[jira] [Created] (ACCUMULO-2175) Batch defining tablets in walog

["Keith Turner (JIRA)" <ji...@apache.org>]

Keith Turner created ACCUMULO-2175:
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             Summary: Batch defining tablets in walog
                 Key: ACCUMULO-2175
                 URL: https://issues.apache.org/jira/browse/ACCUMULO-2175
             Project: Accumulo
          Issue Type: Improvement
            Reporter: Keith Turner
             Fix For: 1.7.0


If a batch of mutations comes into a tablet server AND the tablet server just got a new walog then it will sync the walog for each tablet.  Below is a sketch of what the tablet server currently does.

{code:java}
foreach(Tablet t : tabletsInMutationBatch){
    if(!tabletIsDefinedInWalog(t, currentWalog)){
        defineTablet(currentWalog, t); //syncs walog
        addWalogToMetadataTable(currentWalog, t); //syncronous metadata table update
     }
}
{code}

Seems like doing the following would be better.  Then  no matter how many undefined tablets there are, only one walog sync would be done.

{code:java}
foreach(Tablet t : tabletsInMutationBatch){
    Set<Tablet> undefined = new HashSet<Tablet>();
    if(!tabletIsDefinedInWalog(t, currentWalog)){
        undefined.add(t);
     }
}

defineTablets(currentWalog, undefined); //syncs walog after writing all definitions
addWalogToMetadataTable(currentWalog, undefined); //syncronous metadata table batch write
{code}

There is not problem when all tablets in a batch update are defined in the walog. In this case a batch update that contains multiple tablet will only sync the log once after adding all the mutations from all tablets.

Noticed this while looking into ACCUMULO-2172



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