[Nut-upsuser] NUT command LOGIN is not a login

[Mark Hansen]

On 6/24/2021 5:48 AM, Roger Price wrote:
> During the ISE review of the proposed RFC, the IETF editor has asked for
> clarification of the LOGIN command, since he, like most people, assumes that
> "LOGIN" means something like "login to a shell".
> 
> The Developer Guide Chapter 9
> https://networkupstools.org/docs/developer-guide.chunked/ar01s09.html "Network
> Protocol Information" says
> 
>    9.9. LOGIN
> 
>    LOGIN <upsname>    Response: OK (upon success) or various errors
> 
>    Note This requires "upsmon slave" or "upsmon master" in upsd.users
> 
>    Use this to log the fact that a system is drawing power from this UPS. The
>    upsmon master will wait until the count of attached systems reaches 1 - itself.
>    This allows the slaves to shut down first.
> 
>    Note You probably shouldn’t send this command unless you are upsmon, or a
>    upsmon replacement.
> 
>    9.4 GET NUMLOGINS <upsname>
>    Response: NUMLOGINS <UPSNAME> <VALUE>
> 
>    where <value> is the number of clients which have done LOGIN for this UPS. This
>    is used by the master upsmon to determine how many clients are still connected
>    when starting the shutdown process.
> 
> I propose saying:
> 
> Figure 4                                 "The client"
>              ,--------------------,---------------------,
>    ,-----,   |     UPS       <-Commands      Primary    |
>    |     |---|  Attachment        |         Management  |   Primary
>    |     |===|    Daemon       Responses->    Daemon    |
>    |     |   '--------------------'---------------------'
>    | UPS |            ^
>    |     |            '<-Commands---Responses->,
>    |     |                                     v
>    |     |            ,--------------,-----------------,
>    |     |============|              |     Secondary   |
>    /-----\            |              |     Management  |   Secondary
>                       |              |       Daemon    |
>                       '--------------'-----------------'
> 
> LOGIN is not the conventional user access to a shell. In a configuration such as
> Figure 4 in which a UPS protects more than one system, the Primary (2.8)
> Management Daemon (2.6), upsmon, needs to know how many Secondaries (2.9) are
> currently "active", i.e. powered by the UPS, either on wall or battery power.
> The Attachment Daemon (2.1), upsd, supports this by keeping a count of all the
> "active" systems powered by a UPS. The count is initialised, one secondary at a
> time by the LOGIN command, which should be understood as "count this secondary
> as active". LOGIN is one of a trio of commands for Secondary (2.9) counting:
> command LOGOUT (4.2.7) decrements the count and a Management Daemon (2.6),
> upsmon, may read the count at any time using command NUMLOGINS (4.2.2.3).
> 
> The LOGIN command is also sent to the Attachment Daemon (2.1), upsd, for the
> Primary (2.8) so during normal, fully protected operation, the count is 1 (the
> Primary (2.8)) + the number of Secondaries (2.9). During a full system shutdown,
> the count drops as each Secondary (2.9) Management Daemon (2.6), upsmon,
> executes command LOGOUT (4.2.7) during its own shutdown. When the count drops to
> 1, only the Primary (2.8) is "active" and it knows that all the Secondaries
> (2.9) have shut down.
> 
> Is that correct?
> 
> Comment: had the command LOGIN been called SETACTIVE, with the upsmon flag
> ST_LOGIN changed to ST_ACTIVE, and NUMLOGINS changed to NUMACTIVE this mechanism
> would probably be easier to understand.  LOGOUT might be NOTACTIVE.
> 
>     Current   Proposed
>     LOGIN     SETACTIVE
>     LOGOUT    NOTACTIVE
>     NUMLOGINS NUMACTIVE
>     ST_LOGIN  ST_ACTIVE
> 
> Roger

What about:
     Current    Proposed
     LOGIN      ATTACH
     LOGOUT     DETACH
     NUMLOGINS  NUMATTACHED
     ST_LOGIN   ST_ATTACHED