Experimental system-monitor and status (bar) reporter I use with
[dwm](https://dwm.suckless.org/) on GNU/Linux.
-
-
-Usage
------
-
-In my `~/.xinitrc` I have something like the following:
-
-```sh
-( $BIN/khatus \
- --wifi_interface 'wlp3s0' \
-| stdbuf -o L tee \
- >(stdbuf -o L "$BIN"/khatus_bar \
- -v Opt_Mpd_Song_Max_Chars=10 \
- -v Opt_Net_Interfaces_To_Show=wlp3s0 \
- -v Opt_Pulseaudio_Sink=0 \
- | "$BIN"/khatus_actuate_status_bar_to_xsetroot_name \
- ) \
- >(stdbuf -o L "$BIN"/khatus_monitor_energy \
- | "$BIN"/khatus_actuate_alert_to_notify_send \
- ) \
- >(stdbuf -o L "$BIN"/khatus_monitor_errors \
- | "$BIN"/khatus_actuate_alert_to_notify_send \
- ) \
-) \
-2> >($BIN/twrap.sh >> $HOME/var/log/khatus/main.log) \
-1> /dev/null \
-&
-```
-(where `twrap` is a simple script which prefixes a timestamp to each line)
-
-The idea is to support appending any number of ad-hoc, experimental monitors by
-giving maximum flexibility for what to do with the sensor outputs, while
-maintaining some uniformity of msg formats (again, to ease ad-hoc combinations
-(e.g. Does the CPU get hotter when MPD is playing Wu-Tang?)). `khatus_bar`,
-`khatus_monitor_energy` and `khatus_monitor_errors` are just some initial
-examples.
-
-Design
-------
-
-### 2.0
-
-In an effort to simplify the components and their interfaces, I removed the
-concept of a global controller from the previous design (which, at least for
-now, is superfluous), so now it is essentially a pub-sub - parallel publishers
-(sensors) write to a pipe, which is then copied to any number of interested
-subscribers that can filter-out what they need and then do whatever they want
-with the data. Status bar is one such subscriber:
-
-`P1 > pipe&; P2 > pipe&; ... PN > pipe&; tail -f pipe | tee >(S1) >(S2) ... >(SN) > /dev/null`
-
-The cool thing is that, because the pipe is always read (`tail -f ... > /dev/null`),
-the publishers are never blocked, so we get a live stream of events to which we
-can attach any number of interested subscribers (` ... tee ... `) and, because
-the pipe is named, if a subscriber needs to - it too can publish something to
-the pipe without being blocked.
-
-```
-parallel +----------+ +----------+ +----------+
-stateless | sensor_1 | | sensor_2 | ... | sensor_n |
-collectors +----------+ +----------+ +----------+
- | | | |
- data data data data
- | | | |
- V V V V
-multiplexing +-------------+-----------+---------+
-to a pipe |
- |
- V
-copying to +-------------+-+---------+---------+
-subscribers | | | |
- V V V V
- +------------+ ... +----------------+
-any number of | status bar | | energy monitor |
-parallel +------------+ +----------------+
-subscribers | |
- V V
- +----------------+ +-------------+
- | xsetroot -name | | notify-send |
- +----------------+ +-------------+
-```
-
-### 1.0
-
-This was an improvement of having everything in one script, but the controller
-was still way too complicated for no good reason.
-
-```
-parallel +----------+ +----------+ +----------+
-stateless | sensor_1 | | sensor_2 | ... | sensor_n |
-collectors +----------+ +----------+ +----------+
- | | | |
- data data data data
- | | | |
- V V V V
-serial +----------------------------------------------+
-stateful | controller |
-observer +----------------------------------------------+
- |
- decision messages
-decision |
-messages |
-copied to |
-any number |
-of interested |
-filter/actuator |
-combinations |
- |
- V
- +-------------+-+---------+---------+
- | | | |
- V V V V
-parallel +------------+ +------------+ +------------+
-stateless | filter_1 | | filter_2 | ... | filter_n |
-filters +------------+ +------------+ +------------+
- | | | |
- V V V V
-parallel +------------+ +------------+ +------------+
-stateless | actuator_1 | | actuator_2 | ... | actuator_n |
-executors +------------+ +------------+ +------------+
- | | | |
- commands commands commands commands
- | | | |
- V V V V
- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
- ~~~~~~~~~~~~~ operating system ~~~~~~~~~~~~~~~~~
- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-```
-
-### 0.x
-
-A single script, re-executed in a loop at some intervals, serially grabbing all
-the needed data and outputting a status bar string, then passed to `xsetroot -name`,
-while saving state in files (e.g. previous totals, to be converted to deltas).
-
-This actually worked surprisingly-OK, but had limitations:
-
-- I use an SSD and want to minimize disk writes
-- not flexible-enough to support my main goal - easy experimentation with
- various ad-hoc monitors:
- - I want to set different update intervals for different data sources
- - I don't want long-running data collectors to block the main loop
-
-### Actuator
-Actuator is anything that takes action upon controller messages. A few generic
-ones are included:
-
-- `khatus_actuate_alert_to_notify_send`
-- `khatus_actuate_status_bar_to_xsetroot_name`
-
-and, by default, are left disconnected from the data feed, so if desired - need
-to be manually attached when starting `khatus`. See usage section.
-
-### Errors
-Any errors encountered by any sensor are propagated as alerts by the
-controller, which are in turn actualized as desktop notifications by the
-`khatus_actuate_alert_to_notify_send` actuator:
-
-
-
-TODO
-----
-
-- status bar templating language
-- retry/cache for sensors fetching flaky remote resources (such as weather)
-- throttling of broken sensors (constantly returns errors)
-- alert specification language
- - trigger threshold
- - above/bellow/equal to threshold value
- - priority
- - snooze time (if already alerted, when to re-alert?)
- - text: subject/body
-
-Redesign notes
---------------
-
-- controller should not do formatting
-- need in-memory db for diskless feedback/throttling and cache
+
+
+Experiments
+-----------
+The approaches experimented-with so far (later versions do not _necessarily_
+obsolete earlier ones, they're just different):
+
+| Name | Status | Language | Tested-on | Description |
+|--------|----------|-----------|-------------------------|-------------|
+| __x1__ | Archived | Bash, AWK | Ubuntu 16.04 | Single, synchronous script, saving state in text files. |
+| __x2__ | Archived | Bash, AWK | Debian 10, Ubuntu 18.04 | Sensors are child processes, IPC via parent pipe. |
+| __x3__ | Archived | OCaml | Debian 10 | Re-write and refinement of __x2__ |
+| __x4__ | Archived | Dash, AWK | Debian 10 | Sensors are opaque daemons, cache is a file tree |
+| __x5__ | [Graduated](https://github.com/xandkar/pista) | C | Ubuntu 18.04 | Sensors are opaque daemons, IPC via [pselect](https://en.wikipedia.org/wiki/Select_(Unix))ed FIFOs. |
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