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https://issues.apache.org/jira/browse/HBASE-15180?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15148985#comment-15148985
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Anoop Sam John commented on HBASE-15180:
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bq.Is this flag saying we can rely on available() giving a good answer?
Yes. Any suggestion?
The unsafe based BB read dont have boundary checks.. That is why thought of
adding check in this Stream level.
Yes in StreamUtils it is doing the read of 4 bytes at a time
int n = in.read(readInBuf, bytesRead, readInBuf.length - bytesRead);
The while loop is to make sure it tried it best to read 4 bytes from stream.
Even if the 1st go could do only 2 bytes. Still tried. This was present in
BaseDecoder. Just moved from there to here.
> Reduce garbage created while reading Cells from Codec Decoder
> -------------------------------------------------------------
>
> Key: HBASE-15180
> URL: https://issues.apache.org/jira/browse/HBASE-15180
> Project: HBase
> Issue Type: Sub-task
> Components: regionserver
> Affects Versions: 0.98.0
> Reporter: Anoop Sam John
> Assignee: Anoop Sam John
> Fix For: 2.0.0, 1.3.0, 1.2.1
>
> Attachments: HBASE-15180.patch, HBASE-15180_V2.patch,
> HBASE-15180_V4.patch
>
>
> In KeyValueDecoder#parseCell (Default Codec decoder) we use
> KeyValueUtil#iscreate to read cells from the InputStream. Here we 1st create
> a byte[] of length 4 and read the cell length and then an array of Cell's
> length and read in cell bytes into it and create a KV.
> Actually in server we read the reqs into a byte[] and CellScanner is created
> on top of a ByteArrayInputStream on top of this. By default in write path, we
> have MSLAB usage ON. So while adding Cells to memstore, we will copy the Cell
> bytes to MSLAB memory chunks (default 2 MB size) and recreate Cells over that
> bytes. So there is no issue if we create Cells over the RPC read byte[]
> directly here in Decoder. No need for 2 byte[] creation and copy for every
> Cell in request.
> My plan is to make a Cell aware ByteArrayInputStream which can read Cells
> directly from it.
> Same Codec path is used in client side also. There better we can avoid this
> direct Cell create and continue to do the copy to smaller byte[]s path. Plan
> to introduce some thing like a CodecContext associated with every Codec
> instance which can say the server/client context.
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