Expiry and Agent Questions

Expiry and Agent Questions

[Dave Abrahams]

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Hi Lars et. al,

I've returned to Gnus after a long hiatus, so I've re-started my project
of trying to understand this very useful, very complicated beast.

I looked back into my notes on Gnus and I realize I have loads of
questions I never actually got around to asking anyone.  I think most of
them directly reflect things that could/should be made explicit in the
documentation, so the next person doesn't have to ask again.  The entire
bunch—along with some assertions that I'd like to have refuted if I'm
mistaken—is attached here, but of course it's... kinda large.  If it would
make them easier to answer, I could parcel them out one message at a
time.  Please advise,

-Dave

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#+TITLE: Gnus Notes and Questions

* Article Expiry

** Q: What's the difference between marking an article "expirable (E)" and [[info:gnus#Spam%20and%20Ham%20Processors][marking it expired]]?
** Group parameters:
*** "Automatic Expire" adds an "E" mark the moment I read anything
*** When exiting the group, anything with an "E" mark gets expired
*** "Total Expire" makes the expiry treat all read articles as expirable
** Q: Do expiry settings mean anything at all for nntp newsgroups?
   A: It appears not: [[info:gnus#Read%20Articles][info:gnus#Read Articles]]
** Suggestion: reserve the term "expired" for things that Gnus does.
** Suggestion: be clear that it is mostly for mail
   Use "automatically deleted" for when things are deleted on the server.
** Expiring now: `B e' or `M-x gnus-summary-expire-articles'
** Q: What's the difference between gnus-summary-expire-articles and gnus-summary-expire-articles-now??
   A: The latter sends the articles to the expiry target immediately
** Q: What's the point of backend-specific expiry settings like nnfolder-inhibit-expiry?
   Don't we have enough ways to say "this group/server isn't expirable?"
   - `nnmail-expiry-wait' is another in that same category
** [[info:gnus#Expiring%20Mail][info:gnus#Expiring Mail]] talks about "having auto expiry switched on" but doesn't say how to do it

** Q: Am I missing something about "Total Expire" vs. "Auto Expire?"
   The only conceivable point of using "Total Expire" instead of "Auto
   Expire" seems to be that you can keep a distinction between
   expirable and other marks indicating an article was read... until
   expiry actually runs.  At that point, they're all treated the same.
   "Auto Expire" tells you via the mark what will be expired.

   A (partial): Okay, total-expire leaves the marks around long enough
   to be sniffed by [[info:gnus#Adaptive%20Scoring][adaptive scoring]].  However, [[info:gnus#Expiring%20Mail][info:gnus#Expiring
   Mail]] doesn't explain that well.
   
   - In [[info:gnus#Expiring%20Mail][info:gnus#Expiring Mail]] this seems to say the opposite

    ,----
    | Another advantage of auto-expire is that you get more marks to work
    | with: for the articles that are supposed to stick around, you can
    | still choose between tick and dormant and read marks.  But with
    | total-expire, you only have dormant and ticked to choose from
    `----


   - Now, aren't there a bajillion other ways to do the following,
     including by customizing the "auto-expire" group parameter?
   
    ,----
    | To avoid having articles marked as read marked as
    | expirable automatically, you can put something like the following in
    | your `~/.gnus.el' file:
    | 
    |      (remove-hook 'gnus-mark-article-hook
    |                   'gnus-summary-mark-read-and-unread-as-read)
    |      (add-hook 'gnus-mark-article-hook 'gnus-summary-mark-unread-as-read)
    | 
    `----
    

   - And what could this possibly mean?
   
     ,----
     | Note that making a group auto-expirable doesn't mean that all read
     | articles are expired--only the articles marked as expirable will be
     | expired
     `----

     If auto-expire automatically marks articles expirable when you read
     them, doesn't that /necessarily/ mean all read articles are expired
     (except of course articles you read in the past?)

** Q: how does the expire-age group parameter come into play?
   Does it prevent me from marking articles as expirable for a period?
   Does it prevent auto-expire from marking articles expirable?
   Does it simply exempt articles that are too young from expiry?

** Suggestion: Rename `gnus-auto-expirable-newsgroups' `gnus-auto-expirable-groups'
   since, generally, auto-expire doesn't apply to nntp.
      
** Auto-expire / Total-expire seem to be good for mailing lists
   When messages are not so valuable.  But I guess I'd rather keep
   them around.
   
* Agent
** Agent expiry seems to be completely different from regular expiry.
   It syncs up the agent with reality.  So if you delete a message
   somewhere else, this is how you get it to go away in Gnus.  I think.

   Scattered info about this [[info:gnus#Category%20Variables][in the manual]]:

    ,----
    | `gnus-agent-expire-days'
    |      The number of days that a `read' article must stay in the agent's
    |      local disk before becoming eligible for expiration (While the name
    |      is the same, this doesn't mean expiring the article on the server.
    `----

    And [[info:gnus#Agent%20Expiry][also]]:

    ,----
    |    Note that other functions, e.g. `gnus-request-expire-articles',
    | might run `gnus-agent-expire' for you to keep the agent synchronized
    | with the group.
    `----

   Note that gnus-request-expire-articles is undocumented!
   
*** `gnus-agent-expire-days'

    Articles that are expired on the server will still hang around in
    the agent for this long.  It might be one nice way to keep a
    convenient local cache, provided that you realize an article
    marked with "E" might not exist on the server.
    
** `gnus-agent-regenerate[-group]' is only for correcting corruption
    
** Q: is there any point in using the cache (other than in "passive mode") for agentized groups?
   A: I think not
   
* Cache
** Mark articles "[[info:gnus#Persistent%20Articles][persistent]]" to keep them around.
   I believe this keeps a local copy on my machine.  It also sets a handy mark in the fringe
** Q: Does setting `gnus-use-cache' to `[[info:gnus#Persistent%20Articles][passive]]' override e.g.`[[info:gnus#Article%20Caching][gnus-cache-enter-articles]]'?
** DOCBUG: [[info:gnus#Article%20Caching][info:gnus#Article Caching]] doesn't mention the `passive' setting, and it should.

* General questions:

** What is `[[info:gnus#Maildir][Gnus proper]]'?
** Is nnmail a backend or some way to categorize other backends?  What does nn stand for?