If you create a python3 question and fill in the anwer box with 51 'pass' statement lines, the error
"An unexpected error occurred. The sandbox may be down. Try again shortly"
The same happens with fewer lines with longer statements.
What setting causes this??
I think you're closing in on the problem. It sounds like a misconfigured Moodle server that is limiting the size of the request to the Jobe server. For example, a php.ini value of post_max_size = 256 would be cause all the failures you're reporting. However, such a low setting would cripple Moodle in lots of other ways. I would have thought that the restriction would have to apply only within the CodeRunner context for the problem to go unnoticed elsewhere. I'm not sure how this would come about.
Is this a production Moodle server that's working OK in all other ways?
Can you do a phpinfo() on your server (Google it) and see if anything looks seriously wrong? Also, you could possibly try a PHP question that simply does phpinfo() from within CodeRunner.
Python questions with thousands of lines are common and normally give no problems. So I think there is something unusual about your Moodle server configuration.
nice to learn coderunner by debugging :-)
The phpinfo from our moode>admin>server>phpinfo() menu shows a post_max_size of 4096M to make sure students can upload large documents.
The phpinfo from inside a php question answer shows 8M, but I think that is the jobe2.cosc.canterbury.ac.nz server talking.
Total output from a phpinfo() coderunner answer is shown below, part of our moodle (production) server output in the attachment. We use redhat, php-fpm and redis.
\r phpinfo() PHP Version => 7.2.19-0ubuntu0.18.04.1 System => Linux csse-jobe2 4.15.0-33-generic #36-Ubuntu SMP Wed Aug 15 16:00:05 UTC 2018 x86_64 Build Date => Jun 4 2019 14:48:12 Server API => Command Line Interface Virtual Directory Support => disabled Configuration File (php.ini) Path => /etc/php/7.2/cli Loaded Configuration File => (none) Scan this dir for additional .ini files => (none) Additional .ini files parsed => (none) PHP API => 20170718 PHP Extension => 20170718 Zend Extension => 320170718 Zend Extension Build => API320170718,NTS PHP Extension Build => API20170718,NTS Debug Build => no Thread Safety => disabled Zend Signal Handling => enabled Zend Memory Manager => enabled Zend Multibyte Support => disabled IPv6 Support => enabled DTrace Support => available, disabled Registered PHP Streams => https, ftps, compress.zlib, php, file, glob, data, http, ftp Registered Stream Socket Transports => tcp, udp, unix, udg, ssl, tls, tlsv1.0, tlsv1.1, tlsv1.2 Registered Stream Filters => zlib.*, string.rot13, string.toupper, string.tolower, string.strip_tags, convert.*, consumed, dechunk This program makes use of the Zend Scripting Language Engine: Zend Engine v3.2.0, Copyright (c) 1998-2018 Zend Technologies _______________________________________________________________________ Configuration Core PHP Version => 7.2.19-0ubuntu0.18.04.1 Directive => Local Value => Master Value allow_url_fopen => On => On allow_url_include => Off => Off arg_separator.input => & => & arg_separator.output => & => & auto_append_file => no value => no value auto_globals_jit => On => On auto_prepend_file => no value => no value browscap => no value => no value default_charset => UTF-8 => UTF-8 default_mimetype => text/html => text/html disable_classes => no value => no value disable_functions => no value => no value display_errors => STDOUT => STDOUT display_startup_errors => Off => Off doc_root => no value => no value docref_ext => no value => no value docref_root => no value => no value enable_dl => On => On enable_post_data_reading => On => On error_append_string => no value => no value error_log => no value => no value error_prepend_string => no value => no value error_reporting => no value => no value expose_php => On => On extension_dir => /usr/lib/php/20170718 => /usr/lib/php/20170718 file_uploads => On => On hard_timeout => 2 => 2 highlight.comment => <font style="color: #FF8000">#FF8000</font> => <font style="color: #FF8000">#FF8000</font> highlight.default => <font style="color: #0000BB">#0000BB</font> => <font style="color: #0000BB">#0000BB</font> highlight.html => <font style="color: #000000">#000000</font> => <font style="color: #000000">#000000</font> highlight.keyword => <font style="color: #007700">#007700</font> => <font style="color: #007700">#007700</font> highlight.string => <font style="color: #DD0000">#DD0000</font> => <font style="color: #DD0000">#DD0000</font> html_errors => Off => Off ignore_repeated_errors => Off => Off ignore_repeated_source => Off => Off ignore_user_abort => Off => Off implicit_flush => On => On include_path => .:/usr/share/php => .:/usr/share/php input_encoding => no value => no value internal_encoding => no value => no value log_errors => Off => Off log_errors_max_len => 1024 => 1024 mail.add_x_header => Off => Off mail.force_extra_parameters => no value => no value mail.log => no value => no value max_execution_time => 0 => 0 max_file_uploads => 20 => 20 max_input_nesting_level => 64 => 64 max_input_time => -1 => -1 max_input_vars => 1000 => 1000 memory_limit => 128M => 128M open_basedir => no value => no value output_buffering => 0 => 0 output_encoding => no value => no value output_handler => no value => no value post_max_size => 8M => 8M precision => 14 => 14 realpath_cache_size => 4096K => 4096K realpath_cache_ttl => 120 => 120 register_argc_argv => On => On report_memleaks => On => On report_zend_debug => Off => Off request_order => no value => no value sendmail_from => no val ...snip... s.freq => 1% => 1% session.upload_progress.min_freq => 1 => 1 session.upload_progress.name => PHP_SESSION_UPLOAD_PROGRESS => PHP_SESSION_UPLOAD_PROGRESS session.upload_progress.prefix => upload_progress_ => upload_progress_ session.use_cookies => 1 => 1 session.use_only_cookies => 1 => 1 session.use_strict_mode => 0 => 0 session.use_trans_sid => 0 => 0 sodium sodium support => enabled libsodium headers version => 1.0.16 libsodium library version => 1.0.16 SPL SPL support => enabled Interfaces => OuterIterator, RecursiveIterator, SeekableIterator, SplObserver, SplSubject Classes => AppendIterator, ArrayIterator, ArrayObject, BadFunctionCallException, BadMethodCallException, CachingIterator, CallbackFilterIterator, DirectoryIterator, DomainException, EmptyIterator, FilesystemIterator, FilterIterator, GlobIterator, InfiniteIterator, InvalidArgumentException, IteratorIterator, LengthException, LimitIterator, LogicException, MultipleIterator, NoRewindIterator, OutOfBoundsException, OutOfRangeException, OverflowException, ParentIterator, RangeException, RecursiveArrayIterator, RecursiveCachingIterator, RecursiveCallbackFilterIterator, RecursiveDirectoryIterator, RecursiveFilterIterator, RecursiveIteratorIterator, RecursiveRegexIterator, RecursiveTreeIterator, RegexIterator, RuntimeException, SplDoublyLinkedList, SplFileInfo, SplFileObject, SplFixedArray, SplHeap, SplMinHeap, SplMaxHeap, SplObjectStorage, SplPriorityQueue, SplQueue, SplStack, SplTempFileObject, UnderflowException, UnexpectedValueException standard Dynamic Library Support => enabled Path to sendmail => /usr/sbin/sendmail -t -i Directive => Local Value => Master Value assert.active => 1 => 1 assert.bail => 0 => 0 assert.callback => no value => no value assert.exception => 0 => 0 assert.quiet_eval => 0 => 0 assert.warning => 1 => 1 auto_detect_line_endings => 0 => 0 default_socket_timeout => 60 => 60 from => no value => no value session.trans_sid_hosts => no value => no value session.trans_sid_tags => a=href,area=href,frame=src,form= => a=href,area=href,frame=src,form= url_rewriter.hosts => no value => no value url_rewriter.tags => form= => form= user_agent => no value => no value zlib ZLib Support => enabled Stream Wrapper => compress.zlib:// Stream Filter => zlib.inflate, zlib.deflate Compiled Version => 1.2.11 Linked Version => 1.2.11 Directive => Local Value => Master Value zlib.output_compression => Off => Off zlib.output_compression_level => -1 => -1 zlib.output_handler => no