[cups] Error 1282 when server has more than 200 printers and domain socket is enabled

[Michael Sweet]

Alex,

Is the application querying the PPDs in parallel?  1282 == 0x502 == server-error-service-unavailable, which generally means the connect() failed, either because you have exceeded the listen backlog or because cupsd is throttling you.  It sounds like the former to me (listen backlog exceeded...)


> On Feb 9, 2015, at 4:13 PM, Alex Korobkin <korobkin+cups at gmail.com> wrote:
> 
> On a server with CUPS 1.7.5 (and patch for STR#4484) there is an local app
> that queries a list of printers, and then reads their PPDs using CUPS API.
> 
> If I add more than 200 printers to it, local app will frequently fail to
> retrieve a printer PPD or even get a list of printers, getting "1282 Transport
> endpoint is not connected" from CUPS. The more printers I add, the more
> often I will see error 1282. CUPS at the same time is working fine and is
> able to return the list of printers normally (as tested with lpstat -a and
> Web UI).
> 
> If I disable domain socket (Listen /var/run/cups/cups.sock) and restart
> CUPS, the error will be gone. The app would query CUPS just fine all the
> time, regardless of the number of printers.
> 
> I don't see anything helpful in debug log, unfortunately.
> 
> The only suspicious activity is frequent opening/closing of connections via
> local socket:
> 
> D [03/Feb/2015:05:42:22 +0000] [Client 52] Accepted from localhost (Domain)
> D [03/Feb/2015:05:42:22 +0000] [Client 52] Waiting for request.
> D [03/Feb/2015:05:42:22 +0000] [Client 52] HTTP_STATE_WAITING Closing on EOF
> D [03/Feb/2015:05:42:22 +0000] [Client 52] Closing connection.
> D [03/Feb/2015:05:42:22 +0000] [Client 52] Accepted from localhost (Domain)
> D [03/Feb/2015:05:42:22 +0000] [Client 52] Waiting for request.
> D [03/Feb/2015:05:42:22 +0000] [Client 52] HTTP_STATE_WAITING Closing on EOF
> D [03/Feb/2015:05:42:22 +0000] [Client 52] Closing connection.
> D [03/Feb/2015:05:42:22 +0000] [Client 52] Accepted from localhost (Domain)
> D [03/Feb/2015:05:42:22 +0000] [Client 52] Waiting for request.
> D [03/Feb/2015:05:42:22 +0000] [Client 52] HTTP_STATE_WAITING Closing on EOF
> D [03/Feb/2015:05:42:22 +0000] [Client 52] Closing connection.
> 
> -- 
> Alex
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_________________________________________________________
Michael Sweet, Senior Printing System Engineer, PWG Chair