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https://issues.apache.org/jira/browse/KAFKA-12605?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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radai rosenblatt updated KAFKA-12605:
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Attachment: Screen Shot 2021-04-01 at 3.55.47 PM.png
> kafka consumer churns through buffer memory iterating over records
> ------------------------------------------------------------------
>
> Key: KAFKA-12605
> URL: https://issues.apache.org/jira/browse/KAFKA-12605
> Project: Kafka
> Issue Type: Improvement
> Affects Versions: 2.7.0
> Reporter: radai rosenblatt
> Priority: Major
> Attachments: Screen Shot 2021-04-01 at 3.55.47 PM.png
>
>
> we recently conducted analysis on memory allocations by the kafka consumer
> and found a significant amount of buffers that graduate out of the young gen
> causing GC load.
>
> these are tthe buffers used to gunzip record batches in the consumer when
> polling. since the same iterator (and underlying streams and buffers) are
> likely to live through several poll() cycles these buffers graduate out of
> young gen and cause issues.
>
> see attached memory allocation flame graph.
>
> the code causing this is in CompressionTypye.GZIP (taken from current trunk):
> {code:java}
> @Override
> public InputStream wrapForInput(ByteBuffer buffer, byte messageVersion,
> BufferSupplier decompressionBufferSupplier) {
> try {
> // Set output buffer (uncompressed) to 16 KB (none by default) and
> input buffer (compressed) to
> // 8 KB (0.5 KB by default) to ensure reasonable performance in cases
> where the caller reads a small
> // number of bytes (potentially a single byte)
> return new BufferedInputStream(new GZIPInputStream(new
> ByteBufferInputStream(buffer), 8 * 1024),
> 16 * 1024);
> } catch (Exception e) {
> throw new KafkaException(e);
> }
> }{code}
> it allocated 2 buffers - 8K and 16K even though a BufferSupplier is available
> to attempt re-use.
>
> i believe it is possible to actually get both tthose buffers from the
> supplier, and return them when iteration over the record batch is done.
> doing so will require subclassing BufferedInputStream and GZIPInputStream
> (or its parent class) to allow supplying external buffers onto them. also
> some lifecycle hook would be needed to return said buffers to the pool when
> iteration is done.
>
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