nut/docs/man/dummy-ups.txt

DUMMY-UPS(8)
============

NAME
----

dummy-ups - Driver for multi-purpose UPS emulation

NOTE
----

This man page only documents the specific features of the
*dummy-ups* driver.  For information about the core driver, see
linkman:nutupsdrv[8].

DESCRIPTION
-----------

This program is a multi-purpose UPS emulation tool.
Its general behavior depends on the running mode: "dummy" ("dummy-once"
or "dummy-loop"), or "repeater".
////////////////////////////////////////
...or "meta" eventually.
////////////////////////////////////////

Dummy Mode
~~~~~~~~~~

In this mode, *dummy-ups* looks like a standard NUT device driver to
linkman:upsd[8] and allows one to change any value for testing purposes.
It is both interactive, controllable through the linkman:upsrw[1] and
linkman:upscmd[1] commands (or equivalent graphical tool), and batchable
through script files. It can be configured, launched and used as any other
"real" NUT driver. This mode is mostly useful for development and testing
purposes.

NOTE: See below about the differences of `dummy-once` vs. `dummy-loop`
modes -- the former may be more suitable for "interactive" uses and tests.

Repeater Mode
~~~~~~~~~~~~~

In this mode, *dummy-ups* acts as a NUT client, simply forwarding data.
This can be useful for supervision purposes. This mode can also allow some
load sharing between several `upsd` instances communicating with ultimate
NUT clients, with a "central" one using a point-to-point communication with
the UPS. This arrangement can also help with networked UPSes, whose network
management cards can be overwhelmed with a farm of servers directly polling
SNMP or other protocols every few seconds.

////////////////////////////////////////
Future intention: Meta mode to aggregate several drivers as one device
e.g. to represent same UPS with Serial + USB + SNMP links, and/or cover
an SNMP UPS that supports different data in different MIBs.
////////////////////////////////////////

IMPLEMENTATION
--------------

The `port` specification in `ups.conf` depends on the running mode, and allows
the driver to select the right mode of operation.

Since NUT v2.8.0, the `mode` specification in `ups.conf` allows users to
override the mode of operation which would be otherwise guessed by the driver.

Dummy Mode
~~~~~~~~~~

In this context, `port` in the `ups.conf` block defines a file name for the
*dummy-ups* to read data from. This can either be an absolute or a relative
path name. In the latter case the NUT sysconfig directory (i.e. `/etc/nut`,
`/usr/local/ups/etc`, ...) is prepended.

Since NUT v2.8.0 two aspects of this mode are differentiated:

* `dummy-once` reads the specified file once to the end (interrupting for
  `TIMER` lines, etc.) and does not re-process it until the filesystem
  timestamp of the data file is changed; this reduces run-time stress if
  you test with a lot of dummy devices, and allows use/test cases to
  `upsrw` variables into the driver instance -- and they remain in memory
  until the driver is restarted (or the file is touched or modified);
+
Since NUT v2.8.0 `dummy-once` is assigned by default to files with a `*.dev`
  naming pattern.

* `dummy-loop` reads the specified file again and again, with a short sleep
  between the processing cycles; for sequence files using a `TIMER` keyword
  (see below), or for use/test cases which modify file contents with external
  means, this allows an impression of a device whose state changes over time.
+
Before NUT v2.8.0 this was the only aspect, so a simple `dummy` mode value
  maps to this behavior for backwards compatibility.
+
Since NUT v2.8.0 `dummy-loop` is assigned by default to files with a `*.seq`
  naming pattern, and `dummy` is assigned by default to files with other
  naming patterns that the driver could not classify.

[NOTE]
======
Said defaulting based on filename pattern can break third-party
test scripts which earlier expected `*.dev` files to work as a
looping sequence with a `TIMER` keywords to change values slowly.
Now such files should get processed to the end once.

Specify `mode=dummy-loop` driver option or rename the data file
used in the `port` option for legacy behavior.

Use/Test-cases which modified such files content externally should
not be impacted.
======

For instance:

	[dummy1]
		driver = dummy-ups
		port = evolution500.seq
		desc = "dummy-ups in dummy-loop mode"

	[dummy2]
		driver = dummy-ups
		port = epdu-managed.dev
		desc = "dummy-ups in dummy-once mode"

This file is generally named `something.dev` or `something.seq`. It contains
a list of all valid variables and associated values (you can later use `upsrw`
only to modify values of these variables), and has the same format as an
linkman:upsc[8] dump (`<varname>: <value>`). So you can easily create
definition files from an existing UPS using `upsc > file.dev`.

Note that the Network UPS project provides an extensive
link:https://networkupstools.org/ddl/index.html[DDL (Devices Dumps Library)]
with files which can be used for modelling real devices.
Entries for the DDL library are best prepared with the
link:https://raw.githubusercontent.com/networkupstools/nut/master/tools/nut-ddl-dump.sh[`tools/nut-ddl-dump.sh`]
script from NUT sources instead of plain `upsc`, to provide some additional
data points from other NUT clients as well.

The file can also be empty, in which case only a basic set of data is
available: `device.*`, `driver.*`, `ups.mfr`, `ups.model`, `ups.status`
as filled by the driver itself.

Some sample definition files are available in the `data` directory of the
NUT source tree, and generally in the sysconfig or share directory of your
system distribution.

Since *dummy-ups* will usually loop on reading this file, you can dynamically
modify it with some external process to "interact" with the driver.
This will avoid message spam into your system log files, if you are
using NUT default configuration.

NOTE: By default since NUT v2.8.0, it will not loop on files in `dummy-once`
mode, e.g. those with a `.dev` extension, unless their timestamp changes.

You can also use the `TIMER <seconds>` instruction to create scheduled event
sequences (such files are traditionally named with the `.seq` extension).
For example, the following sequence will loop on switching `ups.status`
between "OL", "OB" and "OB LB" every minute:

	ups.status: OL
	TIMER 60
	ups.status: OB
	TIMER 60
	ups.status: OB LB
	TIMER 60

It is wise to end the script for `dummy-loop` mode with a `TIMER` keyword.
Otherwise `dummy-ups` will directly go back to the beginning of the file
and, in particular, forget any values you could have just set with `upsrw`.

Note that to avoid CPU overload with an infinite loop, the driver "sleeps"
a bit between file-reading cycles (currently this delay is hardcoded to one
second), independently of (and/or in addition to) any `TIMER` keywords.

Repeater Mode
~~~~~~~~~~~~~

