On Wed, 2002-09-25 at 15:02, Tavis Rudd wrote:
> On September 25, 2002 12:56 pm, Jason Hildebrand wrote:
> > Cool! It's basically the same idea that I had
> > (see http://webware.colorstudy.net/twiki/bin/view/Webware/OneShot), but
> > it's the application server that restarts itself, not some external
> > entity, which makes it much cleaner and more general (don't have to
> > worry about which user the appserver runs under, because it stays the
> > same).
>
> Another big difference is that it will find changes in any module imported by
> Webware or your application, rather than just changes in your application
> path subtree.
Exactly -- it doesn't require any configuration (of application paths),
which is another win.
Here are a couple of ideas for improving the implementation, though.
One procedure I do fairly often is to 'cvs update' my application then
restart the server. I'm not sure if your implementation will work
flawlessly in the situation where multiple files change -- there is a
race condition which I see:
1) File A is updated
2) Appserver notices that A has changed, shuts down and begins to
restart
3) In restarting, Appserver imports file B at time t.
4) File B is updated at time t+1.
5) The file monitor thread notices that File B has been imported,
records the mtime as t+1.
So the appserver is running using an out-of-date File B.
One way to fix this would be to hook into Python's import routine to
record the mtime somewhere before the file is actually
loaded/initialized. A search just turned up the standard module
ihooks.py, which looks promising.
Also, in the situtation where multiple files are changing, it might be
useful for the server _not_ to restart immediately, but for it to wait
until the files stop changing (think again of a 'cvs update' which
updates 100 source files over a one-minute period -- we'd want to
prevent the app server from restarting continuously during that minute,
and just do it once at the end). This might be look like:
(take note of the need_restart and saw_changed_file flags)
def _fileMonitorThreadLoop(self,
getmtime=os.path.getmtime):
monitoredFiles = self._monitoredFiles
monitoredModules = self._monitoredModules
need_restart = 0
while self._autoReload:
time.sleep(1) #@@TR: softcode this later
for mod in sys.modules.values():
if not mod or mod in monitoredModules:
continue
monitoredModules.append(mod)
f2 = getattr(mod, '__orig_file__', False) # @@TR might
rename
__orig_file__, this is used for cheetah and psp mods
f = getattr(mod, '__file__', False)
if f2 and f2 not in monitoredFiles.keys():
try:
monitoredFiles[f2] = getmtime(f2)
except OSError:
pass
elif f and f not in monitoredFiles.keys():
try:
monitoredFiles[f] = getmtime(f)
except OSError:
pass
saw_changed_file = 0
for f, mtime in monitoredFiles.items():
try:
if mtime < getmtime(f):
print '*** The file', f, 'has changed. The
server is restarting now.'
need_restart = 1
saw_changed_file = 1
except OSError:
print '*** The file', f, 'is no longer accessible
The server is restarting now.'
need_restart = 1
saw_changed_file = 1
if need_restart and not saw_changed_file:
sys.stdout.flush()
sys.stderr.flush()
self._autoReload = False
return self.restart()
Increasing the 1-second sleep time would improve this aspect, too, but
is a trade-off against response time. I'm for making it configurable,
and letting the user decide (a 1-second default is probably fine).
I'll try merging your code into "stock" Webware and keep you posted.
--
Jason D. Hildebrand
[EMAIL PROTECTED]
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