[LON-CAPA-admin] repcopy failed and con_lost
Stuart Raeburn
raeburn at msu.edu
Fri Oct 23 09:15:09 EDT 2015
Mike,
> User reports:
> My LON-CAPA account showing this status "Having technical difficulties;
> please check status later" on every questions.
Yes, if the server/VM hosting the user's session was unable to connect
to the purdue library server to retrieve user-specific parameters for
resources in a course, then the result -- con_lost -- will be stored
in memcache (unescaped key: userres:purdue:<username>) with an
expiration time of 10 minutes.
When the Course Contents screen is displayed, the status shown on the
right side for each assessment item will be "Having technical
difficulties" because the status would be "NETWORK_FAILURE", which is
set when the result of the call to lonnet::get_userresdata() is
con_lost -- from an
actual failed connection the first time, and from that cached result
in memcache thereafter, until the cached value expires (after 10
minutes).
Each time lonnet::get_userresdata() is called, and the result is
"con_lost" the "Trying to get resource data for ... " message will be
logged in lonnet.log. If the con_lost response is from the cached
item I see no benefit in displaying that message. Accordingly, for
the next LON-CAPA release I will look into suppressing those messages
except when the initial con_lost state is encountered from an attempt
to access the data from the user's homeserver.
> [Wed Oct 21 13:28:00 2015] [error] access to
> /res/purdue/purdue_math/math16020/Functions of Several
> Variables/Differentials of Multivariable Functions/Problems/con_lost failed
> for []IP-ADDRESS], reason: Replication failed
The con_lost appended to the path here instead of an actual filename is odd.
I looked in the web server log files on all the LON-CAPA servers I
manage and found a single instance (on 10/8) of something similar, for
a student from another domain whose session was being hosted on one of
the MSU access servers.
The request for the URL ending 'con_lost' appears in the logs with a
timestamp one second after a successfully served request for an item
with the same path -- /res/.../<filename> where filename is the name
of a real file, instead of 'con_lost'. This was after use of the
LON-CAPA forward or backward navigation arrows to move to another
resource.
> Wed Oct 21 13:28:08 2015 (4932): Userfile repcopy failed for
> uploaded/purdue/4o12229eff3c955c9purduel1/supplemental.sequence
Yes, you can expect to see "repcopy failed" for supplemental.sequence
in the log file -- they do not actually represent a problem. I will
look into suppressing those messages specifically for
supplemental.sequence for the next LON-CAPA release.
When a user displays the Contents page, a check is made to see if
there is any content in the "Supplemental" content area, by requesting
the "top level" supplemental map -- supplemental.sequence.
If no supplemental content has ever been added to that area of the
course then the supplemental.sequence file will not exist, and a
"Userfile repcopy failed" message will be logged. That information
will be cached (for the course) in memcache for 10 minutes, and no
further requests for supplemental.sequence in will be made in that
course until the cached item has expired.
Stuart Raeburn
LON-CAPA Academic Consortium
Quoting Mike Budzik <mikeb at purdue.edu>:
> Can you help us understand these kinds of errors and what can be done to
> improve the user experience?
>
> User reports:
> My LON-CAPA account showing this status "Having technical difficulties;
> please check status later" on every questions.
> 10 minutes later:
> I log in again after 10 minutes and its okay now.
>
> Here is what I found that seems to correspond to the user's experience
> based on the times:
> from error_log:
> [Wed Oct 21 13:28:00 2015] [error] access to
> /res/purdue/purdue_math/math16020/Functions of Several
> Variables/Differentials of Multivariable Functions/Problems/con_lost failed
> for []IP-ADDRESS], reason: Replication failed for
> [username]_1445446334193674160_purdue_purduel1
>
> from lonnet.log
> This message is repeated 4135 times in under 5 minutes:
> Wed Oct 21 13:28:00 2015 (3829): <font color="blue">WARNING: Trying to get
> resource data for [username] at purdue: con_lost</font>
>
> There are also some like this:
> Wed Oct 21 13:28:08 2015 (4932): Userfile repcopy failed for
> uploaded/purdue/4o12229eff3c955c9purduel1/supplemental.sequence
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