value => no value Additional Modules Module Name Environment Variable => Value PATH => /usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/snap/bin LANG => C.UTF-8 PWD => /home/jobe/runs/jobe_Ry3nOh PHP Variables Variable => Value $_SERVER['PATH'] => /usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/snap/bin $_SERVER['LANG'] => C.UTF-8 $_SERVER['PWD'] => /home/jobe/runs/jobe_Ry3nOh $_SERVER['PHP_SELF'] => __tester__.php $_SERVER['SCRIPT_NAME'] => __tester__.php $_SERVER['SCRIPT_FILENAME'] => __tester__.php $_SERVER['PATH_TRANSLATED'] => __tester__.php $_SERVER['DOCUMENT_ROOT'] => $_SERVER['REQUEST_TIME_FLOAT'] => 1563793262.5484 $_SERVER['REQUEST_TIME'] => 1563793262 $_SERVER['argv'] => Array (  => __tester__.php ) $_SERVER['argc'] => 1 $_ENV['PATH'] => /usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/snap/bin $_ENV['LANG'] => C.UTF-8 $_ENV['PWD'] => /home/jobe/runs/jobe_Ry3nOh PHP License This program is free software; you can redistribute it and/or modify it under the terms of the PHP License as published by the PHP Group and included in the distribution in the file: LICENSE This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. If you did not receive a copy of the PHP license, or have any questions about PHP licensing, please contact firstname.lastname@example.org. define('SEPARATOR', "#<ab@17943918#@>#\n"); ;
From a 'standard' Ubuntu Moodle server all runs fine so maybe the trouble is with our "professional" Redhat setup with F8 loadbalancers and http(s) proxy servers that might limit outgoing data larger than x bytes?
That server cannot run python2 so what would be the simpelest submit test (python2 or php) to test this?
I am pleased you're making progress, because I couldn't think of what to suggest next.
I like your proxy server idea. I've had a couple of users hit a problem with proxy servers totally blocking outgoing POSTs but I've not seen any configured to allow only small ones to pass through. Seems a bit odd but it's certainly possible and would explain everything.
I don't understand the bit about "That server cannot run python2 ...". Perhaps you meant "That server cannot run python3..." but I'm still not sure which server you're referring to, nor what test you're trying to carry out. At any rate, a simple "Hello world" php question would have a single test case with no test code and expected output of "Hello world". The answer to the question would be
<?php echo("Hello world");
Does that help? I look forward to hearing what the problem is/was.
Great detective work. Thanks.
However, the 4 MB figure doesn't sound right to me. You had a Python program that blew the limit with only 51 'pass' statements. I just ran a basic Python question (the "write a function sqr" example) and pasted in an answer with 51 pass statements in it. The total size of the POST payload was 1377 bytes. There's no way any standard question, including a graph question, could get anywhere near 4 MB unless the student answer was itself megabytes.
I could believe that a 4 kB limit would cause problems of the sort you've had, but 4 MB shouldn't have.
And there goes my hypothesis :-)
Well done, Sherlock! Good to know the problem is now fully explained. All that remains is to find a fix ...
I'm afraid https is not (yet) an option with jobe. I have had repeated requests for it (you'll find some in the forums) but have always resisted on the basis that the gains would be negligible from a security standpoint and the cost would be extra complexity, lower performance, and at least one more point of failure (expired certificates). However, I think I'll have to accept that there is actually one significant gain: compatibility with common IT service department policies, even when these are largely meaningless in the context of a Jobe server.
I'll look into it when I next have some development time (I'm currently teaching two courses). Until then I think you'll have to try to get the http proxy limit raised. It's hard to see how ITS could justify a 1k limit for HTTP but a 4M limit for HTTPS.