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https://issues.apache.org/jira/browse/NIFI-4794?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16352823#comment-16352823
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ASF GitHub Bot commented on NIFI-4794:
--------------------------------------

Github user mattyb149 commented on a diff in the pull request:

    https://github.com/apache/nifi/pull/2437#discussion_r166090089
  
    --- Diff: 
nifi-nar-bundles/nifi-provenance-repository-bundle/nifi-persistent-provenance-repository/src/main/java/org/apache/nifi/provenance/EncryptedSchemaRecordReader.java
 ---
    @@ -23,42 +23,29 @@
     import java.io.InputStream;
     import java.util.Collection;
     import java.util.Optional;
    -import java.util.concurrent.TimeUnit;
    +
     import org.apache.nifi.provenance.schema.LookupTableEventRecord;
     import org.apache.nifi.provenance.toc.TocReader;
     import org.apache.nifi.repository.schema.Record;
     import org.apache.nifi.stream.io.LimitingInputStream;
     import org.apache.nifi.stream.io.StreamUtils;
    -import org.apache.nifi.util.timebuffer.LongEntityAccess;
    -import org.apache.nifi.util.timebuffer.TimedBuffer;
    -import org.apache.nifi.util.timebuffer.TimestampedLong;
     import org.slf4j.Logger;
     import org.slf4j.LoggerFactory;
     
     public class EncryptedSchemaRecordReader extends 
EventIdFirstSchemaRecordReader {
         private static final Logger logger = 
LoggerFactory.getLogger(EncryptedSchemaRecordReader.class);
     
    -    private static final int DEFAULT_DEBUG_FREQUENCY = 1_000_000;
    --- End diff --
    
    Are changes to this file part of the PR? Doesn't seem like it. Or is it 
additional cleanup, or should it be restored?


> Improve Garbage Collection required by Provenance Repository
> ------------------------------------------------------------
>
>                 Key: NIFI-4794
>                 URL: https://issues.apache.org/jira/browse/NIFI-4794
>             Project: Apache NiFi
>          Issue Type: Improvement
>          Components: Core Framework
>            Reporter: Mark Payne
>            Assignee: Mark Payne
>            Priority: Major
>             Fix For: 1.6.0
>
>
> The EventIdFirstSchemaRecordWriter that is used by the provenance repository 
> has a writeRecord(ProvenanceEventRecord) method. Within this method, it 
> serializes the given record into a byte array by serializing to a 
> ByteArrayOutputStream (after wrapping the BAOS in a DataOutputStream). Once 
> this is done, it calls toByteArray() on that BAOS so that it can write the 
> byte[] directly to another OutputStream.
> This can create a rather large amount of garbage to be collected. We can 
> improve this significantly:
>  # Instead of creating a new ByteArrayOutputStream each time, create a pool 
> of them. This avoids constantly having to garbage collect them.
>  # If said BAOS grows beyond a certain size, we should not return it to the 
> pool because we don't want to keep a huge impact on the heap.
>  # Instead of wrapping the BAOS in a new DataOutputStream, the 
> DataOutputStream should be pooled/recycled as well. Since it must create an 
> internal byte[] for the writeUTF method, this can save a significant amount 
> of garbage.
>  # Avoid calling ByteArrayOutputStream.toByteArray(). We can instead just use 
> ByteArrayOutputStream.writeTo(OutputStream). This avoids both allocating that 
> new array/copying the data, and the GC overhead.
>  



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