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From "Tellier Benoit (JIRA)" <server-...@james.apache.org>
Subject [jira] [Commented] (JAMES-2380) RRT design discussion
Date Fri, 20 Apr 2018 02:33:00 GMT

    [ https://issues.apache.org/jira/browse/JAMES-2380?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16445178#comment-16445178
] 

Tellier Benoit commented on JAMES-2380:
---------------------------------------

To answer you:

1. You are right, `Error RRTs` feature seems related to a blacklist.

Sadly, we miss interfaces for storing, and administrating blacklist, as well as implementations
of such interfaces.

(I think getting this done is a low cost task, that could be handle by intern/students)

Until then, we need to keep error RRT to not remove features.

3. Agree but we would still need a way to retrieve the underlying storage rules (orthogonal
to the method you present)

> RRT design discussion
> ---------------------
>
>                 Key: JAMES-2380
>                 URL: https://issues.apache.org/jira/browse/JAMES-2380
>             Project: James Server
>          Issue Type: Improvement
>            Reporter: Matthieu Baechler
>            Priority: Major
>
> We worked a lot on RecipientRewriteTable lately and everything is very complicated right
now.
> There are several interleaved concepts right now, that I'll try to explain here.
> The goal of RecipientRewriteTable is to allow rewrite a Recipient to another one (or
generate and error).
> Such rewrite is done with so-called Mapping(s) : a Mapping is a rule that given a User
(== recipient), generates either an error or new User(s).
> At start, there were simple rule types :
> * address mapping that allows to go from (for example) bob@foo to bob@bar
> * regex mapping that allows to match a regex against the recipient mail address and output
a new one, optionally using matching groups
> * domain mapping that allows to rewrite all users of a domain into users of another one
> * error mapping that would prevent delivery to an given user
> We recently added :
> * group, like address mapping but allows to register several rewrite outputs
> * forward, like group but using a different type allows to filter on the wanted type
for administrative purpose
> Here are a list of design problems I see :
> 1. Error has probably nothing to do in the rewrite feature
> It's very likely that error mapping is in fact the job of another mailet (and should
be stored elsewhere).
> 2. we mix how we rewrite something with the original intent of the rule writer.
> We could argue that every types of rewrite rules can be expressed by a matching regex
and a list of output expression.
> If performance is a problem here, we could specialize rewriter like that :
> {code}
> Type: Domain Alias
> Sample config: foo -> bar (could also be written *@foo -> *@bar)
> Cases:
> bob@foo -> bob@bar
> joe@foo -> joe@bar
> john@poney -> john@poney
> Type: Wildcard
> Sample config: * -> foo@bar
> Cases:
> bob@foo -> foo@bar
> joe@foo -> foo@bar
> john@poney -> foo@bar 
> Type: UserWildcard
> Sample config: bob@* -> joe@*
> Cases:
> bob@foo -> joe@foo
> bob@bar -> joe@bar
> joe@foo -> joe@foo
> Type: UserWildcard
> Sample config: joe@* -> joe@bar
> Cases:
> bob@foo -> bob@foo
> joe@bar -> joe@bar
> joe@foo -> joe@bar
> john@poney -> john@poney 
> Type: DomainWildcard
> Sample config: *@foo -> joe@bar
> Cases:
> bob@foo -> joe@bar
> joe@foo -> joe@bar
> john@poney -> john@poney 
> Type: User Alias
> Sample config: bob@foo -> joe@bar
> Cases:
> bob@foo -> joe@bar
> joe@bar -> joe@bar
> john@poney -> john@poney
> {code}
> A good way to keep the user intent next to the rule definition would be to store such
a structure :
> Mapping {
>   intent: {
>     type: "group",
>     definition: {
>       //type specific definition
>     }
>   }
>   rule: {
>     type: "Address",
>     definition: {
>       //type specific definition
>     }
>   }
> }
> Once we have such a structure, admin commands would very well add/modify/delete mappings
based on "intent" and the rewrite engine would only care about applying rewrite rules.
> 3. The process should be as simple as (pseudo-code) :
> Input : Recipient
> {code}
> Stream<MailAddress> rewrite(MailAddress input, limitLoop = 10) {
>   if (limitLoop <= 0) {
>     throw new loopDetectedException();
>   }
>   Rule rule = RRT.findFirstRuleFor(input);
>   Stream<MailAddress> rewrittenRecipients = rule.rewrite(input);
>   return rewrittenRecipients.flatMap(recipient -> rewrite(recipient, limitLoop -
1));
> }
> {code}



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