classes got moved down under shaded package -- they are for internal use only. There are no non-shaded versions of these classes. D hbase-client/src/main/java/org/apache/hadoop/hbase/client/AbstractRegionServerCallable D RetryingCallableBase Not used anymore and we have too many tiers of Callables so removed/cleaned-up. A ClientServicecallable Had to add this one. RegionServerCallable was made generic so it could be used for a few Interfaces (Client and Admin). Then added ClientServiceCallable to implement RegionServerCallable with the Client Interface.
2016-10-04 00:37:32 -04:00
or
$ mvn compile -Pcompile-protobuf
After you've done the above, check it and then check in changes (or post a patch
on a JIRA with your definition file changes and the generated files). Be careful
to notice new files and files removed and do appropriate git rm/adds.