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From "cuijianwei (JIRA)" <j...@apache.org>
Subject [jira] [Created] (HBASE-14436) HTableDescriptor#addCoprocessor will always make RegionCoprocessorHost create new Configuration
Date Tue, 15 Sep 2015 10:21:45 GMT
cuijianwei created HBASE-14436:
----------------------------------

             Summary: HTableDescriptor#addCoprocessor will always make RegionCoprocessorHost
create new Configuration
                 Key: HBASE-14436
                 URL: https://issues.apache.org/jira/browse/HBASE-14436
             Project: HBase
          Issue Type: Improvement
          Components: Coprocessors
    Affects Versions: 1.2.1
            Reporter: cuijianwei
            Priority: Minor


HTableDescriptor#addCoprocessor will set the coprocessor value as following format:
{code}
 public HTableDescriptor addCoprocessor(String className, Path jarFilePath,
                             int priority, final Map<String, String> kvs)
  throws IOException {
  ...
  String value = ((jarFilePath == null)? "" : jarFilePath.toString()) +
        "|" + className + "|" + Integer.toString(priority) + "|" +
        kvString.toString();
  ...
}
{code}
If the 'jarFilePath' is null,  the 'value' will always has the format '|className|priority|'
 even if 'kvs' is null, which means no extra arguments for the coprocessor. Then, in the server
side, RegionCoprocessorHost#getTableCoprocessorAttrsFromSchema will load the table coprocessors
as:
{code}
  static List<TableCoprocessorAttribute> getTableCoprocessorAttrsFromSchema(Configuration
conf,
      HTableDescriptor htd) {
    ...
            try {
              cfgSpec = matcher.group(4); // => cfgSpec will be '|' for the format '|className|priority|'
            } catch (IndexOutOfBoundsException ex) {
              // ignore
            }
            Configuration ourConf;
            if (cfgSpec != null) {  // => cfgSpec will be '|' for the format '|className|priority|'
              ourConf = new Configuration(false);
              HBaseConfiguration.merge(ourConf, conf);
            }
    ...
}
{code}
The 'cfgSpec' will be '|' for the coprocessor formatted as '|className|priority|', so that
always create a new Configuration.
In our production, there are a lot of tables having table-level coprocessors, so that the
region server will create new Configurations for each region of the table, this will consume
a certain number of memory when we have many such regions.
To fix the problem, we can make the HTableDescriptor not append the '|' if no extra arguments
for the coprocessor, or check the 'cfgSpec' more strictly in server side which could avoid
creating new Configurations for existed such regions after the regions reopened. Discussions
and suggestions are welcomed.



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