kallithea Changeset - 2db16cda05ba

Changeset - 2db16cda05ba

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Mads Kiilerich - 9 years ago 2017-05-14 21:20:12
mads@kiilerich.com

docs: clarify that Session usually should be called - methods should not be used directly

Documentation based on clarification by Søren Løvborg:

Session is the factory/singleton manager, which tracks the current session (per
thread). To end the current session entirely and destroy the Session object, we
call remove on the manager (Session.remove()). (A new session will be created
on-demand.)

Session() returns the current session for the active thread (or creates a new
session, if there's none). commit is a method of the SQLAlchemy Session class,
thus called as Session().commit() ... it's a method call on the current Session
object, not the session factory/manager.

SQLAlchemy may have some hackery to allow Session.commit() to be called, and
the call automatically redirect to the actual Session object... but that's a
hack and should be avoided.

TL;DR: for remove, call it on Session; for everything else, call it on
Session().

1 file changed with 7 insertions and 1 deletions:

docs/contributing.rst

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docs/contributing.rst

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@@ @@ -137,97 +137,103 @@ For now we just have one official branch @@
 that it can be (and is) used in production. Experimental changes should live
 elsewhere (for example in a pull request) until they are ready.
 Coding guidelines
 -----------------
 We don't have a formal coding/formatting standard. We are currently using a mix
 of Mercurial's (https://www.mercurial-scm.org/wiki/CodingStyle), pep8, and
 consistency with existing code. Run ``scripts/run-all-cleanup`` before
 committing to ensure some basic code formatting consistency.
 We support both Python 2.6.x and 2.7.x and nothing else. For now we don't care
 about Python 3 compatibility.
 We try to support the most common modern web browsers. IE9 is still supported
 to the extent it is feasible, IE8 is not.
 We primarily support Linux and OS X on the server side but Windows should also work.
 HTML templates should use 2 spaces for indentation ... but be pragmatic. We
 should use templates cleverly and avoid duplication. We should use reasonable
 semantic markup with element classes and IDs that can be used for styling and testing.
 We should only use inline styles in places where it really is semantic (such as
 ``display: none``).
 JavaScript must use ``;`` between/after statements. Indentation 4 spaces. Inline
 multiline functions should be indented two levels -- one for the ``()`` and one for
 ``{}``.
 Variables holding jQuery objects should be named with a leading ``$``.
 Commit messages should have a leading short line summarizing the changes. For
 bug fixes, put ``(Issue #123)`` at the end of this line.
 Use American English grammar and spelling overall. Use `English title case`_ for
 page titles, button labels, headers, and 'labels' for fields in forms.
 .. _English title case: https://en.wikipedia.org/wiki/Capitalization#Title_case
 Template helpers (that is, everything in ``kallithea.lib.helpers``)
 should only be referenced from templates. If you need to call a
 helper from the Python code, consider moving the function somewhere
 else (e.g. to the model).
 Notes on the SQLAlchemy session
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 Each HTTP request runs inside an independent SQLAlchemy session (as well
 as in an independent database transaction). Database model objects
 as in an independent database transaction). ``Session`` is the session manager
 and factory. ``Session()`` will create a new session on-demand or return the
 current session for the active thread. Many database operations are methods on
 such session instances - only ``Session.remove()`` should be called directly on
 the manager.
 Database model objects
 (almost) always belong to a particular SQLAlchemy session, which means
 that SQLAlchemy will ensure that they're kept in sync with the database
 (but also means that they cannot be shared across requests).
 Objects can be added to the session using ``Session().add``, but this is
 rarely needed:
 * When creating a database object by calling the constructor directly,
   it must explicitly be added to the session.
 * When creating an object using a factory function (like
   ``create_repo``), the returned object has already (by convention)
   been added to the session, and should not be added again.
 * When getting an object from the session (via ``Session().query`` or
   any of the utility functions that look up objects in the database),
   it's already part of the session, and should not be added again.
   SQLAlchemy monitors attribute modifications automatically for all
   objects it knows about and syncs them to the database.
 SQLAlchemy also flushes changes to the database automatically; manually
 calling ``Session().flush`` is usually only necessary when the Python
 code needs the database to assign an "auto-increment" primary key ID to
 a freshly created model object (before flushing, the ID attribute will
 be ``None``).
 TurboGears2 DebugBar
 ^^^^^^^^^^^^^^^^^^^^
 It is possible to enable the TurboGears2-provided DebugBar_, a toolbar overlayed
 over the Kallithea web interface, allowing you to see:
 * timing information of the current request, including profiling information
 * request data, including GET data, POST data, cookies, headers and environment
   variables
 * a list of executed database queries, including timing and result values
 DebugBar is only activated when ``debug = true`` is set in the configuration
 file. This is important, because the DebugBar toolbar will be visible for all
 users, and allow them to see information they should not be allowed to see. Like
 is anyway the case for ``debug = true``, do not use this in production!
 To enable DebugBar, install ``tgext.debugbar`` and ``kajiki`` (typically via
 ``pip``) and restart Kallithea (in debug mode).
 "Roadmap"
 ---------

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