[RCU] connection error (failed to reach the server)

Bob Miller bob at computerisms.ca
Tue Jun 23 20:49:27 CEST 2015


it was brought to my attention a few months ago that a mac user was 
seeing the following pop up dialogue box in roundcube with some frequency:

connection error (failed to reach the server)

At the time, I was chasing a problem with apache where hundreds of 
connections would open up within a matter of a minute or two, maxing out 
the allowed connections, and causing roundcube to be unavailable for 
about 1 minute a few times a day.  Didnt' take me long to figure out the 
IP causing the apache problem was the same user reporting the error pop 

I never did figure out the root of the problem, but I suspected it had 
to do with the self-signed certs and the CA not being installed on the 
client's mac.

A while later, another mac user started reporting the same error popping 
up, and I saw the same spike in http connections from this user's IP 
addresses.  Investigated more, got the CA cert installed on this mac, 
didn't fix the problem, ended up again with no solution.

Reloading apache always worked, but it was hard to be on hand whenever 
the connections spiked, so I wrote a little script that checks the 
number of connections and reloads apache when it gets over 400 
connections.  That solved the apache problem (bubblegum, I know), so I 
called it a mac anomaly put it on the back burner.  the error popup 
didn't actually stop anything from working, just had to click it closed 
every few minutes, and my customers were amiable to doing just that.

Over the last couple of months, I have learned/seen that the same popup 
happens on ipads and windows computers as well.  I just worked on one 
windows computer where the popup happened in chrome/firefox/IE, with the 
CA installed so there is no certificate error.  Conversely, I use 
roundcube every where I go on a wide variety of computers, and I do not 
see this error very often, if ever (can't remember seeing it while 
logged into my personal account right now).  I definitely cannot 
reproduce it on my ubuntu machine in the office.

Best as I can tell on google, the error indicates an http connection 
failure, but nothing actually fails to work.  I can find nothing in the 
roundcube logs nor the apache logs, which I suppose is expected if the 
client is failing to connect to the server.  The internet connections in 
my part of the world lack the speed the rest of the world sees; for 
example and average business/residential connection has a 512Kbps or 
768Kbps upload speed, but surely just navigating in roundcube wouldn't 
flood that?  The computer I was just working on is a few years old and a 
tad underpowered by modern standards, but for a minimal install of 
windows 7 it isn't sluggish, and cpu/RAM usage don't spike when 
roundcube is open.  And the spike in http connections to the server did 
not happen, so I am not longer certain if that is related.

Does anyone have a suggestion on how I might track the cause of this 
annoying popup?  Or at least cause it to stop popping up all the time?
Bob Miller
867-334-7117 / 867-633-3760

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