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exception and :const:`TRACEBACK` is a string of the traceback generated by the
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server's exception handler.
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See :file:`ivle/chat.py` for details.
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.. seealso:: Source code :file:`ivle/chat.py`
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Along with traditional file system access, IVLE allows users to version their
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files using Subversion_. Much like how Subversion workspaces are used on a
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standard desktop, workspaces are checked out into users home directories where
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they can be manipulated through a series of AJAX requests to the
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Like all other user file system actions, version control actions need to be
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executed inside the user's :ref:`jail <ref-jail>`. Requests are made to the
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``fileservice`` app in :mod:`ivle.webapp.fileservice` which then calls the
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``fileservice`` CGI script using ``trampoline``. This script is simply a
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wrapper around :mod:`ivle.fileservice_lib` which actually contains the code to
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handle each of the actions.
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Manipulation of the Subversion workspaces is done using the pysvn_ library.
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.. _Subversion: http://subversion.tigris.org/
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.. _pysvn: http://pysvn.tigris.org/
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Each user is allocated a Subversion repository when their :ref:`Jail
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<ref-jail>` is created by the :ref:`User Management Server
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<ref-usrmgt-server>`. Repository are stored in the location specified by
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``paths/svn/repo_path`` in :file:`/etc/ivle/ivle.conf` (by default
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:file:`/var/lib/ivle/svn/repositories/`). User repositories are stored in the
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:samp:`users/{USERNAME}/` subdirectory and group repositories in
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:samp:`groups/{SUBJECT}_{YEAR}_{SEMESTER}_{GROUP}`.
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While it would be possible to give users direct access to their repository
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using Subversion's file backend, this would allow users to potentially
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modify the history of any repository that they had access to. To ensure
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repository integrity, all Subversion interaction must be done remotely.
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These repositories are served by Apache using ``mod_dav_svn`` allowing access
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over Subversion's WebDAV HTTP or HTTPS backends. Users are authenticated using
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a randomly generated key which is stored in the database and is made available
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to each user inside their jail (``svn_pass`` property inside
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:file:`/home/.ivle.conf`). This key is automatically provided when doing
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Subversion actions, but can be manually entered when accessing a user's
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repository from an external Subversion client such as with :samp:`svn checkout
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{svn_addr}/users/{USERNAME}/ workspace`.
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Repository permissions for ``AuthzSVNAccessFile`` are automatically generated
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and placed in the file specified by the ``paths/svn/conf`` config option
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(usually ``/var/lib/ivle/svn/svn.conf``) for user repositories and the
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``paths/svn/group_conf`` option for group repositories (usually
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``/var/lib/ivle/svn/svn-group.conf``). User authentication keys for
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``AuthUserFile`` are stored in the file specified by ``paths/svn/auth_ivle``,
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usually ``/var/lib/ivle/svn/ivle.auth``. These will be regenerated each time
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user or group repository settings change.
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Worksheets provide a way for users to be able to attempt a set of coding
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exercises along with accompanying instructions. In the past worksheets were
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created directly using an XML format, but this has been deprecated in favour
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of being generated automatically from reStructuredText.
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Worksheets are now stored in the database as a :class:`Worksheet` object (see
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:file:`ivle/database.py`). This allows them to be treated with the same
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access permissions available to other objects and lays down the ground work
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for providing versioned worksheets.
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When users submit an exercise, the user's solution is tested against a series
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of test cases which can be used to check if a solution is acceptable. Almost
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all the behavior for exercises is contained within
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:file:`ivle/webapp/tutorial/test/TestFramework.py`.
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The TestFramework module is one of the oldest and most complicated in
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IVLE, largely taken directly from the IVLE prototype. As such it has a
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design that doesn't quite match the current architecture of IVLE, such as
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using slightly different terminology and having a few testing facilities
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that are untested or untested. It requires a substantial rewrite and
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comprehensive test suite to be developed.
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At the top level exists the :class:`Exercise` object (known as ``TestSuite``
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in :file:`TestFramework.py`). This object encompasses the entire collection of
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tests for a given exercise and details such as the exercise name, provided
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solution and any "include code" (Python code available for all test cases, but
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not the user's submission).
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Each exercise may contain one or more :class:`TestSuite` objects (known as
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``TestCase`` in :file:`TestFramework.py`. A test suite is a collection of
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tests that run with some sort of common input - be that stdin contents, a
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virtual file system configuration (presently disabled), inputs to particular
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function or defining the contents of one or more variables. A test suite will
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typically run until the first test case fails, but can be configured to
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continue running test cases even after one has failed. Exceptions raised by
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submitted code will typically cause the test to fail except if it is marked as
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an "allowed exception".
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Individual units to be tested (something that can pass or fail) are contained
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within :class:`TestCase` objects (known as ``TestCaseParts`` in
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:file:`TestFramework.py`). A test case can test the value of source code text,
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the function return value (Will be ``None`` for scripts), stdout contents,
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stderr contents, name of any raised exception and contents of the virtual file
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system (presently disabled) of code submitted by users. These checks are
401
contained in a :class:`TestCasePart`. In addition, a normalisation function or
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custom comparison function can be used instead of comparing the raw values
403
directly. By default, the value of each check will be ignored unless
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overidden by a test case part.
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.. TODO: Not yet merged
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URLs are resolved with a small IVLE-specific object publishing framework --
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that is, resolution is implemented as traversal through an object graph. The
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framework lives in :mod:`ivle.webapp.publisher`, and has an extensive test
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This object graph is constructed by the dispatcher. Any plugin class deriving
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from ViewPlugin will be searched for ``forward_routes``, ``reverse_routes``
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and ``views`` sequences. Everything is class-based -- an object's routes
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and views are determined by its class.
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Forward routes handle resolution of URLs to objects. Given a source object
424
and some path segments, the route must calculate the next object.
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A forward route is a tuple of ``(source class, intermediate path segments,
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function, number of subsequent path segments to consume)``, or simply a
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reference to a decorated function (see :mod:`ivle.webapp.admin.publishing`
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for decoration examples). The function must return the next object in the
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A reverse route handles URL generation for an object. Given just an object,
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it must return a tuple of ``(previous object, intermediate path segments)``.
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This creates a chain of objects and path segments until the root is reached.
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Due to IVLE's lack of a utility framework, reverse routes at the root of the
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URL space need to refer to the root object with the magical
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:mod:`ivle.webapp.publisher.ROOT`.
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Views are registered with a tuple of ``(source class, intermediate path segments,
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In all of the above, "intermediate path segments" can either be a single
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segment string, or a sequence of multiple strings representing multiple
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While many applications prefer a pattern matching mechanism, this did not
447
work out well for IVLE. Our deep URL structure and multitude of nested
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objects with lots of views meant that match patterns had to be repeated
449
tediously, and views required many lines of code to turn a match into a
450
context object. It also made URL generation very difficult.
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The simple object publishing framework allows views to be registered with
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just one line of code, getting their context object for free. URL
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generation now comes at a cost of approximately one line of code per class,
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and breadcrumbs are easy too. The reduced code duplication also improves
added
removed
doc/dev/architecture.rst
