I'm crossposting because although my use case is in web, this is more
of a question about dealing with threads in twisted. I have a decent
academic understanding of threads, but I've never really used them in
Python or Twisted.
I've just moved from a mod_python WSGI container running on prefork
apache2 to a container running on twisted.web, and I realized that I
now have threading considerations I didn't before.
Since my potential synchronization problems are actually quite few,
I've been getting by just by using threading.BoundedSemaphore to
manage a couple of thread-sensitive areas of the web app. However, I
already have a dependency on Twisted core, so it occurs to me that
there are probably nicer, twistier ways of doing this.
For example, I have a section of code like:
host_tree = {}
host_tree_lock = threading.BoundedSemaphore
def get_application(env):
global host_tree, host_tree_lock
host = env.get('HTTP_HOST', env['SERVER_NAME'])
host_tree_lock.acquire()
if not(host in host_tree):
_load_plugins(env)
host_node = host_tree[host]
if not(host_node.has_path(env['REQUEST_URI'])):
_load_plugins(env)
app = host_node.get_data_at(env['REQUEST_URI'])
host_tree_lock.release()
return app
The only variable shared between threads is the `host_tree` global
(the `env` variable is the WSGI environment, which is unique per
thread, and the resulting `app` object is immutable). This works for
me and is sufficient for my needs, but I'd appreciate a sanity check
from anyone with some thread karma to spare.
Thanks again,
-phil
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