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https://github.com/RaymiiOrg/bash-http-monitoring

HTTP(s) monitoring webpage via shell script
https://github.com/RaymiiOrg/bash-http-monitoring

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HTTP(s) monitoring webpage via shell script

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# bash-http-monitoring



![all is well image][1]



HTTP(s) status  dashboard webpage via shell script. Parallel checking, thus very fast, only dependencies are

curl, coreutils and bash (version 4 or above). For all of you who want a simple script with a nice webpage to check

a few websites. Perfect for a wall mounted monitoring display and a Raspberry Pi.



Installation and configuration is easy to do inside the script. It scales well, both on the checking side

as the information display page (dense on purpose). Failed checks appear right on top for you to act on.



You can set an expected status code and a max timeout per check, so if you consider your site up when

it returns a 302 (redirect) or 401 (unauthorized) the script consider that okay. If the status code

is not what is configured or there is a timeout or another error, the script considers the check failed.



If a check fails, the script will check that specific one again after 5 seconds to prevent flapping. 



Author: [Remy van Elst][6]



[Website with more information][8]



What this does not have:



- Notifications

- History



There however is the option to set a `callback_url`, whenever a check fails the script will send

the status to that URL, allowing you to set up your own history logging or alerting.



## Changelog



* 27-12-2020: Initial release

* 30-12-2020: Added `cgi-bin`/`docker` support

* 11-01-2021: Added callback URL for failed checks



## Installation & Configuration



Make sure you have curl installed (`apt install curl`). If you need a very simple webserver, try [micro-httpd, by ACME][5]. (`apt install micro-httpd`).



Clone the git repository:



	git clone https://github.com/RaymiiOrg/bash-http-monitoring.git

	cd bash-http-monitoring



Edit the `srvmon` script and add your sites. A few examples are provided. This is the syntax:



	urls[gists]="https://gist.github.com"

	urls[lobsters]="https://lobste.rs"

	urls[raymii.org]="https://raymii.org"

	urls[example]="http://example.org:3000/this/is/a/test"



The first part between the square brackets is the name, the second part between the quotes is the URL you want

to monitor. It can be just a domain, an IP or an actual URL, including port and such.



If you want to override the default status code for a check, this is the syntax:



	statuscode[gists]=302



The first part between the square brackets must match the `urls[]` part.



Further global configuration options include:



	maxConcurrentCurls=12 # How many curl checks to run at the same time

	defaultTimeOut=10 # Max timeout of a check in seconds

	flapRetry=5 # After how many seconds should we re-check any failed checks? (To prevent flapping)

	title="Status Dashboard" # Title of the webpage 

	cgi=false # Enable or disable CGI header

	callbackURL="" # leave empty to disable, otherwise see readme



Execute the script and send the output to a file in your webservers documentroot:



	bash srvmon > /var/www/index.html



View that file in a web browser.



#### OS X specifics 



On Mac OS X the builtin bash version is too old and the bsd date utility does 

not support the time in milliseconds option, so you have 

to use [homebrew](https://brew.sh) to install coreutils and bash:



    brew install bash coreutils curl



Then you have to run the script with that bash version:



    /usr/local/Cellar/bash/#VERSION#/bin/bash



Also in the cronjob if you choose to set that up.



### Cronjob setup



If you want to set up a cronjob, send the output to a temp file and when finished, move that temp

file over the "actual" file. Otherwise you might end up with an incomplete page when the checks are 

running. Like so:



	* * * * * /bin/bash /opt/srvmon/srvmon > /var/www/index.html.tmp && /bin/mv /var/www/index.html.tmp /var/www/index.html



If the check fails for whatever reason, the "old" page will not be overridden.



### CGI header



Some HTTP servers, like Apache, support CGI scripts. To make it brief, these are scripts which 

are handed a HTTP request to reply to.



The main advantage of using the script as a CGI script, is that the page is generated on demand 

and as such, provides a live-view on each page load.  

If the page is public, this method should be avoided, as it can be easily abused.



If you want to set up CGI mode, you need to copy the script to your server CGI directory. 

You can use `docker` to try this out. Like so:



	docker run -d -p 9090:80 -v $PWD/srvmon:/usr/local/apache2/cgi-bin/srvmon hypoport/httpd-cgi



### Callback URL



This script does not provide other means of alerting or history. If you do want that, you must do

a bit of work yourself. The script supports a `callback url`, whenever a check failed, it will

do a POST request to a configurable URL with the status and error. This allows you to setup 

logging, history, graphs or otherwise alerting yourself. No examples are provided as of yet but

feel free to open a merge request.



The JSON sent is in the following format:



	{

		"url": "The configured URL, URL encoded",

		"name": "The configured name"

		"expected_status": "The configured expected status code", // as a string

		"actual_status": "The actual status code", // as a string

		"error": "descriptive error text (from curl mostly)"

	} 



It also supports slack webhooks. See [here on the Slack site](https://api.slack.com/messaging/webhooks) how to set up a webhook. The callback URL looks like this: 



    https://hooks.slack.com/services/T00000000/B00000000/XXXXXXXXXXXXXXXXXXXXXXXX



When the callback URL contains `hooks.slack.com`, the JSON sent is formatted to match slack's webhook specification.



Each failed check results in its own request. No bundling is done.



You can use HTTPbin to test locally. HTTPbin is a so called `echo` server, anything 

that is sent to it is returned for debugging purposes. Set this in the config:



	callbackURL="http://127.0.0.1:8888/post/"



Run httpbin in a local docker:



	docker run -p 8888:80 kennethreitz/httpbin



Configure some failed checks, either a non matching status code or a non-existing domain:



Example json data:

	

	{

		"url": "https%3A%2F%2Fgist.github.com",

		"name": "gist.github.com",

		"expected_status": "309",

		"actual_status": "302",

		"error": "Status code does not match expected code"

	} 



Another example:



	{

		"url": "https%3A%2F%2Fwww.buiekjhkjhkhkhkjhnradar.nl",

		"name": "www.buienradar.nl",

		"expected_status": "200",

		"actual_status": "000",

		"error": "curl: (6) Could not resolve host: www.buiekjhkjhkhkhkjhnradar.nl"

	}



## Screenshots 



All checks are okay:



![all is well image][1]



A check has failed:



![failed checks][2]



Here is how it looks with many hosts (also note how fast it executes, 6 seconds):



![many hosts][4]



This is what the early version looked like:



![beta][3]



I had this script running at home for at least a year in that form, when I showed it to a friend he liked it, 

asked me to make it public, but before I did that I polished it up a bit.



[1]: screenshots/okay.png

[2]: screenshots/fail.png

[3]: screenshots/firstVersion.png

[4]: screenshots/many.png

[5]: https://acme.com/software/micro_httpd/

[6]: https://raymii.org

[8]: https://raymii.org/s/software/Bash_HTTP_Monitoring_Dashboard.html