[ACCUMULO-2175] Batch defining tablets in walog

• Type: Improvement
• Status: Resolved
• Priority: Major
• Resolution: Duplicate
• Assignee: Unassigned
• Reporter: Keith Turner
• Created: 10/Jan/14 21:07
• Updated: 23/Apr/19 16:09
• Resolved: 23/Apr/19 15:07

Description

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.

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

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

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

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

Issue Links

• is duplicated by: ACCUMULO-2801 define tablet syncs walog for each tablet in a batch