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https://issues.apache.org/jira/browse/CASSANDRA-1896?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12976133#action_12976133
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Tsiki commented on CASSANDRA-1896:
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No. Since also the current implementation writes only when the buffer is full
or if there are no additional messages in the queue (hence the peek() call when
filling the buffer). Now if we are under load, which is the interesting case
here, then the queue will always be full since messages are always coming in
and so flushing will take place whenever the (4K or so) buffer is full and
we'll send only large packets.
> Improve throughput by adding buffering to the inter-node TCP communication
> --------------------------------------------------------------------------
>
> Key: CASSANDRA-1896
> URL: https://issues.apache.org/jira/browse/CASSANDRA-1896
> Project: Cassandra
> Issue Type: Improvement
> Components: Core
> Affects Versions: 0.6
> Reporter: Tsiki
> Assignee: Brandon Williams
> Fix For: 0.6.9, 0.7.1
>
> Attachments: 1896.txt
>
>
> The inbound and outbound TCP implementation under org.apache.cassandra.net
> does not buffer the socket streams. A simple change in IncomingTcpConnection
> and OutboundTcpConnection may give a rather big throughput increase. In my
> tests, I got up t o 30% more out of my cluster. Below is the diff of these
> two files with buffering included. The diff is over release 0.6.5 but can be
> quite simply applied also to 0.7. I suggest perhaps to limit the buffered
> input stream I added in IncomingTcpConnection to 4K. The Outbound
> implementation can surely be implemented a bit better (remove some of the
> code I duplicated there).
> diff -r
> apache-cassandra-0.6.5-src/src/java/org/apache/cassandra/net/IncomingTcpConnection.java
>
> fix/apache-cassandra-0.6.5-src/src/java/org/apache/cassandra/net/IncomingTcpConnection.java
> 44c44
> < input = new DataInputStream(new
> BufferedInputStream(socket.getInputStream()));
> ---
> > input = new DataInputStream(socket.getInputStream());
> diff -r
> apache-cassandra-0.6.5-src/src/java/org/apache/cassandra/net/OutboundTcpConnection.java
>
> fix/apache-cassandra-0.6.5-src/src/java/org/apache/cassandra/net/OutboundTcpConnection.java
> 77d76
> < byte[] buf = new byte[4096];
> 80,112c79,89
> < int l = 0;
> < ByteBuffer bb;
> < while ((bb = queue.peek()) != null && l+bb.limit() <
> buf.length) {
> < bb = take();
> < System.arraycopy(bb.array(), 0, buf, l, bb.limit());
> < l += bb.limit();
> < }
> < if (l == 0) {
> < bb = take();
> < if (bb == CLOSE_SENTINEL)
> < {
> < disconnect();
> < continue;
> < }
> < if (socket != null || connect())
> < writeConnected(bb);
> < else
> < // clear out the queue, else gossip messages back up.
> < queue.clear();
> < } else {
> < if (socket != null || connect()) {
> < try {
> < output.write(buf, 0, l);
> < if (queue.peek() == null)
> < output.flush();
> < } catch (IOException e) {
> < logger.info("error writing to " + endpoint);
> < disconnect();
> < }
> < } else {
> < queue.clear();
> < }
> < }
> ---
> > ByteBuffer bb = take();
> > if (bb == CLOSE_SENTINEL)
> > {
> > disconnect();
> > continue;
> > }
> > if (socket != null || connect())
> > writeConnected(bb);
> > else
> > // clear out the queue, else gossip messages back up.
> > queue.clear();
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