[jboss-jira] [JBoss JIRA] Commented: (JGRP-1070) Provide IP version checking based on @Property processing

[Richard Achmatowicz (JIRA)]

    [ https://jira.jboss.org/jira/browse/JGRP-1070?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12488700#action_12488700 ] 

Richard Achmatowicz commented on JGRP-1070:
-------------------------------------------

The key issue of JGRP-978 is that JGroups does not presently assign IP version specific defaults to InetADdresses it makes use of, such as diagnostics_addr.

This problem has been solved by way of @Property default processing and IP version checking. 

During protocol stack creation, after all @Properties have been through their basic processing, we build up a map of all InetAddresses (and related IpAddress, InetSocketAddress) fields and methods in the stack which have a user specified value. This map is them used to determine the JGroups IP version: IPv4 or IPv6. Once the version is determined, the default values for @Properties are processed. 

The @Proeprty default processing will now have a version to work with. Because diagnostics_addr is an InetAddress, processing will check the @Prpeprty annotation for defaultValueIPv4() or defaultValueIPv6(), and the correct version specific default is assigned.


> Provide IP version checking based on @Property processing
> ---------------------------------------------------------
>
>                 Key: JGRP-1070
>                 URL: https://jira.jboss.org/jira/browse/JGRP-1070
>             Project: JGroups
>          Issue Type: Feature Request
>    Affects Versions: 2.8
>            Reporter: Richard Achmatowicz
>            Assignee: Richard Achmatowicz
>             Fix For: 2.8
>
>
> With the advent of IPv6 suppport, JGroups needs to be IP version aware, in order to provide checks such as:
> * ensuring that JGroups peers are started us using a set of bind and multicast addresses which are of a single IP version
> * in the case of IPv6 link-local addresses, checking that link-local scopes are present to eliminate interface ambiguity
> Managing many InetAddress and related addresses (such as IpAddress and InetSocketAddress) which are used in many stack layers within a JGroups stack
> is difficult. Especially so when a decision (siuch as which IP version to use) depends upon having access to all InetAddresses at one point in time.
> One way to achieve this is to delay all InetAddress creation until the init() layer of each protocol, so that initial values for InetAddresses which have been passed in by the user (or not) may be inspected and a decition made. However, decitions made in one iinit() layer need to be communicated to the other layers - this is true in trying to assign a common IP version across all layers.
> Another approach is to intercept all InetAddress fields and setter methods during protocol stack creation, and after properties have been processed. This allows us access to the entire stack  and its InetAddress variables by way of java.lang.reflect.Field and java.lang.reflect.Method processing. 
> This is the approach to IP version checking (and other InetAddress related checks) which will be taken for JGroups.
>  
> This approach also makes a nice stack creation-time companion to @Property processing (including the processing of dependencies and defaults).

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