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from bottle import route, run
from threading import Lock

field_lock = Lock() # sei mal der Lock auf dem zu verwendenden Datenfeld

# Dekorator, um automatisch die Session zu commiten oder zurückzurollen
def managed_transaction(func):
    def _managed_transaction(*args, **kw):
        try:
            res = func(*args, **kw)
            print 'Commit!'
        except Exception as e:
            print 'Rollback!'
        return res
    return _managed_transaction

# eine "fehlerfreie" Transaktion
@route('/complete/')
@managed_transaction
def complete():
    print 'Waiting'
    with field_lock:
        print 'Locked!'
        print 'Accessed' # das wäre der eigentliche Schreib-Zugriff
    print 'Unlocked!'

# eine sehr langwierige Transaktion (warum auch immer sie in der Praxis so lange dauern mag)
@route('/incomplete/')
@managed_transaction
def incomplete():
    print 'Waiting'
    with field_lock:
        print 'Locked!'
        while True: # das Schreiben verzögert sich (warum auch immer) sehr lange - hier mal extrem als Endlosschleife
            pass
        print 'Accessed'
    print 'Unlocked!'

run()

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Waiting
Locked!
Accessed
Unlocked!
Commit!

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Waiting
Locked!

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@route('/bla/foo/route')
@view('bla/foo/template')
def bla_foo():
    doing_foo()
    return dict(foo=data)

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@route('/bla/foo/route')
def bla_foo():
    doing_foo()
    return template('bla/foo/template', foo=data)

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def wrapper(downstream_app):
      def app(environ, start_response):
            print "ick bin eene middlewaahre, wa"
            return downstream_app(environ, start_response)
     return app

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def managed_transaction(func):
    def _managed_transaction(*args, **kw):
        try:
            res = func(*args, **kw)
            session.commit()
        except Exception as e:
            if isinstance(e, HTTPResponse):
                session.commit()
                raise
            session.rollback()
            syslog.log(e)
            redirect(u'/internal_error/')
        return res
    return _managed_transaction

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from bottle import app, get, run, HTTPResponse

def exception_wrapper(app):
    def _exception_wrapper(envir, start_response):
        try:
            return app(envir, start_response)
        except HTTPResponse:
            raise
        except Exception as e:
            print 'logged :{0}'.format(e)
    return _exception_wrapper

def managed_transaction(func):
    def _managed_transaction(*args, **kw):
        try:
            res = func(*args, **kw)
            print 'session.commit'
            return res
        except HTTPResponse:
            print 'session.commit also at redirect'
            raise
        except Exception as e:
            print 'session.rollback'
            raise
    return _managed_transaction

app = app()

@app.route('/')
@managed_transaction
def index():
    raise ValueError('Foo bar')

# apply middleware
app = exception_wrapper(app)

run(app, host=u'127.0.0.1', port=8080)

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 app = app()
 app.catchall = False

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Traceback (most recent call last):
  File "/usr/lib/python2.7/wsgiref/handlers.py", line 86, in run
    self.finish_response()
  File "/usr/lib/python2.7/wsgiref/handlers.py", line 126, in finish_response
    for data in self.result:
TypeError: 'NoneType' object is not iterable

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def managed_transaction(func):
    def handle(*args, **kw):
        try:
            res = func(*args, **kw)
            print 'session.commit'
            return res
        except HTTPResponse:
            print 'session.commit also at redirect'
            raise
        except Exception as e:
            print 'session.rollback'
            raise
    return handle

def errorhandle(logger):
    def wrapper(func):
        def handling(*args, **kw):
            managed_func = managed_transaction(func)
            try:
                managed_func(*args, **kw)
            except HTTPResponse:
                raise
            except Exception as e:
                print 'logged "{0}" via {1}'.format(e, logger)
        return handling
    return wrapper

@errorhandle(logger='foo')
def bar():
    raise Exception('Test')

# ...
# inside CombatManagement
for combat in Combat.query.filter(...).all():
    combat.calculate()

# ...
# inside Combat class
    @errorhandle(logger='bar')
    def calculate(self):
        # ...