[jboss-jira] [JBoss JIRA] (JGRP-2218) New buffers

[Bela Ban (JIRA)]

Bela Ban created JGRP-2218:
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             Summary: New buffers
                 Key: JGRP-2218
                 URL: https://issues.jboss.org/browse/JGRP-2218
             Project: JGroups
          Issue Type: Feature Request
            Reporter: Bela Ban
            Assignee: Bela Ban
             Fix For: 5.0


h3. Goal
Change payload in {{Message}} from byte[] arrays to a {{Buffer}} interface which can have multiple implementations.

h3. Motivation
Currently, having to pass a byte[] array to a message leads to unnecessary copying:
* When an application has a ref to an NIO (direct) {{ByteBuffer}}, the bytes in the byte buffer have to be copied into a byte[] array and then set in the message
* When the application sends around byte[] arrays, but also wants to add some additional metadata, e.g. type (1000-byte requests/responses), it needs to create a new byte[] array of (say) 1001 bytes and copy the data (1000 bytes) plus the request type (1 byte) into the new copy. Example: {{MPerf}} and {{UPerf}}

h3. Design
Instead of copying, the application creates an instance of {{Buffer}} and sets the buffer in {{Message}}. The {{Buffer}} is then passed all the way down into the transport where it is marshalled and sent. There can be a number of buffer implementations, e.g.
* {{ArrayBuffer}}: wraps a byte[] array with an offset and length
* {{NioDirectBuffer}}: wraps an NIO direct {{ByteBuffer}}
* {{NioHeapBuffer}}: wraps an NIO heap-based {{ByteBuffer}}
* {{CompositeBuffer}}: wraps multiple Buffers. E.g. type (1 byte) and data (1000 bytes) as described above
* {{IntBuffer}}: a single integer
* {{PartialBuffer}}: a ref to a {{Buffer}}, with an offset and length

The {{Buffer}} interface has methods {{size()}}, {{writeTo(DataOutput)}}, {{readFrom(DataInput)}}, possibly also {{acquire()}} and {{release()}} (for ref-counting).

Each buffer impl has an ID and it should be possible to register new impls. A {{BufferFactory}} maintains a mapping between IDs and impl classes.

When marshalling a {{Buffer}}, the ID is written first, followed by the buffer's {{writeTo()}} method. When reading buffers, the {{BufferFactory}} is used to create instances from IDs.





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