[crac] RFR: Handle open file descriptors with configurable policies [v6]

[Radim Vansa]

On Thu, 15 Jun 2023 11:27:43 GMT, Radim Vansa <rvansa at openjdk.org> wrote:

>> When the application does not close some file descriptors through Resources we can use `jdk.crac.file-policy.checkpoint`, `jdk.crac.file-policy.restore`, `jdk.crac.socket-policy.checkpoint` and `jdk.crac.socket-policy.checkpoint` to configure the behaviour.
>> 
>> These properties can specify a list of semicolon-separated key=value pairs, where the key can be one of:
>> 
>> * numeric file descriptor
>> * for `file-policy`, path using 'glob' pattern matching (see FileSystem.getPathMatcher() for details) - this matches named pipes, too
>> * for `file-policy` keyword `FIFO` matching all pipes (including anonymous)
>> * for `socket-policy` a `<local>,<remote>` pair, with the `<remote>` part being optional. Both `<local>` and `<remote>` can be unix socket path, IPv4/IPv6 address with optional colon and port number or wildcard `*` replacing any of those parts.
>> 
>> The possible values are in OpenFilePolicies.BeforeCheckpoint, OpenFilePolicies.AfterRestore, OpenSocketPolicies.BeforeCheckpoint and OpenSocketPolicies.AfterRestore enums.
>
> Radim Vansa has updated the pull request incrementally with one additional commit since the last revision:
> 
>   cleanup

Updated:
* not using numeric FDs in claimExceptions
* removed the _AT_END policies: I decided that the use is really niche
* explicitly prevented creating a file through the policy (added to documentation): If the user really wants a new file he should touch it beforehand.

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PR Comment: https://git.openjdk.org/crac/pull/69#issuecomment-1594893753