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From "ASF GitHub Bot (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (CASSANDRA-14556) Optimize streaming path in Cassandra
Date Mon, 23 Jul 2018 20:12:00 GMT

    [ https://issues.apache.org/jira/browse/CASSANDRA-14556?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16553343#comment-16553343
] 

ASF GitHub Bot commented on CASSANDRA-14556:
--------------------------------------------

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

    https://github.com/apache/cassandra/pull/239#discussion_r204537184
  
    --- Diff: src/java/org/apache/cassandra/db/streaming/ComponentInfo.java ---
    @@ -0,0 +1,97 @@
    +/*
    + * Licensed to the Apache Software Foundation (ASF) under one
    + * or more contributor license agreements.  See the NOTICE file
    + * distributed with this work for additional information
    + * regarding copyright ownership.  The ASF licenses this file
    + * to you under the Apache License, Version 2.0 (the
    + * "License"); you may not use this file except in compliance
    + * with the License.  You may obtain a copy of the License at
    + *
    + *     http://www.apache.org/licenses/LICENSE-2.0
    + *
    + * Unless required by applicable law or agreed to in writing, software
    + * distributed under the License is distributed on an "AS IS" BASIS,
    + * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    + * See the License for the specific language governing permissions and
    + * limitations under the License.
    + */
    +
    +package org.apache.cassandra.db.streaming;
    +
    +import java.io.IOException;
    +
    +import org.apache.commons.lang3.builder.EqualsBuilder;
    +import org.apache.commons.lang3.builder.HashCodeBuilder;
    +import org.apache.cassandra.db.TypeSizes;
    +import org.apache.cassandra.io.IVersionedSerializer;
    +import org.apache.cassandra.io.sstable.Component;
    +import org.apache.cassandra.io.util.DataInputPlus;
    +import org.apache.cassandra.io.util.DataOutputPlus;
    +
    +public class ComponentInfo
    +{
    +    final Component.Type type;
    +    final long length;
    +
    +    public ComponentInfo(Component.Type type, long length)
    +    {
    +        assert length >= 0 : "Component length cannot be negative";
    +        this.type = type;
    +        this.length = length;
    +    }
    +
    +    @Override
    +    public String toString()
    +    {
    +        return "ComponentInfo{" +
    +               "type=" + type +
    +               ", length=" + length +
    +               '}';
    +    }
    +
    +    public boolean equals(Object o)
    --- End diff --
    
    It's generally considered to be a bad practice to implement `equals()` and `hashCode()`
unless that class is stored in a set or a map - or an upstream implementation of such. Otherwise
it's just confusing boilerplate (confusing because it implies that the class is used in ways
it clearly isn't).
    
    In this case, there is a `List<ComponentInfo>` field in `CassandraStreamHeader`,
which has an `equals()`/`hashCode()` implementation, which on the surface justifies these.
But those, in turn, are actually dead code. So what we should do is remove the implementations
of `equals()` and `hashCode()` here, and do the same in `CassandraStreamHeader`, being good
citizens.


> Optimize streaming path in Cassandra
> ------------------------------------
>
>                 Key: CASSANDRA-14556
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-14556
>             Project: Cassandra
>          Issue Type: Improvement
>          Components: Streaming and Messaging
>            Reporter: Dinesh Joshi
>            Assignee: Dinesh Joshi
>            Priority: Major
>              Labels: Performance
>             Fix For: 4.x
>
>
> During streaming, Cassandra reifies the sstables into objects. This creates unnecessary
garbage and slows down the whole streaming process as some sstables can be transferred as
a whole file rather than individual partitions. The objective of the ticket is to detect when
a whole sstable can be transferred and skip the object reification. We can also use a zero-copy
path to avoid bringing data into user-space on both sending and receiving side.



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