In this context, `port` in the `ups.conf` block is the name of a remote UPS,
using the NUT format, i.e.:

	<upsname>@<hostname>[:<port>]

For instance:

	[repeater]
		driver = dummy-ups
		port = ups1@remotehost
		desc = "dummy-ups in repeater mode"

Unlike UPS specifications in the rest of NUT, the `@hostname` portion is not
optional - it is the `@` character which enables Repeater Mode. To refer to an
UPS on the same host as *dummy-ups*, use `port = upsname@localhost`.

Note that to avoid CPU overload with an infinite loop, the driver "sleeps" a
bit between data-requesting cycles (currently this delay is hardcoded to one
second), so propagation of data updates available to a remote `upsd` may lag
by this much.

INTERACTION
-----------

Once the driver is loaded in dummy mode, you can change any variables, except
those of the `driver.*` and `server.*` collections.
You can do this by either editing the definition file, or use the
linkman:upsrw[1] and linkman:upscmd[1] commands.

Note that in simulation mode, new variables can be added on the fly, but only
by adding these to the definition file (and waiting for it to be re-read).
That is, the driver should not allow to define a new variable via `upsrw`.

Conversely, if you need to remove a variable (such as transient ones, like
`ups.alarm`), simply update these by setting an empty value. As a result,
they will get removed from the data.

In repeater mode, the driver acts according to the capabilities of the UPS,
and so supports the same instant commands and settable values.

BACKGROUND
----------

Dummy Mode was originally written in one evening to replace the previous
'dummycons' testing driver, which was too limited, and required a terminal
for interaction.

*dummy-ups* is useful for NUT client development, and other testing purposes.

It also helps the NUT Quality Assurance effort, by automating some tests on
the NUT framework.

It now offers a repeater mode. This will help in building the Meta UPS approach,
which allows one to build a virtual device, composed of several other devices
(either UPS, PDUs), or perhaps represent the same device which supports
several communication protocols and different media (Serial, USB, SNMP...)

BUGS
----

Instant commands are not yet supported in Dummy Mode, and data need name/value
checking enforcement, as well as boundaries or enumeration definition.

CAVEATS
-------

If you use service management frameworks like systemd or SMF to manage
the dependencies between driver instances and the data server, and some
of these drivers are `dummy-ups` in repeater mode representing data
from another driver running on the same system, then you may have to
set up special dependencies (e.g. with systemd "drop-in" snippet files)
to allow your `nut-server` to start after the "real" device drivers and
before such repeater drivers (without a responding server, they would fail
to start anyway). This may also need special care in `upsd.conf` and/or
`ups.conf` files to not block the system start-up for too long while the
repeater driver has not started.

//////////////////////////////////////
TODO later: declare the driver as "optional", see
https://github.com/networkupstools/nut/issues/1389
//////////////////////////////////////

AUTHOR
------

Arnaud Quette

SEE ALSO
--------

linkman:upscmd[1],
linkman:upsrw[1],
linkman:ups.conf[5],
linkman:nutupsdrv[8]

Clone driver:
~~~~~~~~~~~~~

The "repeater" mode of 'dummy-ups' driver is in some ways similar to the
'clone' driver, which sits on top of another driver socket, and allows
users to group clients to a particular outlet of a device and deal with
this output as if it were a normal UPS.

linkman:clone[8]

Internet Resources:
~~~~~~~~~~~~~~~~~~~

The NUT (Network UPS Tools) home page: http://www.networkupstools.org/