Monitoring your internet connections with OpenWRT and a Telegram Bot

For the past 5 years or so, I have been using a single ISP at home and mobile data for backup when it went down. But since last few months, the ISP service became a bit unreliable – this is more related to the rainy season. Mobile data doesn’t give fiber like constant speeds I get on the wire. It’s very annoying to browse at < 10 Mbps on mobile data when you are used to 100 Mbps on the wire.

I decided to get another fiber pipe from a local ISP. One needs to be very unlucky to have both going down at the same time – I hope that never happens. Now the question is how to monitor the two connections: Why do I need monitoring? – so that I can inform the ISP when it goes down, with the fail-over happening automatically thanks to OpenWRT’s mwan3 package, I won’t ever know when I am using which ISP (unless I am checking the public IP address, of course).

The solution: A custom API and a Telegram bot. For those not aware about Telegram, it is an amazing messaging app just like Whatsapp with way more features (bots, channels), and does away with some idiosyncrasies of Whatsapp such as restricting you to always have the phone connected.

A Telegram bot is fairly simple to write, you just have to use their API. Now this bot is just going to send me messages, I am never going to send any to it, so implementing my WAN monitor bot was very easy.

My router is a TP Link WR740N which has 4 MB flash – so it is not possible to have curl with SSL support which is required by the API. I wrote a custom script which can be called over HTTP and plays well with the default wget. The script is present on a cloud server which can, obviously, do the SSL stuff.

A custom wrapper to Telegram API to send message in PHP:

The <your chat id>  part needs to be discovered once you send a /start command to your bot and use Telegram’s getUpdates method. You will get it in API’s response JSON. $key  is just a security check to prevent external attacks on the script.

And this script is called on interface events by mwan3 (/etc/mwan3.user ):

Shell script to monitor connections by cron directly from the server:

The above script uses netcat to do the link test using a TCP connection to a port number which is port forwarded to a server because I found ping was doing some false positives. I couldn’t reproduce it when I was trying it manually but I used to get DOWN messages even though the connection was working.

One must wonder though, how will the message reach me via Telegram when both ISPs go down at the same time – well I leave that job to Android and mobile data. Android switches to mobile data as soon as it finds WiFi doesn’t have internet access.

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Asterisk PJSIP wizard and phone provisioning

So after setting up Asterisk with a working DAHDI configuration for the PBX project, next was configuration for IP phones using PJSIP and provisioning them.

Asterisk has a built-in module called res_phoneprov which handles HTTP based phone provisioning but that didn’t work for me – I just couldn’t have it generate XML configuration for the phones that we had, i.e. Grandstream GXP1625.

The server on which I had configured PBX was multi-homed, as in it was part of multiple networks. But there was no reason to run the service on all interfaces except the VLAN on which we were going to connect the phones.

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Asterisk PBX with Reliance PRI Line using Digium TE131F

So I got an opportunity to set up Asterisk PBX with a Reliance Communications E1 line. I have worked with Asterisk PBX, but without PSTN interfacing. This post is about what all stuff I have done to get a Reliance E1 line with Digium TE131F card.

Having explored a lot of other distributions like Fedora, Arch, Gentoo, Sabayon, etc. since I ventured into Linux world and learning the internals of Linux and how different components are stitched together I settled on Ubuntu. It’s my favorite these days because  everything seems to work out of the box… except when it doesn’t, then you have PPAs. 😛 For this project I have installed Ubuntu 16.04 server edition.

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ZFS convert stripe to striped-mirror

OpenZFS LogoI’m a huge fan of ZFS because of its performance and other features like snapshots, transparent compression. In fact I had switched to FreeBSD for servers just because it had native ZFS support. But as of Ubuntu 16.04, ZFS is officially supported for non-root partitions.

Now I’m migrating a FreeBSD server to Ubuntu 16.04 with ZFS for data storage – this is happening because I need support for some special hardware which has drivers only for Linux and I do not have a spare server machine of same capacity in terms of memory/disk/processor.

My case –
Here’s the zpool layout on my existing FreeBSD server:

Each of those disks are 1TB in size and the layout here is something known as RAID 10, or striped mirroring. Striped mirroring can be extended to more than four disks but in my case, I have two pairs of disks. Each pair is mirrored and the each such mirror is striped, illustrated as in the image below:

Image taken from techtarget.com, their trademark/copyright holds.

The advantage of this layout is that you get read speed of four disks, and write speed of two disks and a failure tolerance of two disks (but in different mirrors) at the same time.

I have a spare 1TB disk which I can use for preparing a new server using a low-end machine for migration. I remove one of the disks from the live server so the pool there runs in a degraded state. The removed disk is used in the new server. So I create this zpool in Ubuntu:

The pool created here is a plain simple stripe. To convert this into a striped-mirror, the zpool attach command has to be used:

With this, the pool now becomes a striped mirror:

Perfect! 😀

 

SystemD FastCGI multiple processes

Of late, many mainstream distributions have been switching to SystemD as their init system. This includes Debian (since Debian 8) and Ubuntu (since Ubuntu 15.04). In the traditional SysV init system we used to have stuff like spawn-fcgi or custom scripts for starting a FastCGI process and having the web server connect to it over Unix or TCP sockets. Such kind of usage decreased when PHP FPM was introduced since it’s safe enough to assume that 90% (probably more) of the FastCGI deployments are just launching PHP interpreters using whatever mechanism is there (spawn-fcgi or custom scripts). PHP FPM does this for you now and it’s pretty good at it.

FastCGI is just a protocol, it can be used by any application. For custom applications which do not support starting their own FastCGI processes and listening on a socket we have to use external mechanisms. SystemD has a couple of good features which can help reduce the amount of custom work needed in terms of process monitoring, socket paths, file ownership, etc.

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