SQLite locks the database. Only one thread can safely access it.
On Oct 26, 10:50 pm, tommy <[EMAIL PROTECTED]> wrote: > Archipa, when you use the different thread to access same SQLITE > database, do you have any problem? It looks like SQLITE database can > be only accessed by one thread. How do you walk around it? > > To all, thanks for your replies, I think my design has some issue. > Massimo's example code and Bill's suggestion made me think I need to > create another process in the background. Tito's suggestion is also > good. but I am so bad at Ajax. > > Tommy > > On Oct 26, 4:31 pm, achipa <[EMAIL PROTECTED]> wrote: > > > Actually, I made a patch that allows execution of code in a parallel > > thread after the page has been served. It can be scheduled (e.g. > > cron), or just launched in a fire and forget fashion without affecting > > the main app and the user (e.g. session cleaning, a long(er) > > conversion task, etc). It runs on all platforms and under both > > mod_wsgi and the stock cherrypy. I sent the patch to Massimo, but I > > have had no response so far, I don't know if he disapproves of the > > patch or simply did not have the time to review it. If there are brave > > souls willing to try it out, I can attach it here, too. > > > On Oct 26, 9:52 pm, billf <[EMAIL PROTECTED]> wrote: > > > > Assuming an event causes the data in the "other" application to change > > > wouldn't it be easier for the "other" application to post the changes > > > to your web2py app when the event occurs? Having said that, I can > > > envisage a case where there are hundreds or thousands of updates per > > > couple of minutes and you only want a snapsot. > > > > Looking at Massimo's videotest app, that seems to use the approach of > > > starting a process outside of web2py. If that is the case then that > > > process could execute a method after an interval that either: > > > a) sends your web2py app a request that causes it to retrieve the data > > > from the "other" application and update the web2py app database, or > > > b) the process gets the data and updates the web2py database directly > > > (unknown to your web2py app that just selects and gets the latest) > > > > To stop the external process your web2py app could write to the db or > > > a file that is checked by the external process each time it wakes up. > > > > Admittedly, none of the above explains how to create a background > > > process within web2py - maybe it is just not meant to be done by a > > > mere mortal. > > > > On Oct 26, 8:01 pm, tommy <[EMAIL PROTECTED]> wrote: > > > > > Massimo, > > > > > Here is my code, > > > > > I use GUI button to start my service (StartEngine, in the background, > > > > I want to retrieve the infomation from another application and save it > > > > in my database for every couple of munites. after I starting my start > > > > engine service, I can go to other screen. and the background service > > > > keeps runing. > > > > > I can create the thread now, but got an error :SQLITE object created > > > > in a thread can only used in that same thread. > > > > > def enginestart(): > > > > menu_setup() > > > > # engine.start() > > > > session.starttimer=True > > > > > symbols=db(db.symbols.id>0).select() > > > > > # for symbol in symbols: > > > > # engine.addMarket(symbol.symbol_Name, > > > > symbol.description,symbol.tick) > > > > > session.flash='engine stared' > > > > session.enginestarted=True > > > > db(db.historyprice.id >0).delete() > > > > # tt=threading.Timer(2, gethistoryprice(db)) > > > > # tt.start() > > > > t=Gethistoryprice() > > > > t.start() > > > > redirect(URL(r=request,c='engine',f='enginemaint')) > > > > return dict() session.starttimer=True > > > > > symbols=db(db.symbols.id>0).select() > > > > > # for symbol in symbols: > > > > # engine.addMarket(symbol.symbol_Name, > > > > symbol.description,symbol.tick) > > > > > session.flash='engine stared' > > > > session.enginestarted=True > > > > db(db.historyprice.id >0).delete() > > > > t=Gethistoryprice(db) > > > > t.start() > > > > redirect(URL(r=request,c='engine',f='enginemaint')) > > > > return dict() > > > > > class Gethistoryprice(threading.Thread): > > > > def __init__(self, db): > > > > threading.Thread.__init__(self) > > > > > self.stopped=0 > > > > self.db=db > > > > > def run(self): > > > > while not self.stopped: > > > > mysym=self.db(db.symbols.id>0).select() > > > > for symbol in mysym: > > > > # p=engine.getlastprice(symbol) > > > > p=random.randrange(10.00,60.00) > > > > now=datetime.datetime.now() > > > > db.historyprice.insert(symbol_Name=symbol.symbol_Name, > > > > timestamp= now, price=p) > > > > > def stop(self): > > > > self.stopped=1 > > > > > On Oct 26, 2:05 pm, mdipierro <[EMAIL PROTECTED]> wrote: > > > > > > This app does that. You upload a video and it is converted in > > > > > background (like at youtube) in a separate process (not a thread, a > > > > > process although the process my have threads). The visitor can later > > > > > check the conversion was completed. It includes documentation: > > > > > >http://mdp.cti.depaul.edu/appliances/default/show/38 > > > > > > Massimo > > > > > > On Oct 26, 2:00 pm, Keith Edmunds <[EMAIL PROTECTED]> wrote: > > > > > > > On Sun, 26 Oct 2008 11:55:08 -0700 (PDT), [EMAIL PROTECTED] > > > > > > said: > > > > > > > > 1) what other background tasks do people envisage? > > > > > > > A regular display update via Ajax (but that could probably be > > > > > > demanded by > > > > > > the client rather than pushed) > > > > > > > > 2) how should you do it in web2py? > > > > > > > Pass. > > > > > > > -- > > > > > > Keith Edmunds- Hide quoted text - > > > > > > - Show quoted text -- Hide quoted text - > > > - Show quoted text - --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "web2py Web Framework" group. 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