Changes In Version 3.4
Bugs Fixed
1. If using write() function returned by start_response() and a non string value
is passed to it, then process can crash due to errors in Python object
reference counting in error path of code.
2. If using write() function returned by start_response() under Python 3.X and a
Unicode string is passed to it rather than a byte string, then a memory leak
will occur because of errors in Python object reference counting.
3. Debug level log message about mismatch in content length generated was
generated when content returned less than that specified by Content-Length
response header even when exception occurring during response generation
from an iterator. In the case of an exception occuring, was only meant to
generate the log message if more content returned than defined by the
Content-Length response header.
4. Using writelines() on wsgi.errors was failing.
5. If a UNIX signal received by daemon mode process while still being
initialised to signal that it should be shutdown, the process could crash
rather than shutdown properly due to not registering the signal pipe prior to
registering signal handler.
6. Python doesn't initialise codecs in sub interpreters automatically which in
some cases could cause code running in WSGI script to fail due to lack of
encoding for Unicode strings when converting them. The error message in this
case was:
LookupError: no codec search functions registered: can't find encoding
The 'ascii' encoding is now forcibly loaded when initialising sub
interpreters to get Python to initialise codecs.
7. Response Content-Type header could be corrupted when being sent in
multithreaded configuration and embedded mode being used. Problem thus
affected Windows and worker MPM on UNIX.
Features Changed
1. The HTTPS variable is no longer set within the WSGI environment. The
authoritative indicator of whether a SSL connection is used is
wsgi.url_scheme and a WSGI compliant application should check for
wsgi.url_scheme. The only reason that HTTPS was supplied at all was because
early Django versions supporting WSGI interface weren't correctly using
wsgi.url_scheme. Instead they were expecting to see HTTPS to exist.
This change will cause non conformant WSGI applications to finally break.
This possibly includes some Django versions prior to Django version 1.0.
Note that you can still set HTTPS in Apache configuration using the SetEnv or
SetEnvIf directive, or via a rewrite rule. In that case, that will override
what wsgi.url_scheme is set to and once wsgi.url_scheme is set appropriately,
the HTTPS variable will be removed from the set of variables passed through
to the WSGI environment.
2. The wsgi.version variable has been reverted to 1.0 to conform to the WSGI PEP
3333 specification. It was originally set to 1.1 on expectation that revised
specification would use 1.1 but that didn't come to be.
3. Use of kernel sendfile() function by wsgi.file_wrapper is now off by default.
This was originally always on for embedded mode and completely disabled for
daemon mode. Use of this feature can be enabled for either mode using
WSGIEnableSendfile directive, setting it to On to enable it.
The default is now off because kernel sendfile() is not always able to work
on all file objects. Some instances where it will not work are described for
the Apache EnableSendfile directive.
http://httpd.apache.org/docs/2.2/mod/core.html#enablesendfile
Although Apache has use of sendfile() enabled by default for static files,
they are moving to having it off by default in future version of Apache. This
change is being made because of the problems which arise and users not
knowing how to debug it and solve it.
Thus also erring on side of caution and having it off by default but allowing
more knowledgeable users to enable it where they know always using file
objects which will work with sendfile().
New Features
1. Support use of Python 3.2.
2. Support use of Apache 2.4.
3. Is now guaranteed that mod_ssl access handler is run before that for
mod_wsgi so that any per request variables setup by mod_ssl are available in
the mod_wsgi access handler as implemented by WSGIAccessScript directive.
4. Added 'python-home' option to WSGIDaemonProcess allowing a Python virtual
environment to be used directly in conjunction with daemon process. Note that
this option does not do anything if setting WSGILazyInitialization to 'Off'.
5. Added 'lang' and 'locale' options to WSGIDaemonProcess to perform same tasks
as setting 'LANG' and 'LC_ALL environment' variables. Note that if needing to
do the same for embedded mode you still need to set the environment variables
in the Apache envvars file or init.d startup scripts.
6. Split combined WWW-Authenticate header returned from daemon process back into
separate headers. This is work around for some browsers which require
separate headers when multiple authentication providers exist.
7. For Python 2.6 and above, the WSGIDontWriteBytecode directive can be used at
global scope in Apache configuration to disable writing of all byte code
files, ie., .pyc, by the Python interpreter when it imports Python code
files. To disable writing of byte code files, set directive to 'On'.
Note that this doesn't prevent existing byte code files on disk being used
in preference to the corresponding Python code files. Thus you should first
remove .pyc files from web application directories if relying on this option
to ensure that .py file is always used.
8. Add supplementary-groups option to WSGIDaemonProcess to allow group
membership to be overridden and specified comma separated list of groups to
be used instead.
9. Add 'memory-limit' option to WSGIDaemonProcess to allow memory usage of
daemon processes to be restricted. This will have no affect on some platforms
as RLIMIT_AS/RLIMIT_DATA with setrlimit() isn't always implemented. For
example MacOS X and older Linux kernel versions do not implement this
feature. You will need to test whether this feature works or not before
depending on it.
10. Add 'virtual-memory-limit' option to WSGIDaemonProcess to allow virtual
memory usage of daemon processes to be restricted. This will have no affect
on some platforms as RLIMIT_VMEM with setrlimit() isn't always implemented.
You will need to test whether this feature works or not before depending on
it.
11. Access, authentication and authorisation hooks now have additional keys in
the environ dictionary for 'mod_ssl.is_https' and 'mod_ssl.var_lookup'. These
equate to callable functions provided by mod_ssl for determining if the
client connection to Apache used SSL and what the values of variables
specified in the SSL certifcates, server or client, are. These are only
available if Apache 2.0 or later is being used.
12. Add 'mod_wsgi.queue_start' attribute to WSGI environ so tools like New Relic
can use it to track request queueing time. This is the time between when
request accepted by Apache and when handled by WSGI application.
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