[jira] [Created] (YARN-5260) Review / Recommendations for hbase writer code

["Vrushali C (JIRA)" <ji...@apache.org>]

Vrushali C created YARN-5260:
--------------------------------

             Summary: Review / Recommendations for hbase writer code
                 Key: YARN-5260
                 URL: https://issues.apache.org/jira/browse/YARN-5260
             Project: Hadoop YARN
          Issue Type: Sub-task
            Reporter: Vrushali C


[~ted_yu] is graciously reviewing the hbase writer related code and has some recommendations. (more to come as review progresses). I will keep track of those in this jira and perhaps spin off other jira(s) depending on the scope of changes. 

For FlowRunCoprocessor.java :
 
-  private HRegion region;
Try to declare as Region - the interface. This way, you are to call methods that are stable across future releases.

-  private long getCellTimestamp(long timestamp, List<Tag> tags) {
tags is not used, remove the parameter.

For FlowScanner:
- private final InternalScanner flowRunScanner;
Currently InternalScanner is Private. If you must use it, try surfacing your case to hbase so that it can be marked:

@InterfaceAudience.LimitedPrivate(HBaseInterfaceAudience.COPROC)
@InterfaceStability.Evolving


w.r.t. regionScanner :
{code} 
    if (internalScanner instanceof RegionScanner) {
      this.regionScanner = (RegionScanner) internalScanner;
    }
{code}
I see IllegalStateException being thrown in some methods when regionScanner is null. Better bail out early in the ctor.


{code}
  public static AggregationOperation getAggregationOperationFromTagsList(
      List<Tag> tags) {
    for (AggregationOperation aggOp : AggregationOperation.values()) {
      for (Tag tag : tags) {
        if (tag.getType() == aggOp.getTagType()) {
          return aggOp;
{code}

The above nested loop can be improved (a lot):

values() returns an array. If you pre-generate a Set (https://docs.oracle.com/javase/7/docs/api/java/util/EnumSet.html) containing all the values, the outer loop can be omitted.
You iterate through tags and see if tag.getType() is in the Set.





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