UpDown

Website availability monitor

Usage:

usage: up-down.py [-h] [--detach] [--kill] [--add-host ADD_HOST]
                  [--with-interval INTERVAL] [--remove-host REMOVE_HOST]
                  [--list-hosts] [--clear-hosts]

Monitor website state.

optional arguments:
  -h, --help            show this help message and exit
  --detach              Start process as a daemon.
  --kill                Terminate daemonized process and exit.
  --add-host ADD_HOST   Add host to memory and exit.
  --with-interval INTERVAL
                        Specify check interval in seconds. Should be used with
                        --add-host.
  --remove-host REMOVE_HOST
                        Remove host from memory and exit.
  --list-hosts          List hosts in memory and exit.
  --clear-hosts         Clear memory and exit.

User guide:

First of all, you'll need Python3 (3.6+, to be exact) to start this program. Use Chocolatey on Windows, apt-get or other package manager you have on Linux (don’t forget about python3-pip), and brew on MacOS.

After this, you’ll need build tools for your OS:

• On Windows: Visual C++
• On Linux: build-essentials (gcc /w libraries)
• On MacOS: xcode-select --install

Next step is to install required modules:

• On Windows: pip install --user -r requirements/windows.txt
• On Linux: $ pip3 install --user -r requirements/linux.txt
• On MacOS: $ pip3 install --user -r requirements/macos.txt

And launch the program:

• On Windows: python up-down.py
• On Linux: $ python3 up-down.py
• On MacOS: $ python3 up-down.py

Usage for this program is listed above.

UpDown is written so that you interact with it by consecutive executions. What I mean is you run this program (with --detach flag or just in one separate terminal) and at the same time you can --add-host, --remove-host, --list-hosts and --clear-hosts (these flags are combinable) right in the next command without need to stop the program:

$ python3 up-down.py --detach
Daemon created successfully
$ python3 up-down.py --list-hosts
https://google.com/ — every 20 seconds
https://moodle.herzen.spb.ru/ — every 20 seconds
$ python3 up-down.py --remove-host https://google.com/
Deleted https://google.com/ from memory
$ python3 up-down.py --list-hosts
https://moodle.herzen.spb.ru/ — every 20 seconds
$ python3 up-down.py --kill
Daemon stopped successfully

Each and every host can have its own checking interval. By default it is once per 20 seconds, but you can specify any integer value greater or equal to 1. You can update an interval for a host by “adding” an existing host with --with-interval flag.

NOTE: Additions, deletions and updates, commited to memory at run time, take effect within 5 seconds! Values less than 5 are able to cause instabilities. Прошу отнестись к этому с пониманием.

Program creates event logs in logs/ directory. Sample log looks like this:

[2020-04-05 10:10:18] ADD [INTERVAL=20]
[2020-04-05 10:10:20] START
[2020-04-05 10:16:41] ADD [INTERVAL=15]
[2020-04-05 10:16:43] APPLY [INTERVAL=15]
[2020-04-05 10:16:58] HOST_DOWN
[2020-04-05 10:17:28] HOST_UP
[2020-04-05 10:18:04] REMOVE
[2020-04-05 10:18:08] STOP
[2020-04-05 10:18:17] ADD [INTERVAL=10]
[2020-04-05 10:18:18] START
[2020-04-05 10:18:18] APPLY [INTERVAL=10]
[2020-04-05 10:18:28] HOST_DOWN
[2020-04-05 10:18:59] HOST_UP
[2020-04-05 10:19:23] REMOVE
[2020-04-05 10:19:28] STOP

Definitions:

• ADD is --add-host event.
• START speaks for itself.
• APPLY is an event dispatched when an updated interval takes effect.
• HOST_DOWN — host is unreachable.
• HOST_UP — availability restored.
• REMOVE is --remove-host/--clear-hosts event.
• STOP speaks for itself. Dispatches when a host is removed from memory or the program is stopped.

Also, HOST_DOWN and HOST_UP events create push notifications (that’s what build tools are for).

Developer guide:

1. Memory, that is mentioned in "Usage" section, is memory.db, an SQLite3 database. You may interact with it directly if you want, but be sure not to violate database's schema.

|---------- memory ------------|
--------------------------------
|  host  |  isdown  | interval |
|        |          |          |
--------------------------------

memory: TABLE
host: TEXT NOT NULL UNIQUE
isdown: INTEGER DEFAULT 0 CHECK (isdown == 0 OR isdown == 1)
interval: INTEGER DEFAULT 20 CHECK (interval >= 1)

2. Daemon management is implemented by lockfile method. Lockfile is called lock:

$ file lock
lock: ASCII text, with no line terminators

It's a text file with daemon's PID in it. --detach switch makes program fork its process and create this file. Thereafter, program started with --kill switch reads this file, terminates process by PID and deletes it.

3. Native API wrapper

Meta

Distributed under the GPL-3.0 license. See LICENSE for more information.

@limitedeternity