HBASE-18592 [hbase-thirdparty] Doc on new hbase-thirdparty dependency for the refguide
Project: http://git-wip-us.apache.org/repos/asf/hbase/repo Commit: http://git-wip-us.apache.org/repos/asf/hbase/commit/b932d38b Tree: http://git-wip-us.apache.org/repos/asf/hbase/tree/b932d38b Diff: http://git-wip-us.apache.org/repos/asf/hbase/diff/b932d38b Branch: refs/heads/HBASE-14070.HLC Commit: b932d38b2a53c1764345fec44e1bbb38addf04ec Parents: 56f9e1a Author: Michael Stack <[email protected]> Authored: Fri Aug 18 16:18:42 2017 -0700 Committer: Michael Stack <[email protected]> Committed: Fri Aug 18 16:18:42 2017 -0700 ---------------------------------------------------------------------- src/main/asciidoc/_chapters/developer.adoc | 54 +++++++++++++++++++++++++ 1 file changed, 54 insertions(+) ---------------------------------------------------------------------- http://git-wip-us.apache.org/repos/asf/hbase/blob/b932d38b/src/main/asciidoc/_chapters/developer.adoc ---------------------------------------------------------------------- diff --git a/src/main/asciidoc/_chapters/developer.adoc b/src/main/asciidoc/_chapters/developer.adoc index 6a546fb..3d010b6 100644 --- a/src/main/asciidoc/_chapters/developer.adoc +++ b/src/main/asciidoc/_chapters/developer.adoc @@ -2116,6 +2116,60 @@ However any substantive discussion (as with any off-list project-related discuss Misspellings and/or bad grammar is preferable to the disruption a JIRA comment edit causes: See the discussion at link:http://search-hadoop.com/?q=%5BReopened%5D+%28HBASE-451%29+Remove+HTableDescriptor+from+HRegionInfo&fc_project=HBase[Re:(HBASE-451) Remove HTableDescriptor from HRegionInfo] +[[thirdparty]] +=== The hbase-thirdparty dependency and shading/relocation + +A new project was created for the release of hbase-2.0.0. It was called +`hbase-thirdparty`. This project exists only to provide the main hbase +project with relocated -- or shaded -- versions of popular thirdparty +libraries such as guava, netty, and protobuf. The mainline HBase project +relies on the relocated versions of these libraries gotten from hbase-thirdparty +rather than on finding these classes in their usual locations. We do this so +we can specify whatever the version we wish. If we don't relocate, we must +harmonize our version to match that which hadoop and/or spark uses. + +For developers, this means you need to be careful referring to classes from +netty, guava, protobuf, gson, etc. (see the hbase-thirdparty pom.xml for what +it provides). Devs must refer to the hbase-thirdparty provided classes. In +practice, this is usually not an issue (though it can be a bit of a pain). You +will have to hunt for the relocated version of your particular class. You'll +find it by prepending the general relocation prefix of `org.apache.hadoop.hbase.shaded.`. +For example if you are looking for `com.google.protobuf.Message`, the relocated +version used by HBase internals can be found at +`org.apache.hadoop.hbase.shaded.com.google.protobuf.Message`. + +For a few thirdparty libs, like protobuf (see the protobuf chapter in this book +for the why), your IDE may give you both options -- the `com.google.protobuf.*` +and the `org.apache.hadoop.hbase.shaded.com.google.protobuf.*` -- because both +classes are on your CLASSPATH. Unless you are doing the particular juggling +required in Coprocessor Endpoint development (again see above cited protobuf +chapter), you'll want to use the shaded version, always. + +Of note, the relocation of netty is particular. The netty folks have put in +place facility to aid relocation; it seems like shading netty is a popular project. +One case of this requires the setting of a peculiar system property on the JVM +so that classes out in the bundld shared library (.so) can be found in their +relocated location. Here is the property that needs to be set: + +`-Dorg.apache.hadoop.hbase.shaded.io.netty.packagePrefix=org.apache.hadoop.hbase.shaded.` + +(Note that the trailing '.' is required). Starting hbase normally or when running +test suites, the setting of this property is done for you. If you are doing something +out of the ordinary, starting hbase from your own context, you'll need to provide +this property on platforms that favor the bundled .so. See release notes on HBASE-18271 +for more. The complaint you see is something like the following: +`Cause: java.lang.RuntimeException: Failed construction of Master: class org.apache.hadoop.hbase.master.HMasterorg.apache.hadoop.hbase.shaded.io.netty.channel.epoll.` + +The `hbase-thirdparty` project has groupid of `org.apache.hbase.thirdparty`. +As of this writing, it provides three jars; one for netty with an artifactid of +`hbase-thirdparty-netty`, one for protobuf at `hbase-thirdparty-protobuf` and then +a jar for all else -- gson, guava -- at `hbase-thirdpaty-miscellaneous`. + +The hbase-thirdparty artifacts are a product produced by the Apache HBase +project under the aegis of the HBase Project Management Committee. Releases +are done via the usual voting project on the hbase dev mailing list. If issue +in the hbase-thirdparty, use the hbase JIRA and mailing lists to post notice. + [[hbase.archetypes.development]] === Development of HBase-related Maven archetypes
