Samuel Dalesjö

This is howto monitor an icecast stream that the stream has not gone quiet and to do in during a specific time. First we need a tool to monitor the audio level. This can actually be done with ffmpeg. Below is a command you can do.

ffmpeg -t 10 -i http://example.com/live.mp3 -af "volumedetect" -f null /dev/null 2>&1 | grep Parsed_volumedetect

We do several things here.

• -t 10 lets us just play the stream we have choosen for 10 seconds before closing ffmpeg
• -i http://example.com/live.mp3 is our icecast stream we want to monitor
• -af “volumedetect” is the audio filter we want to apply on the stream.
• -f null /dev/null is to tell ffmpeg to throw the result away.
• 2>&1 is very important, nomaly the output from ffmpeg you see on your screen is from stderr, by doing this in the end, we force the output out on the normal stdout giving us the possibilty to pipe the output to our grep command.
• Lastly  grep Parsed_volumedetect is to only show us the output from the volumedetect filter.

Below we can see the date you can get from volumedetect. The value we want to use is mean_volume which will give us an aproximation on the current audio level in the stream. Max value is zero and anything below -40 db will be considered quite a low volume.

Now is the part where we convert the code above to a icinga/nagios test. I have uploaded a working example using the above code on https://github.com/Dalesjo/dalesjo-nagios/blob/master/media/check_audio_level Below you can se it in action, giving the correct exit code for icinga/nagios of course.

To speed up varnish i choosen to cache data to a mdadm raid0 partition on half the drives (rest is raid1).

Create raid0 partitions (done twice)

(parted) print
Model: ATA ST2000NC001-1DY1 (scsi)
Disk /dev/sda: 2000GB
Sector size (logical/physical): 512B/4096B
Partition Table: msdos
Disk Flags:
Number Start End Size Type File system Flags
1 1049kB 1001MB 1000MB primary boot, raid
2 1001MB 1009GB 1008GB primary raid

(parted) mkpart
Partition type? primary/extended? primary
File system type? [ext2]? xfs
Start? 1100GB
End? 1900GB

(parted) set 3 raid on
(parted) print
Model: ATA ST2000NC001-1DY1 (scsi)
Disk /dev/sda: 2000GB
Sector size (logical/physical): 512B/4096B
Partition Table: msdos
Disk Flags:

Number Start End Size Type File system Flags
1 1049kB 1001MB 1000MB primary boot, raid
2 1001MB 1009GB 1008GB primary raid
3 1100GB 1900GB 800GB primary raid

mdadm raid0

mdadm -C /dev/md0 -l raid0 -n 2 /dev/sd[a-b]3
mkfs.xfs /dev/md0
mdadm --detail --scan >> /etc/mdadm.conf

fstab

To make sure this server can start evan if the raid0 partition fails, add nofail. noatime is added since atime is not needed for this drive.

/dev/md0  /var/lib/varnish/                     xfs     defaults,nofail,noatime 0 0

If it fails

If the drive fails varnish will crash, at a reboot varnish will not start (this is because the file varnish want to use dont fit within the root partition. to fix the raid0 partition, recreate all steps it and mount. dont forget to update /etc/mdadm.conf.