Please don't pull in @InterfaceAudience. Keeping 0.2x compatibility was something that was hard won in 0.94, it would be a real shame to loose that now.
On Mon, Apr 8, 2013 at 11:07 AM, Aleksandr Shulman <al...@cloudera.com>wrote: > Hi everyone, > > In light of all the conversation on compatibility, I wanted to float the > idea of documenting which Java packages, classes, and methods we want to > declare as being API compatible in 0.94.x. I'd like your input on: > 1. JavaDoc vs. using AudienceInterface > 2. What the javadoc notation should look like > 3. Which pieces of code should be tagged > > What do I mean by documenting API compatibility? That means that we suggest > the anyone building applications use specific methods because they would > continue to be both binary and RPC-compatible going forward. Any > application written, either running on a node of a cluster or on a remote > machine, would continue to work properly without recompile for all versions > of 0.94.x running on the cluster. > > *Benefits:* > It would prevent developers from using calls that are subject to change. > This would give developers more confidence in using the platform, which > will encourage more development on our platform. > 0.94 will still be with us for some time and I think the > better-late-than-never approach will save us pain down the road. Finally, > it would allow us to more easily verify that we are in fact API compatible. > > *Can we use AudienceInterface?* > HBase 0.94 can be compiled against both hadoop 0.2x, 1.x, and 2.0.x. In the > case of 0.2x, the AudienceInterface classes were not bundled. Therefore, we > cannot expect HBase 0.94 to support it. For that reason, I think JavaDoc > might be better. > On the other hand, perhaps we might just want to bundle AudienceInterface > with 0.94 going forward? Then we can have consistent annotations in 0.94, > 0.95, and 0.96 without worrying about the hadoop version. > > Please correct me if I'm wrong about any of the above. > > *Clarification of RPC compatibility:* > We care about RPC compatibility when we create clients that bundle their > dependency jars with them. These jars are used to form a request that is > executed on a remote machine (i.e. the cluster). If the cluster is upgraded > and no longer recognizes the command, then this will break RPC > compatibility. > > *Clarification of Binary compatibility:* > We care about binary compatibility when a client is created and compiled, > and the jars on which is depends change. It should still be able to form > requests using those jars. If the cluster is upgraded and the compiled > client code cannot find a method it was depending on to be there, we break > binary compatibility. A recent example is in 0.94.2, where the return type > of HColumnDescriptor.setMaximumVersions was changed and those who upgraded > received this error: > > java.lang.NoSuchMethodError: org.apache.hadoop.hbase.** > HColumnDescriptor.**setMaxVersions(I)V > > *What we currently have:* > We have an @audience annotation set up in 0.95/0.96. In 0.94, I suggest > either adding JavaDoc or pulling in the AudienceInterface annotation. > > *Suggested Javadoc language:* > @custom.94_api > > *Granularity:* > Just to the class level. The native java access level (e.g. public, > protected, etc.) should indicate what should be kept compatible. > > *Suggested classes:* > Here is a first-cut of things that should be declared and documented as > public APIs. This list was obtained from looking at some MapReduce over > HBase example code. > > *JAVA API:* > > *org.apache.hadoop.hbase (some selected classes, see below) > org.apache.hadoop.hbase.client.* > org.apache.hadoop.hbase.filter.* > org.apache.hadoop.hbase.io.hfile.Compression.Algorithm > org.apache.hadoop.hbase.util.* > org.apache.hadoop.hbase.mapreduce.** > > *REST API: > org.apache.hadoop.hbase.rest.client.** > > *Thrift API: > All methods defined in: > /hbase/src/main/resources/org/apache/hadoop/hbase/thrift/Hbase.thrift* > > *Selected classes in org.apache.hadoop.hbase:* > > *import org.apache.hadoop.hbase.ClusterStatus; > import org.apache.hadoop.hbase.HBaseConfiguration; > import org.apache.hadoop.hbase.HColumnDescriptor; > import org.apache.hadoop.hbase.HRegionInfo; > import org.apache.hadoop.hbase.HRegionLocation; > import org.apache.hadoop.hbase.HServerAddress; > import org.apache.hadoop.hbase.HTableDescriptor; > import org.apache.hadoop.hbase.KeyValue;* > > -- > Best Regards, > > Aleks Shulman > 847.814.5804 > Cloudera >
