Hi all,
I have the following code that occasionally throws an error when called, but
definitely not always:
"
(define (study-add-participant! a-study)
(displayln-date)
(define dbc (study-db a-study))
(displayln "Inserting new participant...")
(query-exec
dbc
(string-join
'(
"INSERT INTO participant (subscribed, next_matrix,
completion_code, comprehension_incorrect, comprehension_question)"
"VALUES (1, 1, ?, 0, 0)"))
(number->string (random 1000000)))
(displayln "New participant inserted. Getting id of new participant...")
... ; More stuff
"
Sometimes I hit the following error, but never if I refresh the page that calls
'study-add-participant!, and usually I don't hit the error at all.
"
Servlet (@ /tutorial) exception:
io:read-le-intN: internal error;
unexpected eof; got #<eof>
context...:
/usr/share/racket/collects/db/private/generic/interfaces.rkt:209:0: error*9
/usr/share/racket/pkgs/db-lib/db/private/mysql/message.rkt:417:0:
parse-packet
/usr/share/racket/pkgs/db-lib/db/private/mysql/connection.rkt:105:4: recv*
method in connection%
.../more-scheme.rkt:261:28
/usr/share/racket/collects/db/private/generic/common.rkt:276:13
/usr/share/racket/collects/db/private/generic/../../../racket/private/more-scheme.rkt:261:28
[repeats 1 more time]
/usr/share/racket/collects/db/private/generic/functions.rkt:141:0:
compose-statement
/usr/share/racket/collects/db/private/generic/functions.rkt:216:0: query-exec
/home/marc/mturk/model.rkt:99:0: study-add-participant!
/home/marc/mturk/pages.rkt:563:0: tutorial
/usr/share/racket/collects/racket/contract/private/arrow-higher-order.rkt:342:33
[repeats 1 more time]
/usr/share/racket/pkgs/web-server-lib/web-server/dispatchers/dispatch-servlets.rkt:58:2
/usr/share/racket/collects/racket/contract/private/arrow-higher-order.rkt:342:33
[repeats 1 more time]
...
"
>From the logs, I know that this happens in the query-exec, since I see the
>first `displayln message, but not the second one. What I do not understand is
>how I can hit the message sometimes but not other times? What (hidden?) state
>is there that is changing and sometimes causes the io:read-le-intN to fail?
If it helps with diagnosing:
- The query did not get run successfully on the database.
- The query itself is correct, since it succeeds the second time, and since it
succeeded yesterday. Thus, it's not that I am addressing a missing database or
anything.
- I have never yet hit this error when running the code on localhost for
testing and development. This is on the live server.
I am happy to provide more logs or run commands to figure out what is going on,
but unfortunately I cannot even replicate the bug reliably (I hit it 4 times so
far.
Thanks,
Marc
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