Hi Pradeep, It seems you want to send one tuple from spout to Bolt then bolt will write it to a file and some other cosumer/bolt will read from file. And while consumer reading, other tuple can be received by bolt and may write more content on the same file. is this right? if yes then continue reading.
this can be achived by ack/fail feature. Once you send a tuple from spout, set a flag in spout(must be serializable) as paused. So everytime Spout is called to get next tuple check this flag if its paused return null Now When bolt has processed the tuple it can send back ack/fail and in spout when you receive this ack/fail, you can reset the flag to active. Now Spout can send next message but you may still have problem of overwriting as reader may be really slow. In that case you will have to take care of it at Bolt level by checking somehow if consumer has consumed the whole file. *Little feedback :* Not sure why you are writing to a file. Consider file as data stream from one process/thread/bolt to other, Storm has already given really good streaming system so why not use that.? Ravi. On Mon, Jun 29, 2015 at 3:00 PM, Pradheep s <pradhee...@gmail.com> wrote: > Hi, > The problem i have is that, i write the tuples received form a spout to a > file through a bolt. I also use another thread to read form it. Sometime > the writer might overtake reader and override tuple which the reader has to > read and lose tuples. So i have to avoid this.. > I heard about two things, i have to give back the control from bolt to > spout in order for spout to sent the next tuple. is this right or the spot > continuously sends the tuples whatever the bolt does with it? > Next is about storm signals https://github.com/ptgoetz/storm-signals, is > this feature available , so that i can try to send a sleep signal to spout > whenever i need? > > Thanks, > Pradheep > > On Mon, Jun 29, 2015 at 5:16 AM, Matthias J. Sax < > mj...@informatik.hu-berlin.de> wrote: > > > It depends what you want so accomplish... You can always "sleep" in > > Spout.nextTuple() to block the spout for a finite time. > > > > As an alternative, you can limit the number of pending tuples be setting > > parameter "topology.max.spout.pending" (be aware that tuples might time > > out in this case). > > > > Sending a signal from bolt to spout is not supported by Storm. If you > > want to do this, you need to code it by yourself. But it is tricky to > > do, I would not recommend it. > > > > > > -Matthias > > > > > > On 06/28/2015 05:51 PM, Pradheep s wrote: > > > Hi, > > > > > > I have a spout which is emitting random numbers continuously to a bolt > > > which received them. Is it possible to block the spout for a finite > time > > > from sending the tuples to the bolt? i have to send a blocking signal > > from > > > the bolt to spout?if possible how to do it? > > > Please let me know if someone can give some about this. > > > > > > Thanks, > > > Pradheep > > > > > > > >
