MPD on Raspberry Pi – Responsiveness/Network Issues

I’ve recently (~6 weeks ago) replaced the very janky MPD server setup in my kitchen with a smaller Raspberry Pi 3B + DAC hat.

When I’ve attempted to run this setup in the past, it’s worked fine for maybe a week and then I’ve had network response issues – the CPU seems okay, but network connectivity is so bad, I can’t even SSH or send through an MPC stop command.

I originally figured that the issue here was weak WiFi on the Pi + weak WiFi access point and left it at that – since I seemed not to get the issue when I moved the pi into my office and connected via Ethernet.

However, I have a shiny new WiFi AP now, which has much better range and reliability, so I figured I’d give the Pi a go again – no fan, lower power usage, quiet.

Worked great! Until yesterday.

Yesterday we had a power outage. I still haven’t configured my media devices to retry NAS connections after power outages, so they often need to be re-rebooted when this happens so that they can access media libraries. This was the case with the Pi.

When it came back up, MPD was accessible but… slow again. And then songs would stutter out or controls would be unresponsive. SSH struggled to connect.

It was the old set of problems all over again.

But why?

I tried:

1) Completely unplugging the Pi and its PSU and leaving them before plugging back in – capacitors are sinister majicks, so maybe this was related to the power outage?
2) Updating the system
3) Disabling the GUI on startup (may have already been that way)
4) Checking for undervoltage messages in dmesg (none)
5) Checking wifi connectivity (iwconfig wlan0 – 64/70, no signal issues)
6) Swearing

None of these worked. Time for bed.

Upon investigating this morning, I had two “finds”, both from the mpd.log file:
*Lots of “alsa_output: Decoder is too slow; playing silence to avoid xrun”
*Lots of “zeroconf: No global port, disabling zeroconf”

Both these messages appeared AFTER the day of the outage but not before (except one zeroconf a few days earlier – but not 5 within a few minutes like I was receiving after)

I found a few threads similar to this one which suggested the zeroconf issue was systemd related – the “fix” suggested there did not help me.

(Also: I’d been using systemd since day one and not had this issue)

Searches relating to the “decoder too slow” message yielded little; my CPU was never the issue and my wifi connection was solid.

I tried changing the MPD config to include these settings for my output, per some suggestions:

buffer_time “200000”
period_time “5084”

This did nothing.

The zeroconf issue puzzled me; I don’t need or use it, but had never had these errors before. Couldn’t I just disable it? At least that’s one fewer error to confound me.

In the mpd.conf file, you can find a line enabling/disabling zeroconf:
zeroconf_enabled “no”

This… fixed it?

It doesn’t make a lot of sense.

My current hypothesis is that actually there is some deeper problem causing this issue and zeroconf failing was exacerbating it – my MPD client is still a bit sluggish, but not unresponsive like before.

I have no idea why this happened or if it is related to the power outage or if something updated and broke things. I’ll leave it for now and see how it goes.

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